Just fore the fun of it:)

[Soundman67]

When is Canadian Thanksgiving?

Thanksgiving Day in Canada has been a holiday on the second Monday of October since 1957

[TR]

So at long last we've finally got a series of righting arm curves to stare at........



Above you see three curves, heel angle is along the bottom and righting arm length in decimal feet up the side. We can see max righting arm is around 20 degrees in all cases. Angle of vanishing stability (where the curve crosses zero righting arm) ranges from approximately 43 degrees for Lightship condition to above 60 degrees for Full Load condition. Remember operating condition is between Full Load and Arrival (10% liquids). Also note there still some righting force at 55 degrees heel in the full load condition.

Obviously these curves are very different from those of ballasted sailboats that many have seen. Often the AVS (angle of vanishing stability) is well above 100 degrees for typical sailing yachts. These curves represent a protected water cruiser which would not be intended for open water crossings though with prudence she could certainly undertake such. Turtle Bay is of a type that would qualify for ISO category C or D operation. Cat C allows operation in waves up to 2m in height, wind force of Beaufort 6, and wind speed of 17m/sec(33 knots).....They mention exposed inland waters, estuaies, and coastal waters.

The GM at 57.3 degrees (one radian) and Slope lines represent a basic check of the curve slope at small angles of heel.

One thing not obvious from this is that downflooding does not occur on this boat even at 55 degrees heel. The windows and forward cockpit are above water even at high angles. I'll try and get a representation of that together now. I would guess that she will lay right over on her side, running out of stability and then gaining it back (due to the huge shift in I as her side enters the water) to become almost impossible to invert.

[TR]

Phil was a pretty smart guy and here's some more evidence.....This is Windermere heeled 55 degrees. The bottom edge of the side windows (the open seam) are just kissing the water line (This is Arrival condition) and the cockpit edge is well above the water. I'll guess the forward cockpit will stay above waterline even at 90 degrees heel......

[Sailor]

WOW, that's pretty impressive. Much more respect for the Bolger boxes after seeing that. Thanks for all this work. I tried to send you a question by PM but it was too long..... (It included a paper I wrote recently though so I guess I had to expect that) It was pertinent to this stability topic we've been following along.

[essaunders]

but what about the beer cooler? Wasn't it on the roof? Of course, from what I read it won't stay full for long.

Seriously though, this is really nice information. Thanks for putting it into context with the Cat C or D reference.

Some other reading I've done referenced a replica dutch barge that was expecting a Cat C rating but got a Cat B - perhaps due to stronger glazing. Would stronger glazing and/or shutters bump Windermere up on the scale too?

[TR]

Sailor,

Just email me, tadroberts-at-shaw.ca

[TR]

ess......

Awarding the ISO Category is moderately complex (perhaps we should look at that in more detail), there are a bunch of factors involved including wind heeling, area under the righting arm curve, size of cockpit, etc. If you install strong enough windows at some point they become hull ports (though size counts) and are considered watertight and not downflooding points. The reality is I doubt this makes much sense as they get heavy and VCG goes up.........

[P.L.Lenihan]

So at long last we've finally got a series of righting arm curves to stare at........



Above you see three curves, heel angle is along the bottom and righting arm length in decimal feet up the side. We can see max righting arm is around 20 degrees in all cases. Angle of vanishing stability (where the curve crosses zero righting arm) ranges from approximately 43 degrees for Lightship condition to above 60 degrees for Full Load condition. Remember operating condition is between Full Load and Arrival (10% liquids). Also note there still some righting force at 55 degrees heel in the full load condition.

Obviously these curves are very different from those of ballasted sailboats that many have seen. Often the AVS (angle of vanishing stability) is well above 100 degrees for typical sailing yachts. These curves represent a protected water cruiser which would not be intended for open water crossings though with prudence she could certainly undertake such. Turtle Bay is of a type that would qualify for ISO category C or D operation. Cat C allows operation in waves up to 2m in height, wind force of Beaufort 6, and wind speed of 17m/sec(33 knots).....They mention exposed inland waters, estuaies, and coastal waters.

