Sender: <marv@lancaironline.net> (Marvin Kaye)
To: lml@lancaironline.net
Date: Thu, 13 Nov 2003 16:20:42 -0500
Message-ID: <redirect-2730685@logan.com>
Reply-To: "Dan Schaefer" <dfs155@earthlink.net>
From: "Dan Schaefer" <dfs155@earthlink.net>
Subject:  Re: Closing Surfaces With Epoxy/Flox Vs. Hysol?
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FWIW:

My early (pre-Hysol) 235 (kit No. 52, started in about '86, if memory
serves) had the aft bond lines of the control surfaces closed out with
epoxy/flox and after flying for over 10 years, shows no distress. Skins to
spars, the wing fuel bay close-outs (bottom panels) and fuselage overlaps
were bonded with an epoxy-based two-part structural adhesive (3-M 3310 or
3316, again if memory serves) that remains very slightly resilient to this
day.

Pull (shear loading) and peel tests of the adhesive on various coupon sizes
and overlaps resulted in failure of the parent material rather than the bond
lines. Pull tests on the parts bonded with epoxy/flox were also satisfactory
while peel tests were as expected - bonds failed at substantially lower
loads relative to their shear properties.

During construction, bond load paths were considered and all critical (IMHO,
at least) bonds were made with the appropriate material, i.e., in most other
shear load paths, I used either material depending on ease of construction
while all peel loads were bonded with the 3-M product. (I say "ease of
construction" because the 3-M stuff was definitely non-thixotropic and
potentially could run out of a non surface-to-surface bond area, like the
elevator or flap aft edge close-out, before it started to set-up).

Dan Schaefer
N235SP