Builders' Forum Archives
Re: Weights: Fact or Fict
Posted by James on Jul 20, 2006
Hmmm.... Interesting technique. I'll have to experiment with TP.
One suggestion that works for me in keeping weight down is to work out the weight of epoxy required to maintain a 50/50 glass epoxy ratio. And try your best to keep under this amount. With care it is possible and you'll be sure that you didn't soak way too much on there. This is made easier if you use low viscosity resins for wetting out.
I use vacuum bagging for small work like hatch covers, and paddle blades. This combined with weighed epoxy at 55/45 glass epoxy ratio gives very good strength to weight. I routinely end up with a fair amount of excess epoxy in the bleeder so my real ratios are lower still and I have no starvation.
Another way to help reduce the weight is to get the hull as fair as possible before any glass or epoxy is applied. Fairing before glass reduces weight, after glass is applied fairing can only add excess weight.
Finishes are heavy, as is filling glass weave manually (when you vacuum bag it comes out smooth if your plys are stiff enough). A 16' canoe can easily have 3-5 lbs of paint or varnish on it. Most varnishes/paints are at least 50% solids (many manufacturers publish specs) so if you weigh your can of finish before and after use your can make a good estimate of how much weight you just added. A gallon of regular spar varnish weighs around 7-8 lbs not including the can, to help ballpark it.
Personally I don't store my boats outside so I'm not really worried about UV damage, so I use very little or even no finish on my personal boats.
In Response to: Re: Weights: Fact or Fict by Darryl on Jul 13, 2006