A discussion ...."Marie Michon" ?

[PeterSibley]

There has been a brief but interesting discussion here ,
http://www.woodenboat.com/forum/showthread.php?p=2202010&posted=1#post2202010
about the yacht "Marie Michon" .An older type of very heavy displacement designed by Bevil Warrington-Smythe in the late 1920s I believe .She was reputedly a good sailer , comfortable and seaworthy .Here are a few photos from a book by Francis Cooke (courtesy of Dick Wynne ).

http://pic40.picturetrail.com/VOL282/9443996/17245530/364808955.jpg

http://pic40.picturetrail.com/VOL282/9443996/17245530/364808956.jpg

http://pic40.picturetrail.com/VOL282/9443996/17245530/364808957.jpg

I wonder why such designs have been so overwhelmingly displaced by lightweight designs ? It seems that "Michon Marie " would suit many as would the US designed version featured in WB No. 85 in 1988 "Corineus " ,a very slightly smaller version of the same concept .

What does the panel think ?

[PeterSibley]

Here are a couple of photos of the US version , Corineus .I really like her !

http://pic40.picturetrail.com/VOL282/9443996/17245530/364814668.jpg

http://pic40.picturetrail.com/VOL282/9443996/17245530/364814665.jpg

[Paul Pless]

Peter, what is it that you find appealing in this design in particular? The phrase 'very heavy displacement' seems to catch me a bit out... Does the lack of deckhouse create any headroom issues that would be easily accomodated otherwise? That's one hell of a bowsprit too, and this coming from someone that finds that type of rig appealing...

[PeterSibley]

A flush deck ,a solid motion ,1900's fishing boat rig on Marie Michon.Probably very close to standing headroom on MM ,5 foot or so in Corineus .

The bowsprit isn't a problem if you run sail out on a ring .

Did I mention a flush deck ! Something like a big 1890s pilot cutter in miniture .

[rufustr]

I really like the look of these boats Peter.

They are great designs.

The flush deck would be good for lots of reasons too.

But heavy traditional construction would be a lot more work and cost these days, and to my way of thinking that would be the limiting factor with one of these boats.

I reckon Gartside has achieved good compromise with his designs.

http://www.gartsideboats.com/pgimages/109Best2.jpg

Are you just discussing these designs, or are you thinking of starting your build again?

[PeterSibley]

I really like the look of these boats Peter.

They are great designs.

The flush deck would be good for lots of reasons too.

But heavy traditional construction would be a lot more work and cost these days, and to my way of thinking that would be the limiting factor with one of these boats.

I reckon Gartside has achieved good compromise with his designs.

http://www.gartsideboats.com/pgimages/109Best2.jpg

Are you just discussing these designs, or are you thinking of starting your build again?

Now theres a question ! I've really liked this kind of design ,ever since I saw the WB article on "Corineus " years ago .Corineus was a design on it's own in many ways , not least that it was isolated from the normal yachting culture .

As you may know .I haven't done anything on my build for 2 1/2 years , since the family upsets .I have a backbone structure that is remarkably similar to MM's .....it would be very easy to change at this point .Thinking,thinking ..... :)

As to expense of traditional heavy wooden construction .Rufus ! No , it's cheap ! Much cheaper than the delicate route .My planking cost me $2000 ,28 foot lengths of spotted gum .Keel $300 .Stem and stern posts ironbark salvage bridge timbers .The little pile of 40mm thick bends for sawn frame stock cost $300 from a post splitter and $1000 to bandsaw through and through .

I have to admit it's very much easier if you don't live in the city .The bush is made of trees .:)

No epoxy ,no glass ,no Western Red Cedar .:)

[PeterSibley]

If anyone happens by who could add some wisdom regarding the sailing characteristics of this type of hull and rig ....I would very much like to hear !

[rufustr]

I don't know how similar they are to Oyster Smacks, but does this link help in any way?

http://www.betty-ck145.de/docueng/index.html

[PeterSibley]

Rufus , yes I know that site .Lot's of great stuff !

[PeterSibley]

Rufus ......
frame stock .

http://pic40.picturetrail.com/VOL282/9443996/17245530/364829644.jpg

[Wiley Baggins]

I wonder why such designs have been so overwhelmingly displaced by lightweight designs ?

What does the panel think?

I think Paul Pless may have hit one of the nails on the head with his comment about the heavy displacement catching him a bit out. That displacement also implies more materials and more cost. The boats do look best flush decked which (re)introduces another point Paul Pless raised - headroom...and light...and ventilation below.

Mind you, I think they are wonderful to look at and there are a couple of beauties (Cockle and Carlotta), one new build and one restoration up in building and repair, as you know. I have a very soft spot for the similarly configured Itchen Ferry type.

Ashley Butler has done some nice work with the type. I'm thinking specifically of his Mayflower Class design - http://www.butlers-wooden-boats.co.uk/projects.asp?project_id=5.

As to their sailing characteristics, there was much gnashing of teeth over their reported less than desirable qualities on the forum some years back, but most articles I've seen are favorable. I'm sure some of that being the result of writers and editors "never" encountering a boat they don't like because no one wants to read about that. Another factor may be that only the best or most sorted out designs last or are found worth of reproducing. I’ve not sailed the type but I am sure there is both good and bad in their handling as there is in any creation constrained by compromises.

I’m embarrassed to say I just went looking for a drawing of your design and I couldn’t find it. I am approaching (if not 100%) certain you shared the drawings with us previously.

Great topic!

[PeterSibley]

Wiley I have a pdf of the lines which I'll post but I have no idea how ! jpgs via Picturetrail OK ,but pdfs ?

[rufustr]

I realize there is still excellent material available Peter.

I used to get Hardwood house frames from a Sawmiller named Fred Shipman at Glenreagh in Northern NSW years ago.

He eventually proved far too unreliable and although his timber was excellent quality I had to go elsewhere.

Currently I am getting some of the best looking hardwood I have ever seen from a local supplier.

I suspect it's mainly Blackbutt, but I'm not sure.

The ability to build a flush deck design gives plenty of room, but nowhere to hide out of the weather.

[PeterSibley]

I guess the point I was making Rufus is that it's not really expensive , not compared to the exotics .

[PeterSibley]

Wiley .

http://pic40.picturetrail.com/VOL282/9443996/17245530/364832565.jpg

My current design ,which I am really quite happy with .

[rufustr]

http://i359.photobucket.com/albums/oo39/rufustr/PETERSIBLEYSDRAWING2.jpg

[PeterSibley]

Thanks Rufus , your version is much improved .

[Wiley Baggins]

My current design ,which I am really quite happy with .

She looks a bit like an amalgam of the traditional model and the more yacht-like French pilot boat towards the back of John Leather's book on the gaff rig – which is to say better than either. Off topic (slightly), thanks too for that photo of Jolie Brise in the Carlotta thread. That particular image really allows one to see the sheer of the hull separate from its bulwarks.

[rufustr]

Have you seen this site Peter?

http://www.pilotcutter.co.uk/portfolio.html

[rufustr]

A drawing from the site posted above.

http://www.pilotcutter.co.uk/images/pilotcutterway_full.gif

[Andrew Craig-Bennett]

Well, I have sailed on boats of this type and I do like them.

There is, as they say, no replacement for displacement.

Good points:

1. You can load her full of stuff and it makes no difference.

2. Much less sick-making and much less fatiguing motion at sea. There are generations of yachtsmen who have no experience of this.

3. Superior light weather performance (big sail area in relation to wetted surface

4. You can make her jolly strong, and she is easy to repair.

5. With traditional construction, you can use the more easily available local materials (eg in my case larch planking and grown oak frames - but for a better example see Peter's figures, above, for Australia) which are much, much, cheaper than fancy stuff and epoxy.

6. Regarding the flush deck, personally I like to go down into the cabin and get out of the elements; I am not interested in looking out from below.

7. This sort of boat was built by people who had limited facilities - Marie Michon was built by a firm of fishing boat builders, Gilbert and Pascoe, who were "discovered" by the Warrington-Smyth family because they were extremely cheap - they had not built a yacht before. I recall from somewhere that Marie Michon cost £200 in 1927 which was very cheap indeed - with the salvaged hatch and skylight and with internal fitting out done by the owner. This makes them practical boats for amateurs to build so long as one is in the sort of size where one man can cope with the frame members and strakes of planking.

[downthecreek]

2. Much less sick-making and much less fatiguing motion at sea. There are generations of yachtsmen who have no experience of this.


6. Regarding the flush deck, personally I like to go down into the cabin and get out of the elements; I am not interested in looking out from below.



On the first point - you can say that again! I have very little experience of the mass produced commodity yachts, but a ride up the Wallet, wind over tide, in a friend's Janneau was a revelation in the other direction!

On the second - entirely agree. I shall never forget my first trip in the pilot cutter "Kindly Light" when I was about 15. Only a "ferry" trip from Portsmouth to Cowes, under power and in the dark. The enchantment of that deep, plain, comfortable cabin with it's single oil lamp turned down low and the delightful contrast with the rather black and unforgiving night outside lives with me still. :)

Our own boat, incidentally, although not of this type, behaves very much like a Hillyard in a seaway. Having sailed both in an 8 tonner and a 14 tonner of that breed (the latter through some of the biggest seas I have ever encountered in a sailing boat) I've been quite struck with the similarities.

[PeterSibley]

Thanks Andrew ...just what I wanted to hear !

Now about the hull shape ,very slack bilges (especially when compared to my drawing above ).Which is the more comfortable in a seaway ? Heaves to most easily ?

They are very different concepts .

[Andrew Craig-Bennett]

Slack bilges = heavy displacement = comfortable in a seaway and easy heaving-to.

This sort of boat will heel a bit right, away, but it is really difficult to get the rail under.

[PeterSibley]

Compared to my drawing Andrew ? Does Mirelle resemble the drawing or MM more closely .....or neither ?

[Andrew Craig-Bennett]

Mirelle is closer to your drawing. her lines are in fact based on those of WA Robinson's Alden ketch "Svaap". You probably have the book.

However, her draft was reduced to 5ft to suit her home waters.

[Paul Pless]

Well, I have sailed on boats of this type and I do like them.

There is, as they say, no replacement for displacement.

Good points:

1. You can load her full of stuff and it makes no difference.

2. Much less sick-making and much less fatiguing motion at sea. There are generations of yachtsmen who have no experience of this.

3. Superior light weather performance (big sail area in relation to wetted surface

4. You can make her jolly strong, and she is easy to repair.

5. With traditional construction, you can use the more easily available local materials (eg in my case larch planking and grown oak frames - but for a better example see Peter's figures, above, for Australia) which are much, much, cheaper than fancy stuff and epoxy.

6. Regarding the flush deck, personally I like to go down into the cabin and get out of the elements; I am not interested in looking out from below.

7. This sort of boat was built by people who had limited facilities - Marie Michon was built by a firm of fishing boat builders, Gilbert and Pascoe, who were "discovered" by the Warrington-Smyth family because they were extremely cheap - they had not built a yacht before. I recall from somewhere that Marie Michon cost £200 in 1927 which was very cheap indeed - with the salvaged hatch and skylight and with internal fitting out done by the owner. This makes them practical boats for amateurs to build so long as one is in the sort of size where one man can cope with the frame members and strakes of planking.
So Andrew, what are the bad points as you see them, or are there none?or asked another way, why haven't you traded Mirelle on such a boat?;)

[Andrew Craig-Bennett]

I do in fact favour this sort of boat.

Mirelle has not been traded in for one because I am very fond of her.

Oh, and because I live on the East coast of England where our waters are shallow. Marie Michon was built in Cornwall where the water is deep.

[PeterSibley]

...and the crucial question Andrew , which do you think is the better sea boat ?

[Paul Pless]

Mirelle has not been traded in for one because I am very fond of her.Fair enough... and quite understandable!:)

[PeterSibley]

[quote=Andrew Craig-Bennett;2202413

Mirelle has not been traded in for one because I am very fond of her.

[/quote]

Very understandable !:) She is a delight !

[Andrew Craig-Bennett]

Oh, Marie Michon would be the better seaboat, undoubtedly.

The two are pretty similar; the difference is really quite small, but the advantages of Marie Michon as a seaboat seem to be these:

1. Better windward performance, espescially in strong winds, due to her deeper draft and higher ballast ratio.

2. Stronger construction, with no coach roof.

3. Would probably lie-to better.

Mirelle is pretty good, but her weakness is her windward performance, which is handicapped by her draft being kept down to 5ft.

