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Sunday, September 27, 2015

Canoe Building: Trouble with strips lifting from the form

Right about now I've got a problem.  As I worked my way stripping up the side of the canoe, I started to get the strips lifting off of the molds near the stems.  It seemed like a major problem, and since everything has been glued together, it wasn't like I could just undo everything and it would be ok.  There are two ways to fix the problem: push from the outside, or pull from the inside.  Pushing from the outside is the easy way to fix things, but that creates the problem of making it fiberglass and epoxying the outside a physical impossibility.  I must consult the internet!
I looked around and didn't find much in the way of solutions until I found one on the woodenboat forum:

"There are several more noteworthy points to complete these directions, the first and most important being that you need to watch out for where the previously laid strips begin to pull away from the stations in spots, due to the fact that there is no line of staples holding each strip down. When this begins to happen, you must take alternate steps to hold the developing hull against the stations. My method is to take a piece of scrap wood, say 1 x 2 x 4" long, and shape one end on a belt sander so that it will fit the inside contour of the hull at the point at which you'd like to push the hull in. This point needs to be right at a station - you can select a spot by pushing the hull in against the stations with your hands and checking if the hull lays nicely against the forms. Glue the end of the block against the inside of the hull at that location, holding it in place with a clamp passed through one of the clamping holes in the station. At this point, while gluing, the hull is not against the station, but may be even further out while the block is pushing firmly against it. Once the glue is dry, loosen the clamp on the block of wood, push the hull in tightly to the form, and retighten the clamp to hold it. You can then drive a screw through the block to free up the clamp. (I predrill and countersink the blocks for screws to make it easier.) In total, I wind up using 1 to 2 dozen such blocks to hold the hull in place. After the hull is off the mold, I give each block a tap with a hammer to break it out, and all traces of the glue are removed as you're sanding the inside of the hull."

So I thought I'd give it a shot.  I glued a few handles to the strips, let them dry, then pushed from the outside as I screwed them to the mold on the inside.  After a few of the handles were on, I was getting some good results in one area, but it was transferring the lift elsewhere.  I realized that if I want to finish this anytime soon, I'd be in trouble.  Lesson learned: if you're getting lifting, affix the "handles" to the inside as you go along on an as-needed basis.

A friend suggested emailing where I got the plans from and asking if the lifting was really a problem,  Great idea!  I emailed Northwest Canoe and got this response:

"We typically build with fasteners for that very reason.. strips can lift away from the forms. The ‘cheek’ in the NWC River dramatically shortens the waterline length when you heel the canoe. Presenting a rounder shorter mid-section allows for snappier turns in moving water and is preferred by many freestyle paddlers too. The slight re-design you-re making on the fly may handle a bit differently, but should still make a fine paddling canoe. Have fun with your canoe building project. Please keep us in mind for fiberglass, epoxy and your other material needs."

So after spending lots of time thinking up a solution, I decided that the best solution in my situation is to do nothing.  The canoe may handle a little differently then designed, but should still be a good canoe.

The changes resulting from me doing nothing are pretty straightforward:
The rocker (difference in height along the keel line) is cut in half from 2 inches to about 1 inch. This should make the boat slightly more stable, but less nimble.
The cheeks will be fuller and not as narrow as in the original design.  Again, this makes it a little less nimble.  Basically, the changes make the canoe a little more of a lake and flatwater canoe.  Since I don't canoe much in rapid water, I'm ok with the changes.

I'm glad I've alternated strips as I've worked on the canoe, since the forces on each strip will be approximately the same since each came from adjacent places in each board.

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