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Re: REFLECTOR: Re: FW: COZY: Loud Pop???

At 07:26 PM 9/16/98 -0500, Ron Needham wrote:
>What Is hard shelling Prior to glassing?

Hard shelling is a process in which you apply microballoon slurry to the
foam surface, let it cure, sand it and then lay up the glass on the "shell"
so formed rather than on the foam directly. The "hard shell" prevents runny
epoxy from seeping into the foam.

Before I started on my plane, when hard shelling was being discussed, as
part of my glassing training I did a trial run on a piece of foam half with
hard shelling and half straight on the foam. After cure, the glass on the
hard shelled portion peeled off easily while the glass on the foam would
not come out without tearing out a layer of foam. Either the hard shelling
micro was dry as Alan suggested or the shell was not sanded properly after
cure or the dust after sanding was not cleaned off properly. Whatever the
reason, it convinced me not to hard shell my wings at all because there was
a potential to screw up. 

I did do something that people had recommended which was to slurry the foam
and wait an hour or two until the slurry gelled but was still tacky before
applying the glass. The theory is that the slurry has gelled enough to not
let epoxy pass through thus accomplishing the same purpose. Besides, the
tacky slurry holds the cross fibers more firmly than a runny slurry and
will not distort the cloth as much when you toil away pulling the fibers at
the ends.

As no one seems to build their own wings anymore, the above may be seem as
an archaic step that only us old-timers will reminisce about.

Velocity 173 Classic being built one glass fiber at a time.