Another point is that Marie Michon would be quite a bit easier to build. No counter, no coach roof...should be a very easy hull to plank with the soft bilges...

[rufustr]

Am I right in thinking you would modify the lines and keep the work you have already done on the keel?

If I remember correctly your keel is a big structure and you are well advanced with it.

[PeterSibley]

That would be right Rufus , I would remove the counter timbers and use the existing backbone and ballast casting .It is quite workable , but needs a bit more thought .I have a fair investment in the existing design but this type is pleasing in many ways .

[Paul Pless]

. . . but needs a bit more thought .he's a crazy man ;)

[RFNK]

Peter
Where are you planning to sail? If you're going to sail in the tropics, do you really want to dispense with the coachroof and do you want deeper draft? If you're planning to go south or to the far north (Europe/Canada), then it would make more sense, wouldn't it? I'd be happy to spend time in the sun on deck and down below when it's unpleasant around Tassie but up north (tropics) I want to be in the shade and have plenty of breeze just about all the time. Rick

[PeterSibley]

Rick ,my prefences are mainly South ,Tassy and NZ .An Atlantic voyage on day ?

I spent time on trawlers up North and I find heat and humidity on a boat difficult ! Oppressive !
If I wanted to sail the Pacific ,I'd build a Wharram cat ,open air and 2 foot draft .

[John B]

All right , I can't stand it any longer.
Peter , you have a design of your own , to build it will be a massive achievement ,( "No , its my design and I built it , yes it goes very well , no ...no problems with the Tasman etcetc "
Stop playing around with this other sweet little thing shakin' its tail feathers at you for goodness sake.

[rufustr]

I've printed out the lines of the three boats in involved, and I really can't see why you would consider changing your plans.

You can probably achieve a flush deck with your design and have as much room below as with the other two.

The three boats would be similar in displacement, your boat would probably be stiffer with its fuller bilges, and you can use the traditional rig from Marie Michon.

[PeterSibley]

John ,nothing's is happening boat wise at the moment .I'm building extra accomadations for the brood ....so just thinking ....also, we have had 380 mm of rain over the last 3 days and I'm spending way too much time figuring , drawing and playing on the 'puter .I'd rather be driving nails .

That said , I like MM ,the Corineus design I posted was a favorite of mine years ago .The thread linked at the top opened pandoras Box !:D

[PeterSibley]

I've printed out the lines of the three boats in involved, and I really can't see why you would consider changing your plans.

You can probably achieve a flush deck with your design and have as much room below as with the other two.

The three boats would be similar in displacement, your boat would probably be stiffer with its fuller bilges, and you can use the traditional rig from Marie Michon.

:o:o Quite true ! Silly of me , but I still like MM .Perhaps sanity will return when the rain stops .:)

[rufustr]

I was to be back on my job this morning but had had something in my eye for a couple of days, (while the rain event was happening) and went and got my Doctor to remove it.

His advice was to go home and rest the eye for the day.

That's why I'm here in the office.:(

Back to work tomorrow.:(

[PeterSibley]

Good timing ! I'm just nailing on champhers , right under the drip line .I'm glad I choose not to put the t&g down until I finished the walls .

[WX]

Peter, i would go with what you have, if you are happy with it of course. I wouldn't want to have to go back and redesign and redo anything but I'm speaking from the "this has already taken me too long" viewpoint.

Rufus, i didn't know you were a KDE man?

[rufustr]

OK Gary, Ill bite.

KDE Man?

[PeterSibley]

Operating system on your computer ?

[rufustr]

OK, I looked it up.

No Gary, at least not consciously.

Edited to add.

I went back and looked at the enhanced drawing of Peter's boat's lines.

The format already existed with Peter's drawing before I enhanced it.

[WX]

http://i359.photobucket.com/albums/oo39/rufustr/PETERSIBLEYSDRAWING2.jpg

The program you are using is a linux application. So i figured you are running Linux as your operating system and using KDE as your desktop.

[rufustr]

Insert Big Grin Here.

[rufustr]

Peter,

I took this photo of Storm Bay coming in at Hobart.

I like the forward cabin entry with Spray Dodger, and perhaps something like this would give ample protection in bad weather, while leaving the deck uncluttered with a cabin top.

http://i359.photobucket.com/albums/oo39/rufustr/WOODENBOATFESTIVALTRIP2009048.jpg

[rufustr]

A photo of a flush deck from here.

http://www.ssa-uk.org/mary.htm

http://www.ssa-uk.org/mary_files/image006.jpg

[PeterSibley]

Thanks Rufus ....they're lovely aren't they ?

[Andrew Craig-Bennett]

There's amazingly little room in a Colchester smack. Shoal draft and inside ballast and basically you have crawling room only.

[PeterSibley]

Yes , 4 foot 6 is about the minimum liveable ,5 foot would be better , with somewhere to stand occassionally , an extended scuttle , skylight perhaps .

[Andrew Craig-Bennett]

There's a Catch 22 - I've sailed on small flush decked boats and if you can stand in the companionway and stand under the skylight you are OK but invariably the area under the skylight is where you want to put the saloon table!

Edited to add - the fifthe edition may have Nereid II in it - about as small as a flush decked boat can get but very comfortable and goes like a rocket. (She is currently for sale in Maldon and in desperate need of a competent new owner).

[PeterSibley]

No Nereid II ,however the 5th edition has plates on Rona ,Aristene ,Vindilis ,Alethea ,Driac 11 ,Cherub 111 ,Talisman 11 .:)

Andrew can you suggest any lines etc for boats similar to Marie Michon ?

[PeterSibley]

Here's Nereid II.
http://www.albertstrange.org/?p=203
I wish she were closer .

[Andrew Craig-Bennett]

http://www.albertstrange.org/wordpress/zenphoto/zen/i.php?a=Boats%2FNereid+II&i=Nereid+II+Drawing.JPG&s=450

Laws (sometimes spelled Lawes) was a clever designer - you will notice the trick whereby the companion hatch slide merges into the high pitched butterfly skylight - in effect he gives the boat a coach roof with six foot headroom over the length and width of the cabin sole - just where you need it - whilst preserving the appearance and convenience of a flush deck. The toe to the ballast keel allowing her to be slipped or to lie on a wall or posts easily was thirty years ahead of other designers. She's also quite the pocket rocket.

I do feel desperately guilty about this boat - I knew her well and coveted her as a boy - but I absolutely cannot take her on.:o

[mmd]

So... somebody put a bug in my ear that told me to drop in on this thread. Nice boats; what's the question being discussed?

[Andrew Craig-Bennett]

Well, its Peter's thread, but any comment from you would be most welcome, I'm sure.

Peter was taken with the "Marie Michon" design and was wondering whether that would suit his purposes better than his own design. They are of course very similar. Marie Michon has heavier displacement.

Associated with this is the issue of having a flush deck rather than a coach roof. I cited Nereid II as a clever design for a flush deck in a smaller boat.

[mmd]

I noticed the hatch/skylight feature that you pointed out, Andrew. Very slick. I also agreed with the commentary that a flush-decked, non-deckhoused deep boat would not be the ideal boat in the tropics. I was aboard a similar type of cutter in the Windward Islands and it was abominable below.

I get the feeling that the outstanding question of the thread is stability & seaworthiness of the type as opposed to that of modern cruising hull forms. Is that an accurate summary? If so, this could become a thread worthy of the idea of a boat forum. I'll wait until Peter wakes up and has a coffee to see what he's like to add to the steering of the thread. However, I'm obliged to apologise early for future spotty attendance - we're in the last two weeks of the fireboat build before launch, so I'm going to be a touch busy.

[boatbuddha]

I thought this thread needed a picture of one of these wonderful ships.

http://www.sandemanyachtcompany.co.uk/uploads/126/23619.JPG

[Paul Pless]

oooofda.... okay I'm sold!;)

[Dave Lesser]

Wow!

[rufustr]

Lovely, a touch bigger than Peter had in mind.:D

[boatbuddha]

Lovely, a touch bigger than Peter had in mind.:D

Yeah it seems that most of the ones I have found are closer to 45 feet. Although the extra size would probably add a few more inches of headroom below deck.

[PeterSibley]

I get the feeling that the outstanding question of the thread is stability & seaworthiness of the type as opposed to that of modern cruising hull forms. Is that an accurate summary? If so, this could become a thread worthy of the idea of a boat forum. I'll wait until Peter wakes up and has a coffee to see what he's like to add to the steering of the thread. However, I'm obliged to apologise early for future spotty attendance - we're in the last two weeks of the fireboat build before launch, so I'm going to be a touch busy.

Thank you for your attendance Michael :) .Yes ,you have nicely captured the idea .

As you can see from a few of my posts above , I have completed a drawing of a "relatively modern" design , dating in concept from the 1920s ! The scan of the lines of "Michon Marie " ,while drawn in 1927 originate in an earlier time .
A US built boat called "Corenius" was built in the 30s following Michon Maries general inspiration .WB85 ,1988.
There seems to be general approval of the type from it's owners and admirers .


The aim of the thread was a discussion of the comparitive advantages (and disadvantages ) of the modern heavy and medium displacement cruiser versus the old type .

Michael ,your opinion would be much valued !

* Andrew , has given us a very positive list of advantages , a few of the disadvantages would be worth knowing too !

[Don Kurylko]

An advantage is that such a boat will draw many admirers and compliments. :) The disadvantage is that you will be replying to the same endless stream of questions from them all! :D

[mmd]

Hi, folks; just popping in to say that I've seen the recent posts on this and am thinking of you. Busy as all get out today, so probably can't answer Peter's question properly at this time. Will consider my reply & hopefully address this fully over the weekend.

I always worry about giving opinions - they are like a-holes: everyone has one, but some are stinkier that others... <grin>

[Wiley Baggins]

[G.U. Law's] Nereid II.


<start drift>

Nereid II (image posted by ACB above) looks a lot like a boat which may have been Law's work and was featured in one of the British yachting magazines 30+ years ago probably. I think the name was "Snickersnee" or something similar and she was reputed to be exceptionally slippery.

<end drift>

[peter radclyffe]

I thought this thread needed a picture of one of these wonderful ships.

http://www.sandemanyachtcompany.co.uk/uploads/126/23619.JPG
fantastic picture, is that mascotte

[boatbuddha]

fantastic picture, is that mascotte

Yes it is.

[peter radclyffe]

Yes it is.
i worked on her in gloucester, my sister sailed on another ,Alpha , beautiful pilot cutters

[Andrew Craig-Bennett]

As a working rule, a Bristol Channel pilot skiff's displacement is roughly equal to her Thames tonnage.

That might serve as a measure of "heavy displacement" for the purposes of this thread.

[PeterSibley]

If I used the MM body sections between my perpendiculars (31'10") the Thames tonnage would be 9.8. Interestingly ,the stem,keel and stern assembly are remarkably similar to MM 's....even the external ballast is the same size , 2.5 ton .

[Andrew Craig-Bennett]

That's why I pointed you at the design. I think if you did that you would come out with a helluva good boat, with good standing headroom under the skylight/hatch and certainly very good sitting headroom elsewhere (rule of thumb - you want three feet over a bunk to sit up or sit back on/in it).

[PeterSibley]

Well done Andrew ! Thank you :).

My wife is in favour of the change , she likes a short ended boat with a simple wind vane setup ,an easy motion also received a vote !

Still thinking and awaiting Michael's inputs .

[WX]

I wouldn't want to own her but some time on the tiller would be fun.
Stunning photo of a stunning yacht.
http://www.sandemanyachtcompany.co.uk/uploads/126/23619.JPG

[rufustr]

I'd like to see your revised drawings when you get them done Peter.

I assume you are drawing them up at this moment.

I will admit I'm a fan of a plum stem and no overhang on the transom.

How much will you lose in your LOD?

[PeterSibley]

I'd like to see your revised drawings when you get them done Peter.

I assume you are drawing them up at this moment.

I will admit I'm a fan of a plum stem and no overhang on the transom.

How much will you lose in your LOD?

Length on deck would go from 34'6" to 30'10" ,not a huge loss .A gain would be easy self steering .I'd reduce beam to around 9 foot too .

No drawing yet but ( I need a sheet of drafting film :D ,don't have any do you ?),I've been measuring big lumps of wood .

