Surfboard Glassing: How to Apply Fiberglass & Resin

When you think of building a surfboard, many people just think about the shaping of it – planers, rasps, and sanding blocks mowing foam.

But, one of the most important parts of the build process is often overlooked – glassing & sanding.

You can shape a perfect surfboard from a foam blank, but without a proper glassing and sanding, it’ll be no good.

This is also where you’ll need to determine your final step and whether you’ll stop with a sanded finish or a gloss finish.

Fiberglassing a Surfboard

Glassing a surfboard is the step that waterproofs and finishes the board. Fiberglass, resin, and any tints, color, and art are added to provide the board with strength, rigidity, and its overall style.

The glassing step influences a board’s final weight as well as resistance to dings and abuse.

For many surfboards – its overall production is handled by a number of people. Someone shapes the blanks and then it goes to the glasser for glassing and sanding. But, if you’re making your own boards, you can glass and sand the surfboard yourself.

Basic materials needed for glassing and sanding a surfboard:

  • Fiberglass Cloth
  • Resin
  • Mixing Cups
  • Mixing sticks
  • Scale (if measuring resin/hardener by weight).
  • Scissors
  • Squeegee/Resin Spreader
  • Masking Tape
  • Chip Brushes
  • Power sander
  • Hard, Medium, and Fine Grit Sanding Pads

You’ll also want proper safety equipment including:

  • Gloves.
  • Eye protection.
  • Respirator mask, if necessary.

Glassing Schedules

The first step in glassing your surfboard is to determine the glassing schedule.

A glass schedule refers to how many layers and what weights of fiberglass cloth will be used on the top and bottom of your surfboard.

Fiberglass rolls for surfboards is typically available in 4oz and 6oz. Some common glassing schedules include:

  • 2 layers of 4oz on the top, 1 layer of 4oz on the bottom
  • 2 layers of 4 oz on the top, 1 layer of 6oz on the bottom
  • 1 layer of 4 oz and 1 layer of 6 oz on top, 1 layer 6 oz on bottom
  • 2 layers of 6 oz on top, 1 layer of 6oz on bottom

Lighter glass schedules are typically used on shortboards, while heavier glass schedules are used for heavier board (longboards, retro shapes, etc.).

The more glass on a board, the heavier and the stronger it will be.

You may also see glassing schedules that use partial layers on the top or bottom. These are extra layers of glass used in areas that have to stand up to the most abuse – fin box, tail area, etc.

Measuring & Mixing Your Resin

Another important step in the glassing process is making sure to accurately measure your resin.

There are two main reason you need to accurately measure your resin.

First, you need to make sure you have enough resin to complete the job you’re doing. That means enough to saturate the full weave across the length of the board during the laminating stage, and enough to complete a nice even hot coat.

You’ll use a little more resin during the laminating stage than you will during the hot coat.

You do not want to have to scramble to mix more resin and hardener mid-way through a lamination.

Next, you’ll need to make sure that you’ve got the right resin to hardener ratio – many epoxy systems work in a 2:1 ratio by volume or a 2.2:1 ratio by weight. Measuring by weight typically gives you a little more accuracy.

If your ratios are not correct, the resin will not cure properly, and will cause problems when you try to sand it.

After you’ve measured accurately, you need to make sure to mix the resin and hardener thoroughly as well. And improperly mixed resin can lead to the same situation as an improperly measured resin. Be sure to mix the entire mixture fully so that it will cure. Scrape the sides and bottom of your mixing cup and stir steadily for a least 1 minute to get everything.

How to Glass a Surfboard

Glassing a surfboard is not necessarily difficult, but it is certainly a step that’s prone to errors if you’re not careful in your preparation.

The best way to do a good job on your first few times is to make sure you’ve got all the tools and materials you need, mix enough resin, and move smoothly and cleanly.

How to glass your surfboard:

  • Start with the bottom, and roll out the fiberglass cloth.
  • Cut evenly around the glass so it can wrap the rails.
  • Cut a notch near the nose and tail or any other hard corners where the cloth will need to wrap – this prevents wrinkles.
  • Mix your resin – adding any tints or color pigments you plan to use.
  • Start by pouring resin around the center of the board and following it around the board towards the rails with your spreader.
  • At the rails, saturate the overhanging cloth and wrap it around. You can spread any pooled resin from the center of the board if necessary.
  • Finish tucking the rails all the way around and try to clean up any stray threads or wrinkles.
  • Check the board for any air bubbles or wrinkles – fix if necessary.
    • With Epoxy, you’ll have more time to fix mistakes, once polyester resin kicks, you won’t really be able to fix anything.
  • Allow the bottom to cure.
  • Once the glass is hard, you can flip the board, clean up the laps with a medium grit sanding pad – being careful not to sand into any foam.
  • Repeat the process on the top.
  • Start with the heavier weight cloth first.
  • Mix a little more resin than you did for the bottom since you’ll be using more glass.
  • Allow the top to cure.
  • Clean up any laps, bumps, and imperfections.
  • Remove dust and debris with air, denatured alcohol, and a clean rag.
  • Glass on fins and leash loop at this stage.
  • Get ready for the hot coat.

Laminating Resin vs. Sanding Resin

For best results laminating resin is often used during the lamination stage (described above) and sanding resin is often used during the hot coat stage (described below).

Depending on the brand or type of resin you’re using, you may be able to purchase your laminating/sanding resin pre-mixed or you can mix it at home.

Laminating resin is used to saturate the fiberglass weave and adhere it to the foam core.

Sanding resin has an additive mixed it with it to make it easier to sand. The sanding resin, or hot coat, is designed to fill in any remaining gaps left by the lamination phase. This coat is then sanded smooth without sanding into the fiberglass layer.

Surfboard Hot Coat

The hot coat proceeds pretty similarly to the laminating layers, but should be a bit easier.

The purpose of the hot coat is to fill in any remaining gaps and bumps in the fiberglass weave. This prevents any water from seeping into the cloth overtime and gives you a nice smooth finish.

To hot coat your surfboard:

  • Start with the top and use masking tape to tape around the rails – starting about midway on the rail.
  • Mix your resin.
  • Start by pouring the resin down the middle of the board and pushing it with your chip brush.
  • Continue towards the rails.
  • Follow the rails at the tape line with your brush.
  • The key is to work quickly so that there’s an even layer of resin that can level itself out over the board.
  • Remove the tape before the resin cures completely.
  • Allow the top hot coat to fully cure.
  • Flip the board, tape the rails, and repeat for the bottom.

Epoxy Fish Eyes

Fish eyes, bubbles, and imperfections in the cured epoxy hot coat can be a common problem for those who don’t have much experience working with resin.

Eliminating epoxy fish eyes comes down to prep and execution.

First, you’ll want to make sure your entire workspace is clean, free of dust, and has low air flow to prevent any particles from disrupting the cure. You’ll also want to be sure your work area and resin mixture is of a constant temperature.

Next, you’ll want to wipe down your cured lamination coat with a lint-free cloth and some Denatured Alcohol to remove any dust and oil that remain.

It can be a good idea to wipe down and clean any mixing cups, squeegees/brushes, mixing sticks, and gloves you’ll be working with as well.

Avoid over-brushing or over-working your hot coat. After you apply it, allow it to flow naturally without being disturbed and walk away.

If you notice some problem areas, you can try to pour on a little more resin. Avoid brushing over fish-eyes as this can often make things worse.

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