At 02:31 PM 3/16/2017, you wrote:
Years ago - about 1970 - Harry Schneider laid up a sheet of GRP on a
base of Vorgelat. The cured sheet was nailed up on the Eastern wall
of the workshop after it had been divided into three sections. One
remained in the original Vorgelat gel-coat and the other two were
covered respectively with a coat of white and red acrylic lacquer.
The Vorgelat surface began to fail after a short time while that
covered by the lacquer showed no deterioration until we removed
small areas of lacquer then failure occurred as it had on the
original surface. Harry also laid up another small sheet, half of
which was on Glasflugel's original epoxy gel- coat and the rest on
Schwabelac. After more than 20 yrs. neither surface showed sign of
cracking though the epoxy gel did display surface chalking which
could be restored to its original gloss with a cut and polish. That
surface did have a finite life and eventually needed a coat of paint
when the primary structure began to appear as a light shade of grey.
Rudi Lindner realised this issue early on after being involved in
the design and
Thanks for that Noel.
As we discussed about 30 years ago IIRC, acrylic lacquer is not a bad
paint for composite gliders. Waterproof, easy to use, very light
weight compared to gelcoat or two pack paints, much less toxic than
urethane to spray and seems to adequately protect underlying
structure and even vorgelat. Very easy to patch and repair and if
your glider looks a bit tired after ten years a good wet sand with
280 or 320 and a very light respray and it looks like new. Not as
hard as gelcoat or urethane but pretty good. My Mini Nimbus wings
were done in acrylic laquer after the re-profile. Didn't have any
trouble with it. Light weight means your control surfaces weigh less
and need less mass balance. If worried about UV do the Rutan thing
recommended to Varieze and Longeze builder and use a black primer
undercoat before spraying the topcoat.
I have a document here that was written by a bloke who was one of the
early developers of polyester resins. Vorgelat type resins are low
quality, cheap ortho resins and designed to be painted over for
finishing. You need the highest quality isopthallic resins if you
want to use them facing the environment.
Mike
Borgelt Instruments - design & manufacture of quality soaring
instrumentation since 1978
www.borgeltinstruments.com
tel: 07 4635 5784 overseas: int+61-7-4635 5784
mob: 042835 5784 : int+61-42835 5784
P O Box 4607, Toowoomba East, QLD 4350, Australia
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