Building my own Kevlar - Carbon canoe

The Mold

Canoe project forum

Running total of cost

Canoe Project Home - The Strongback - The Form - The Mold (part 1) - The Mold (part 2)
The Layup (part1) - The Layup (part 2) - The Layup (part 3) - Project Finish (gunwales) - Project Finish (floats) - Project Finish (seats)

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08-04-2005 The mold starts with 4 x 8 feet sheets of 1 inch think construction foam. I initially purchased two sheets as this is how I understood the directions of the book (one more would be needed) Remember I am trying to keep the cost down and any extra cost I want to go into the boat.

As per the book's instruction I measured 1 5/8 inch with about an 8 degree angle to cut the strips of foam. This would have been fine if I had use of a table saw, I did not. It turns out that my with the guide on my circular saw set at 1 5/8" a the foam strip was much wider because of the angle of the blade. Due to the limitations of my tools I cut strips 3 1/4", rotated the strips 180 degrees and cut them in half.

At first I just had the foam sitting on sawhorses to cut, however the foam would keep moving under the saw until I made a fence on which to cut the strips. Here we are about to cut one of the 3 1/4" strips in half.

There was quite a pile of foam strips resulting from two sheets of construction foam. I had to recharge the saw batteries twice to finish cutting the strips.

Being one that does not build anything I am surprised the little waste foam I had. Even though this was 'waste' most of it was still used.

Some of my strips actually appeared to be trapezoidal as per the book's instructions, some did not. I found that it did not matter much in the end.

I mounted the first foam along the gunwale of the the canoe form using a hot glue gun, in doing so I received a burn from the hot glue. As I type I feel the resulting blister as it hits the keys. I found that the inexpensive claps which I purchased to be inadequate but had to make do, thus the burn. I tapered the inside of the foam to have more surface area for which to adhere the foam to the angle of the bow and stern stations.

The boat being 18' long it took more than two full strips to cover the length of the gunwale.

The first foam strip in place I could better visualize the boat.

After I had placed the first three courses of strips from bow to stern I second guessed myself and thought 'maybe I should not have tapered the inside of the foam strips to attach to bow and stern', the book does not give much detail here. I then began to glue the foam strips to the ends without tapering them and replaced the ends of the finished strips. The illustrations in the book looked as if maybe the end V shape was produced after the foam was in place. BIG MISTAKE.

The author may have formed the V shapes after the foam was attached to the form, I do not know. Unable to ask the author and the publisher being no help I pressed on. By not tapering the inside of the foam there was less surface area for which the glue to stick. The mold ends kept popping apart and needing to be glued again. My glue gun has two setting (low and high) on the low setting I would often find the glue setting before I had the strip in place, the high setting the glue melted the foam.

I found that I needed another sheet of construction foam (three in all) to completely cover the form. While the book says not to worry about gaps I filled any large gaps with scraps of foam.

With the form covered completely I had the rough mold. I could really see the shape of the boat (should I ever finish it). I found making the mold to be more work than I had anticipated, however, that perception may have arisen from the 95 F degree temp and high humidity we are experiencing here in mid-michigan.

I was satisfied with the rough mold except for the shape of the bow and stern. I did not have a sharp V shape which would give better boat performance. I considered removing the foam from the bow and stern stations and redoing it tapering the inside of each piece of foam to have it tighter to bow and stern stations. As it is most of the work done with the hand plane to taper the bow and stern stations was wasted and the foam keeps coming unglued from the form.

I decided to make the best of the situation and try to fix the bow and stern profile in the drywall compound stage. After the foam strips are attached to the form (thus giving you the rough mold) the book calls for 'fairing' the mold. 'faring' the mold is starts with sanding uneven and overlapping foam, the entire surface if faired. I presume the faring of the mold is not only to smooth rough spots, but also to make a surface to which the drywall compound better adheres.

08-09-2005 - We start to cover the construction foam mold with some old drywall compound. I used old compound that I had in the basement, it was runny and had some clumps which I used to fill spaces in the foam. Use of this old drywall compound was a bad idea, it did not cover well and made for a little extra work when I started the 'real' first coat.

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Next: The Mold (part 2)