resin amount and cloth weight

With the option of 4oz and 6oz fiberglass, how does this effect the amount of resin used? I'm building a 10' canoe that is 28" wide and wondering if I need Mas #1 or #2 kit.

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RE: resin amount and cloth weight

Ideally, the lamination should be 60% resin by weight. There's all sorts of ways to calculate this, but my rule of thumb is to multiply the glass area in square yards by the weight of the cloth in ounces and take 60% of that as the number of fluid ounces of mixed epoxy resin that you'll need to wet out that glass.

The sharp-eyed out there will notice that I'm ignoring the fact that glass weight is stated for tailors' yard, not land yards and that I'm using weight ounces to directly determine volume ounces. But, in an accident of the Universe almost as astonishing as the fact that Earth's Moon and Sun both have almost exactly the same angular diameter (letting us see total solar eclipses), this actually works out. Score one for the Imperial weights and measures, sorry metric.

So once I know how much epoxy I ideally need, I use a wastage factor to allow for the stuff that stays in the bottom of the cup and on the tools, the stuff that hardens before I can use it, the stuff I have to mix but not use because my mixing method is not fine enough and the stuff that I can't get out of the bottle. Notice that each one of these things can be controlled as you acquire skill with epoxy and glass. Back in my newbie days I assumed 15% waste. These days it's a whole lot less.

Or, you could use the CASE (Copy And Steal Everything) method, and see that the CLC Sassafras 12 canoe, which is 2 feet longer than the one you propose to build, uses the #1 kit. This is backed up by the Nymph Canoe, which is 10 feet long and with a 25 inch beam, also using the #1 kit.

Have fun,




RE: resin amount and cloth weight


RE: resin amount and cloth weight

Hi Jim, 

i was looking at your question and thought i would come at a slightly different way.  my thinking is motivated as somebody who likes to build light and I have often substituted 4 oz cloth for 6 oz cloth to achieve this end.

So a simple answer is that you could expect to use about 1/3 less the amount of epoxy with a 4 oz layup than a 6 oz layup…..and this comports pretty well with my actual experience and typically adds up to a significant weight saving if you can afford to have a bit less sturdiness.

Laszlo is correct that at the end of the day the #1 epoxy kit is the way to go….and should leave you with some extra for repairs and other little projects if you are careful.

On Laszlo’s equation, I am a bit confused as I would have assumed you would have had to take the number he calculated and divided by .4 given the ratio he mentioned.  This would calculate out to a significantly higher number of oz then simply multiplying by .6.

A composite site I frequently reference explains it this way….with a nod to Laszlo that hand layups 60 percent of the weight being resin is a reasonable starting point.   They also recommend adding a 30% buffer on top of that calculation to take into effect things like filling the weave, epoxy absorption by the underlying wood and wastage.   i have done a couple builds where i measured out everything and can say the equation and buffer of 30% comports reasonably well to my actual build experience.

From that site:

For hand Layups, the fiber / resin ratio is usually ~50% at best. For exact science, one would say 207 grams of fiber is the same as 207 grams of mixed resin. But if you are estimating, it is better to use a higher figure to ensure there is enough resin for a job. The ratio is always going to be proportional to this ratio.

Example 1: 50/50 Fiber / Resin Ratio: 207 g Fiber & 207 g of Resin

Example 2: 40/60 Fiber / Resin Ratio: (207 g Fiber * 60%) / 40% = 310.5 Grams of resin

Anyway, i hope the additional thoughts are useful.  Laszlo is right at the end....just go with the number 1 kit :)


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