sealing lapstrake seams

[Glen]

I recently acquired a lapstraked Fulk boat built in the late '40's/early 50's. It's been in the yard since August and I'm trying to get it back in the water. It was hauled last spring, and at that time, the seams were caulked with 5200 and then the bottom was painted. I know this wasn't the correct way to seal the seams, and the 5200 squeezed out and took chunks of the bottom paint with it (requiring the re-haul in August). Could somebody detail the proper way to seal these seams for me?

Thanks,
Glen

[nedL]

There are a number of guys here that own Folk boats that can give you specific details of their experiences with the same thing. First, 3M 5200 to caulk a lapstrake bottom = mistake (IMHO). Lapstrake boats will dry out when on land and usually ---leak like an old peach basket-- for the first day or so after launching. This is just the nature of the beast. I would pull off all the beads of 5200 that you can, inspect the seams & if in good condition use nothing more than an underwater seam compound that will stay soft (Slick Seam, etc.).
If there are questions about the seams / fastenings, that is a separate issue.

[Bob Cleek]

Oh yea, what Ned sed... :eek:

[Don Olney]

Based on my admittedly limited experience with 5200, I don't understand how it "squeezed" out of the seams. That stuff is pretty flexible and tenacious to say the least. Perhaps it was not applied properly. For caulking smaller lapstrake boats, Harry Bryan uses a method of applying 5200 that works quite well. I'm not sure if this method is used on the larger Handy Billy, but I believe so. The seam is first scored slightly with a rounded over screwdriver so that there is a concave depression along the seam. That depression is filled with an ample bead of 5200. If one were to simply apply 5200 along a regular seam, there probably wouldn't be enough caulk in the seam to get a good bond between both strakes. This might allow the 5200 to open up as opposed to flexing with plank movement.

If a large lapstrake boat is going to leak for the first day or so after it is launched, in the short term, what is the advantage of seam compound over 5200?

What to do with a large, heavy, trailered lapstrake boat that is day sailed? It isn't in the water long enough to swell up before it is taken out again.

This is the problem faced by my local Revolutionary War militia and their 18th century whaleboat replica, the HENRY SCUDDER. Length 25'. Construction is 5/8" white cedar over oak frames. Garboard is 3/4" white cedar. Stem, sternpost, keelson, etc., are white oak. Strakes are copper riveted. Caulked with seam compound. I'm told that the last time it was lauched last summer, it filled almost to the gunwales overnight. My guess is that the worst possible thing for a heavy, lapstrake boat like this is a long haul over bumpy roads in the summer heat-- which is how it has been used. Any suggestions for the seams?

http://www.imagestation.com/picture/sraid28/p7f4414207da2625cfaca51711bff3dbb/fdf5b346.jpg

http://www.imagestation.com/album/?id=4292057137

[ 02-19-2002, 09:14 PM: Message edited by: don olney ]

[Glen]

Thanks for the advice...does that mean I don't need to worry about packing cotton in the seams? I've heard it both ways. I have a feeling this boat's going to get me a huge education.

[Wayne Jeffers]

Regarding 5200 and lapstrake seams:

Over the weekend, I was reading through Steward's "Boatbuilding Manual" chapter on planking. For older lapstrake boats that have become "a bit weepy in the seams," he mentions cutting grooves at the outside of the plank joint using a small gouge called a veiner, and then applying a bead of polysulfide sealer, such as 3M-101 or BoatLife LifeCalk, or (his preference) a polyurethane adhesive sealant, such as 3M #5200 or Sikalex 240. Robert M. Steward, Boatbuilding Manual, Fourth Edition, page 195.

I can't say that Steward's description constituted a ringing endorsement for 5200 in lapstrake seams, but clearly he finds no great fault with the idea, at least for older boats which no longer take up properly. Perhaps this is an extreme measure to try only after all other more moderate solutions have failed?

Wayne

[Noah]

Glen, great to hear about your Folkboat! They are the greatest boats known to man...or something close anyway. Yes, I do have one...

It is hard to know exactly what is going on with your seams. If it was leaking well then it needed some kind of a fix. After a few days (maybe a week) in the water a lapstrake boat shouldn't leak too badly. Unfortunately mine does... (On my Folkboat, the other two boats I have are a 16.5 ft Lyman, and a Whitehall rowboat. Neither leaks a drop after the first launching, and both live on a trailer)

It seems that the proper thing to do would be to "harden" up the roves. This basically means that you are tightening up the rivets. It is a two person job, one on the outside hitting the rivet, and someone on the inside reclenching it. I need to do this on my boat this spring. If you do a search on the forum you should be able to find info on this technique.

In a perfect world, your boat shouldn't need any caulking. I would imagine that putting some cotton in the seams would work, and also if you are desperate try putting 3m 4200 or 5200 in there. If you have a clean seam it should stick. One thing to note, is if the boat is too dry, when the planks swell you will have problems.

Good luck, and if you have any questions at all please email me. I just went through this process last summer with a derelict Folkboat. You can see my work at www.morebutter.com/patience (http://www.morebutter.com/patience)

Noah

BTW, please post pictures, or email them to me! I would love to see another Folkboat.

[Ruaridh]

Hello
Is there some confusion starting, or have I misread....?
I refer to cotton in the seams....in a clinker (lapstrake) boat there is no way one should be trying to put cotton in the overlapped seams between the planks, this will only prise them apart further along and cause no end of problems.
The only areas on the folkboat which should have caulked seams are the stem and sternpost at the ends of the planks and the seam between the garboard and the keel (that's how it is on mine anyway).
I do have some cotton at the very aft end of a couple of other seams but I think it's been put there as part of a previous (dodgy) repair.
As to 5200, I agree with those who think it shouldn't be a problem if the seams are prepared correctly, so much so that I'm applying it to my Folkboat as we speak. It doesn't actually go into the seam at all, but rather lies in the 90 degree angle between the bottom edge of one plank and the front face of the next.
I've also harderned up all the rivets below the waterline, so possibly don't need it, but the boat simply didn't stop leaking last season and I live too far away from her to deal with that. If the 5200 comes off I'll just put it down to experience but at least the way I'm applying it its not doing any harm.
As Noah said, search posts on 'clinker / lapstrake leaking' etc., some very good advice was already given to me on how to harden up the rivets etc. Advice on sealers, I'm afraid is much more dependant on personal opinion.
Good luck,
Ruaridh

[Dave Carnell]

Glen,

The Cape Fear Museum had a reproduction whaleboat built by Bruce Mackenzue when he wasthe boatbuilding instructor at CFCC. It was stored in a building on Wrighstville Ave., and the seams opened badly. With permission from the curator, I sprayed the inside of the boat with ethylene glycol antifreeze. The seams tightened and stayed tight in the outside storage of the old boat shed.

Antifreeze treatment isn't permanent, but it attracts water and is also attracted to the wood. In outside storage, I had to bore a drain hole in the bottom of the boat to prevent rain water from accumulating.

[nedL]

NO cotton in the lapped seams! I'm not to sure I'd endorse it in the rabbets either, but certainly less chance for damage there.