Good day all,

I am constantly in need of information for weight of epoxy for a given layup. For instance: 4 oz. cloth versus 6 oz. What is the weight per square foot? Has anyone ever done a test similar to One Ocean's infamous epoxy durability test, but a test instead just to see how much stuff weighs. If only I had time and resources enough, I would do something like this:

Test 1: Five pieces of wood, each 12" x 12" x 1", weighed before and after epoxying. Epoxy each with a different layup. Personally I'd like to see 3.25 oz, 4 oz, 6 oz, Double layered 3.25 oz, and double layered 4 oz. Then weigh each one after the layup and subtract the original weight. How much weight was added per layup?

Before this was more a passing interest, but now I am building wood boards and kayaks for other people and especially for surfboards weight is a big issue with people. I feel it's a big misunderstanding that surfers have regarding weight, but I will spare you that dissertation. Anyway, so suppose someone wants a board and I say "Okay, I can use 4oz top and bottom if you want lightweight, or I can put 2x 3.25oz on the top for durability and you will add a little weight." First question out of their mouth- "How much weight?" My response, "Well, the weight of the glass cloth is 3.25oz, but each cloth soaks up more or less resin based on weight and weave so it's hard to say exactly how much it would add." I need better data.

I have this kind of data for wood, and use it religiously on a regular basis. Wood "x" is "x" pounds/cu ft. If I use 1.5 cu ft. of wood "x" then I have 1.5x weight. I factor in a ballpark weight for glue based on the size of the project (for the latest 11-foot board I was shocked to use three bottles of glue!) and then I have to guess at the fiberglass. By this process so far I have guessed weights very accurately- within a pound or so.

The next test I would like to do is a drop-ball durability test. There are standards for this set up somewhere by some governing agency because I know that when you ship sunglasses into the US you have to have a drop-ball form showing they passed the drop-ball test. It is a given weight dropped at a given height, which I believe is 6 feet. Anyway, no matter what height or weight, do a test to simply measure how big of a dent it made for given layups. I would think a 5 lb dumbell weight dropped at 6 feet would give a good idea of durability. I am not at all knocking Raka- I buy from them and I love them, but they claim their 3.2oz is close in strength to a plain weave 5oz. Well I want to see data. I want to test it and be able to know if I put 3.2oz Raka on a project I can give a customer some idea of how durable they can expect it to be. ... I used that as an example, but would like to see it for 4, 6, 7 oz as well. (I skipped 5 because I had bad luck with 5oz cloth that didn't wet clear and I steer away from it.)

Another test would be to take five or six different woods commonly used in kayak and wood board construction and weigh them before and after glassing. I know for certain that balsa soaks up more epoxy than mahogany. I have seen it first-hand when repairing a board. The balsa has a layer of resin-soaked wood going a few mils deep. The mahogany is just "coated" and not penetrated very deep at all. This one is really more of a curiosity, but we always say "Use wood 'x' because wood 'x' is lighter," but I've built using very hard, heavy woods, and gotten pretty lightweight end results. I believe part is the glassing schedule- for hard woods I can use lighter layup, but I also believe that the hardwoods don't absorb as much resin. I would like to do some tests on this.

Anyway, before I go lathering wood up with epoxy for no reason, are there any tests of this nature that any of you can link me to? Any scientific data for epoxy would be appreciated. I already have volumes of data on wood!

All the best, and sorry for constantly mentioning wood surfboards here, but both the kayak forum and the wood surfboard forum have a lot of talent and I am just being resourceful. The knowledge works the same for either application.

Malcolm