Gelcoat

The layer of opaque resin on the outside of a composite kayak. Gelcoat gives the kayak its colour and protects the underlying composite layup from UV damage.

There are two types of gelcoat that you can buy.

• Unwaxed gelcoat is used for making things in a female mold. The gel coat is sprayed, rolled or brushed into the mold and then the composite layers (fabrics and resin) are added. The composite layers cover the gelcoat and it cures without contact with air. If you use unwaxed gelcoat to repair chip or crack in a kayak, the gelcoat must be covered with something to prevent contact with air or the gelcoat will not cure properly. A low-surface-energy plastic (polyethylene, polypropylene) can be spread over the surface to help the gelcoat cure. Household wrap (Saran Wrap or similar) will work, though a thicker plastic will be easier to work with. Release film is available at auto repair shops. You can also coat the surface with PVA mold release - available at shops that sell gelcoat.

• Waxed gelcoat is used to repair composites where the gelcoat is exposed to air while curing. The wax rises to the surface and prevents air from inhibiting the curing of the gelcoat.

Oxidation causes the surface of old gelcoat to become white and powdery looking. This can be removed with a polishing compound.

Gelcoat tints

Gelcoat can be coloured to achieve almost any colour. The tints come in little tubes and one drop goes a long way. Like paint, gelcoat comes in both neutral base and white base formulations. The final colour is dependent on which base is used. Consult the tint's colour chart to determine which base to use to achieve the colour you want.

Why use gelcoat?

That's a good question. Composite boats have been made with gelcoat for decades. While conventional, it is not necessarily the best solution. Gel coat is cheap, but it is not particularly strong. It contributes little to the kayak other than to protect the underlying resins from UV radiation. For the weight, replacing the gelcoat with a thin layer of fiberglass and tough paint would provide more strength and durability than gelcoat. The extra fiberglass would be quite abrasion resistant and the paint would be very easy to fix when scratched.

Some racing boats do not use gelcoat. Racing sculls can have a carbon fiber hull painted with an epoxy paint. As well, some sea kayak manufacturers now offer clear coat finishes on carbon fiber or Kevlar hulls.

How do you fix gelcoat?

See Gelcoat repair