Chain plates - inside or outside? [Archive]

Larks

07-08-2009, 10:54 PM

I thought there had been a thread or discussion a while back on the merits of chain plates being fitted inside or outside the hull but can't find it.

I'm pretty keen to mount my chain plates on the outside of the hull when I refit it and was reminded of it when I was taking off my deck last weekend. The current set up is some stainless plates inside the hull but they had obviously leaked and were my main concern for any rot when I bought the boat. Fortunately there was none in the hull but the deck area around the chain plates was quite soggy.

http://i260.photobucket.com/albums/ii11/Larks_01/P7010200.jpg
Also I noticed when taking off the deck that at least one plate has one of the deck frame copper rods running through it which has obviously corroded from the electrolytic action between the two metals.

http://i260.photobucket.com/albums/ii11/Larks_01/P7010198.jpg
I do remember someone making a very valid comment about external chain plates making for a wetter ride when they are in the water but other than that, are there any problems or concerns with refitting my chain plates outboard?

I prefer the look of them, they won't create the problem of sealing around them and I'd have new ones cast up similar to these which I think were on a H28 in Brisbane:

http://i260.photobucket.com/albums/ii11/Larks_01/05022008001.jpg

Ian McColgin

07-08-2009, 11:06 PM

I very much agree that chainplates should be outside.

The Bigfella

07-08-2009, 11:09 PM

I had this exact discussion the other day with Bazza re the Yellowtail.

Outside.... much stronger resistance to the applied forces.

donald branscom

07-08-2009, 11:59 PM

Which two metals are you talking about?
Copper and ?

It is probably bronze.

Larks

07-09-2009, 12:56 AM

Which two metals are you talking about?
Copper and ?

It is probably bronze.

316 stainless steel strap

floatingkiwi

07-09-2009, 02:31 AM

Greg, I believe the thread was my "a folkboat found me", where you read about putting the chainplates on the outside and the resulting problems that may arise from doing so.
Kerry

floatingkiwi

07-09-2009, 02:36 AM

Yes, it was near the beginning of the thread and this was posted from you.

Your boat is clinker. You cannot put the chainplates on the outside - you'll be arrested if you do that, and if not, you should be! .quote]

You boat isn't clinker is it mate? LOL.
Cheers mate.

RFNK

07-09-2009, 03:37 AM

Your boat is clinker. You cannot put the chainplates on the outside - you'll be arrested if you do that, and if not, you should be! .quote]

Oi Kerry - it was me not Larks! The H28 isn't clinker.

The question is an interesting one. R.M. Steward states "Inside chainplates are to be preferred, as on the outside they will show ....... and the metal may bleed and discolour the topside paint" There doesn't seem to be a structural reason. However, both my boats have internal chainplates. The Folkboat because it's clinker, of course. In both boats the chainplates have a little shelf that fits under the sheer clamp so that the chainplate is prevented from being pulled up, so reducing strain on the planking. On both these boats the chainplate slots had leaked through the deck but the sealing around the chainplates was pretty pathetic. When I replaced this on the Folkboat, I made an epoxy slot for the chainplate through the ply deck and glass sheathing. I cut a little chamfer around the edges of the slot. After the chainplates were installed I made little rectangular collars from tufnol and formed a seal with Sikaflex under it. The collar is fastened down with 4 screws, all set in epoxy a la Gougeon recommendations. The Sikaflex squeezes up around the chainplate and makes a very good seal. After nearly 4 years now there's no sign of any leaking at the chainplates. Let me know if you want any pictures of the collar or the little shelf arrangement on the chainplates. Rick

Andrew Craig-Bennett

07-09-2009, 04:01 AM

External chain plates on clinker hulls are not uncommon in Britain; you just use packing pieces. But more commonly on the more voluminous type of boat; I've not seen them on Folkboats or Stellas.

RFNK

07-09-2009, 04:29 AM

External chainplates on any clinker boat would be ridiculous, surely. Why on Earth would you do it? Rick

Andrew Craig-Bennett

07-09-2009, 05:26 AM

I have to say they don't look good. But I've seen it done.

mmd

07-09-2009, 06:36 AM

"Why on Earth would you do it?" - RFNK

Oh, I can think of several reasons right off the top of my head. Increased shroud base, ease of fitting plank fastenings, ease of installation, no deck penetration to allow leaks, ease of inspection of fastenings, etc.

After many years of pondering such questions, I have come to the conclusion that if something on a boat is rediculous, it doesn't last much more that a generation. External chainplates on clinker hulls have been around for many, many generations; ergo, they are not rediculous.