Actually I'm waiting for a few words from Michael .

[rufustr]

I do my drafting on A3 these days Peter, and I do have some of that.

If you would like some I could put it in a postal tube and get it off to you.

[PeterSibley]

That would be very kind Rufus :) ! It's getting hard to get in these days of CAD.
The sheets I use are roughly 820x620 .

Some kind of synthetic , wonderful to work with .

[rufustr]

Peter,

Received your PM.

A3 is roughly 420 x 300.

The size you use is A1.

http://www.smartype.com.au/images/pdfs/International%20Paper%20Sizes.pdf

I don't have any A1, but I can check with my normal source next week, and get you some if it's available.

[PeterSibley]

Ah ! I have 4 sheets of A2 ,big enough if I draw at 3/4" to the foot (16:1 ) .I do prefer 12:1 if possible .Especially on a drawing this size .

If you could make that call ,I'd be grateful !

[rufustr]

Peter,

Just been through my old plan filing cabinet, and I've found some sheets of A1 drafting film.

I'll get a postal tube in the next couple of days and send some to you.

How many sheets do you think you will need?

[PeterSibley]

If you could spare 3 ?
Lines , sail plan and one for a stuff up ! Thanks Rufus .

[PeterSibley]

I could do it at 16:1 but accuracy is that much better at 12:1 .

[rufustr]

OK Peter,

I'll let you know when they are in the post.

[PeterSibley]

Payment in Coopers :D

edited to add , I don't know what it costs so I'd better offer folding stuff ! Include a bill please Rufus .:)

[rufustr]

Peter,

There is no way I'll take payment other than a beer or two at some stage when we meet.

If my small effort helps you firm up your design, then that will be great.

[The Bigfella]

Besides, he's expecting you to host an Oz Politics WBF EBS aboard... which reminds me, I've got your stove....

[rufustr]

Besides, he's expecting you to host an Oz Politics WBF EBS aboard... which reminds me, I've got your stove....

Of course.:D:cool::D

[shamus]

I don't think you should be swayed. I can see the attraction of MM, but I can see even more in yours. MM might plunge her bow under a bit I think, plumb stem, not much flare.

[RFNK]

which reminds me, I've got your stove....


Cripes, how wide an area did you drag for that lost mooring? :eek: Rick

[mmd]

Ah, the best laid plans of mice and naval architects. I had planned to do a brief comparative analysis of the two hull forms by entering the un-faired shapes into my 3D modeling program and from these calculating a righting moment graph to compare the relative righting energy and stiffness of the two hull forms, but between vehicle maintenance, yard maintenance, house maintenance, family maintenance, errands and social commitments, my time sort of evaporated this past weekend without accomplishing this task. Sorry.

But I have at least thought about the question. Without the crutch of the stability graph I am loath to opinionate on such a significant topic as initial and dynamic stability, but I don’t mind running off at the mouth on other features of the hulls. One of these topics is the longevity and water-tightness of traditional hulls. It makes sense to me that a slack-bilged, fully-planked hull (let’s hereafter refer to this type as the “Slacker”) should retain its structural integrity better than a hull with a similar underwater profile but with hard bilges and a keel built up with deadwood (hereafter called the “Deadwood”). For instance:

Consider for a minute the stress put on a hull caused by a grounding on a sand bar (this scenario is selected so that all loads are somewhat evenly distributed over the hull structure, rather than on the rocks which would point-load the planking). The Deadwood takes the ground on her keel and as the tide recedes and the boat heels, the deadwood keel acts as a lever and the fulcrum is the garboard plank. If the deadwood lever is long (deep) enough, the stress on the garboard can be great enough to crush the edge of the plank. Even though the grounding is soft, when the tide returns and the boat refloats, the caulking has been squeezed out and the plank edge crushed, resulting in a garboard seam leak. At best this is bothersome and requires a haul-out to properly repair; at worst, the boat does not re-float as the tide floods into the hull. The Slacker has a much shorter lever arm when it falls over onto its side, making the stress on the garboard seam much less and resulting in little or no crushing of the garboard seam.

Another point of structural integrity would be the stresses placed on individual planks during construction and the long-term effects of this, especially in a rambunctious seaway. If a plank has to be twisted, bent heavily and severely edge-set to conform to the described shape of the hull, it stands to reason that if suddenly loaded, as happens when slamming into a head sea or falling off a breaking wave, it would be more likely to spring clear of its fastenings than a plank that was less stressed during installation. (Yes, I understand that planks form to their shape, with or without steaming, but there still is residual stress in the plank). As the Slacker has easier plank lines than the Deadwood, it stands to reason that the Slacker is less likely to spring a plank in heavy weather than the Deadwood. Ergo, a safer boat in extreme weather.

Almost time to get back to my day job; one last point before I go (and just a teaser at that): In the Slacker, because the volume of the hull is carried deeper in the hull form, the vertical centre of buoyancy (VCB) is much closer to the vertical centre of gravity (VCG) than in the Deadwood. This impacts how the boat will behave in a seaway. I’m working on the explanation of this, complete with illustrations. Next installment…

[Andrew Craig-Bennett]

Just to illustrate MMD's point about grounding stresses, Mirelle has at present got a tension fracture in a grown frame, below the turn of the bilge and immediately above the wrought iron floor.

I know when I did it - going aground, in fine calm weather, on hard sand. It was on the side that was trying to straighten out, not the side being compressed. It's on the list for the next big refit, meanwhile I'm watching it...

[Paul Pless]

So then... this hull type has no negatives compared to Peter's original design?

[PeterSibley]

Very interesting Michael ,certainly a few things I had not even considered .

I await the next installment !

[PeterSibley]

Ah, the best laid plans of mice and naval architects. I had planned to do a brief comparative analysis of the two hull forms by entering the un-faired shapes into my 3D modeling program and from these calculating a righting moment graph to compare the relative righting energy and stiffness of the two hull forms,

That will be extremely welcome Michael .I'd expect MM to have poor intitial stablity but harden up at around 15 degrees of heel .The difference in motion is something I don't really know how to express ,period of motion ? jerkiness ? ...the less tiring the better .

[shamus]

That's a really interesting discussion MMD. I would really like to see a diagram with some arrows representing the assumed forces acting on the fulcrum. My own boat is quite the wineglass shape, and with a couple of tons of lead on the bottom I would have thought that when it is occasionally well heeled (unlike its owner!) those couple of tons unsupported except by water would be acting as a moment about the centre of bouyancy which might be equally stressing the lower garboard seam as the situation you outline above stresses the upper one. Except that when the boat is aground and lying gently on its side the ballast would be sitting directly on the ground and the weight stressing the garboard is that much less. I would have expected the damage to be mostly in the bumping around as she lay down and began to float again if there was any wave action.
As a complete aside if Peter is really thinking of doing is boating down here, going aground is not something to make many plans about. I can't think of anyone I know personally who has ever been aground- there is little tide, few bars, all pretty straightforward.

[PeterSibley]

Agreed Shamus , but up this way ....in my local weekend sailing waters it is pretty well normal practice ! Moreton bay is a constantly changing collection of water , sand and mud ....good sailing with the occassional bump !

[shamus]

Oh yeah! I hear it gets as deep as 6 foot here and there!
I'm really interested in the forces thing. Although we think in terms of centre of bouyancy and moments, the actual floating (is it the 'weight of the upthrust'?) is evenly spread across the submerged area I guess. Tricky. I'm sure it can be easily explained by the experts.

[PeterSibley]

I just drew a pile of diagrams and now I'm totally confused ! :D

re Moreton bay , stick to the channels ! Do not trust the appearance of water .:rolleyes:

[shamus]

What I mean by wineglass shape. That horrible stripe was the first thing to go!

http://i221.photobucket.com/albums/dd277/shamus1955/Ronita02.jpg

I guess one of the jobs the frames do is resolve those forces into their longtitudinal direction. No doubt the tighter the curves, the harder that is and the easier they bust.

[PeterSibley]

Here are a couple of closs cropped images of my lines ...



http://pic40.picturetrail.com/VOL282/9443996/17245530/365343585.jpg

and the lines of "Corineus" ....for comparison .

http://pic40.picturetrail.com/VOL282/9443996/17245530/365343586.jpg

[PeterSibley]

and remarkably similar to the one I've drawn above .

[PeterSibley]

which makes Ronita very pretty indeed !:):)

[Larks]

Well for the life of me I don't know how I missed this thread!!! Very very interesting indeed. And I am sure that I have very recently read an article on the stresses that MMD and shamus have pointed out here, which I will try and find and scan tonight. (I can't remember if it was in a magazine or one of the Naval Arc' books that I've been loaned but I'm pretty sure I have it here in Darwin).

I've loved this style of hull for many years as well Peter, ever since discovering the likes of William Crealock and his journeys in the Brixham trawler Arthur Rogers, ("Vagabonding under sail" and "A cloud of islands", two of my favourite books).

[rufustr]

Peter, the package is in the mail.:cool:

[PeterSibley]

Thank you Rufus ,I've done a few useful photocopies to scale ....this is going to be enjoyable .

[mmd]

Just for you, Shamus:

http://i32.photobucket.com/albums/d19/mmd_ns/hullonbottomsketch.jpg

As "Deadwood" lies on the soft sand bottom, it's centre of gravity wants to become one with the centre of the earth, so tries to push the hull flat to the bottom. The skeg is acting as a brace on the hull, and the offset distance between the CG of the hull and the skeg's point of contact with the bottom - the couple, depicted as the circular arrow on the sketch - tries to pivot the skeg up. This puts the structure under the skeg in tension and the structure above the skeg in compression. The skeg acts like a lever, with the tip of the skeg trying to lift skyward using the CG of the boat as the focus, and the keel where the skeg is attached as the fulcrum. The deeper the skeg, the bigger the lever, and consequently, the greater the stress on the keel.

"Slacker" wouldn't suffer so much because the unsupported hull - between the tip of the keel in the sand and the rabbet - is so much less, making the lever acting on the structure much shorter, making the forces acting on the garboard plank and underlying structure so much less.

Boats suffer the same forces in a seaway when the ballast keel is holding one end of the skeg and buoyancy the other, and they fight for control of the boat. Sometimes the keel structure isn't up to the challenge and seams open or, in the case of modern fin-keel racing sleds, the whole fin/ballast keel breaks off with appropriately catastrophic results, as happened to Simon LeBon's racing yacht Drum some years ago.

[PeterSibley]

Thanks Michael ,that was pretty well what my diagram looked like , but not nearly as neat !

When you have time could you add a few comments about the motion of the two types in a seaway ? Degree of heel etc ?

[mmd]

http://i32.photobucket.com/albums/d19/mmd_ns/hullcomparisonsketch.jpg

Here’s an comparison between a slack-bilged, built-down hull and a hard-bilged, skeg-built hull form. In order to keep this as simple as possible, I have used only hull sections for comparison – no complications due to the shapes of the hull ends, etc. The two hull sections shown, Slacker on the left and Deadwood on the right, have the same freeboard, the same beam, the same draft, the same centre of gravity, the same waterline beam, and the same underwater area. Translated to a real-world boat, this would be analogous to a thirty-foot sailboat of about seven tons displacement. For the purposes of this discussion I’ve heeled both hulls to twenty degrees.

Given the similarities in the imaginary hulls, the roll period of the hulls will be the same (about five and a quarter seconds), and I suspect that the initial and ultimate stability of the hulls will be very similar. (I hesitate to say that they will be similar, because I haven’t crunched the numbers and I don’t like to make assumptions.) So what is different? Well, that’s the point of this thread, isn’t it?

When the hulls are heeled, the shape of the underwater portion changes and the centre of buoyancy (CB) moves from its initial position on the ship’s centerline to somewhere off on the submerged side of the hull. This is common to all hulls, but what we are interested in is the differences between these two differing hull shapes. Slacker’s CB has moved to a point 12-15/16” off centre, but Deadwood’s CB has moved farther, to 14-3/8” OC.

The distance between CB and CG is referred to as the righting lever. This distance multiplied by the hull’s displacement is the righting moment. The bigger the righting moment, the more energy is available to force the hull back up to the upright position. Slacker has a righting moment of (7 x 2240) x (12.94 / 12.00) = 16,908 lb-ft; Deadwood has a righting moment of (7 x 2240) x (14.375 / 12.00) = 18,783 lb-ft.

What does this mean?