The GM at 57.3 degrees (one radian) and Slope lines represent a basic check of the curve slope at small angles of heel.

One thing not obvious from this is that downflooding does not occur on this boat even at 55 degrees heel. The windows and forward cockpit are above water even at high angles. I'll try and get a representation of that together now. I would guess that she will lay right over on her side, running out of stability and then gaining it back (due to the huge shift in I as her side enters the water) to become almost impossible to invert.

Hi Tad,


What a wonderful surprise to be greeted with,here at work! I am as amazed by the 3D modeling as I am unclear about the chart. By unclear, I mean simply I lack the skill to interpret what it all means.A genuine neophyte,as it were.

To begin, I remain mildly intrigued by her "light ship" displacement of 9033lbs considering Bolger's 7 odd thousand pound displacement figure shown on the plans. That is, I have difficulty seeing where and/or how I managed to add about a ton of extra weight to the boat. But as I say, I am intrigued but not worrying over the difference.At least she floats right side up!

So, if you were teaching a fresh class of wannabe designers or passionate builders and popped up your graph on the overhead projector, how would you begin to explain, in near laymans' terms, what the curves suggests?

To give you an idea of the "denseness" of one of your "students", allow me to open with how I am understanding the chart:

I see how the three curves represent the same boat in three different load states as it begins to heal. The right hand column is showing the force required to get the boat to heal,in feet, or the number of feet to right her from that angle? How much does a foot weigh?


I see also that up to and a little over 15 degrees of heal, it requires a steady increase in force to get her to heal but that after around 20 degrees it requires less force to continue putting her over on her side or would that be less force to right her from greater angles of heal?


The dashed "slope" line,is an arbitrary line showing how an un-tip-able boat would plot as force was applied to heal her?

As I am not familiar with how other boats would plot on the same graph, I'm not clear whether the boat is an easy push-over or a bulldog full of healing resistance.


I'm obviously out of my element in understanding the chart and terminology.For example: is downflooding the opposite of upfloating or does it mean the point where a boat begins to sink beyond rescue?

I look forward to this wonderful new method of understanding my boats' characteristrics, as do others too I imagine.

Thank you very much Tad for this opportunity and the effort you have clearly put into this online education exercise!




Cheers!


Peter

[P.L.Lenihan]

You know, during the building of this boat, I had many wonderful dreams of cruising around, gracefully taking in the scenery, soaking up cold beers and chatting away with Nat about how spoiled we are. Never once did I have a nightmare about the boat. Sure, there was some pesty fretting at launch time as to how she would float but nothing a cold beer(s) couldn't deal with and it was of short duration.

These two model images however are the stuff of nightmares! And this is in her "arrival" condition?? I really hope I am understanding things ass-end-backwards(wouldn't be the first time!). I also hope Nat doesn't see these before she goes to bed or she will have nightmares and begin thinking this has all been some sort of plot and that I'm out to drown us all!

In the mean time,I'll just keep repeating to myself,"Tad is the man!Tad will explain!" "Tad is the man!Tad will explain!"
That ought to keep my mind busy enough to not engrave these two models in my head.

Cheers!


Peter, the optimistic ten thumbed chimp.


P.S. I'm secretly dazzled by these 3D representations of my boat.....amazing technology!

[flyinwall]

Peter, you have to be out in some kind of lunatic weather for your boat to be in that kind of predicament (i sure hope you are not that kind of fool)

[P.L.Lenihan]

Peter, you have to be out in some kind of lunatic weather for your boat to be in that kind of predicament (i sure hope you are not that kind of fool)

Whaddya mean "some kind of lunatic weather"....just by the size of those waves the wind has to be under 10 knots and,and,and.....it looks like the sun is about to break through the haze any minute! More ice for the beer cooler!!

