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Step 11: Fiberglassing the Bottom

Glassing, fiberglassing, laminating, all three of these terms mean the same thing: applying a layer of fiberglass and epoxy resin to the surfboard. Since this is a wooden board, I could probably get away with just applying a sealer, varnish or epoxy directly on the wood and go surf it. I opted to fiberglass the board as it adds an incredible amount of strength and durability. The glassing takes place in two steps, first the bottom is fiberglass and then the board is flipped and the deck is glassed.

The fiberglass weight I will be using is 6 oz fiberglass cloth, that means for every square foot of fiberglass it weights 6 ozs. I probably could go as low as 4 oz cloth since this is a wooden board and inherently has strength unlike a foam surfboard.

Since the surfboard will be glassed in two stages (bottom and deck) there will be an overlap where the fiberglass meets. There are two ways in dealing with this overlap, with a free lap or cut lap. A free lap is where the fiberglass is left free and is laminated directly to the board and once set is sanded to feather it into the board. A cut is lap is where a layer of masking tape is layed down on the board and the fiberglass is laminated over the tape. Once the epoxy is set, using a sharp razor or hobby knife, the fiberglass over the tape line is cut and then the tape is pulled off and with it the fiberglass as well. This leaves a nice clean line that is easy to sand, my preferred method is to do a cut lap for all my surfboards. Finally the cutlap is sanded to feather into the rest of the board.

Glassing the Surfboard Bottom

I started by applying tape to the rail of the surfboard where I wanted my cut lap, then rolling out the fiberglass cloth onto the bottom of the surfboard, then cutting around the board leaving the fiberglass so it overlaps the tape but not so much that it hits the deck of the surfboard. Then I make relief cuts around the tail and the nose of the surfboard so there will be no creases when laminating. Keep the excess fiberglass scraps and cut them into pieces, these can be used to clean up excess epoxy later. I laid down some thick plastic sheet to the floor, this is to catch any epoxy during the glassing and hotcoating.

Next is to mix up the resin, the resin I use is epoxy resin, specifically Resin Research, an epoxy that is very clear unlike a lot of boat building resins. This entire process could be done with polyester resin as well but I like using epoxy because it is low VOC and is stronger than polyester resin. When working with epoxy you can either measure it by volume for weight it. My preferred method is weighting it as I think it is a much more accurate method and you don't need graduated measuring containers.

Tips:

  • Get a cheap digital kitchen scale and save yogurt or similar containers.
  • Read the epoxy manufacturers directions, it will give you direction on the mixing ratios.
  • Use only good quality masking tape.
  • Only work with epoxy resin when the temp is above 15C and the surfboard is at that temperature too. Or else the resin will be too viscous and hard to spread.

To determine how much total mixed epoxy resin you will need for glassing, depends on how big the board is, the shape of the board, the type of fiberglass and layers of fiberglass. As a general guideline, I found 80 grams of total mixed resin per linear foot of surfboard is a good starting point for a single layer of 6 oz fiberglass cloth.

Grab a pair of disposable gloves, put on a respirator (epoxy hardener does have some VOCs) and set aside a plastic spreader. Using a digital scale and weight out the epoxy resin, then add the proper amount of hardener. Using a flat mixing stick, mix the epoxy well, scraping the sides and bottom, but do not whip the mixture as that will add air bubbles into the epoxy.

Once the epoxy is mixed, pour the entire contents onto the board in a long stream along the length of the stringer. Using the plastic spreader move the epoxy around giving it time to soak into the fiberglass. Spread the epoxy all over the board but avoid the rails until the main part of the board is covered and transparent. Then move resin out to the rails and let it soak in, using your other hand hold the fiberglass and use the spreader to saturate the fiberglass. Go back to the main body of the board and start "scraping" out some of the resin, not so much that it leaves the fiberglass dry but no so much that the resin pools, you want to be able to slightly see the weave of the fiberglass.

After the rails of the fiberglass has time to soak in, it's time to wrap the rails starting from the middle of the board, take the plastic scraper and fold over the fiberglass onto the masking tape. If any strands of fiberglass become loose and fray from the edge, cut off the excess with a pair of scissors. Using fiberglass scraps wipe off the plastic spreader to get rid of any excess epoxy. Work around the main sections of the board then fold over the nose and tail relief cuts at the end. Look over the board to make sure that there are no loose areas of fiberglass, let it harden for a few hours.

Come back after a few hours, depending on the temperature will affect how quickly the epoxy sets up. You want the epoxy to be set up so that it is tack free, then cut the fiberglass around where the tape line is, then pull the tape and fiberglass off. Let the epoxy harden then sand the cut lap so it feathers into the surfboard, including the nose and tail relief cuts. The better the feather the better the glassing job will turn out. Also from now on only touch the surfboard with gloved hands, this is to avoid oils from your hand from contaminating the surface.