WET LAYUP METHODS

When applying fiberglass or carbon fiber with laminating resins via wet layup, several techniques can be used depending upon the weight of your fabric. Fiberglass or carbon parts can also be made through the vacuum bagging process. We’ll describe best practices for applying fiberglass and carbon fiber based on your fabric weight.

Lightweight Fabrics

Lightweight (4 – 6 oz.) fiberglass cloth, popular in surfboard laminations, is easy to wet out from the top. It will become transparent when fully wet out with Entropy Resins epoxy.

  1. Prepare the surface as you would for bonding.
  2. Position the cloth over the surface and cut it several inches larger on all sides and let it drape over the edges of your core or substrate. When doing overlaps (or laps) make sure you have enough cloth to overlap the layers by approximately 2”.
  3. Mix the desired amount of epoxy using the appropriate dispensing, measuring, and mixing epoxy in Basic Instructions.
  4. Pour a small pool of epoxy near the center of the cloth. Use a plastic spreader at a low angle to spread the epoxy out to the edges. Reserve ¼ of the epoxy batch for laminating the edges.
  5. Spread the epoxy over the cloth surface with a plastic spreader at a low angle, working the epoxy gently from the pool into the dry areas. Properly wet-out fabric turns translucent and white areas indicate dry spots. If applying the cloth over a porous surface, be sure to leave enough epoxy to be absorbed by both the cloth and the surface below it.
  6. Although pressure should be applied to help the epoxy saturate the fiberglass, do not overwork the epoxy into the fiberglass. Overworking the epoxy will result in micro air bubbles suspended in the epoxy, which will turn it cloudy and potentially weaken the laminate. If you have to cut a pleat or notch in the cloth to lay it flat on a compound curve or corner, make the cut with a pair of sharp scissors and overlap the edges.
  7. Squeegee away excess epoxy before the first batch begins to gel. Slowly drag the spreader over the fabric at a low (almost flat) angle, using even-pressured, overlapping strokes. Use enough pressure to remove excess epoxy that would allow the cloth to float off the surface, but not enough pressure to create dry spots. Excess epoxy appears as a shiny area, while a properly wet-out surface appears evenly translucent, with a smooth, cloth texture. Later coats of epoxy will fill the weave of the cloth. Check for dry areas (especially over porous surfaces) and re-wet them with epoxy as necessary before proceeding to the next step.
  8. Trim overhanging fabric with a utility knife when the epoxy is still wet or at the gel stage. Or allow the epoxy to cure and sand it.
  9. See the Hot Coating section for how to fill the weave of the fabric once the epoxy used to wet out the fiberglass is gelled or cured.

 

Heavyweight Fabrics

Heavier weight fabrics (12 oz or more) are more difficult to wet out from one side. Best practice for wet layup of heavyweight fabrics is to apply epoxy to the surface first to ensure the fabric wets out on both sides.

  1. Prepare the surface for bonding. Pre-fit and trim the cloth to size. Roll the cloth neatly so you can conveniently roll it back into position later.
  2. Apply a coat of epoxy on the surface.
  3. Unroll the glass cloth over the wet epoxy and position it. Surface tension will hold most of the cloth in position. Work out wrinkles by lifting the edge of the cloth and smoothing from the center with your gloved hand or a plastic spreader.
  4. Apply a second coat of epoxy with a thin foam roller, plastic spreader, or stiff bristle brush to thoroughly wet out the cloth. A thin foam roller or a stiff bristle brush is best when applying epoxy to vertical surfaces. Smooth wrinkles and position the cloth as you work your way to the edges. Check for dry areas (especially over porous surfaces) and re-wet them with epoxy as necessary before proceeding to the next step.
  5. Remove the excess epoxy with a plastic spreader or stiff brush using long, overlapping strokes. The cloth should appear consistently translucent with a smooth cloth texture. Do not overwork the epoxy.
  6. Trim overhanging fabric with a utility knife when the epoxy is still wet or allow the epoxy to cure and sand it.

 

Dry Layup Method

This is a popular method for laminating surfboards.

  1. Prepare the surface as you would for bonding.
  2. Position the cloth over the surface and cut it several inches larger on all sides. If the surface area you are covering is larger than the cloth size, allow multiple pieces to overlap by approximately two inches. For non-surfboard applications that may have sloped or vertical surfaces, hold the cloth in place with masking or duct tape, or with staples.
  3. Mix a small quantity of epoxy 3 – 4 fluid ounces. Note: when applying fiberglass on a surfboard typically need 12 – 16 oz. of epoxy for 6’ shortboards for 2 layers of 4 oz. cloth and 22 – 28 oz. of epoxy for 9’ longboards for 2 layers of 4 oz. cloth.
  4. Pour a small pool of epoxy near the center of the cloth. Note: Pour ¾ of the epoxy batch down the center of the board over the fiberglass cloth. A plastic spreader could be used at a low angle to spread the epoxy out to the rail. The remaining ¼ cup of epoxy can be used to laminate the rails.
  5. Spread the epoxy over the cloth surface with a plastic spreader, working the epoxy gently from the pool into the dry areas. Use a foam roller or stiff bristle brush to wet out fabric on vertical surfaces in other applications. Properly wet out fabric is translucent. White areas indicate dry fabric. If you are applying the cloth over a porous surface, be sure to leave enough epoxy to be absorbed by both the cloth and the surface below it. The more you “work” the wet surface, the more micro air bubbles are placed in suspension in the epoxy. This is especially important if you plan to use a clear finish or no finish. You may use a thin foam roller or a stiff bristle brush to apply epoxy to horizontal as well as vertical surfaces. Smooth wrinkles and position the cloth as you work your way to the edges. Check for dry areas (especially over porous surfaces) and re-wet them with epoxy as necessary before proceeding to the next step. If you have to cut a pleat or notch in the cloth to lay it flat on a compound curve or corner, make the cut with a pair of sharp scissors and overlap the edges.
  6. Squeegee away excess epoxy before the first batch begins to gel. Slowly drag the spreader over the fabric at a low (almost flat) angle, using even-pressured, overlapping strokes. Use enough pressure to remove excess epoxy that would allow the cloth to float off the surface, but not enough pressure to create dry spots. Excess epoxy appears as a shiny area, while a properly wet-out surface appears evenly translucent, with a smooth, cloth texture. Later coats of epoxy will fill the weave of the cloth.
  7. Trim overhanging fabric with a utility knife when the epoxy is still wet or allow the epoxy to cure and sand it.
  8. See the Hot Coating Surfboards for details on how to fill the weave of the fabric once the epoxy used to wet out the fiberglass is gelled or cured.

 

Vacuum Bagging

The vacuum bagging process can follow either the wet or dry method of applying fiberglass, depending on the fabric weight. Vacuum bagging consolidates the part while the epoxy is curing and achieves a higher fiber weight ratio and therefore a stronger part. For more information on vacuum bagging, check out our vacuum bagging instructions.

Suggested Uses:

  • Laminating
  • Wet Layup
  • Vacuum Bagging
  • Coating
  • Applying Fiberglass

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