On the other hand, are you suggesting that the boat will only heal like that in weather most extremis? That would be a relief as I certainly would not intentionally put myself in harms way like that...I hope!

Perhaps then it is just the limits of the computer program that Mr.Roberts is using which does not show 2+ metre waves?



Cheers!



Peter

[Hwyl]

This thread has taken yet another completely cool turn

[A.Greever]

I am actually very impressed with just how stable she is, for such a narrow beamed boat.

Thank you for taking the time to do that Tad.

Ten Thumbs: Did you do a top speed test while she was in the water? You could probably run to shelter quite easily if you keep an eye on the weather. I see no reason why she couldn't safely do The Great Loop. Stop by Muskegon, Michigan when you take the trip, we can go sailing on SevenSundays!

[MoMan]

Peter, you have to be out in some kind of lunatic weather for your boat to be in that kind of predicament (i sure hope you are not that kind of fool)

... or he would have to have a crazy number of bikini-clad nymphs line dancing on the roof! Sorry to generate yet another nightmare to haunt Nat.

Tad--can you do a 3-D model of that? (I bet Ryden and his Photoshop skills will drop in shortly)

[knottyBuoyz]

I see no reason why she couldn't safely do The Great Loop.

He has to wait till I'm finished mine then I'll drag him through the loop if I have to! *hehehe* ;-)

[Cogeniac]

Note Peter that the boat should be more stable under a full load (providing that the load is not up top as MoMan suggests!!).

I'd love to figure this out for my boat.

[TR]

To begin, I remain mildly intrigued by her "light ship" displacement of 9033lbs considering Bolger's 7 odd thousand pound displacement figure shown on the plans. That is, I have difficulty seeing where and/or how I managed to add about a ton of extra weight to the boat. But as I say, I am intrigued but not worrying over the difference.

Right, there is no point worrying about this, the boat is built. But knowledge is power and the more you know about your boat the better your decisions can be......Thus your plans for a rooftop hot-tub may require reconsideration...... Seriously, we have no knowledge of the designer's weight study.....but simply put if the boat floats deeper than the design waterline, she weights more than her designer thought she might. This is one of my main points in this exercise, real world is different than theoretical, and it shows the folly of taking seriously stability curves based on published numbers. The good part is that an increase in displacement increases stability.......

I see how the three curves represent the same boat in three different load states as it begins to heal. The right hand column is showing the force required to get the boat to heal,in feet, or the number of feet to right her from that angle? How much does a foot weigh?

To return to our terms diagram above note the Righting Arm is a distance in feet, just as the curves show a specific righting arm length for each heel angle. This is due to the movement of B (center of buoyancy) as the boat heels. The correcting force that rights the boat is called the righting moment (righting arm multiplied by the displacement) and is measured in foot pounds or pound-feet.

I see also that up to and a little over 15 degrees of heal, it requires a steady increase in force to get her to heal but that after around 20 degrees it requires less force to continue putting her over on her side or would that be less force to right her from greater angles of heal?

To explain it the other way the curve shows a steady increase in righting arm length (thus righting force) up to a peak at something over 20 degrees and then returning to below zero. At zero righting arm she will fall over (no righting force) to a point where everything changes again (because the waterplane (B) has changed drastically with her side in the water). At the curve's highest point is where the most effort will be required to heel her one degree further. One often reads people describing a sailing boat that heels 15 degrees and "stiffens up" and will heel no further.....the effect of this curve is what's being described......

The dashed "slope" line,is an arbitrary line showing how an un-tip-able boat would plot as force was applied to heal her?

No, the slope line is specific to your boat at this load condition, it's just a mathematical proof that our righting moment curve is correct(at low heel angles). The basis is complex but I can get into that in a bit.....

As I am not familiar with how other boats would plot on the same graph, I'm not clear whether the boat is an easy push-over or a bulldog full of healing resistance.

