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This is one of my favorite videos. The creator walk through epoxying fiberglass to a foam surfboard core.
In the video, the creator shows how they preparing the bottom surface so that the fiberglass can be wrapped from the top around to the bottom in a way that allows cleanly cutting the edge so you have a beautiful surface. Wrapping the fiberglass ensures the board yields a is very strong structure. The wrapped edge will distribute any stress around the edge. If one were to cut the fiberglass on the edge, the seam where the top and bottom edges meet would be very weak. If the fiberglass is rolled from the top to the bottom and then again from the bottom to the top, that double layer will make it even stronger.
When you are using fiberglass, if the epoxy is transparent or semi-transparent, the grain of the fiberglass strands will be visible. The creator takes time to make sure the fiberglass threads are aligned on the center of the board. This is really a professional touch.
When mixing, the creator notes, stir until you think you're done, then stir some more. Fully mixing your epoxy is critical!
In this video, the creator mixes color into the epoxy without a specific measurement. He mixes in a little bit of colorant, mixes it and then dabs it on some fiberglass to see if he likes the color. He does this a couple times and ends up with a color he's happy with.
When coating a surfboard, you are generally working with a quicker setting epoxy because you want it to start setting up when you wrap the fiberglass to the underside of the board. If it's not close to setting up when you do that, the epoxy will slowly peel away from the surface and you will not end up with a nice smooth wrap. What peels up will have to be sanded off, which reduces the strength of the wrap.
When coating a surface with fiberglass and epoxy, you really need to wet the underlying surface and the fiberglass. If either is not fully wetted, the fiberglass will not adhere to the surface and it will be a spot that would need to be reworked. Taking the time to get a really good finish will ensure that you end up with a beautiful board that doesn't require rework and doesn't suffer the imperfections from that rework.
While a perfect finish is what everyone wants, if you are making your first board, its not going to be perfect. It takes time to perfect the techniques for glassing a surfboard. Don't worry, if that first board requires some rework and ends up looking far from perfect, you're still going to absolutely love that board. Your second board will be much better!
Notice how this creator has everything out so that his focus is not distracted. He's got a bucket for cleaning his squeegee so that when he's pressing the lap against the bottom side, he can quickly clean it and get back to work. When the epoxy is starting to gel, you have to work quickly if you don't get everything done in time, you'll end up with something that will need to be fixed.
After finishing the top, but before the epoxy has fully hardened, he cuts the edge of the lap with a razor. Its very important to do this before the epoxy fully hardens. If done at the right time, its an easy operation and you'll get a beautiful edge. If its done too late, its going to be very difficult and you are likely going to end up with a terrible edge. Keeping a timer running that allows you to precisely time this operation will help enormously.