New construction: deadwood joints

[Seth Wood]

I'm building a 30' traditional plank-on-frame sailboat with white oak keel and deadwood. The timbers were all coated with CPES and red lead, sealed with bottom paint and then roofing tar before assembling and bolting.

Yet as they dry, the timbers are opening up along some of the joints, in some spots (below the WL) as much as 1/4". This is worrying because a) I've lost my once-tight fits, and b) I'm preparing to cut the rabbet and I worry that if the timbers swell at launch and close the joints, the rabbet crossing those joints will be in trouble.

If I assume that the wood will swell back up at launch, then I'm leaning towards heating or thinning some Dolphinite and funneling it down into the joints, so it can get squeezed out.

I'm reluctant to simply tighten up the bolts and close the joints -- that seems like it would risk splitting the wood when it swells up.

So my first question is how common and serious is this? Second question is: what can I do about it?

Advice, questions?

[ 01-06-2006, 08:27 AM: Message edited by: Seth Wood ]

[Seth Wood]

Does anybody have any experience with the deadwood drying out in new construction?

It's similar to what happens when you haul a traditional boat and the seams open up ... but not quite the same.

Again, any advice or comments would be welcome. Thanks..

[seayou77]

Seth, There are many unknown bits like where you are building ie concrete slab or radiant heat which could be adding to the natural drying. But untill others can chime in look up stopwater on great googly; a half inch cedar dowel let into the joint covered by the hood ends of plank or garboard. I'll see how this washes out and we may all learn a bit.

[ken.bryant]

A question, Seth: What do you figure the moisture content of those timbers was when you first fitted them?

[Seth Wood]

The moisture content was high, unfortunately. They were trees that had been felled for a year before they were sawed into the 10x10s I then shaped into the timbers. I sealed the ends and the sides, but they still had a lot of water to lose.

I guess the main issue is figuring whether, or how much, they will swell at launch.

The shrinkage is mainly at the edges of the pieces, as is typical when big pieces like this dry out. I can check with a hacksaw blade and flashlight, but I bet the center of the joint is still pretty tight. Small consolation.

[sdowney717]

I have read of people on thisa forum using roofing tar for filling these gaps in the deadwood.

[ken.bryant]

I haven't built a boat yet, but my intuition as a woodworker is that after a few months submerged those timbers will return to dimensions pretty much like what they were before the tree was cut. So my (uneducated) guess is that you don't have a major problem.

[sdowney717]

yes as long as they dont twist.
With an open gap you have an invitation to lunch for a water worm or gribble.
Probably a good idea to fill the gap with something soft.

[MRJarret]

Hey there, Seth.
I had a similar situation, also with an Oak backbone on a plank-on-frame thirty footer. Thought the timbers were a bit dryer than they were... Poisened and tarred 'em before the final put-together. I ended up with a shy eigth inch gap at the stern, very little forward. I didn't want any movement after the planks went on, so I tightened everything back up snug. My experience says she'll be fine come launch day. We'll see...
What are you building? How far along are you? send me an email, maybe we can trade photos.
M. R. Jarret

[ken.bryant]

"The shrinkage is mainly at the edges of the pieces"

Maybe then the deadwood timber has "cupped". Is the timber aligned "heartside" in, "barkside" out? In that case, as it dries the "barkside" contracts faster and curls up the edges, leaving the center more or less where it was. If this is the process, it should definitely (more or less) even out again when it soaks: "barkside" will now expand more, then push the "curled edges" back down.

If so, and if the bolts are all on the centerline (making a lot of assumptions here!), then tightening them wouldn't make much or even any difference: assuming the wood is face-sawn, the bolts in the center would be in the part that doesn't shrink much -- in a radial direction. If you tried to screw or bolt down the "curly edges", my woodworker's sense says (but what do I know about boats?) that there'd be hell to pay later--when it swelled again, it'd be likely to split.

Tightening fasteners after wood movement is not, generally speaking, a good idea -- unless you're pretty sure it's not going to move the other way. I agree with the earlier writer who said fill it with something soft for now. Wait to see what it does when it's wet again.

[ 01-06-2006, 07:24 PM: Message edited by: ken.bryant ]

[Thad]

I would say that if the pieces were about the same dry and the joints were tight then when she gets wet they will get tight, tighter than before. I would say to carry on and expect it all to work out well, don't put anything in the joints that might impede them geting tight again.