Gelcoat crazing repair cracked#
The technical note goes on to say that cracked gelcoat must be removed entirely and a new surface finish applied. There is a Schleicher Technical Note which states that from a structural standpoint, cracking of the gelcoat down into the matrix (epoxy) is not detrimental, but the unknown effects of exposing the fiber to moisture and ultraviolet is to be avoided. The cracking will continue to grow down to the structure or actually grow into the epoxy matrix. If you don't remove the micro cracks they will grow into deep cracks. There are a limited number of times you can sand and polish, eventually you will wear through.
The process will be slowed, but the newly exposed surface will also break down. If at first signs of micro cracking, the deteriorated surface is removed by sanding and polishing carefully. These cracks quite often align with the factory sanding lines running chord wise on the wings and along the longitudinal axis of the fuselage. This is because the deterioration is accelerated on the surface as it is exposed to air, moisture and ultraviolet light. The stress first shows itself as micro cracking on the surface.
This process leads to stresses in the gelcoat. Polyester continues to shrink and harden as it ages. Keeping the surface sealed with wax and carefully removing any oxidation on the surface helps prolong its life but eventually they all break down. For various reasons, some breakdown faster than others however, they all deteriorate. The polyester gelcoat on your glider deteriorates with time. Our technicians at XU Aviation are experts at refinishing gliders in gelcoat and if only an area needs to be refinished (because of a repair) we’re good at blending the edges of the new gelcoat into the original finish. Gelcoat has some advantages over polyurethane paint (link to article) but does deteriorate over time. Until recently, composite gliders were almost always finished with polyester gelcoat.
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