Well, this is the interesting bit. Deadwood, with its larger righting moment, will stand up to an outside heeling force – the wind – better than Slacker. Its up-side is that the boat can carry more sail longer as the wind rises than Slacker can, and the hull stays more upright which makes living on board much more pleasant. The down-side is that this resistance to the heeling forces of the sails places more strain on the sailing rig and hull structure. This means that the shrouds, masts, chainplates, and frames have to be heavier to resist the additional forces. It also means that because of this added resistance to heeling, the rig is at greater risk of damage if a sudden gust of wind catches the sails, where Slacker will roll easier and spill the wind before damage can happen.

The other difference between Slacker and Deadwood is what is referred to as "angle of loll”. When a hull is at rest in calm water, it is easy to roll it back and forth a few degrees; beyond this and it begins to submerge a portion of the hull on one side , gains heeling resistance and “hardens up”. Although my illustrations above don’t show this phenomena, I hope you’ll trust me in my saying that Slacker will have a much smaller angle of loll than Deadwood due to the shape of her hull. What this means to anyone on board is that Deadwood will roll from upright to the point where she begins to harden up much farther and faster than Slacker will, making rolling about in light airs much more pronounced.

So, in a nutshell, the slack-bilged, built-down Slacker will roll farther in a puff but with a gentler motion than Deadwood, but Deadwood can carry more sail longer at the expense of a more lively motion on deck.

[WX]

Do not trust the appearance of water

On my sail south last year we came across a patch of green water, this usually indicates shallow water over sand but we had 200 feet of water under the keel...felt strange.
Okay back to Peter's design:D

[WX]

http://i32.photobucket.com/albums/d19/mmd_ns/hullonbottomsketch.jpg

My plan is to use a set of yacht legs attached to the now unused chainplates to avoid this problem. Of course all the stress will then be on the keelson.

[PeterSibley]

Thank you very much Michael ! Just what I was after .I've read it once , now I'll read it again .:)

[Larks]

Terrific stuff Michael, one of the more valuable threads on the forum (along with the Brewer Catboat thread) it must qualify for a sticky by now???

[Andrew Craig-Bennett]

The other difference between Slacker and Deadwood is what is referred to as "angle of loll”. When a hull is at rest in calm water, it is easy to roll it back and forth a few degrees; beyond this and it begins to submerge a portion of the hull on one side , gains heeling resistance and “hardens up”. Although my illustrations above don’t show this phenomena, I hope you’ll trust me in my saying that Slacker will have a much smaller angle of loll than Deadwood due to the shape of her hull. What this means to anyone on board is that Deadwood will roll from upright to the point where she begins to harden up much farther and faster than Slacker will, making rolling about in light airs much more pronounced.



I remember seeing this point illustrated quite beautifully one fine day in Hong Kong harbour.

HSBC keep a big old heavy displacement powerboat called the Wayfoong*. She was originally built as a steam powered floating security van, to go round the bank's branches in the outlying islands of Hong Kong with the cash. She must be as old as the hills; slender funnel, big ventilators, low coach house, straight stem, counter stern, maybe 70ft LOA and draws maybe 10ft on modest beam. The classic "slacker"! She is now used for corporate hospitality and with her glowing brightwork, polished brass and scrubbed teak she certainly sets the tone..

She was waiting off Blake Pier to pick up a party as were about twenty modern power craft - mostly motor junks but also some planing powerboats.

There is always a confused swell here due to the traffic in the harbour - the junks and fast motorboats were rolling like pigs and nobody could have enjoyed being aboard one and eating and drinking would have been out of the question.

The Wayfoong just sat there, steady as a rock - not a drop of champagne would have been spilled...

* the Chinese name of HSBC. It means, "Money Coming In Bank! ;)

[PeterSibley]

"generally a week spent at anchor in a harbour somewhere being jostled by the wake of every passing boat".

Precisely ,but getting back to the original query ,"why has the heavier type of hull been displaced in popular use ",it seems Michael has answered that too . A heavier boat requiring more materials,more ballast and very likely a larger sail area for the same water line .Comfort be damned ! The modern hull shape is cheaper for the mass builder !

[shamus]

Thanks for the nice clear diagrams MMD.

Peter, I still don't think there is enough between your design and MM to scrap your backbone and rebuild it. Your design is by no means extreme, and after Ed B had some input and gave it the tick I would think it has a fair guarantee of being a pretty good boat.

[Ed Burnett]

Peter,

I have not read and ingested every post on this thread, so may have missed the finer points, however if you will permit me I will say the following:

A while ago, you set out on the course of building one particular sort of boat and you have been working on that for some time. You have a long way to go before she is complete. During that time there are going to be many occasions when your resolve relating to previous decisions is tested, but if you are ever to finish the project you are going to have to keep moving forward. There is plenty to do already without doing any of it twice.

The hull lines you have drafted are pretty moderate in all respects. Yes, changing them to reflect one influence or another will change the characteristics of the boat, but don't forget that whatever you do she will still be quite some way from the light displacement forms of modern production boats.

If you want to have a fundamental design rethink then fine, but do it properly by starting with an examination of your requirements. Good design is all about steady progress towards one solution. Knee jerk reactions to something you see and suddenly like the look of will confuse the end result and can easily stall your project if you let them. There are enough part built boats in the world as it is.

Ok. Lecture over. Sorry if that's out of place.

As for stability, the thing that makes understanding everything easier is to recognise that stability is a response mechanism. Righting moment is developed as the boat heels in response to some sort of external influence, be it the heeling moment from the rig or a weight moving on board. In essence, the boat wants to sit level in the water.

The fun starts when the water isn't level. As a wave passes under the boat, bits of her are immersed or emerge, in exactly the same way as they would when she is heeled over. Her stability causes her to respond to this disturbance and she will try to re-establish equilibrium. The thing to note here is that the stability of the boat is causing her to respond to the disturbance of the water, ie, to roll or pitch as is required.

So, the stiff boat that carries her sail well is also the boat that will respond sharply to any disturbance of the ocean. The tender boat may heel more to her sail, but waves pass under her without causing so much disturbance. Considered in this way it is all pretty intuitive, albeit ironic that the very virtue that is frequently associated with comfort is at the root of the mechanism that can destroy it!

As to comparing attributes that determine stability, I believe the easist thing to do is to examine the cause and effect of the changes on the key points we use to consider stabilty, ie. the centres of gravity and buoyancy, and the metacentre. It all comes back to these three points in the end. I wrote an article on this a while ago, and I think a link to it has been posted on this forum before but that is probably long dead now. I can probably dig it out if there is demand.

[PeterSibley]

Peter, I still don't think there is enough between your design and MM to scrap your backbone and rebuild it. Your design is by no means extreme, and after Ed B had some input and gave it the tick I would think it has a fair guarantee of being a pretty good boat.

That's the point Shamus , I can use the existing backbone .I would be very unwilling to scrap the work so far but the current stem ,stern assembly ,keel and ballast casting are all applicable .As are my planking and frame stock .The MM type would be easier to plank , a consideration for the Robinson Crusoe types :D .I'd just have to scounge another 2 ton of lead ! 30 buckets of wheel weights @ $20 go .

I think my design would be a very good boat but there is a bit of a move around the house to slightly lesser beam and no counter .Simplicity regarding a self steering vane is a consideration with transom versus counter .Actually simplicity all 'round ,the design drawing seems to be drawing me into a more sophisticated boat than I had originally envisaged .Again ,a hard thing to quantify and it's all happening between my ears !:o

I'm still thinking but the idea is certainly attractive ....and I have to admit that it is a little hard to say why .The main advantage of the MM type is ease of motion and it seems obvious that she would be gentler than my existing drawing ,how much so is a difficult question to answer .I have no experience of the type and no one I know has sailed in such a boat .ACB possibly excepted .

The balance at the moment is largely positive for the MM type .

Are there disadvantages ( in a cruising boat ) that haven't been aired yet ?

[PeterSibley]

Bump .

Andrew ?

[mmd]

Peter, have you designed your boat on paper on using a computer program?

[PeterSibley]

On paper Michael ,using Chapelle ,"Yacht Designing and Planning",and some very good advice from Ed Burnett .

[PeterSibley]

Peter,

I have not read and ingested every post on this thread, so may have missed the finer points, however if you will permit me I will say the following:

A while ago, you set out on the course of building one particular sort of boat and you have been working on that for some time. You have a long way to go before she is complete. During that time there are going to be many occasions when your resolve relating to previous decisions is tested, but if you are ever to finish the project you are going to have to keep moving forward. There is plenty to do already without doing any of it twice.

The hull lines you have drafted are pretty moderate in all respects. Yes, changing them to reflect one influence or another will change the characteristics of the boat, but don't forget that whatever you do she will still be quite some way from the light displacement forms of modern production boats.

If you want to have a fundamental design rethink then fine, but do it properly by starting with an examination of your requirements. Good design is all about steady progress towards one solution. Knee jerk reactions to something you see and suddenly like the look of will confuse the end result and can easily stall your project if you let them. There are enough part built boats in the world as it is.

Ok. Lecture over. Sorry if that's out of place.

As for stability, the thing that makes understanding everything easier is to recognise that stability is a response mechanism. Righting moment is developed as the boat heels in response to some sort of external influence, be it the heeling moment from the rig or a weight moving on board. In essence, the boat wants to sit level in the water.

The fun starts when the water isn't level. As a wave passes under the boat, bits of her are immersed or emerge, in exactly the same way as they would when she is heeled over. Her stability causes her to respond to this disturbance and she will try to re-establish equilibrium. The thing to note here is that the stability of the boat is causing her to respond to the disturbance of the water, ie, to roll or pitch as is required.

So, the stiff boat that carries her sail well is also the boat that will respond sharply to any disturbance of the ocean. The tender boat may heel more to her sail, but waves pass under her without causing so much disturbance. Considered in this way it is all pretty intuitive, albeit ironic that the very virtue that is frequently associated with comfort is at the root of the mechanism that can destroy it!

As to comparing attributes that determine stability, I believe the easist thing to do is to examine the cause and effect of the changes on the key points we use to consider stabilty, ie. the centres of gravity and buoyancy, and the metacentre. It all comes back to these three points in the end. I wrote an article on this a while ago, and I think a link to it has been posted on this forum before but that is probably long dead now. I can probably dig it out if there is demand.

Ed ,I'm sorry ,I missed your post .I can see the point of your lecture and very well deserved it is too !

However ,in my defence I've outlined a few points in the post just prior to this one ,post 125.The design you helped me with is as you say ,moderate and I think probably very good .I'm happy with it but ........ it may just end up being more boat than I need .

I assure you that this is not a knee jerk reaction but more a reminder of a degree of simplicity that seems to have escaped me in the earlier drawing .

I think you reminded me at one stage not to let the drawing process take over from the requirement .I think that perhaps that is what has happened .A very good drawing that grew a little larger than required .

[shamus]

Dr Johnson quoth thus

"Sir, it is no matter what you teach them first, any more than what leg you shall put into your breeches first. Sir, you may stand disputing which is best to put in first, but in the mean time your breech is bare. Sir, while you are considering which of the two things you should teach your child first, another boy has learnt them both."

Build them both..:D

[mmd]

Well, darn. I am a big fan of "traditional design" - the tools as well as the style of boat - but doing stability analysis is worlds faster on a 'pooter. I was going to suggest that you jiffy up a new set of lines for the slack-bilged version you are considering and doing a comparitive stability analysis of both hulls, but that is a pretty large amount of work when done non-electronically.

That said, please be comforted that the amount of motion difference between the hull you are planning and the one you are considering will be minmal. Between a modern fin-keel boat and "Slacker" would be very pronounced, but a trad-built wooden full-length keel cruiser such as you are in the process of building will not gain much motion improvement. Make sure your floors are stout and deep, and maybe make your garboard plank either a bit thicker or of a harder species of wood than the surrounding planking and you will happily hand over your boat to your grandchildren when you decide to swallow the anchor.

[WX]

Is there any decent open source design software out there that could be used? Preferably on Linux.

[WX]

Answered my own question.
http://sourceforge.net/projects/freeship/
I'l DL it and see how well it runs under Wine and Crossover Office.

[WX]

Okay it installs and runs fine in Wine on the Ubuntu 9.04 platform.
Freeship is designed to run on Windows machines as well.

