To Double layer the bottom ?

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AlanWS
Posts: 209
Joined: Thu Mar 17, 2005 4:30 pm
Location: Shorewood, WI

Re: To Double layer the bottom ?

Post by AlanWS » Thu Apr 21, 2016 9:18 am

How strong it is, how much epoxy it takes, and how heavy the canoe winds up are all related.

When you apply epoxy to the glass, it soaks in and makes an uneven layer. Canoecraft explains the best way to fill the weave using extra layers of epoxy, then sand down to a smooth surface without cutting through any of the glass and weakening the structure. This is the most consistent way to make a strong and beautiful structure, but if your goal were to use the epoxy in the most conservative way, you are removing a noticeable amount as dust.

It's the glass that provides most of the strength, as long as it's bonded to epoxy. If you could have the same amount of glass embedded in a thinner layer of epoxy, that could be lighter and almost as strong, as long as you did not cut through the glass fibers. If it could be done with wet epoxy, it could conserve on that too. While a lot trickier to do with the compound curves of a woodstrip than the simple curves of a stitch and glue design, there is a way to thin the epoxy layer without compromising the glass.

The idea is that on wetout of the glass with epoxy, you can cover it with a plastic film (test to be sure it does not stick!) and roll it smooth. This squishes down the weave of the glass, forming a smooth layer with no weave to fill, despite the use of less epoxy. This idea was taken from a guy who used to call himself "Dr. Dichroic", and there may still be photos somewhere online showing the process. (I think his actual name is Blazy.)

I have used the method on compound curves where it's trickier to do, but not on an entire canoe surface at once. I used a heavy polyethylene film that I first heated with a heat gun and stretched to fit the curvature of the canoe. If you can't get the film to follow the curve and lie flat without creases, don't use this method. It might be easiest for use only with the second layer of glass, applied only at and below the waterline. It can very effectively be used to feather in extra reinforcing layers of cloth, since they can be squeezed down to almost nothing at the edges, which saves a lot of sanding.
Alan

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Jim Dodd
Posts: 1173
Joined: Wed Feb 08, 2006 11:08 pm
Location: Iowa

Re: To Double layer the bottom ?

Post by Jim Dodd » Fri Apr 22, 2016 4:20 am

Alan I've tried the plastic "Heat Shrink Window Film". It would work, but you need a very slow setting epoxy.
A better method, is Peel Ply. It's a finely woven polyester cloth. The good stuff is treated with a release agent.
I used this one time, and generally it worked, but getting the wrinkles out was very difficult. That's how I know you need a very slow setting epoxy.
The peel ply worked for me. It reduced the amount of resin, and helped keep the cloth close to the hull.

A trick I've learned from a good friend, is to cut the peel ply into manageable strips, say two foot wide, and lay them on in an overlapping pattern.

Peel ply is about $8 a yard, and is thrown away when you pull it off the hull.

Jim
Keep your paddle wet and your seat dry!

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