Re: cotton flock as thickening agent
My local fiberglass guy was showing me cotton flock as an alternative to cabosil as a thickening agent. Much less nasty dust to deal with. Anyone have experience using it in boats?
It seems to me the job would dictate the type of filler you select.
Fumed silica (Cabosil) is a non-crystalline silica, the material that comprises sand, only the processing leaves it bumpy and lumpy rather than crystal like smooth sided for greater surface area and hold with the resin.
Mix resin with cabosil and it not only thickens, but it hardens. So if your gap fill or gusset needs a hard/strong resin mix I'd think this or something similar would be the choice.
The other strengthening filler is chopped or milled fibers, usually glass.
Between the two you could compare them to adding aggregate stone or rebar to concrete as strengthening agents.
The other type fillers bulk up the resin so it's not runny, but their other effect is to modify hardness. These include talc, plastic or glass micro-bubbles, wood flour, wheat flour, and I guess cotton flocking.
Resin fluffed up by these fillers would fill gaps and be easier to sand, but though strong by their own accord would not be the same sort of hard strong the first batch of fillers would be.
If you are fairing or wood crack filling, cotton flocking might work ok, but if you are setting a new transom it could be a little wimpy.
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