[WX]

http://i.d.com.com/i/dl/media/dlimage/67/73/5/67735_large.jpeg

[shamus]

Takes a bit of getting the hang of, at least it did for me. I can make it do a few things now. Bruce Taylor is pretty good at it IIRC.

[PeterSibley]

Takes a bit of getting the hang of, at least it did for me. I can make it do a few things now. Bruce Taylor is pretty good at it IIRC.

If I remember Shamus you are OK at AutoCad , so you have something of an advantage over me .I find cad inpenetrable .:D

I need a child to help me !

[Duncan Gibbs]

Great thread Peter! I shall go and examine the lines of Fore'n'aft after dinner tonight, for which I must thank you! (The lines, not the dinner! :D)

[Ed Burnett]

Fair enough Peter. Simplicity is a perfectly valid goal.

I have to say I think it would be hard to get any properly representative results out of a computer analysis without doing rather a lot of work. To make a worthwhile comparison you would need a reasonably correct VCG for each model, and that isn't something you are going to want to work out.

I would suggest it would be better to concentrate on a bit of parametric analysis to be sure that the basic form and proportions of your revised hull are in the right ballpark. You may remember we did a bit of this as part of the revision of your first set of lines - the aim is simply to see where your boat is relative to others and to flag up any characteristics that are abnormal. Different isn't necessarily bad, but you want to know when you are being different and to understand the likely effects on the boat.

This is actually one of the most fun stages of generating a design as you very quickly fine down on a set of numbers that will determine a large proportion of the boat's performance. By the time you start drawing, you have already established a valid balance of propotions and compromises so the end result is more likely to be a good boat.

[WX]

Tony you mean that's not what he's after? :D

[PeterSibley]

http://pic40.picturetrail.com/VOL282/9443996/17245530/364808957.jpg

[PeterSibley]

http://pic40.picturetrail.com/VOL282/9443996/17245530/364814668.jpg

Ed , these two are the basis for the current idea ,both are 28 foot OA ,25 foot WL ,8'6' beam ,MM has 5'6" draft with around 1/2 here ballast outside , the rest inside .Corineus has 5' draft and all her ballast inside .

By some fortunate chance (and ACB's good eye ) the backbone profile of these boats is very similar to the backbone I have built .The primary difference is that my perpendiculars are little further apart ,giving a waterline for me of 28 ' 10" and an OA of 30'9".A 10% increase .

I could acommodate the stations from Corineus (or simialar ) between my stem and sternpost quite nicely .I have cast my ballast (lead ) ,5400 pound ,I would need approximately another 2 ton internally ,possibly a little less , bearing in mind the weight of my timbers .The keel profile would be simlar to MM .

What do you think ?

I don't know of too many hulls of this type to compare with .

[WX]

Peter if you are interested I can install freeship on your puter next time I'm out.
I have the PDF manual for it as well.

[PeterSibley]

Peter if you are interested I can install freeship on your puter next time I'm out.
I have the PDF manual for it as well.

You are a gentleman Gary !...can you show me how to drive it ?

[WX]

I can try, we shall read the manual together:D

[PeterSibley]

I can try, we shall read the manual together:D

OK ...that might work ! :D

[Ed Burnett]

Ok, well you have good data for two boats that have proven themselves, so that's not a bad place to start. As a matter of interest, I looked after Corineus for a winter in Vineyard Haven but never got a sail on her which was a shame.

You have what you need for Corineus, if you don't have a displacement for MM it would be worth calculating it from her lines. There are plenty of boats like this around, and a good analysis will also consider a few to either side of where you think you want to be. You can pull data from my website (look at no.119), you might also find something appropriate on Paul Gartside's site. A good field of data enables you see how changes in one ratio are balanced by changes in another which helps with blending the various influences.

Work out length / beam and displacement / length (using D/(0.01 LWL)^3) for each and see how they compare. You are then in a position to decide on an appropriate displacement / length ratio for your new hull, and given that you have already established LWL the target displacement will pop out. The known LWL will also determine beam based on the beam / length ratio that you decide upon.

Go for the maximum draught you can possibly tollerate. These boats need and benefit from every inch. You might also want to do a quick sketch sailplan based on your initial profile to check where you are with helm balance - heavily raked sternposts can land you in trouble here and you don't want to encounter problems down the road.

[PeterSibley]

Draft ...I'd rather like to keep it to 5'6' , maybe 5'9" ...any more would be really restricting up this way .However ,I can see multiple advantages to as much depth as possible.

I have an outline of the type of parametric analysis you mean from last time ...I'll insert some new numbers .....after I figure out how to calculate displacement ! I have a couple of books that should help .

What are the disadvantages of this type Ed ? There have been lots of generally positive comments but nothing as yet on the negative side .

[Larks]

Peter, I'd be interested to see if I can use this as a bit of an exercise to get my head around working out whatever I can from whatever known measurements you have (or propse) using some of this stuff that I'm "trying" to learn at the moment. Tomorrow is a dedicated study day for displacement, volume, moments, centre of gravity, centre of buoyancy etc etc.

[Larks]

BTW, I've found this site quite useful:
http://www.vinamaso.net/naval-architecture/

[Ed Burnett]

I think Chappelle explains how to calculate displacement. Skenes certainly does.

I would start by working out the area of each section and drawing the curve of areas. This is the starting point for all sorts of useful stuff including displacement (the area under the curve), LCB (where a cut out of the curve ballances) and prismatic coefficient (area under the curve / the area of the box that encloses it). Having to fair a curve through the points also picks up any mistakes you may have made in determining the areas.

As for the disadvantages of the type, well, in my view at least you need ample draught to make them work, so we may have identified compromise issue no. 1! Slack bilges give you good volume low down for internal ballast and a broad cabin sole, but with this sort of midsection you do end up with an interior that is a bit like a railway carriage. The slack bilge leads to a relatively low centre of buoyancy, which is one of the contributing factors to stability, and as with any relatively narrow boat, power to carry sail becomes a big issue which means you really need to work on getting the centre of gravity good and low. Follow this type of hull to the extreme and you end up with the sort of plank on edge cutters that were encouraged by Thames tonnage measurement. Not exactly the most effective sailing boats ever devised.

All these things go by degrees however, and the process of looking at the numbers helps you to identify where you want to be with the fundamental stuff and keeps you away from the cliff edge.

[mmd]

Firstly, I’d like to express appreciation to Ed Burnett for stepping up here to help you out, Peter. I’m sorry that I don’t have the time right now to assist as much as I’d like to, but I think that you couldn’t be much better served than by Ed, anyway. Thank you, Mr. Burnett.

Secondly, if I may presume to answer ahead of Ed, some of the downsides of the hull type are precisely what their proponents see as advantages: depth and mass. As you have already alluded to, the depth of these types of hulls causes some limitations to where you can go; it is an advantage at sea but a detriment near shore. The hulls are also heavy: This is again an advantage in a seaway as you are not getting bounced around by every wavelet, but when becalmed and hoping to make some headway in zephyrs of breeze, that mass becomes an anchor.

Another issue can be the low form stability (lack of “stiffness”) of the hull: Because the boat heels easily (up to a point), it can be tiresome to be sleeping, cooking, and peeing at twenty degrees of heel on long passages. (A comfortable, gimbaled chair at the nav station is a real bonus.) This large heeling angle can also tend to keep the decks wet, especially if the sheer line is not just right.

I find it useful to do a form check on the hull after completing a.) the weight check to determine CG, b.) a stability check to find out where the comfortable angle of heel will be, c.) a check on the sail area she can carry to put her over to the ‘happy place’ angle of heel. When these all agree, then I draw the heeled waterline across the body plan and adjust its position to ensure that the displacement is correct. A final adjustment of the waterline to reflect the shape of the dynamic waterline (bow & stern wave higher, midship trough lower according to hull speed – Pierre Guetelle’s book on sailboat design addresses this nicely) and I have a reasonable representation of how the hull will float when underweigh. Now I can see if the line of the sheer is appropriate for keeping the waves in their proper place, and adjust it if necessary.

I fully realize that I am being a bit (a lot?) obsessive about such details, but… A day boat or weekend warrior is not so critical in getting little details such as exact sheer shape and placement just so, but on a boat that will spend weeks at sea the difference that an inch or two of sheer can make in keeping decks dry can mean the difference between a pleasant boat to live on and one that is, well, less so. I don’t fear the open ocean (love it, in fact), but have a healthy respect for how insignificant small boats are when far from shore, so I tend to get pretty fussy over wee details to make the experience both survivable and as pleasant as possible. It is not necessary to jump through all of these hoops, but it’s my way of going about such things.


Edit to add: Oops! Ed posted ahead of me...

[PeterSibley]

Peter, I'd be interested to see if I can use this as a bit of an exercise to get my head around working out whatever I can from whatever known measurements you have (or propse) using some of this stuff that I'm "trying" to learn at the moment. Tomorrow is a dedicated study day for displacement, volume, moments, centre of gravity, centre of buoyancy etc etc.

Sounds good Greg :) ,are you using a Marine Architecture program on your 'puter ?

[Larks]

Sounds good Greg :) ,are you using a Marine Architecture program on your 'puter ?

No, I've got to learn how to do it myself in this instance, the best I can do is use a calculator for the moment.

[WX]

You can do round bilge with Freeship. I played around with it a bit last night.

[PeterSibley]

Here's a photo of the lines of Claud Worth's "Tern111" ,a much bigger boat at 44'wl ,12'3" beam and 7'6" draft .

http://pic40.picturetrail.com/VOL282/9443996/17245530/365817143.jpg

It is however ,a very similar type .

[PeterSibley]

This is the lugger ,"Alert " ,image from the April 2009 Classic Boat .
LOA 37', Beam 11'8" ,Draft 6'3"

http://pic40.picturetrail.com/VOL282/9443996/17245530/365821203.jpg


Quite a lot beamier in proportion to draft .How would that affect her motion and angle of heel ? Anyone ?
Intuitively the greater beam and bouyancy closer to the WL would reduce her angle of heel while increasing her displacement and ballast requirement considerably .

[Andrew Craig-Bennett]

Here's a photo of the lines of Claud Worth's "Tern111" ,a much bigger boat at 44'wl ,12'3" beam and 7'6" draft .

http://pic40.picturetrail.com/VOL282/9443996/17245530/365817143.jpg

It is however ,a very similar type .

There is a nice comment on this midsection in an excellent little book, "A Manual for Small Yachts", by RD Graham and JEH Tew (the late Helen Tew's father and husband, incidentally) - I quote from memory:

"It is instructive to compare the lines of Tern III ("Yacht Cruising") with those of Tern IV ("Yacht Navigation and Voyaging") Tern IV has a harder bilge and less displacement. We suspect Tern III of being slow..."

[PeterSibley]

There is a nice comment on this midsection in an excellent little book, "A Manual for Small Yachts", by RD Graham and JEH Tew (the late Helen Tew's father and husband, incidentally) - I quote from memory:

"It is instructive to compare the lines of Tern III ("Yacht Cruising") with those of Tern IV ("Yacht Navigation and Voyaging") Tern IV has a harder bilge and less displacement. We suspect Tern III of being slow..."

Oh ...cruel !:D She really doesn't look slow !

[Andrew Craig-Bennett]

Marie Michon was not slow, in terms of the passages she made. But there may be another factor - she is small enough for sail changes to be easy, Tern III although owned by an expert and carrying a paid hand would have been much slower to make sail as conditions moderated.

Which of course is why "all" cruising yachts make 100 miles a day...

[PeterSibley]

At the moment I'm trying to work out the angle of heel at which Marie Michon would "comfortably " sail , the sweet spot .Any idea Andrew ?

[rufustr]

Peter,

My friend with the Hess Serafynn has her out at the moment for antifouling.

I'll get some photos tomorrow and post them here.

[PeterSibley]

They would be very good to see Rufus !

[Andrew Craig-Bennett]

At the moment I'm trying to work out the angle of heel at which Marie Michon would "comfortably " sail , the sweet spot .Any idea Andrew ?

About this much:

http://pic40.picturetrail.com/VOL282/9443996/17245530/364808955.jpg

My father had, and I cannot now find, a photo of her under topsail, balloon staysail working jib and full mainsail -the angle of heel was about the same.

