Netters,
A couple of topics:
1. Varnish. The only place varnish should be used in modern aircraft
building is over epoxy sealed wood that is going to be left natural
("bright" in boatbuilder's terminolgy) and will be exposed to sunlight. The
varnish protects the clear epoxy from ultraviolet light. Every other place
where varnish was formerly used should instead be protected with epoxy. The
epoxy is a much better sealer and allows parts to be epoxy glued after sealing.
2. Vinylester resins. These resins are "prepromoted" at the time of
purchase and then are cured with MEKP when used. The problem is that the
promoted resins have a short shelf life, after which they will not cure no
matter how much MEKP you use. Mike Bundy, the guy that does the tooling and
production runs for the certified stuff I produce, tells me that VE resins
are prepromoted with cobalt drier and that additional cobalt can be added
to "past date" VE resins. He didn't have any ratio figures, but says that a
couple of experimental samples should give the correct numbers.
Regards,
Tracy O'Brien
www.tracyobrien.com
