Filler-Coating
Filling the weave and creating a sandable surface
Overview
The filler coat (also called the hot coat) is a thin layer of resin that fills the texture of the fiberglass weave and gives you a smooth, sandable surface.
Detailed Steps
1
Mix resin with surfacing agent
Add wax solution so the surface cures tack-free.
2
Brush on evenly
Apply a thin, even coat across the entire surface.
3
Watch for runs
Keep an eye on drips and smooth them before they set.
4
Let it cure
Full cure before sanding — patience is key.
Technical Specs
Coat thicknessThin — just enough to fill the weave
Surfacing agentStyrene wax solution (for polyester)
Cure time2 to 4 hours at room temperature
Expert Tips
“Thinner is better. A thick filler coat just means more sanding.”
“Work in long, even strokes from nose to tail.”
“Temperature matters — too cold and it won't cure; too hot and it goes off too fast.”