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I have been using Superfil on composite aircraft paint jobs for a couple of
years and am pleased with the product. However, it is NOT a substitute for
epoxy/micro for large contouring/filling applications. I'll use Superfil
for filling the weave on glass structures or as a skim coat for final
blocking, never more than 1/8" thick. It is not for use on leading edges,
corners, door frames or other areas that receive a lot of abuse. These
areas need epoxy/micro, epoxy/flox or even a layer of glass in some
instances. Superfil is as light-but not lighter-than a thick epoxy/micro
mixture and is slower to harden than Jeffco, so what is gained in
substituting it for resin? A general rule is; substitute Superfil for
Bondo-not micro.

Regarding the ability of fillers/topcoats to withstand the abrasion
generated by the speeds of IV's, it all starts with inadequate quality
topcoats. I have used PPG urethane and polyurethane base/clear systems on
several IV's with good results. A few years ago I saw a Lancair 320 that
had been painted with Dupont Centari that, at 20-25 hours, the pilot
encountered light rain and the leading edges of the wings and horizontal
stab suffered erosion damage. There was no damage to the epoxy/micro used
as filler however. These areas were refinished using a higher quality
clearcoat and have since held up fine.

Brad Simmons
Airframes Inc.
btsim1@iswt.com