Weight control
To build a light airplane you have to control the weight of every part. 100 lbs
over target weight is not much more than 10 %. 10% wet on the layups, 10% wide
on the bid tapes, a few more instruments, 10% more paint. and that's easy!
That's how the extra weight creeps in.
One way to end up with a heavy layup is to do it on a cold day. The extra
viscocity of the resin makes it hard to squeegee the excess out and also reduces
the capability of the resin to wet out glass.
Big layups like wings have to be done hot and fast. It's no good working slowly
because the layup will start to cure before you are finished.
My technique is as follows. First micro slurry the foam, using the micro as dry
as you can manage. Squeegee off as much of the micro as possible, It's only
purpose is to fill the pores of the resin. Next lay the cloth in place, you will
be able to move it about because the micro is dry, (not cured). Then pour on the
pure epoxy, moving it about quickly but lightly with a large rubber squeegee to
get the whole of the cloth covered with resin. The resin will soak into the
cloth without effort. Then go back and add more resin where needed and squeegee
out the excess. As the resin is pushed through the glass from centre to edge it
drives the air out in front of it.
Graham
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