The gel coat is applied to the surface which was coated with a release agent before. Edges and breakthroughs should be pre-coated thinly at the beginning. So air entrapments can be avoided. After the surface is dry to the touch (i.e., no build-up on the finger or threads are pulled), the second layer of gel coat is applied. Two layers of gel coat are recommended for you to achieve a higher layer thickness. This is very important in subsequent work, such as grinding or polishing.
For a good bonding of the gel coat and sufficient potlife for secondary treatment, apply a thin layer (max. 1 mm) of coupling paste on partly gelled but sticky surface.
Ramming a back body
A general purpose resin is enriched with granular fillers such as aluminum grit to a ramming mass. This is stamped in several layers onto the coupling layer. Through the stamping, the material condenses to a compact mass, which has a high compressive strength when cured and can generate a good price-performance structure depending on the filler.
Laminating a back body
From fiberglass fabric and resin a laminate is built. The laminate should be made symmetrical and with as little resin as possible. Instead of using fabrics, you can also work with laminate paste here. The stiffening of the laminate layer is carried out by a frame construction.