imusuallyuseless;3805640; said:
... basing it off of 80'Sq...
I'll stick with 80 sq. ft. and also use overkill for the film thickness.
For any resin system, you can coat 80 sq. ft. at 20 mils dry thickness with a gallon of resin, assuming a smooth surface. This also assumes the resin is 100% solids by volume so this does not apply to epoxy paints like Sweetwater.
Once you have a nice thick coat of cured resin is when you want to add a final layer of cloth for abrasion and impact resistance. You don't want to start applying cloth layers right to the plywood, at least for epoxy and probably not for vinyl ester and some of the higher end polyesters either. In fact at least two epoxy companies recommend fiberglass go on the OUTSIDE of the tank. I don't necessarily agree with this and think it's best in the final layers for the reasons you've already mentioned.
For each square foot of cloth (note cloth, not mat) it takes on ounce of resin per square foot of cloth multiplied by the ounce rating of the cloth. So one ounce cloth takes a fluid ounce of resin per square foot. Three ounce cloth takes three fluid ounces of resin per square foot of cloth.
So let's say you used 3 ounce cloth, which I tend to think would be sufficient for impact resistance, you would need 240 fluid ounces of resin to wet that cloth out. Or bit over two gallons in addition to the gallon you need to lay down your initial cloth-less coats.
Given that the 20 mil inital coat is overkill for epoxy and that 80 sq. ft. is an overestimate for your tank, I feel like 3 gallons of laminating epoxy would be a reasonable goal for your tank.
Please notice that it only takes a gallon of epoxy to get a sufficient waterproofing membrane but it then takes twice that much to wet out even a single layer of 3 ounce cloth. Given that some companies don't even recommend the cloth for plywood tanks I would encourage you to research carefully.
If you read AnythingFish's threads he only used a higher grade polyester and only applied cloth at the seams, not on the continuous runs of plywood. And his takes are massive.
I have had good luck with the tech people at West Systems although that was one company that had such good faith in their product that they recommended fiberglass go on the outside of the tank if it was even necessary. A company called US Composites has also been helpful so getting their take might be good.
One company I have not dealt with but have heard good things about is Raka. Likewise, the company that Buckdog used has a good reputation.
