How to Apply Fiberglass Cloth and Tape with WEST SYSTEM Epoxy

1. Surface preparation and dewaxing

Proper prep is the foundation of a durable laminate. Sand to a keyed surface (80–120 grit for composites), remove dust with a vacuum or tack cloth, and dewax any gelcoat or waxed surfaces with solvent as needed so epoxy bonds predictably. Cleanliness and dry surfaces reduce pinholes and voids, and a well-prepared substrate saves you sanding and rework later.

2. Choosing the dry vs wet method

Decide whether to use the dry (saturate after laying) or wet (pre-saturate then lay) method based on access and laminate size. The dry method gives you better control on complex contours and overheads; the wet method speeds large flat layups. Match the method to the job: small repairs and awkward shapes often favor dry, while big tables or panels commonly use wet for efficiency.

3. Mixing epoxy in small batches

Mix epoxy in batches sized to your working time and the temperature, WEST SYSTEM epoxy sets faster when warm. Accurately measure resin and hardener, mix thoroughly (scrape sides and bottom) to avoid uncured spots, and only mix what you can use within the pot life. Small batches reduce waste, prevent premature thickening, and make consistent wet-out easier.

4. Positioning and cutting cloth or tape

Cut cloth and tape oversized for overlaps and drape, and mark grain/directional weaves for strength-critical layups. For repairs, cut tapered overlaps to feather the laminate; for structural layers maintain constant width so load paths remain predictable. Lay pieces in sequence so you can smooth each panel without stepping on or disturbing earlier layers.

5. Pouring and spreading epoxy

Pour controlled amounts of mixed epoxy onto the work area and use a notched or flat spreader to push resin into the cloth uniformly. Work progressively across the cloth to avoid dry spots and keep a wet edge to prevent lapping lines. For large areas pour frequently in small ribbons rather than a single large puddle to keep resin flow manageable.

6. Wetting out with the wet method

With the wet method pre-coat the backing surface or pre-soak the cloth on a flat roller tray before laying; then transfer the saturated cloth onto the substrate. Use a plastic squeegee and a short-nap epoxy roller to consolidate and remove air as you lay the pre-wet cloth. This method speeds throughput and is useful for multi-layer panels where you want consistent resin distribution from the start.

7. Wetting out with the dry method

For the dry method lay the dry cloth or tape onto the substrate, then apply epoxy and work it through the fabric with spreaders and rollers until transparent and fully wetted. Start with a liberal pour but be ready to squeegee off excess; work slowly so resin penetrates the weave rather than puddling on the surface. The dry method lets you position and adjust fabric with minimal slip before committing to final epoxy distribution.

8. Squeegeeing excess and controlling cloth-resin ratio

Use a rigid squeegee to remove excess resin until the cloth looks uniformly translucent without globs, this helps hit the correct cloth-to-resin ratio. Excess resin not only adds weight but also increases runs and sag on vertical surfaces, while too little resin leaves dry fibers and weak panels. Aim for a sheen that shows even saturation but no puddles; remove runs quickly to prevent drip marks.

9. Trimming overlaps and timing

Trim overlaps and stray fibers after the laminate has reached initial cure (when it’s firm but not fully hard) to avoid tearing the still-flexible glass. Immediate wet trimming can smear resin and cause frayed edges, while trimming too late is harder and creates dust. Use a sharp razor or scissors timed to the epoxy’s initial set window for clean edges.

10. Filling the weave and fairing

After the first laminate cures, plan multiple finishing coats to fill the weave and fair the surface before painting or gelcoat. Apply thin epoxy or a WEST SYSTEM fairing mix in successive coats, sanding between coats to shape and remove pinholes, until you achieve a smooth substrate. Fairing early enough but not before full cure avoids trapping uncured resin or creating adhesion problems.

11. Vertical and overhead laminates

For vertical or overhead work take measures to control sag: use slightly thicker epoxy mixes, apply thinner, tighter layers of cloth, and remove runs immediately. The dry method and small batches help since you can saturate and squeegee in tight turns; also consider temporary taping or staples to hold cloth in place during wet-out. Use rollers with short nap and fast consolidation to prevent pooling and drips.

12. Final surface finishing and paint/gelcoat prep

Once your laminates are fully cured and faired, sand through sequential grits to remove high spots and feather edges before applying primers, paint, or gelcoat. Clean the final surface with solvent to remove sanding residue, and apply recommended barrier coats if you’ll gelcoat or paint over epoxy. Multiple finishing coats are usually required to fully fill weave and produce a paint-ready surface, plan time and material for them.