: I have used both the glass and phenolic microballoons. They are intended
: primarily as a fairing filler, but I used the glass ones for my Guillemot
: endpours. I mixed 6 oz. of balloons (by volume!) with 3 oz. of epoxy and
: it was still flowable.

: I think if you added about 1 part glass balloons to 1 part wood flour and 1
: part epoxy, and then use cabosil to "thicken to taste", it would
: work well.

: Cabosil is one of the strongest fillers, by far, but it's also very heavy and
: hard to sand.

: Your best bet is to keep the fillets as small as possible. It's my
: understanding that they're mainly there to make a smooth (read: stronger)
: transition for the glass tape from the side panel to the bottom panel.

: You're glassing the inside (with at least tape) and the outside, so the
: strength of the fillet is much less of an issue.

: Yes, you can use some lightweight fillers, but keeping the fillet size down
: will be your most effective weight-saving tool.

: Shawn

Hi Shawn,
The Cabosil (silica thickener) I use is about a light as goose down. It is fluffy stuff, 2 ounces would fill a quart container. It makes a light fillet. The microballons I have (phenolic) are MUCH heavier than the silica thickener. Glass fibers are the heavy filler I have used.

Larry C.