Andrew Craig-Bennett

07-09-2009, 10:22 AM

Here you are; an everyday East Coast of England boat (an Alan Platt Finesse, actually) clinker built with outside chain plates.

There are dozens of these up and down the Thames Estuary; a good honest family centreboarder, built just about entirely of iroko - Mr Platt only stopped turning them out when age caught up with him, a few years ago - he still had a waiting list!

http://i535.photobucket.com/albums/ee352/acraigbennett/Finesse.jpg?t=1247152698

Peerie Maa

07-09-2009, 11:50 AM

Oh, I can think of several reasons right off the top of my head. Increased shroud base, ease of fitting plank fastenings, ease of installation, no deck penetration to allow leaks, ease of inspection of fastenings, etc.

After many years of pondering such questions, I have come to the conclusion that if something on a boat is rediculous, it doesn't last much more that a generation. External chainplates on clinker hulls have been around for many, many generations; ergo, they are not rediculous.

Add to that, faying surface in compression, fastenings in shear only and not shear and tension.

RFNK

07-09-2009, 07:20 PM

I didn't really want to get into an argument about this and I'm not making any comment about the structural merit of internal or external chainplates (although I believe the arrangement whereby the tension on the planking is shared with the sheer clamp is a better arrangement than a planking only arrangement - especially in a clinker hull). However, to me, clinker hulls are beautiful because of the distinctive lines of the planking. They sail beautifully and easily due, at least partly, to their carefully designed, flowing plank lines. To break that up with chainplates and blocking/packing, to me, is ridiculous because the alternative works so well - it's actually really easy to prevent leaking through the deck. The most successful clinker yachts, i.e., Folkboats, don't have external chainplates. Why not? Folkboats have been around for 60 years.

The yacht in Andrew's picture above looks fine (in fact, I think it looks a lovely boat) with its external chainplates, IMHO. I'm surprised, really. But, also IMHO, it would look better if they were installed internally, and look how short they are! It's unlikely that in this high-sided yacht the chainplates would get wet all that often but, I'll bet they and their packing make quite a splash when they do and, if they were of a decent length, imagine the splash they'd make! I also wonder what sort of structure is required inside to render such short chainplates worthwhile? The chainplates in a Folkboat extend below the waterline.

I'm sorry, but, while external chainplates on so many traditional-style yachts look great and obviously work well, I'll still contend that to put chainplates and the necessary packing on a clinker hull is ridiculous when the alternative is so effective and looks much better. In 5 minutes I could list plenty of things that have been common for decades but are nevertheless bad ideas. Rick

htom

07-09-2009, 10:13 PM

Neatest chainplates I ever saw (on a ketch whose name I don't remember, in Florida in the '60s) were (I was told) custom-cast bronze, flush and set into a lapstrake hull. I don't know how they were backed; having gone to that trouble for the exterior, there was probably a matching cast piece internally. No visible screw or bolt heads on the outside. They wouldn't splash, but I'm not sure how much they'd weaken the hull where plank was carved away for them. I would think they'd make for stress risers in the planks, but it was an old boat, so maybe extra thick planks where they were, for the length of a couple of frames?

Larks

07-09-2009, 10:48 PM

Now that raises an interesting question or option. I intend to get new chain plates cast, possibly similar to the photo in the first post above or with some element of design or more shape in them.

How would the strength of having them cast with their own bolts incorporated into the casting (so that they have no visible screw/bolt heads) compare to having to bolt them on to the vessel with pan head bolts?

oznabrag

07-10-2009, 12:23 AM

Larks, if that's what you want, you might look into separate bronze bolts brazed into through-holes, ground flush and polished. I think it would be a whole lot less involved (expensive).

John B

07-10-2009, 12:25 AM

Think of the issues with fitting them that way Larks. Its a bit like screw head orientation.. actually better to get the correct torque over aesthetics. You want those bolts in exactly the right place for the job and that means perpendicular to the hull surface at that point surely , rather than every one of them perfectly aligned to the same angle( parallell) so they can be driven in.
My view for what its worth, is that if you can make a dead sure excellent job of internal chainplates , they'll be better than exposed. Mind you, thats only after the last 20 something years of watching and ducking spray generated by external plates.:rolleyes:

Larks

07-10-2009, 01:37 AM

Thanks Oz, John, I hadn't thought about the curve of the hull and fitting it. The bronzing idea may resolve that issue if I was to do it.

John, the issue of spray was the one real detriment to external chain plates that I recall from the previous thread (other than possible staining) - it must have been yourself or Rick that raised that point back then.