[peter radclyffe]

There is a nice comment on this midsection in an excellent little book, "A Manual for Small Yachts", by RD Graham and JEH Tew (the late Helen Tew's father and husband, incidentally) - I quote from memory:

"It is instructive to compare the lines of Tern III ("Yacht Cruising") with those of Tern IV ("Yacht Navigation and Voyaging") Tern IV has a harder bilge and less displacement. We suspect Tern III of being slow..."
we restored tern 4, s sister ship near here, gracie 3, now called alzavola,

[PeterSibley]

About this much:

http://pic40.picturetrail.com/VOL282/9443996/17245530/364808955.jpg

My father had, and I cannot now find, a photo of her under topsail, balloon staysail working jib and full mainsail -the angle of heel was about the same.

Thanks Andrew , that looks fine :)

[rufustr]

This is my friend Mike's Hess Serafynn.

He built it strip planked and cold moulded over a period of ten years in his backyard.

The boat is beautiful everywhere you look.

http://i359.photobucket.com/albums/oo39/rufustr/MIKESBOATMATTHEWJ015.jpg

http://i359.photobucket.com/albums/oo39/rufustr/MIKESBOATMATTHEWJ008.jpg

http://i359.photobucket.com/albums/oo39/rufustr/MIKESBOATMATTHEWJ014.jpg

http://i359.photobucket.com/albums/oo39/rufustr/MIKESBOATMATTHEWJ013.jpg

http://i359.photobucket.com/albums/oo39/rufustr/MIKESBOATMATTHEWJ004.jpg

http://i359.photobucket.com/albums/oo39/rufustr/MIKESBOATMATTHEWJ007.jpg

[rufustr]

Two more.

http://i359.photobucket.com/albums/oo39/rufustr/MIKESBOATMATTHEWJ005.jpg

http://i359.photobucket.com/albums/oo39/rufustr/MIKESBOATMATTHEWJ006.jpg

[Larks]

So Rufus, I'd say Peter needs to undertake some meaningful inclining experiments on just such a hull and my current studies warrant that I "survey" those experiments with a view to ensuring that they are done to an appropriate level. When can we hit your mate up for a sail on Mathew:D??

[PeterSibley]

A very hansome boat Rufus !! Very nice indeed .

Thanks for adding to the confusion !:D:D

[rufustr]

Steady on, I.ve been pestering him for months now while he is waiting for a new Jib after refurbishing his mast and rigging.

I'll mention it to him though in the next few days and see what he says.:D:D

[PeterSibley]

Me too ! :D:)

[shamus]

All that Hess boat needs is a bit of overhang in front to stop it plunging to the bottom of the deep blue sea, and it would be a fine fine vessel, instead of just a fine vessel. IMHO if you want a good boat to sail off the coast of Oz, look to the best Australian designers, and forget about the foreigners who have designed fine craft for their own waters. Start with anyone with the surname 'Payne' IMHO!

[PeterSibley]

Reason: to add a space ? :D

Here's an interesting bit of reading , pertinent to the MM thread too .Pretty well what I've been considering .The current # is my backbone ,which gives me 31 foot OA and 29 foot WL (115% of MM) with an approximation of the MM stations widened to 9 foot 2 Inches (108% ).Draft is 5'6".

http://www.boatdesign.net/forums/stability/roll-acceleration-what-s-best-crossing-oceans-20655.html

[mmd]

"...forget about the foreigners who have designed fine craft for their own waters." - shamus

While I agree with the thrust of shamus' statement, I disagree with the actual wording. I agree that what make a design "work" in one particular area may well be a detriment in another (the subtle differences between Cape Island and Down East lobsterboats is the example I use often to illustrate this fact), it shouldn't preclude using a design or designer from another area of the world. The salient point is that the design should be suitable for the regional conditions, or that the designer is cognizant of the local conditions that he is designing for. A good example of this is the happy circumstances that have allowed the Northumberland Strait type fishing boat hulls developed in Prince Edward Island and New Brunswick in eastern Canada to be very successful in North and South Carolina. Though geographically distant, the sea conditions are similar, so the hull type transitioned easily.

This is not to denigrate the fine Oz designers - they have, by what I have seen posted on these pages, created some mighty fine lookin' boats. And I am all for supporting your local designers and designs. But you shouldn't be limited to them, either. Just make sure that the designer from away is on the ball enough to evaluate the local conditions.

As for plumb bow versus overhanging bow, well, there was a rather long and occasionally heated discussion here on the WBF a few years ago on this topic. If I reccollect, it was agreed that plumb bows maximized waterline length, thereby enhancing speed potential, but there was rigorous disagreement over whether an overhanging bow was an enhancement or a detriment to seakeeping ability. For the record, I was (and am still) on the side of enhancement. I also prefer the aesthetics of a moderately overhung bow.

[peter radclyffe]

All that Hess boat needs is a bit of overhang in front to stop it plunging to the bottom of the deep blue sea, and it would be a fine fine vessel, instead of just a fine vessel. IMHO if you want a good boat to sail off the coast of Oz, look to the best Australian designers, and forget about the foreigners who have designed fine craft for their own waters. Start with anyone with the surname 'Payne' IMHO!
gday mate, arthur payne, alfred payne, cynthia payne,

[shamus]

I must have been feeling patriotic last night, I think, and not entirely serious. MMD makes his points well. I'm biased on the overhang question: I see my own moderate overhangs doing a lot of good work as reserve bouyancy, which seems to me to make for comfort. No doubt they were influenced by the rating rules of the time, and could be a little less expressed and still do the same job. I don't see all that many true plumb stems around here, among any boats you'd want to own (there are plenty in the modern stuff) though I used to greatly admire an old fishing boat of the type. I was told she was a submarine, and this probably is the root of my prejudice. I still like the look of them.

My reference to Payne is somewhat tongue in cheek, but when he came up with 'Solo' he had something which performed very well in the Tasman Sea, and won every race going several times over, performing particularly well in heavy weather. Then her owner cruised her all over the world with one or two young ladies along as crew. Later David Lewis took her to Antarctica. At 56ft she was a bit big for a family boat I guess, which was why the smaller boats were designed along her lines. Sorry about the thread drift- I'll behave in future.

[WX]

I had my first real big boat sail on an Alan Payne design...I could have walked on water afterwards I was so happy.

[rufustr]

All that Hess boat needs is a bit of overhang in front to stop it plunging to the bottom of the deep blue sea, and it would be a fine fine vessel, instead of just a fine vessel. IMHO if you want a good boat to sail off the coast of Oz, look to the best Australian designers, and forget about the foreigners who have designed fine craft for their own waters. Start with anyone with the surname 'Payne' IMHO!


Given that this is the design that the Pardeys sailed around the world, I would think it's sea keeping abilities have been well proven.

http://www.ukhalsey.com/newsletter/oct2005/Pardeys_sm.jpg

My preference aesthetically is for plum or nearly so stems and sterns.

[mmd]

Thank you, Shamus, for the compliment. I also wish to convey to him that the type of thread drift he as committed is the nourishment of good discussions about boats, Please misdirect similarly at will...

I'll add that I'd be as interested as my current time will allow (I'm launching the fireboat in three weeks time) to revisit the discussion about plumb-vs-overhung bows if anyone is interested in adding considered thought or personal experiences to the commonweal.

[rufustr]

I'm extremely interested in this thread, and hasten to point out that I have no experience at all in the field.

I am looking forward to all the discussion about to take place.:cool::cool:

[The Bigfella]

Excuse the slight materials drift, but plumb stems and bowsprits seem to have made a bit of a comeback in Oz in recent years. Three Sydney to Hobart wins in a row isn't it?

http://newsimg.bbc.co.uk/media/images/42342000/jpg/_42342549_sailing_416.jpg

[mmd]

Bigfella, I'll grant that plumb bows make for a faster boat if the LOA is similar, but flat-out racing boats are not the best boats to cruise on. Race crews are used to - and expecting - rough, wet rides. If I may steer the conversation for a while, I'd like to discuss people's experiences and thoughts on how the shape of the bow affects the ride/comfort/dryness of plumb versus overhung bows. Speed potential is a given, but is there a penalty in comfort to pay for that bit of extra mpd?

[shamus]

Rufus- no denying that. My comment was a hamfisted way of expressing my preference.

MMD-I'd be very interested: I remember some discussion of it in a thread comparing Vertues with Serrafyn's, as usual people seemed rather partisan, and I don't know that a lot of light was thrown the design principles really. I would be interested to know whether this aspect of form has any particular relevance to balance of the helm. Ours is very balanced, and doesn't gain any weather helm as she lies down. Some kind of magic there, compared with some I've seen.
'Tis a long weekend here, and I'm headed up bush for a couple of days, in the rain! so if I don't post here 'tis not from lack of interest. I'll look with interest when I get back.

[shamus]

Bigfella, The front ten feet of those things is so shallow, you could nearly argue it is an extreme form of overhang. Gotta go now!

[The Bigfella]

Fair enough - enjoy your trip - I'm off to the Rugger soon.

[PeterSibley]

A sea kindly and non violent hull form is my aim .Something that will not tire its crew on a reasonably long voyage .

My very amatuer thoughts are that the overhang or lack thereof is to be considered with hull fineness ,fore and aft hull shape balance, ballast distribution ,sea conditions that are going to be the norm for the boat ....

Which comes down to pitching and continuing to move along ,not coming to a halt with every wave on the nose ! There does seem some advantage in being able to shift a proportion of your inside weights , either as ballast pigs or anchor chain , to suit conditions .

Again the aim is a seakindly motion ,a reasonably dry deck and continued progress .

[rufustr]

Mike's Serafynn weighs in at 4.5 tons I think, and he commented the other day, than in the short 1.5 metre high chop in the bay she shouldered her way through, remaining steady and not reacting to the waves.

When I asked if this was a wet ride, he replied that the deck didn't even get wet.

Obviously in an ocean swell she would rise and fall with the swell, but the surface chop would not cause her to move around.

[PeterSibley]

Shamus , a report on your expedition on return please ? :):) Have fun !

[PeterSibley]

Mike's Serafynn weighs in at 4.5 tons I think, and he commented the other day, than in the short 1.5 metre high chop in the bay she shouldered her way through, remaining steady and not reacting to the waves.

When I asked if this was a wet ride, he replied that the deck didn't even get wet.

Obviously in an ocean swell she would rise and fall with the swell, but the surface chop would not cause her to move around.

Well compared to a modern racer she's a rock but compared to some of the station drawings I've posted above she is quite buoyant with her very firm bilges .A good boat for sure ,bu rather different to some of the others I've been drawing attention to .

Bear in mind the MM is a very old fashioned English / French shape .Serrafyn is quite American in inspiration ....two quite different traditions .

[rufustr]

I'm well aware of that Peter, and only posted this info as support for your argument for heavier displacement, and because the boat is on the hard at the moment.:D:D

I'm going down in the morning to give Mike a hand replacing his through hull fittings.

I admit that I'm also a fan of the English and French types.

I used to have a photo of the Itchen Ferry Cutter that Uffa Fox featured in one of his books, but I can't find it now.

As another distraction here is a drawing of Paul Gartside's interpretation.:cool::cool:

http://www.gartsideboats.com/pgimages/101rev-profile.jpg

[peter radclyffe]

I must have been feeling patriotic last night, I think, and not entirely serious. MMD makes his points well. I'm biased on the overhang question: I see my own moderate overhangs doing a lot of good work as reserve bouyancy, which seems to me to make for comfort. No doubt they were influenced by the rating rules of the time, and could be a little less expressed and still do the same job. I don't see all that many true plumb stems around here, among any boats you'd want to own (there are plenty in the modern stuff) though I used to greatly admire an old fishing boat of the type. I was told she was a submarine, and this probably is the root of my prejudice. I still like the look of them.

My reference to Payne is somewhat tongue in cheek, but when he came up with 'Solo' he had something which performed very well in the Tasman Sea, and won every race going several times over, performing particularly well in heavy weather. Then her owner cruised her all over the world with one or two young ladies along as crew. Later David Lewis took her to Antarctica. At 56ft she was a bit big for a family boat I guess, which was why the smaller boats were designed along her lines. Sorry about the thread drift- I'll behave in future. no need to apologise, its good to hear your views

[PeterSibley]

This quotation from mmd's Post #115 seems to best describe the attributes I'm looking for ...thought I'd post it again .Thanks mmd .:)


"Well, this is the interesting bit. Deadwood, with its larger righting moment, will stand up to an outside heeling force – the wind – better than Slacker. Its up-side is that the boat can carry more sail longer as the wind rises than Slacker can, and the hull stays more upright which makes living on board much more pleasant. The down-side is that this resistance to the heeling forces of the sails places more strain on the sailing rig and hull structure. This means that the shrouds, masts, chainplates, and frames have to be heavier to resist the additional forces. It also means that because of this added resistance to heeling, the rig is at greater risk of damage if a sudden gust of wind catches the sails, where Slacker will roll easier and spill the wind before damage can happen.