I just compared your curve with that of a 26' welded aluminum crew boat I did some years ago. The crew boat has a max beam of 9'6" but I'll guess her waterline beam is similar to Turtle Bay. She is a typical high-speed vee-bottom with a large cabin and with 11 people aboard her VCG is higher than that of Turtle Bay. So her righting arm maxes at about the same length as Turtle Bay's, 6-7", but she has flaired topsides and 18" more beam so the RA curve stays flat longer than that of TB.

is downflooding the opposite of upfloating or does it mean the point where a boat begins to sink beyond rescue?

Downflooding is the point where the heeled boat starts to fill (sinking or drastically altering G), this can be a side door, window, or cockpit edge. Regulatory agencies consider the downflooding point to be the end of any stability.

[TR]

You know, during the building of this boat, I had many wonderful dreams of cruising around, gracefully taking in the scenery, soaking up cold beers and chatting away with Nat about how spoiled we are. Never once did I have a nightmare about the boat. Sure, there was some pesty fretting at launch time as to how she would float but nothing a cold beer(s) couldn't deal with and it was of short duration.

These two model images however are the stuff of nightmares! And this is in her "arrival" condition?? I really hope I am understanding things ass-end-backwards(wouldn't be the first time!). I also hope Nat doesn't see these before she goes to bed or she will have nightmares and begin thinking this has all been some sort of plot and that I'm out to drown us all!

In the mean time,I'll just keep repeating to myself,"Tad is the man!Tad will explain!" "Tad is the man!Tad will explain!"
That ought to keep my mind busy enough to not engrave these two models in my head.

Cheers!


Peter, the optimistic ten thumbed chimp.


P.S. I'm secretly dazzled by these 3D representations of my boat.....amazing technology!

Okay......Main thing is these images are not intended to worry, they are information that empowers you the operator. There is no chance that Turtle Bay will heel 55 degrees in any normal weather condition. We can look at wind heeling some time but again these renderings are just to illustrate how far she has to heel (in this load condition) before downflooding may begin......IE...the boat is very safe. I've delt with passenger vessels where downflooding starts at 23 degrees heel......now...that's the stuff of nightmares.......

But for instance, say you travel to a place of large tides and put the boat ashore on a sloping (athwartships) rock ledge with the tide going out......If that rock ledge has a slope of 60 degrees you'll get worried and block her up, but if that rock ledge has a slope of 25 degrees you'll not break a sweat............Because you know TB is positively stable at 25 degrees heel.

[M. J. Notigan]

Peter,
The US Coast Guards' fleet of standard boats (41' UTB, 44"MLB) had a book published by the Commandant, US Coast Guard, called a Type Manual for that particular class small boat. Much like a very detailed automobile owners manual, every prospective crewmember, engineer or coxswain recieved a copy of the Type manual for whatever class small boat they were trying to qualify to run on. I think I still have my old 41 and 44 Type Manuals laying around somewhere...... The type manual lists every single detail pertaining to that vessel; length, height above waterline, draft, weight, fuel capacity, engine and transmission types and particulars, electrical system types. From stem to stern, each compartment is broken down in detail. Lots of clear drawings and pictures identifying the compartment and what is found in that space.
It got me to thinking after seeing Tads' detailed graphs and charts for Turtle Bays' Righting Arm Curves and Weight Tables: along with the final fitting out projects, your boat deserves a Type Manual written up for this, the WINDERMERE Class of Bolger Boats. There is so much pertinent info you could input into this manual: sling location fore and aft, maximum height of vessel at mast top (handy to know for both you and Nat when transiting various waterways).....vessel operating parameters-highest max.wind speeds/heighest max wave heights allowed....fuel consumption charts for various engine rpms and vessel loadings....... Tads charts and graphs should be incorporated into the manual as a separate chapter onto itself. A complete electrical schematic would aid in future electrical troubleshooting/repair.
Just my 3 cents chiming in about a Type Manual...... I'm going to have to go back to review the weight experiments to get a full picture of the whys and hows. It's got to be comforting to know that a naval architect has worked on verifying the capabilities of YOUR vessel, not a design study with all the different variables that could present
itself...... Hope all is well up there.
Take Care,
Mike

[Durnik]

There is so much pertinent info you could input into this manual:

Plus, important things, such as Opportune Locations of Beer Caches.. ;-0

Seriously,

Tad, this thread has grown ever larger as the.. well, time, goes by, and your contributions have become a great part of the wonder of it all.
Thank you.

