Caulking

[tcmers]

We've started removing the bottom paint and sanding the hull of our Skiff Craft. The hull is lapstrake construction. There is a silicone type caulking along all of the seams below the waterline that is coming out as we sand/scrape. What is the best material to use to replace this? The seams are tight, and this is a very fine bead applied along each of them. Thanks.

[Jack Heinlen]

Um, hard to say without being there, but here's a shot from the hip.

Lyman and Chris Craft pioneered ply lapstrake construction with polysulphide in the laps. It worked wonderfully. Hulls fifty years old that are still sound and tight.

I don't know what Skiffcraft used, but my take is to leave it alone. The stuff you are scraping off is what squidged out when the boat went together. Don't muss it anymore! Leave it alone while scraping, sanding and painting and there should be no need to refill the seams. If it wasn't leaking, definately don't frick with it! The bit you are taking out with a scraper shouldn't matter because the 'gasket' is in the seam, but don't go digging!

Jack

P.S. If the squidged out stuff bothers you it would be acceptable to cut it off with a knife run down the lap, but don't dig at it, you'll just pull the gasket out. We don't want that.

[ 06-20-2004, 11:35 AM: Message edited by: Jack Heinlen ]

[sdowney717]

It is probably polysulphide caulk
Silicone caulk would have been a very poor caulk to have used.
If it is that loose that it is falling out of the seams, why not get out the loose stuff, clean the seams and just recaulk it with new polysulphide caulk.
I wonder if a previous owner just wiped some caulk on the jointed laps.

[tcmers]

It does look like someone just wiped on some caulk on the seams. It is only in some areas. Most of what we see does indeed look like oozing from the original construction. We'll see what it looks like after we're done sanding. The joints all are tight, with no signs of seeping inside the hull. We may just sand it, paint it, and see what it looks like when we launch. We can always go back over the seams later if needed.

[RGM]

Check out www.skiffcraft.com (http://www.skiffcraft.com) , e-mail them or call them up and ask them what they recommend these days. They'll probably tell you 3M 5200. My better half Annie just bought a 1964 19' Skiff Craft runabout. She is hoping to receive it in about two weeks, it's coming from Upper Michigan. What exactly is your Skiff Craft? As Jack has suggested, avoid the "digging", you're still in the discovery phase of this task.

[Jack Heinlen]

The joints all are tight, with no signs of seeping inside the hull. Definately a case of "if it ain't broke, don't fix it."

Trying to 're-do' this would be a mistake, unless there is a leak. Re-doing it properly...well we won't go there. Trust me on this. And when the boat leaks like a seive you can sue me. :D

[tcmers]

Thanks for the input. Our Skiff Craft is an X210 Cabin model. We've been working on it today, and have found that most of the caulking on the bottom is in good shape. Using care when we sand, it looks like we can follow Jack's advice, and just leave it alone. I've contacted Skiff Craft, we'll see what they say. It will probably be a couple of weeks before we're ready to paint, so we have some time.

[RGM]

Good luck with the boat. Sounds like the hull is in pretty good shape. Any chance you could post some pictures? We're very visually oriented here.

[Jack Heinlen]

A little more, just so you know your boat a little better.

Traditional lapstrake boats made of solid wood depend upon wood's natural tendency to move across its width, but not much across its thickness. The wood to wood joint at the lap doesn't move much, which is why they are still used for ship's boats and dinghys. You can dump them in the water after a year out and they won't leak, much.

Sometimes a traditional lapstrake boat that has been out of the water will need to 'soak up' before not leaking, but unlike carvel planked boats they don't have to live in the water to be happy.

You have a different proposition with your Skiffcraft. Its strakes are plywood, which being wood moves around like any other, but not nearly so much as solid wood. What the designers at Chris and Lyman realized, carried on by Skiffcraft, was that if you take ply strakes and put them together with the newfangled sealants available circa 1950, they won't leak at all. Unlike with a solid planked boat there was no need to soak up before being tight. They've got a flexible gasket sandwiched between two very stable pieces of wood.

What the sealant(a viscous liquid that hardens into a kind of rubbery stuff) did was form a flexible, adherant gasket in the laps.

You don't want to muck with that gasket unless something has happened and the boat is leaking. Repairing it, in the event of something untoward, involves unfastening the adjoining planks, cleaning out the seam, re-gooping, then refastening. So you see why I'm saying to you, begging you, DON'T FRICK WITH THAT GASKET! smile.gif

Sorry to be pedantic, but I know these boats, and I've known a few where people made mistakes with reefing irons and tubes of caulk.

Jack

[tcmers]

Thanks for the education Jack. Very informative. My only experience with wooden boats is my dad's ply Chris Craft Cavalier (sold long ago), and the several cedar strip kayaks that we have built. The area that we noticed the caulking was up towards the bow. The inside of the hull at this point shows no evidence of being wet. We're dealing with the fun of titling a trailer that was untitled and purchased in another state, along with waiting for the boat title, so it will be several weeks before we can get her on the water. We'll try to get some pics posted as we get the film developed. Thanks again. Great info.