: What situation demands cabosil instead of sawdust for thickening? Thanks

The fiberglassing materials and techniques we use were not originally designed for making wood boats. originally they were meant for making objects of resin (probably polyester resin) and glass fibers in either mat, woven, roven or chopped varieties. I suspect the use of cabosil as a thickening and reinforcing material descended into our realm from its use in fiberglas construction techniques that did not involve any wood at all.

We use a wood core for our construction methods, and sanding that wood gives us plenty of wood dust which can serve as a thickener instead of cabosil.
Pity those poor folk who make solid fiberglas boats and don't have the choice of materials that we do. Lucky us.

PGJ