& Peter for starting the thread & Nat for being the 'good woman behind every good man' (well, 'one' good man ;-)) & all the many humorous contributors who keep me smiling! - Hey, where's that lil fella? He in the bilge drinkin' or some such? With Turtle Bay on-the-hard, he needs to be getting back to work, eh? ;-)

Ok, so I have trouble with serious.. ;-)

enjoy
bobby

[P.L.Lenihan]

plans for a rooftop hot-tub may require reconsideration...... The good part is that an increase in displacement increases stability.......

To return to our terms diagram above note the Righting Arm is a distance in feet, just as the curves show a specific righting arm length for each heel angle. This is due to the movement of B (center of buoyancy) as the boat heels. The correcting force that rights the boat is called the righting moment (righting arm multiplied by the displacement) and is measured in foot pounds or pound-feet.

.

Hi Tad,

I am taking comfort from your explainations,despite not entirely understanding the complexities involved. It is also a relief to know I can toss all plans for roof top additions and wet-t-shirt contests out the window(sorry MoMan )

Regarding "increased displacement increases stabilty".....would that depend on where that increased"weight" is coming from or located on the boat? For example: say that extra ton my boat weighs,if that comes from my building the entire roof structure way over the designers' specs, would the boat not be more top heavy thus less stable? I can see where if that ton is because I went all hog on the bottom structure would increase stability though..........


If I am understanding the "righting arm" properly I see the following: at "full load" status and the boat healing at aprox.11 degrees, there is a RM of 3532.7 lbs(RA X Displ.) ; is this the force required to make her heal to 11 degrees or is this the force(buoyancy?) resisting any further healing? Then again, should I see this sort of like a teeter-totter whereby I load it up with 10598 lbs of weight(full load displacement) and shift the weight to one side until the board is tilting 11 degrees and then 3532.7 lbs(RM) is placed on the other side(at about four inches from the pivot point) to prevent the board from tilting(healing) any further?


I need another coffee...........




Cheers!


Peter

[Ryden]

(I bet Ryden and his Photoshop skills will drop in shortly)

This is a job for...

BICYCLE REPAIRMAN!!!

Or more likely, his sidekick, the Photoshop Boy!

May I proudly present
The Turtle Bay Hockey Club Woman's Team!

[orbb]

That is, I have difficulty seeing where and/or how I managed to add about a ton of extra weight to the boat.

Epoxy fillets?

Imagine the weight difference if you didn't like sanding as much as you do.

[snow(Alan H)]

The poor hockey player on the far right has had a malfunction with her self inflating lifesaver vest - it appears to have gone off

[Figment]

Purely out of morbid curiousity: What happens to the curve with an extra 1000lbs of gear aboard? ("Full Load" +1000)

Is there a loading condition past which the shape of the curve is dramatically different, or is that really more a function of hullform than it is a function of loading?

Yes, a seriously nerdy-cool turn on what was already a thread for the ages!

[TR]

Regarding "increased displacement increases stabilty".....would that depend on where that increased"weight" is coming from or located on the boat? For example: say that extra ton my boat weighs,if that comes from my building the entire roof structure way over the designers' specs, would the boat not be more top heavy thus less stable? I can see where if that ton is because I went all hog on the bottom structure would increase stability though..........

Ha!......I see Peter you are starting to get the hang of this stability stuff....good......

Absolutely correct, we need to remember that stability is a function of a complex series of interrelationships. And I should know better than to make blanket general statements.....First we go back to our fundamental equation, BM =I/V....

