I laminated some 8" x 24" XPS foam test pannels a while back. As a hack, the best I could do with 6 oz E-glass was 2.25 oz epoxy (resin + hardener "volume") per square foot of XPS. As a hack, I suspect I would need more for PU and EPS. For a 7-6 board, my number is very close to the high recommendation on the Greenlight Chart.
Brian said his Greenlight Chart is for units of weight in oz. Resin Research and Green Room epoxies can be mixed by volume, 100:50 (2:1) -- 100 oz resin by volume = 110 oz by weight; 50 oz hardener by volume = 49 oz by weight; 150 oz by vol of resin + hardener = 159 oz by weight. Multiply (mixed) weight recommendation by 0.94 to get mixed "volume" of resin needed (150/159 = 0.94.)
My assumption for "estimating" surface area to laminate one side of a surfboard is that the surfboard is an ellipse that is 6" wider and 6" longer than the actual surfboard. Surface area of an ellipse is 1/2 width x 1/2 length x 3.1416 (pi).
Bottom line, John Mellor's method and/or the GreenLight chart are a good place to start. For a hack like me, I go with the highest recommendation plus a few extra oz.
John Mellor at Swaylocks.com:
"In the past, I used to recommend that people start their calculations with: The length of the board, the weight of the cloth, and the number of layers.
Do the math and figure out the total weight of the cloth being used and multiply that by 1.5. That should give you a ballpark estimate on how much total resin to use.
A 9 foot board will need about 3 yards of cloth. If the cloth is 6 oz fabric and you're doing a double layer for the deck, the weight of the uncut cloth will be 36 ounces... less after you cut it to fit the outline. Sooo... 36 X 1.5 = 54 ounces of mixed resin. The Greenlight chart says 36 - 50 ounces of resin for the same glass schedule. Close enough.
That's just my recommendation for a 9 footer, double 6 deck lamination and allows for some waste. A beginner using MEKP catalyzed resin will likely find himself 'flooding' the board and squeegeeing off a lot of excess in an effort to save time. If you're using UV catalyzed or epoxy resin, you will have more time and can get by with using resin more sparingly. Epoxy is more expensive so there is definitely an argument for wasting as little as possible. With epoxy blends of slow/normal cure times, a beginner has the luxury of not having to hurry like with MEKP catalyzed polyester."
