Cotton Pox - Micro-Balloons
Model III and IV Owners - Serial #1143 Thru Serial #1420
Denney Aerocraft Company
should have received recently our Service Bulletin #7, which dealt with
cotton fox and fiberglass micro balloons. This letter is a follow-up.
3M technical representative we contacted said there should be no
difference in bond adhesion or strength of the 3M #2216 Structural Epoxy
whether cotton fox or micro balloons are used as “thickening” agent,
or whether any other inert agent is used, or no stiffening agent at all.
He did say that the epoxy with micro balloons may be less elastic when
conducted tests here at the factory which basically substantiated his
conclusions. The peel strength and tensile strength of the two
substances proved almost identical. The shear strength of the epoxy with
micro balloons was a bit less than that with cotton flox. The tests were
conducted on samples that had cured for about one week. We did mix the
micro balloons at a very high ratio, and it was slow to cure, appearing
more rubbery than the cotton fox mix for the first few days. It may take
a little longer to fully cure than straight epoxy or the cotton fox mix.
The structural epoxy with micro balloons is acceptable for use in
the construction of the Kitfox™.