Andrew Craig-Bennett

07-10-2009, 04:19 AM

RFNK

07-10-2009, 05:20 AM

John, the issue of spray was the one real detriment to external chain plates that I recall from the previous thread (other than possible staining) - it must have been yourself or Rick that raised that point back then.

I was only talking about external plates on a clinker hull - the spray issue is probably not worth worrying about on any smooth hull, although there's John saying that he's had bad experiences even then! As far as the fastenings go, I'd go with Andrew's advice. Bolt heads visible on chainplates look fine.

I have to say this - imagine cutting a trench in clinker planking to accommodate external chainplates. As Alice might have said: ridiculouser and ridiculouser! Rick

mmd

07-10-2009, 07:00 AM

Rick, I guess what got my attention in your original post was describing the external chainplates on a clinker hull as "ridiculous". You have since explained that you find them aesthetically unpleasing, and have described a detrimental feature (splashing), both of which I would grant to you, though I disagree on the first count. Personally, I don't find them unattractive in most instances, but beauty is in the eye of the beholder so I can't fault you for that. But (as per my Oxford Canadian Dictionary) finding them "unreasonable", and "absurd" is a bit beyond an aesthetic concern, and branding them as "worthy of ridicule" is rather strong. They are certainly not "outrageous" nor "astounding".

Better off to just call 'em fugly and be done with it, eh? <wink, grin>

RFNK

07-10-2009, 08:11 AM

It's not just a bit of splashing though is it? We're not talking about just a chainplate - a chainplate on a clinker hull has to have packing under it so that it's not just resting on the plank edges etc. It's the packing that, to me, interrupts the steamlining of the clinker hull and I would imagine that in the case of chainplates of any real length, there'd be one heck of a lot of splashing - and for what?. I don't think it looks ugly really (did I mention aesthetics? - don't think so) - it just looks wrong to me to interrupt these flowing lines unnecessarily. Okay, I'm happy to concede that ridiculous might be a bit strong but please bear in mind that when this issue first came up in Kerry's thread, my comment was in response to the notion of external chainplates being fitted to a Folkboat - worse than ridiculous!! Sacrilege! Rick

Dick Wynne

07-10-2009, 01:00 PM

... the notion of external chainplates being fitted to a Folkboat - worse than ridiculous!! Sacrilege! Rick

Not to mention:

http://farm1.static.flickr.com/50/162475639_df7d13f8f5.jpg http://farm1.static.flickr.com/55/114758295_0567b33945.jpg

Nary a leak so far.

RFNK

07-11-2009, 01:36 AM

Beautiful work Dick! Rick

Dick Wynne

07-11-2009, 04:05 PM

Beautiful work Dick! Rick

Ta Rick, I can only claim the credit for good taste, the man to praise is builder Fabian Bush, pictured. In fact, right at at the outset I was for external chain plates but Fabian rightly persuaded me out of them, it didn't take him long. There were a number of things like that where I came to appreciate his common sense over my own ill-informed preconceptions, for example I originally wanted the topsides oiled not painted, and a glance back at some of our other email exchanges makes me squirm at times -- but I wouldn't give way on the spruce spars - he was all for carbon but I just couldn't do it somehow. We both found this project to be incredibly absorbing & rewarding. Unfortunately Faban slipped in the yard half-way through and broke his leg in three places, making for a 3-year elapsed time, but as I said to him, she's worth a broken leg in anyone's money...

There are a number of build pictures here (http://www.flickr.com/photos/dickw/sets/165297/)

The Bigfella

07-11-2009, 05:27 PM

Dick - those photos are stunning. Do you have any on the water shots?

Candyfloss

07-12-2009, 12:19 AM

Mate! That is one cool boat.:cool:

Dick Wynne

07-12-2009, 05:38 AM

Dick - those photos are stunning. Do you have any on the water shots?

With apologies to all the forumites already familiar with Constance:

I don't have any on-the-water snaps from this year yet, although she is seeing plenty of action.

There is a mildly amusing (towards the end) yarn from last month here (http://www.albertstrange.org/?p=428)

Here are some snaps from her first day out in 2006 --

http://farm1.static.flickr.com/58/200918529_78f9fcd65b_b.jpg

http://farm1.static.flickr.com/68/200918525_ac6061d56e_b.jpg

More here:

First sail (http://www.flickr.com/photos/dickw/sets/72157594215957627/)

Albert Strange Meet 2007 (http://www.flickr.com/photos/dickw/sets/72157603772763265/)

She now has nameboards on the cabin sides -- I had some oak / gold leaf boards made, couldn't figure out how best to attach them, so I used heavy-duty velcro. So far so good.