A quick rough estimate of It (Inertia of waterplane, transverse) is It = .04 * LWL * BWL^3

For 9000 pound displacement......
So I = .04 * 30' * 512 = 614.4
And V = 9000 / 62 = 145
So BM = 4.23'

Now in a more "usual" hull form with flared sides and overhangs fore and aft, I increases quickly as the hull sinks in the water, but not so Turtle Bay as she has no overhang anywhere. So as weight and displacement increase BM gets shorter.....

For 10,000 pound displacement........
I = .04 * 30 * 512 = 614.4
And V = 10,000 / 62 = 161
So BM = 3.81'

But in the case of Turtle Bay the major increases are the liquids in her tanks, which are as low as possible in the hull. So G goes down towards the hull bottom but G also gets down closer to the heeling point (approximately the waterline) because with increased displacement the boat floats deeper in in the water. B (center of buoyancy) has also moved deeper as the boat draws more water. The result is seen in the curves. The righting arm at low heel angles (5-10 degrees) is higher for the lightship, then as the heel angle increases past 20 degrees the heavier displacement (lower VCG) condition shows longer righting arms, as does the arrival condition.

Indeed it would be a different story if the displacement increase was on the roof, G would go up, approaching M, and righting arm length would be much reduced. The curve would then drop quickly after it's peak at roughly 20 degrees, giving a smaller range of positive stability. Conversely if you were to fit an outside ballast keel and lower G significantly, your range of positive stability (were the curve crosses zero righting arm) would increase to 70,80, or 90 degrees, or more.......

If I am understanding the "righting arm" properly I see the following: at "full load" status and the boat healing at aprox.11 degrees, there is a RM of 3532.7 lbs(RA X Displ.) ; is this the force required to make her heal to 11 degrees or is this the force(buoyancy?) resisting any further healing? Then again, should I see this sort of like a teeter-totter whereby I load it up with 10598 lbs of weight(full load displacement) and shift the weight to one side until the board is tilting 11 degrees and then 3532.7 lbs(RM) is placed on the other side(at about four inches from the pivot point) to prevent the board from tilting(healing) any further?

Right, the Full Load righting arm at 10 degrees is 0.37', so .37 * 10,598 = 3921 lb/ft
So to correct a heel of 10 degrees you would place 3921 pounds one foot from the centerline on the high side. Or if you don't have 3921 pounds, use 1960 two feet from centerline, or 980 pounds 4 feet from center, or rig a 10' boom out over the side and hang 392 pounds from it.......Incidentally the RM1 (righting moment at one degree) at full load is 391 pounds, so a one degree heel can be corrected with 391 pounds one foot from centerline.

[TR]

Purely out of morbid curiousity: What happens to the curve with an extra 1000lbs of gear aboard? ("Full Load" +1000)

Is there a loading condition past which the shape of the curve is dramatically different, or is that really more a function of hullform than it is a function of loading?

We see in the curves above the difference between 9000 pound lightship load and full load at 10,600 pounds. The character of the curve changes little with movement of G or increases of V........The curve changes character drastically with change of form, wider or deeper hull for instance. This is because I changes as the boat heels, and this is where a watertight deckhouse can make a huge difference........

[P.L.Lenihan]

Full Load righting arm at 10 degrees is 0.37', so .37 * 10,598 = 3921 lb/ft
So to correct a heel of 10 degrees you would place 3921 pounds one foot from the centerline on the high side. Or if you don't have 3921 pounds, use 1960 two feet from centerline, or 980 pounds 4 feet from center, or rig a 10' boom out over the side and hang 392 pounds from it.......Incidentally the RM1 (righting moment at one degree) at full load is 391 pounds, so a one degree heel can be corrected with 391 pounds one foot from centerline.

