State of the art for strip plank seams

[pbmaise]

Topside seams on my 15 yo vessel are already opening up. Planks are 2" thick Albizia acle commonly known as akle, acle, or East Indian walnut. As the name walnut implies this wood is extremely heavy and rot resistant.

I suspect seaming was accomplished with cotton. Likely, a local brew compound like red lead or cheap non-sag epoxy might have been employed over the cotton.

As for newer technology I am aware of Interlux Seaming Compound. I believe I can import to do this job over new cotton.

Questions

Any rule of thumb how much compound to buy based on number of seams and/or boat LOA? I cannot simply run down to the local marine supply store.

How long should I expect a proper job to hold?

I read where some people cover top sides with shade cloth to keep sides out of sun. Good idea for a vessel spending months on a mooring and only occasional sea time?

Is there a synthetic alternative to cotton? I am wondering if cotton slowly rots away which is why the repairs are needed in first place. If Dyneema fibers are pounded in place they would never shrink. They would also never swell. Hydrophilic synthetic cotton?

The vessel is very sound and planks extremely solid. I would entertain the idea of epoxy seaming the planks together. I think people who have tried this before largely fail because their plank wood is softer and not as sturdy as "walnut".

[pbmaise]

Pictures

[Simi 60]

Posted in your other thread about what we use.

[Jim Cate]

Can't offer advise about caulking, but is that not carvel planking rather than strip planking? Our strip planked boat has no caulking at all for the "planks" are edge glued together permanently.

Jim

[AndyEss]

My wood plank hull experiences are from rebuilding a 26ft mahogany on oak sloop in the 1970's and 80's.
Wood expands and contracts across the grain much more than along the grain. It does respond to moisture -- and extreme heat (causing drying) from the sun. At least your topsides are painted white.
I don't think you have any chance of just epoxy glueing the planks together. Planked construction was never intended to be so rigid. As for the Indian walnut being possibly stronger than other woods - it also might not give a good surface for epoxy to adhere to.
I do remember reading about a technique of routing out the seams to a greater, uniform width, and gluing in thin strips of wood to join the planks. No clue as to effectiveness of this technique, as wooden boatbuilding dropped off of my radar about 35 years ago.
Staying with oakum and some sort of elastomeric cover is the tried an true method used for centuries in wooden plank boat construction.
Living with less than perfectly painted topsides due to seam expansion and contraction is part of the charm of having a wood boat. A less rigid topside paint, one that expands and contracts at similar rates as the planking will help minimize cosmetic defects.
Keep fresh water out of your boat at all costs - that is what causes "dry rot". Keep teredos from eating up your below the water line hull.
From a former wood boat owner - go see a doctor soon and get your head examined.

[HopCar]

Like Jim I think you have traditional plank on frame construction, not strip planked where the planks are glued together.

This looks like a good tutorial on calking your type of boat. Near the end he discussed using the Interlux Seam Compound.
https://youtu.be/jM6R81SiKgA

[Wotname]

Yes, that looks like a traditional carvel planked hull.
My understanding is that you don't want a synthetic caulking.

Remember the wood is always expanding and contracting - that is the nature of a carvel hull. The organic (oakum [tarred hemp] or cotton) caulking expands when wet to fill the seam and the whole arrangement remains flexible.

Oakum (hemp with Pine Tar AKA Stockum Tar) is the preferred material but cotton is cheaper and easier to use. I understand it doesn't last as long as Oakum. Oakum will last many decades. IIRC cotton is also used when the planks or fastening have weakened over time.

When I re-caulked my carvel hull in the 1980s, the old material was first removed, the seams cleaned and painted, the new caulking was hammered in, the seams again painted and finally the remaining part of the seam was filled with mix of linseed oil putty and Pine Tar. Finally the planks and seam were repainted with a topcoat of the desired colour.

Maybe there now is a modern shortcut?????

[MartinR]

Originally Posted by Wotname

Yes, that looks like a traditional carvel planked hull.
My understanding is that you don't want a synthetic caulking.

Remember the wood is always expanding and contracting - that is the nature of a carvel hull. The organic (oakum [tarred hemp] or cotton) caulking expands when wet to fill the seam and the whole arrangement remains flexible.

Oakum (hemp with Pine Tar AKA Stockum Tar) is the preferred material but cotton is cheaper and easier to use. I understand it doesn't last as long as Oakum. Oakum will last many decades. IIRC cotton is also used when the planks or fastening have weakened over time.

When I re-caulked my carvel hull in the 1980s, the old material was first removed, the seams cleaned and painted, the new caulking was hammered in, the seams again painted and finally the remaining part of the seam was filled with mix of linseed oil putty and Pine Tar. Finally the planks and seam were repainted with a topcoat of the desired colour.

Maybe there now is a modern shortcut?????

THIS! I use 1 strand of cotton first and then hemp. There is no modern shortcut. Compounds will fail after a while.

For the caulking, first treat the seams with lead paint if possible. Then wet them with a mix of linseed oil and tar just before caulking. The caulking has to be driven in "lubricated". Caulking is not hard to learn, but you need somebody to show you. It needs technique. For the putty, red lead paste is perfect below the water, above water use normal linseed oil putty. You can make your own.

Cotton caulking lasts a long time if set in lead, tar and linseed oil.