Larks

07-12-2009, 05:41 AM

She is absolutely charming Dick, lovely work!!

RFNK

07-12-2009, 05:53 PM

Really beautiful! Thanks!!! Rick

Steveh

07-16-2009, 04:50 AM

Chain plates and clinker aside Larks its a 50/50 here in NZ on the classics. Personally I prefer the chain plates external from an aesthetic view point, and less chance of water ingress internally, (and I'm speaking of triple skin construction) but can't say I've seen any thing bad from boats that have been pulled apart having internal chain plates. Rawene for instance the chainplates run sandwiched between the triple skin planking so are not visible externally or internally. Very tidy. Sorry don't have any photos of Ngatira's chain plates fitted. Mental note to take some next time up at the yard.

Larks I had a reputable builder put copper rod though bolts peened over a stainless steel saddle on the rudder stock. Took 5 years for electrolysis to almost eat the copper away. I could feel the fizzing when holding the copper in my hand.

Larks

07-16-2009, 05:18 AM

Hi Steve, nice to hear from you. I do think I'll go for the external chain plates, it really does seem the way to go for my needs, particularly because I also like the aesthetics. I don't remember seeing yours, were they in that bundle of deck bling fittings that you showed me?

ARW123

07-16-2009, 05:39 AM

These are the ones on my boat; with reference to the above posts they are bronze and were cast for the job about 30+ years ago:

http://www.means2.com/Assets/Corsair/Chain_plates.jpg

Ignoring the additional holes made by the drill-crazed muppet who snapped the screws, it can be seen how they follow the contours of the planking and do not exert undue pressure on the plank edges.

It is also an illustration I imagine of how destroy planking by insufficient or incorrect use of bedding compound......another job to the list, along with the recasting of the now aeriated chainplate!

Larks

07-16-2009, 05:45 AM

I noticed those on your thread, are you getting them all recast ot just that one? Also I'm wondering if it can't be repaired rather than recast?

ARW123

07-16-2009, 05:52 AM

Just that one. I had thought of a repair - possibly filling the holes with a brazing torch and redrilling, though I would need a chat with a metallurgist to understand if there would be any electrolitic conflict beween the 2 similar but different metals.

I will use her predominantly on freshwater, though occassionally have to navigate brackish water to pass between two river systems.

Larks

07-16-2009, 06:06 AM

With a bit of luck Peter Sibley may be along here and he may be able to offer some advice on repairing it. It'd seem a shame to have to recast it and have it standing out somewhat from the others.

PeterSibley

07-16-2009, 05:26 PM

Hi , seeing you are in GB there is a good chance that they are cast in leaded bronze ....gun metal .A foundryman's favourite .

You could have a oxy acelyene repair or TIG but there is a chance of stress creation and that is a bit beyond my abilitiies to predict .

I'd have them recast in the same metal then work out how to patinise to the same finish .Leaving the new ,polished casting in a damp urine soaked rag for a week or two will work .There are other ways too !:D

PeterSibley

07-16-2009, 06:03 PM

I should add that if you use the original as a pattern ,fill the screw holes with automotive "bog" .The replacement will be 3% smaller ,assuming your chainplates are 500mm long ,that would be 15mm .It might be worth moulding a bit on the lower under so they appear the same .

The plank lap steps may be very slightly out of position ,but I don't think it would be much at all ,seeing that they aren't sharp .

ARW123

07-17-2009, 02:19 AM

Larks: sorry for nicking your thread mate!!

Peter: I thought as much - have spoken to a local foundry and I am awaiting their reaction (and quote for making a pattern.......ouch!). Hadn't thought about the patination - suppose one way is to polish the remaining 3 and let them age gracefully together...

PeterSibley

07-17-2009, 02:22 AM

Use the original as a pattern ...dead easy to cast .A fresh pattern could run into hundreds of quid !

ARW123

07-17-2009, 02:30 AM

That's what I said, but during brief the conversation (before sending a picture) it was intimated that wasn't possible! I figured it was an "opening gambit" from their perspective and don't seriously expect it to be the case...

PeterSibley

07-17-2009, 02:42 AM

Mate , if they can't cast from the original they need a new leading hand ....even I could do it ! Find another foundry , note my comments about increasing the size a bit , gunmetal has around 3% shrinkage .

Foundries are pretty good at charging , especially if they suspect you are new to the game .Drop the 3% figure into the conversation ,it implies some understanding of the process .It might help :D:) .Ask what they charge for , there might be things , like fettling ( cleaning up the rough casting ) that you might choose to do yourself .