Gunwale holding, fitted thwarts

[catsittingstill]

The epoxy appears to have worked.  I took all the clamps and tape off and pried gently at the gunwale and the crack stayed closed.

So I sanded and fitted the thwarts.  I expected this to take a few hours but it ended up taking all day.  This is largely due to me deciding that I didn't want to weaken the inwales any further, for instance by drilling holes in them.  My thwarts will be flush with the gunwales, because I think this looks nice and besides I need the back thwart to be as high as possible.  I want to epoxy the thwarts to the gunwales, but end grain (like, for example, the ends of thwarts) doesn't glue well to *anything* because the end grain "drinks" glue and pulls it away from the joint.  (This is the materials-science reality of wood that leads to things like mortise and tenon joinery, actually.)  To glue well, I want long-grain-to-long-grain contact.  The solution to this is to glue an extension (called a knee) to the underside of the thwart, and then glue the knee, which runs under the gunwale all the way to the hull, to the gunwale.  The grain crosses, but that's okay--or more okay than trying to glue end grain.

Though if I were going to glue end grain I would paint it with epoxy until it had drunk all it wanted, let the epoxy solidify, sand it with 80 grit, and then glue the end grain to whatever it was with epoxy while the original epoxy was still green enough to get a chemical bond.  I'm not entirely sure that joinery has caught up to the potential of epoxy.  But I digress, and anyway I'm going to do this the traditional way and be safe.

So, I needed to make four knees--one for each end of each thwart.  That was kind of fun actually--I got to do a little bandsaw carving, where you cut curves with the band saw, then tape the pieces back together, flip the workpiece 90 degrees and cut more curves.  Then I got to secure the little knees with my benchdogs and wonderdog and use the chisel to carve everything into smooth, flowing curves (at least I flatter myself they are smooth and flowing.)

Next I need to epoxy the knees to the thwarts, but to position them correctly I need to have everything sitting in the canoe, and the sun is on the canoe right now so I have it under cover.  Plus I have worked for about six and a half hours and my hands and back are tired.

But I'm a bit bummed as I had planned to do so many things today that I didn't get to.  Fit and epoxy in the blocks for the seat, for example, and paint the gunwales and decks with epoxy.

I have a full working day tomorrow, but Thursday I'll only be able to snatch an hour here and there, and Friday through Sunday I'll be gone to OVFF.  Which has its own compensations, of course, but that's three more days I won't be working on Constance.

Comments

[peteralway.livejournal.com]

In rocketry, it's common to glue the end-grain of wood, so the double-glue trick--applying wood glue, letting it dry (wood glue is better about gluing to itself than fully cured epoxy), and then gluing the part in place--is second nature to me. I learned the trick in a book by G. Harry Stine, who also wrote science fiction under the name Lee Correy.

Reminds me of an epoxy trick high-power rocketeers use--epoxy rivets. They drill holes through the body tube, and apply enough epoxy to ooze through the holes to not only fill them but to make rivet heads inside the tube.

[peteralway.livejournal.com]

Oh, and I'm looking forward to seeing you at OVFF! I hope we get a bit of time to jam at some point.

[catsittingstill.livejournal.com]

I'm looking forward to seeing you too! I would love to jam, though I'm not very good at it.

[catsittingstill.livejournal.com]

On the one hand I'm a little disappointed to know that I was re-inventing the wheel, coming up with that trick, on the other hand it's nice to know that it actually works. WooT!

And the epoxy rivets trick is very clever!

[peteralway.livejournal.com]

I picked it up from The Handbook of Model Rocketry, found that it was effective, and have used it for decades--But oddly I never gave much thought to how it works until I read your reasoning.

[catsittingstill.livejournal.com]

I first noticed this when varnishing--anyplace that end-grain shows on a piece always needs twice as much varnish as anything else in order to get shiny. And sometimes you put plenty of varnish on it, and then you varnish the rest of the piece, and you come back and the end-grain looks dry again.