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Re: Fiberglassing Techniques

Cash, Gene <CASH@...>
 

I read something ages ago saying that Rutan (RAF) clearly poo-pooed the
practice of sprinkling microballoons on wet lay-ups because it would tend to
pull up epoxy and starve the lower layers of needed adhesive. For the same
reason the practice of laying peel-ply over the entire wing surface lay-up
was nixed.

There doesn't seem to be an easy way out of the surface finish work.

Gene Cash

-----Original Message-----
From: David J. Gall [SMTP:David@...]
Sent: Wednesday, December 06, 2000 9:38 AM
To: Q-LIST@...
Subject: Re: [Q-LIST] Fiberglassing Techniques

Jon,

I must have missed this item. Did RAF ever endorse the hard-shell
procedure?
If not, did they ever renounce it? Either way, can you narrow down the
approximate year in either the CSA or RAF newsletter so I don't have to
dig
so deep?

On a related issue, I do recall the big debate over sprinkling micro on
the
surface of a still-wet layup to save on post-cure filling and sanding. Do
you have an opinion on that technique?

Thanks,


David J. Gall

----- Original Message -----
From: Jon Finley
To: Q-LIST@...
Sent: Wednesday, December 06, 2000 12:13 PM
Subject: RE: [Q-LIST] Fiberglassing Techniques


Oh yea, as I recall the weight penalty on large items (wings, winglets)
was
pretty small. Seems like the big items weighed a pound or two more when
hard shelled. Again, see CSA back issues for details/confirmation.

Jon
-----Original Message-----
From: Jon Finley [mailto:finley@...]
Sent: December 06, 2000 11:10 AM
To: Q-LIST@...
Subject: RE: [Q-LIST] Fiberglassing Techniques


I have seen layups use both techniques. The Q plans call for the micro
to
be wet (not dry) when you apply the glass. The EZ community has done a
lot
of experimentation with what they call "hard shelling." They cut the
cores,
sand them, apply micro, sand it, and then apply the glass. The idea is
that
the micro can be sanded to achieve a near perfect contour before
applying
the glass. It also results in an easy layup (generally) and is much,
much
easier to get all the air out. To be clear: I am not talking about
applying
micro to low spots in the core or repairing core damage. I am talking
about
applying a micro shell around the core before applying the glass.

I have always understood that the purpose of micro is to provide some
"bite"
into the foam (like little fingers going into the foam). The foam (if
properly prepared) is smooth and contoured already it just has lots of
little holes in it.

Yes, the quality of the bond was an issue. The conclusion was that the
glass to (dry) micro bond is a lot stronger than the micro to foam bond
is
so it is not a concern. This was tested by quite a few folks with
different
techniques but the result was always the same. Peeling the glass up
always
pulled the micro and bits of foam with it. You could reference CSA back
issues for details.

My personal conclusion (from reading and doing a hard shell layup) was
that
I would never do another wet micro layout as the "hard shell" layup is
so
much easier. I just glassed my replacement tail cone and didn't want to
have to hangar warm for several days (day or two for micro to cure and
then
another day or two for glass to cure) so I did a "traditional" (per Q
plans)
layup. I now remember exactly why I decided to use the hard shell
technique!

If you are a "follow the plans" guy, disregard everything I have said
and
FOLLOW THE PLANS!!
Jon Finley
Q1 N54JF - 1835cc VW
Q2 N90MG - Subaru EA-81 DD Turbo
Apple Valley, MN




-----Original Message-----
From: Chris McAtee [mailto:Subcanis@...]
Sent: December 06, 2000 8:44 AM
To: Q-LIST@...
Subject: Re: [Q-LIST] Questions questions


Dave-
Yes, you do need the to sand the micro before you add the glass. The
micro,
from what I understand, just makes the surface more true in reguards
to
smoothness and contour, resulting in less post-glass filling in.

Chris McAtee


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