Question about cabosil

[Emerger]

I replaced the transom in my project over the weekend and used cabosil for the first time to round the inside corners prior to glassing over it. It was the first time I ever used it and was impressed at how easy it is to use.

Is cabosil a good choice also for filling holes and fairing? If so or if not, does anyone know the limitations on using it, i.e., maximum thickness, surface area, etc? Thanks

 

[JB]

Re: Question about cabosil

CabOSil, or diatomaceous earth, makes an excellent thickener for resins, but it does not offer any added strength. Where there is a strain, use glass fibers.

I have cast external engine parts (reed plates and intake manifolds) from just Cabosil and polyester, but if the part needed any strength I used chopped glass and epoxy instead.

One caution: Cabosil particles, though very small, are also sharp and abrasive. Always wear a breathing mask when working with it.

 

[ondarvr]

Re: Question about cabosil

Cabosil is actually fumed silica, and like JB said, it has little or no strength. You can use it to fill small stuff, but polyester resin isn't very strong and is brittle, so if the area flexes it will crack easily. Since resin is hard it can be difficult to sand when compared to a sanding or fairing putty but works well for how you used it.

 

[Boomyal]

Re: Question about cabosil

Use 3M glass bubbles for your fairing compound. It is lighter and will sand easier. Use your cabosil for making adhesives.

http://www.uscomposites.com/fillers.html