The other difference between Slacker and Deadwood is what is referred to as "angle of loll”. When a hull is at rest in calm water, it is easy to roll it back and forth a few degrees; beyond this and it begins to submerge a portion of the hull on one side , gains heeling resistance and “hardens up”. Although my illustrations above don’t show this phenomena, I hope you’ll trust me in my saying that Slacker will have a much smaller angle of loll than Deadwood due to the shape of her hull. What this means to anyone on board is that Deadwood will roll from upright to the point where she begins to harden up much farther and faster than Slacker will, making rolling about in light airs much more pronounced.

So, in a nutshell, the slack-bilged, built-down Slacker will roll farther in a puff but with a gentler motion than Deadwood, but Deadwood can carry more sail longer at the expense of a more lively motion on deck.

[shamus]

Hi Rufus- That is design No 109 isn't it? I bought the study plans for her some years ago, and I still like her. I've got 4 sets of study plans from Paul over the years (2 motor sailers). It's a pleasure just to look at his drawings. My ideal retirement boat when you might want to live aboard for weeks at a time in a changeable climate, and with no plans for world cruising would be the 42 foot motor sailor. No way it is going to happen unless I win tattslotto.

[PeterSibley]

or the price of gold continues up .

Thread drift !!!!

[shamus]

I haven't got enough of it. Anyway in AU dollars it's fairly stagnant just now!

[PeterSibley]

This coming year might help .Depends on the bond market .

[PeterSibley]

Now , some comments on the MM type of hull ? :)

[shamus]

I spent the weekend cabin bound in the rain, occasionally getting wood in to stoke the fire, and read the last WB magazine quite thouroughly. I was interested in the article about Maggie B which discusses some of these 'comfort at sea' matters.

[shamus]

I also browsed in LFH, from which I can tell you that the right ship to go to sea in will look something like Tioga, or Bounty. :D

[PeterSibley]

I thought you rugged Tasmanians just tramped onward?:D

Maggie B is a fine animal ,but a bit outside my parameters ,size , crew , $ .

Simplicity ,easy of motion and cheapness are the key words .

[PeterSibley]

I also browsed in LFH, from which I can tell you that the right ship to go to sea in will look something like Tioga, or Bounty. :D

Marco Polo was always my favorite from Sensible Cruising Designs .Equally unachievable .:D

[shamus]

We do, we tramp from the woodshed to the fire:

Lots of discussion of MP on the LFH thread. Also some praise of slack bilges. I was interested that someone said of a slack bilged boat, that while good at sea

But she had slack bilges, and had a reputation for rolling horribly. In fact, sitting tied to the dock a passing aluminum skiff could get her lurching around like a drunkard.

So there mut be degrees of this angle of loll being less with slackers? Or have I misunderstood it.

[PeterSibley]

Here's mmd on the subject ,it interests me ,I tend to spend more time at anchor than sailing on occasion ..I better go and have a look at LFH .MP.

The other difference between Slacker and Deadwood is what is referred to as "angle of loll”. When a hull is at rest in calm water, it is easy to roll it back and forth a few degrees; beyond this and it begins to submerge a portion of the hull on one side , gains heeling resistance and “hardens up”. Although my illustrations above don’t show this phenomena, I hope you’ll trust me in my saying that Slacker will have a much smaller angle of loll than Deadwood due to the shape of her hull. What this means to anyone on board is that Deadwood will roll from upright to the point where she begins to harden up much farther and faster than Slacker will, making rolling about in light airs much more pronounced.

So, in a nutshell, the slack-bilged, built-down Slacker will roll farther in a puff but with a gentler motion than Deadwood, but Deadwood can carry more sail longer at the expense of a more lively motion on deck.

[shamus]

That's what I thought he said. So maybe the boat referred to didn't really have slack bilges, or they were slack but the wrong sort of slack. Apparently she was fine at sea.
Any way MM is apparently all right, given ACBs input, and you seem to like her looks, which I think quite pleasing too: and with boats not everything has to be justified by fine analysis anyway. So bearing in mind the parable of putting the legs in the trousers... you'd better get on with it?

[PeterSibley]

Yep ....drawing a few lines tomorrow .I'm giving her 8" more beam (8% ) as the WL is 15% more on the backbone I have set up .Closer to the cross section of Tern 111.Try to reduce the heel a little , a compromise .
WL 28'10" versus 25'.These things have to be in imperial measure .:D
Draft is the same , 5'6" .

I've had the flu for a week and my brain wouldn't work ...a bit better now !:)

[shamus]

Those lines I was mucking about with on the other thread now begin to resemble MM a bit.
http://i221.photobucket.com/albums/dd277/shamus1955/Newmodel3.jpg

With the background image.
http://i221.photobucket.com/albums/dd277/shamus1955/Newmodel4.jpg

Now it needs the profile and plan sorted, but I don't think I have an image of them. Presuming that Freeship reads the old files from Delftship I could email you the file- you'd soon sort the other dimensions out.

[mmd]

Hi, all. I'll see if I have my text on stability over at the apartment. If so, I'll try to unearth some info on angle of loll and set about creating a sketch & explanation. Have patience with me please, though; its only twenty-four days to launch and my cup runneth over with preparation tasks...

[PeterSibley]

Hi Michael ....that would be good .Drop in when you can !

[PeterSibley]

Those lines I was mucking about with on the other thread now begin to resemble MM a bit.
http://i221.photobucket.com/albums/dd277/shamus1955/Newmodel3.jpg

With the background image.
http://i221.photobucket.com/albums/dd277/shamus1955/Newmodel4.jpg

Now it needs the profile and plan sorted, but I don't think I have an image of them. Presuming that Freeship reads the old files from Delftship I could email you the file- you'd soon sort the other dimensions out.

Remarkable Shamus ! I REALLY wish I was a bit closer to Hobart .....so many questions !

BTW ,yours looks a bit slacker in the mid sections than Corineus .

[Larks]

Hi Peter, I've been dragging the chain too mate, spent the weekend at home playing on my tractor instead of studying (I thought you guys said the weather was crap down there????).

I have a mass (mess) of Excel spreadsheets with areas, centroids, moments etc from what I've scaled off of your scanned drawings but that's as far as I've gotten. I can see why all of my engineering/nav arch' mates have forgotten this and let their computers do the work.

[PeterSibley]

I'm feeling very intuitive these days Greg ! :D

[Larks]

I'm feeling very intuitive these days Greg ! :D
Yeah, thought you might :o

[PeterSibley]

I can hear Freeship calling .

[mmd]

Note: I have edited out a couple of stupid errors in the text. Sorry to the first few readers... mmd 09/06/09 19:12ADT

Angle of Loll

First, some basics: I think that everyone following this thread is familiar with the terms and concepts of Centre of Gravity (G) and Centre of Buoyancy (B), so I won’t repeat the obvious. Other terms that show up below might need a bit of definition; please forgive me if I am being pedantic. Referring to the diagrams below, please note the following definitions:

Metacentric Height (M) is the point where a vertical line passing through B of a heeled hull intersects the hull centerline. At angles of heel of up to around 15 degrees, it can be assumed that the metacentre is at a fixed point, called the initial metacentre. Beyond fifteen degrees or so of heel, the metacentre moves enough on the ship centerline to require graphically or mathematically calculating its new position at each successive angle of heel.

Righting lever (GZ) is the right-angle distance between the force of gravity acting downwards through G and the buoyant force acting upwards through B. If G lies outboard of line BZ, then the righting moment is negative and the boat will roll away from vertical until equilibrium is reached. Plotting the righting lever’s magnitude at various angles of heel on a graph produces the “GZ curve” or “curve of stability” and gives a visual reference to a hull’s stability characteristics.

http://i32.photobucket.com/albums/d19/mmd_ns/LOLL1.jpg

As shown in the illustration above , when a ship with a negative initial metacentric height (initial metacentre is below G, as occasionally happens in narrow hulls with a high CG) is inclined to a small angle, the righting lever is negative, resulting in a capsize moment.

http://i32.photobucket.com/albums/d19/mmd_ns/LOLL2.jpg

At a larger angle of heel, as illustrated above, the centre of buoyancy B will have moved farther outboard as the hull side submerges. This new location of the CB is marked as B1. The force of buoyancy can no longer be considered to act vertically through M, the initial metacentre. If, by heeling, the centre of buoyancy moves outboard far enough to lie vertically under G, the righting lever GZ and thus the righting moment will be zero and the hull will be stable at this attitude. The angle at which this condition occurs is referred to as the angle of loll and may be defined as the angle to which a ship with negative initial metacentric height will lie at rest in still water.

http://i32.photobucket.com/albums/d19/mmd_ns/LOLL3.jpg

If the ship should now be inclined to an angle greater than the angle of loll, as shown above, the righting lever GZ will be positive, giving a moment to return the ship to the angle of loll. Because the ship is slightly unstable at angles of heel below the angle of loll, it is very easy to roll the ship across the upright position to the opposite angle of loll. For example, if a yacht with negative initial metacentre is lying at a dock on her outboard angle of loll of, say, five degrees, and you step aboard from the dock, she will easily roll under your weight from the outboard angle of loll to the inboard one, a total of ten degrees. This can be pretty disconcerting! One of the other nasty features of a boat with negative initial metacentre is its tendency to oscillate back and forth between port and starboard angles of loll, even in virtually still conditions. This can make cooking or sleeping aboard somewhat uncomfortable. It also explains why some boats are "restless" at their moorings in apparently calm conditions, and why they rock back and forth incessantly, clanging their halyards against their (always!) aluminum masts and disturbing your otherwise quiet anchorage.

So what does all this mean to Marie Michon? Well, that depends – maybe (probably) nothing. However, deep, narrow, displacement hulls tend to have a high CG, sometimes resulting in a negative initial metacentre which, in turn, will create the conditions for a significant angle of loll. If so, the only reasonable solution is to lower G by shifting ballast and/or other heavy objects in the hull, as much as is possible. The shape of the hull is a strong determinant of G and B, but it isn’t reasonable to consider changing the shape of an existing hull. But if you are at the design stage, it is much easier – if you do a stability investigation to determine the GZ position at various angles of heel. Personally, I would not consider a design to be properly designed if there has not been a stability investigation performed so I could see a GZ curve. After looking at lots and lots of hulls and GZ curves, one can get a “feel” for what hull shape is likely to have stability issues, so some can be accepted as “good enough” (jeeze, I hate that term!) without a stability report, but there are some hulls that just plain need it to convince me. And deep, narrow, heavy displacement hulls such as being discussed here fall smack into that category.

Let me see if I can describe this succinctly: The very things that make a sea-going hull of this type a good sea-going hull – deep, narrow hull of full displacement and slack bilges, initial tenderness that firms up as the hull is heeled, high CG, low form stability – are the things that contribute to a low initial metacentre and risk an angle of loll greater than zero. I’d want to know whether the boat was going to flop back and forth when at anchor or becalmed before I built or bought it. For that I would want to do or see a detailed weight estimate and stability investigation. Of course, I’d want to see or do this for any boat that I was planning to take the wife & kids across the wide, terrible sea in.

But that’s just me…

[Larks]

Thanks Mike, from all of us interested bystanders to Peters design. I've been following this with interest as I'm working through studying some of it at the moment, I've dealt with metacentric heights and angles of loll when doing my commercial marine tickets but applying it to actual design is new but very interesting. I'd say there are quite a few here learning quite a bit from this very informative thread.

[mmd]

Well, I guess I killed this one. I didn't realize that stability discussions were so toxic... <wink, grin>

[Duncan Gibbs]

My brain will deal with it once I'm having a weekend and I get more than 10 minutes at the forum at a stretch! Great information Mike!!

[maxwaterline]

Likewise, Peter, Mike, Ed, others, great thread, enjoying this very much.

Peter, I think the Ghost lines may be of interest you, except for the mild cutaway to the forefoot and slight drag to the keel.

