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<< Lancair Builders' Mail List >>
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Recent comments pointing to layups for the most significant weight
saving are right on the mark. Good factory layups (vacuum bagged, pre-preg,
etc.) come in with resin weight at, typically, 45% or less of the total,
sometimes as low as 35%. What's needed is just enough to fill the weave and
not a milligram more. Builders' layups typically have anywhere from 50% to
as much as 80% resin by weight. I would guess that something like 50 to 100
pounds can easily be added to any airframe by resin-rich layups.
Interestingly, the folks with the new twinjet kit have it designed so that
no layups are done by the builder. Their stated reason is that that is the
only way they can get the builders to come in at anything like the design
weight.
I apply my roller pretty vigorously to my plastic sandwiches after
wetting, then use peel-ply on everything, even flox pads. I've also got a
big junk box of various soft foam pieces, and often add a layer of thin
plastic sheet over the peel-ply, a piece of foam, and then a clamp or
sandbag, depending on the configuration. This helps squeeze more resin out
during cure. (Sort of a poor man's vacuum bag.) I tried adding a paper
towel layer outside the peel-ply, but it wicked too much out, resulting in
dry layups with lots of voids.
Just for fun, next time you do a 6- or 8-ply layup, make some extra.
Cut out a square after cure, sand off any excess resin bumps on the outside,
weigh it, and then weigh a piece of cloth the same size. With a little
arithmetic, you can calculate what your resin weight is in the final layups.
Jim Cameron, ES builder
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LML website: http://www.olsusa.com/Users/Mkaye/maillist.html
LML Builders' Bookstore: http://www.buildersbooks.com/lancair
Please send your photos and drawings to marvkaye@olsusa.com.
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