"toller" wrote in
:

I have a 10' canoe. The gunnels are a pair of 3/4"x5/8" pieces of
what looks like spruce. (one pair on either side)

One piece has about 2' rotted away. We are still using the canoe, but
it can't be a good idea.

Replacing the entire gunnel would be difficult, both because of the
way the canoe is build and my inability to cut a 10' strip of wood.
So, I would like to replace the rotten part, plus some good wood on
either size, for a total of 4'.

I cut 2 5/16"x3/4" pieces of cherry 4' long. (somewhere I read that
cherry is rot resistance, plus I happened to have a suitable scrap of
cherry). I can easily bend the strip to the required size. So, what
I plan is to install one 5/16" piece to the canoe by screwing it to
the other half of the gunnel. Then I will glue the second 5/16"
piece to the first, holding it in place with screws and some clamps.

1) Does this make any sense? Will the cherry strips ever relax, or
will they always be under tension?
2) Is Titebond2 adequate, or should I use epoxy?

Oddly, one 5/16" strip is much more flexible that the other,
eventhough they came from the same 3/4" piece of wood and look
identical.




1) Cherry heartwood is supposed to be rot-resistant, strong, and
flexible. You could also find some spruce, Douglas fir, Eastern White
cedar (Western Red cedar is too soft), hactmatack, black locust, etc.
Make sure the grain is very straight.

2) Building up a laminated gunwale should work just fine, but you should
cut strips thin enough to bend easily, since you won't be steaming them
to make them more flexible.

3) If you just cut the rotten pieces out with 90-degree cuts the gunwale
will develop "hard spots", or kinks, in the sweeping curve of the
gunwale, right at the places you cut. You need to cut scarfs, or sloping
ramp-like cuts, at each end of the gunwale piece you are removing.
Ideally the scarf will have a 12:1 ratio, i.e., the "ramps" will be 7-1/2
inches long, assuming the gunwale is 5/8 inches deep. You could probably
get away with 8:1, or 5-inch-long scarfs.

4) Epoxy would be best, but since the gunwales won't be continuously
immersed in water (right?), Titebond II should work alright, if you
believe the bottle.

5) Be sure you clamp the scarfs well so that they are tight right up to
the thin ends. You might even want to make the repair just a little fat
and smooth it down to match the existing gunwale.

6) Be sure to dry-clamp everything before you apply glue, just to make
sure it's going to work out well. If clamping distorts the gunwale, you
could fashion a thick caul, or backing plate, which matches the curve of
the gunwale, and clamp it on the side opposite the repair. This should
keep the gunwale from distorting while clamping.

--
John Snow
"If I knew what I was doing, I wouldn't be here"