Hi Tad,

Just to flesh things out and check if I am following the above correctly; if I were to invite dear Ryden's roof top bevy of buxomed bikinied bathing beauties inside the cabin, I could maintain a relatively flat/stable transverse attitude simply by having them shuffle their money-makers one side or the other of the centerline? Would this be something like the free-surface effect I might experience from my transverse 52 gallon water bladder at half capacity?

Also, if they were to all stow-away in the bilges, would this added weight be a plus for stability or would it,as you mention to Figment, drastically change things for the worse as the hull would then be immersed deeper and the BM would become shorter since G is brought down closer to the healing point?

Off to get more coffee....



Cheers!


Peter

[Sailor]

Peter, here it is in simple terms, if they shake their money makers and said money makers are large there would be an increase in stability if the money makers were below the CG..... If however they all went to see Dr. Silicone and came back to visit you... the stability would decrease as the added weight would be above the CG. Easy right? Here's to hoping your boat has enough stability to handle all that silicone.
(that Silicone has NOTHING to do with the newer types of silicone bottom paint)

Cheers,
Daniel

[orbb]

Peter, here it is in simple terms, if they shake their money makers and said money makers are large there would be an increase in stability if the money makers were below the CG..... If however they all went to see Dr. Silicone and came back to visit you... the stability would decrease as the added weight would be above the CG. Easy right? Here's to hoping your boat has enough stability to handle all that silicone.
(that Silicone has NOTHING to do with the newer types of silicone bottom paint)

Cheers,
Daniel

On the bright side, if they did see Dr. Silicone, they would give you added buoyancy. The boat would never sink below chest level.

[P.L.Lenihan]

I hear ya Daniel and that is why I alluded to free surface effect....especially if they were all laying down in the bilge.

Besides that, what do you think of the results so far? Pretty damned nifty if you ask me and I'm a little bit intimidated(readver my head with grasping things in day-to-day terms) by the precision and effort Mr.Roberts has brought to the table for us to feast on. I am also,despite my short comings in the numbers dept., gaining a better sense that my boat will handle itself well and I can perhaps slack off worrying so much about it just falling over. If I knew how to swim I would perhaps worry even less still but hell, I like being on the water,not in it!

Are you swinging by this way over the holidays?


Cheers!


Peter

[P.L.Lenihan]

On the bright side, if they did see Dr. Silicone, they would give you added buoyancy. The boat would never sink below chest level.

Ah yes,buoyancy.But wouldn't they have to be under the boat or strung along the side like......sponsons?



Cheers!


Peter

[Figment]

We see in the curves above the difference between 9000 pound lightship load and full load at 10,600 pounds. The character of the curve changes little with movement of G or increases of V........The curve changes character drastically with change of form, wider or deeper hull for instance. This is because I changes as the boat heels, and this is where a watertight deckhouse can make a huge difference........

Yes, I was curious more about the, um.... practical (?) stability; that which doesn't get the deckhouse wet.

(but you answered the question, yes, thanks)

[Sailor]

Steer clear of sponsons. You want those the silicone sponsons facing inboard not outboard. Except when you're sitting on the dock enjoying a cold refreshing drink. I will be passing through there over the holidays. Twice, once on the way out and once on the return trip. I think so far Mr Roberts has done some amazing things for you. I love this forum for just that sort of cooperation that goes on. It's right up there with the thread to redraw and design a new version of Sogjin. What a cool thing to be able to do. All thanks to the interwebnetthingy. I'm sure many would love an NA to personally do up the stability curves and data for their own boat. I think you owe it to the rest of us to put together some sort of book or reference manual for that boat of yours and maybe make it available to anybody else who builds to that design. It was mentioned earlier in possibly another thread that a "user's manual" of sorts would be a good thing to have. It sure would. This is the sort of info to include in it. This thread just keeps giving back to the forum. That's why it's still the best thread on the forum in my eyes. Keep it up Ten Thumbs, we all benefit from it.
Thanks,
Daniel

[essaunders]

I'm just waiting for another WB article by Tad featuring Turtle Bay!