A viable alternative above water would be to rout out the seams and glue in slightly tapered strips of wood, maybe 1/4" to 1/2 inch thick (depends on the planking). Do not use epoxy. Aerodux is a better glue for this application. Epoxy tends to fail after a while, do not ask me why.

[pbmaise]

Originally Posted by MartinR

THIS! I use 1 strand of cotton first and then hemp. There is no modern shortcut. Compounds will fail after a while.

For the caulking, first treat the seams with lead paint if possible. Then wet them with a mix of linseed oil and tar just before caulking. The caulking has to be driven in "lubricated". Caulking is not hard to learn, but you need somebody to show you. It needs technique. For the putty, red lead paste is perfect below the water, above water use normal linseed oil putty. You can make your own.

Cotton caulking lasts a long time if set in lead, tar and linseed oil.

A viable alternative above water would be to rout out the seams and glue in slightly tapered strips of wood, maybe 1/4" to 1/2 inch thick (depends on the planking). Do not use epoxy. Aerodux is a better glue for this application. Epoxy tends to fail after a while, do not ask me why.

Thank you for the replies, I also posted on wooden boat forum and the general wisdom there is I might only be looking at simple paint failure owing to the fact the paint doesn't hold very well to the seam compound used.

The seams are not leaking and boat is bone dry so tenatively I am thinking of just stripping off paint in the areas of failure, and building back up using a seaming compound that is both flexible and accepts paint.

Alternately, a more flexible paint?

Thanks everyone for the ideas.

[GordMay]

Interlux Seam Compound, both Brown 30 (below the waterline) & White 31 (above the waterline):
Theoretical Coverage - 60 sq ft/Gal yields 60 mils thickness

30 ➥ https://international-yachtpaint.com...902.1559639675

31 ➥ https://international-yachtpaint.com...902.1559639675

[a64pilot]

Originally Posted by pbmaise

Thank you for the replies, I also posted on wooden boat forum and the general wisdom there is I might only be looking at simple paint failure owing to the fact the paint doesn't hold very well to the seam compound used.



The seams are not leaking and boat is bone dry so tenatively I am thinking of just stripping off paint in the areas of failure, and building back up using a seaming compound that is both flexible and accepts paint.



Alternately, a more flexible paint?



Thanks everyone for the ideas.

My guess would be that a wooden boat forum would be a great place to get advice, beyond that I’ll bow out as I know next to nothing about the subject

[MartinR]

Of course, if it is not leaking, you should not caulk. This is only cosmetic. What caulking material is used now, putty or some rubbery stuff?

[TrentePieds]

A small linguistic correction, in case you have to go shopping: It is not "Stockum" tar, but "Stockholm" tar. Named in days of yore for the capital of the land whence the stuff came. Sweden (including Finland) and the Baltic countries were covered with the pine trees whence this high quality tar was distilled.

Baltic traders had black hulls because in the days before industrial paints, they were tarred. The seams in the planking didn't show till you came close :-)

TP

[Dougtiff]

Having been a Shipwright for over 40 year's, and done miles of caulking, i would rake out a small amount of caulking, maybe a couple of inches, and see if it is rotten, and kind-of blackish, if not, resetting is the way to go, now caulking is a real art, and it takes alot of practice to get it right, i.e., not to tight and blowing thru the plank, boy have i seen alot of that, best way to go, is remove old seam compound carefully, then reset the cotton with a roller like a pizza cutter, roll the wheel along the seam, [assuming the cotton is good], you want 1/4 to 3/8 " depth of seam for the seam compound, if more cotton is need to arrive at the required depth, you can add some cotton "STRING ", and roll it in with the pizza roller, then PAINT the SH@#$% out of it with oil based , really saturate the cotton, do it a couple of times over a couple of day's, this will bind the cotton to the plank edge, and stop creeping, the seam compound gets puttied into the seam, insure that the paint is dry, or you will have a mess, DO NOT paint the seam then caulk, it will be a complete mess, after removing any excess putty with a putty knife, allow the putty to skin over for a couple of day', then paint. I have fond memories of S.E. Asia, spent 20 year's in the area, working as a Oil Field Diver, and in my off time sailed all over the place, this back in the 70'S and 80'S, used to anchor of the fresh water lake there in Langkawi, back in those day's, there was only one village at i think KUAH ?, that whole area was pristine and unspoiled, no body there, hardly ever saw another yacht, could sail up both coast's from Spore, where i was based to Thailand, and never see another cruiser, anyway, hope this info helps.

[Wotname]

Originally Posted by TrentePieds

A small linguistic correction, in case you have to go shopping: It is not "Stockum" tar, but "Stockholm" tar. Named in days of yore for the capital of the land whence the stuff came. Sweden (including Finland) and the Baltic countries were covered with the pine trees whence this high quality tar was distilled.

Baltic traders had black hulls because in the days before industrial paints, they were tarred. The seams in the planking didn't show till you came close :-)

TP

Yes, thanks for the correction. It was a typo on my part - not sure how that slipped past my proof reading !!!

As an aside, it has always being know as "Stockholm Tar" in Australia AFAIK. A container of it was (is?) a standard feature in every shearing shed and in many stables. Only recently (courtesy of the w.w.w.) have I found it to known Pine Tar in some other parts of the world.

It's good stuff and it's odour (or better, it's scent / aroma / fragrance / perfume / bouquet) is one of the quintessential maritime experiences of a "proper" sailing boat.