Tried to attach a PDF but this didn't work, will try another way. I like what you've done. I suspect that a design like you've drawn may be a lot more "tunable",ie, able to shift ballast around, change sail area in front of or behind the mast without too much trouble, unlike a more modern design.

Have just read Yachting and Cruising for Amatuers by Frank Cowper, he describes several vessels of similar design to yours, but widely ranging size/displacement, that he bought and sailed thoroughly. He describes some of the things he had to do to get them to sail correctly. This book was written before the First World War so I think the boats he describes would be the "normal" boats of the day. Anyway, may provide some good insight for you if you have or can get a copy.

Regards

Adrian

[PeterSibley]

Michael ,it's gone beyond the ability of most of us to comprehend .....most of us are not engineers !

But ....from the above and other , if the C of g is say 1.4 m below the water line on a 2.7m beam your conditions don't seem bad at all .The lack of initial stability , ie buoyancy high up close to the waterline would seem to reduce the likehood of the kind of really annoying movement you get when some fool zooms past throwing a big wake .

Less stabilty but less inital movement from the surface disturbances ?

to quote you .
"
The other difference between Slacker and Deadwood is what is referred to as "angle of loll”. When a hull is at rest in calm water, it is easy to roll it back and forth a few degrees; beyond this and it begins to submerge a portion of the hull on one side , gains heeling resistance and “hardens up”. Although my illustrations above don’t show this phenomena, I hope you’ll trust me in my saying that Slacker will have a much smaller angle of loll than Deadwood due to the shape of her hull. What this means to anyone on board is that Deadwood will roll from upright to the point where she begins to harden up much farther and faster than Slacker will, making rolling about in light airs much more pronounced.

So, in a nutshell, the slack-bilged, built-down Slacker will roll farther in a puff but with a gentler motion than Deadwood, but Deadwood can carry more sail longer at the expense of a more lively motion on deck. "

[PeterSibley]

Adrian ,if it is convenient a couple of scans with dimensions would be very much appreciated right now ! I'm find it a little difficult to find many other boats of comparible hull form ...I've found a few ,but as you say it was from an earlier era with less published material than now .

[norseman]

All I can say Peter is that she looks a bit triangular in section.

[Eric D]

Peter,

You have quoted this often, however, I seem to have lost your true intent. Are you looking for a boat that is comfortable at rest or more lively at sea? I guess, to say it another way, which side of the fence are you on? Deadwood or slacker? I believe this would drive the design question further.

So, in a nutshell, the slack-bilged, built-down Slacker will roll farther in a puff but with a gentler motion than Deadwood, but Deadwood can carry more sail longer at the expense of a more lively motion on deck.

One other comment, the flush deck vs deck/cabin house is often discussed or bantered about about the proper height. I tell you the world of sailers is full of midgets either in the design field or the sailors because when this 6'4" guy gets on one of these, about the only place for me is on deck, I could not imagine going down in a house that is "happily at 5' " talk about straining for any length of time.

I too enjoyed Ed's MMD's and others inputs. Nothing like some mental exercises to awaken those dusty neuron's. Thank you gentlemen.

Peter, good luck with what you decide. I have enjoyed all of this discussion.

[PeterSibley]

Hi Eric , for clarification ,I'm interested in the "Slacker" type and I'm 5'8" .

I'd be adding a low house , probably 12" high .

[Larks]

Well, I guess I killed this one. I didn't realize that stability discussions were so toxic... <wink, grin>


Definitely not Mike ,I had a bit more of a play with this last night but like Duncan I'm just waiting for the weekend to get a decent run to "immerse" myself in it. I managed to corner an engineering mate on the weekend to get a bit more understanding of moments and centroids so it's all making more and more sense.

[mmd]

Good. This is the type of discussions I believe a forum such as this should encourage, at the expense of politics and weapons. Lately it's been pretty thin pickings for decent boat-related conversations.

A good spin-off from the present topic would be Curves of Stability, a subject sorely lacking in discussions of yacht design.

[maxwaterline]

Peter, if you can pm me an email address, I could send you a pdf. The Hiscock book Cruising under Sail has some line drawings in it.

Whatever you build, you'll have something to be truly proud of. I sometimes think these is a desire these days to get everything "perfect" before something is started. Of course it would be foolish to design and build a boat without doing all the necessary calculations so that some major mistake is not made, but I think an awareness of the limitations of a design (and I'm sure all designs have some limitation or less desirable characteristic), and enjoying the advantages of a design, is worthwhile.

The little boat I sailed in Sweden/Denmark looked wonderful, beautiful lines, but when you are easily overtaken upwind in the rain by a modern design pointing higher and faster in poor weather while you are being stopped by the choppy conditions, can be a powerful force for contemplation. I haven't really done much sailing so I dont feel that I can comment usefully on the potential of a particular design. A proper engine installation may certainly make up for the odd occasion in unsuitable conditions.

Regards Adrian

[Eric D]

Hi Eric , for clarification ,I'm interested in the "Slacker" type and I'm 5'8" .

I'd be adding a low house , probably 12" high .

Thanks Peter, that helps.

Darn midgets I tell you, no wonder I am stuck with powerboats, I can't climb down into any of the ones I can afford. :D

12" high house adds a pleasing line to my eye.

Sorry bout the drift, carry on.

MMD, I can't add anything to the discussion, but I am now reading up on all the finer points so that I have a better understanding. Thank you for adding to this and pushing us on to other concepts for further reading/discussion. Fireboat pics??? :cool:

[mmd]

Thank you for the compliments, though they are highly unjustified.

No fireboat pics until launch day, in two weeks and three days. Don't want to get anyone's knickers in a twist over what might be shown that ought not be. But it is starting to look like a fireboat, all red and white and purposeful-like...

[PeterSibley]

I'm well into the new drawing .Stations roughed in (12 at 717mm spacing ).Buttocks looking OK ,3 diagonals run and fair .

A little bit of argument between one diagonal and one buttock on 2 stations .

Better than expected for the hours expended so far .

No displacement calculations yet .

[Larks]

No displacement calculations yet .

Peter, I've been slack here too mate, I haven't picked up my study papers for so long I have forgotten where I was at with the centre of buoyancy and stability on your other drawings. I had your own drawings all roughly scaled (from the scanned copy) and the table all completed but hadn't proven that what I'd calculated was correct (or valid). I've got a meeting today at 1200 with my boss and am hoping that may resolve my work situation so that I can get back into study this afternoon and tomorrow without the distraction of worrying about what's going to happen after 30 June..:o.

I'm now three assignments behind, Naval arch', maritime law and marine insurance, so need to extract the digit!!:eek:

I think I at least now understand what a "moment" actually is and what it provides....which was the bit that had me flumoxed!!

What are you like with Excel? If I send you a table that I've made up to calculate the centroids of each cross section of your drawing, could you measure your new drawing when it's done and update the measurements in the table? It's basically the lengths (ordinates) of each station from the centreline out on each cross section or layer of the hull.

Have you got your Skene's yet?

[PeterSibley]

Yes , Skenes arrived ..Very useful !

Excell is a bit of a mystery to me not being in the line of work that needs it .I'll either use Simpsons or the Trapezoid method to get displacement .Trapezoid probably with 12 stations .I'll get the fairing of buttocks versus diagonal right first ....a little bit of fun right now !

[PeterSibley]

I just dug out the articleTony,a lovely boat ,but the article is sadly lacking in specifics !:D I'll read it again tonight .
There's always something pleasing about an article with numbers !:D

All lines run ,displacement worked through ...off to get it scanned tomorrow .:)

[Larks]

All lines run ,displacement worked through ...off to get it scanned tomorrow .:)

Woops, ignore my question on Oz Politics, I should have looked here first.

[Andrew Craig-Bennett]

Just a general point - you'll notice Marie Michon's sail area which is not exactly modest (although it is pretty easily managed with the exception of the yard topsail - I have had a yard topsail and I speak with feeling here! )

In fact Marie Michon has the same sail area as Mirelle (Mirelle is admittedly undercanvassed, but not wildly so)

[PeterSibley]

Andrew , I worked the displacement of my 15% longer version today at 8.3 ton .At 85 square foot per ton ,(the Pardey's number ) that gives 700 square foot .Corineus has 730 .

What is Mirelle's displacement ? Around 10 ton ?

A friend has a Curlew style topsail and it is a pleasure to set !

[Andrew Craig-Bennett]

20,000lbs - 9 tons - as designed.

She still sits on her scribed waterline as I have removed numerous galvanised iron tanks etc and some of her internal ballast has "walked" over the years. After a year afloat she will have sunk an inch or so due to soakage and accretion of clobber on board...for practical purposes I reckon on ten tons.

[PeterSibley]

Reworking the drawing , the aim is 10 ton ,9 foot 4 inch beam on 28 foot WL .

Andrew ,do you have a drawing of Mirelle's lines , or even a rough outline ? Would you call her shape "slack" or more modern ?

[Andrew Craig-Bennett]

Yes, I have a full set of her drawings and the Table of Offsets. But not in a size that I can readily post here!

[PeterSibley]

Paper or pdf ? Can I guess ? :D

[PeterSibley]

Here is my current drawing .
OA 31'5"
WL 28'10"
Beam 9'3"
Draft 5'6" to 5'9"
Displacement at 5'9" draft 10.1 ton D/L 422

Feel free to criticse :D.I'm open to changes .

http://pic40.picturetrail.com/VOL282/9443996/17245530/368286865.jpg

[peter radclyffe]

Here is my current drawing .
OA 31'5"
WL 28'10"
Beam 9'3"
Draft 5'6" to 5'9"
Displacement at 5'9" draft 10.1 ton D/L 422

Feel free to criticse :D.I'm open to changes .

http://pic40.picturetrail.com/VOL282/9443996/17245530/368286865.jpg
very impressive

[Larks]

Here's a pic' of Foxhound halfway down this page

http://www.mbyachts.co.uk/custom-built-yachts.html

[PeterSibley]

Thank you gentlemen ,
here's a photo of Foxhound's interior ....very nice indeed !

http://pic40.picturetrail.com/VOL282/9443996/17245530/368304766.jpg


Pretty much what I aspire to .:)

[Larks]

Pretty much what I aspire to .:)

I've got no idea why...??!!!:D

[Andrew Craig-Bennett]

Here is my current drawing .
OA 31'5"
WL 28'10"
Beam 9'3"
Draft 5'6" to 5'9"
Displacement at 5'9" draft 10.1 ton D/L 422

Feel free to criticse :D.I'm open to changes .

http://pic40.picturetrail.com/VOL282/9443996/17245530/368286865.jpg

Big tick from me. Better than the earlier design - I don't think that counter would have "worked" visually and it would have been a swine to construct. I also like the slacker bilges and increased displacement. The tumblehome in this design is an excellent feature in terms of appearance and strength. Sheerline looks nice to me.

[rufustr]

Thank you gentlemen ,
here's a photo of Foxhound's interior ....very nice indeed !

http://pic40.picturetrail.com/VOL282/9443996/17245530/368304766.jpg


Pretty much what I aspire to .:)


I'm with Larks.

Can't see why.:rolleyes:

[Andrew Craig-Bennett]

Peter, looking at your plan, you have good sitting headroom (3ft+) over the settees with a good width of floor, so you could dispense with a coachcroof and go for a companion hatch and skylight.

[PeterSibley]

I've been looking at that Andrew , seeing that a companion hatch and skylight are necessarily narrow , perhaps 30" .Is there room to work at a gallery bench while standing ? It looks doubtful on paper .

[Andrew Craig-Bennett]

Typically, you stand upright and use your forearms and hands over the bench, sink, cooker, icebox, whu...

[PeterSibley]

Typically, you stand upright and use your forearms and hands over the bench, sink, cooker, icebox, whu...

I was thinking more of the line of sight ,being able to see the work area with your head in a relatively narrow skylight area . I've drawn it up and there appear to be problems .I'll mock it up insitu first to know for sure .Either would be fine .

[rufustr]

The nice broad side decks would be a great advantage, and if you keep the cabin top as short as possible the foredeck would be uncluttered.

The great thing about the photo is the open feeling of the interior.

Bulkheads and enclosures clutter up an interior and make spaces feel even smaller than they are.

http://pic40.picturetrail.com/VOL282/9443996/17245530/368304766.jpg

[The Bigfella]

Oh OK, I'll have one too please Peter. 2 metre headroom please. When can you have her finished?