Brian,
Your work looks excellent. Within the next year I
am going to
have to build a complete cowl from scratch and as
yet know nothing
about glass work, mold making, weave to use,
layers to use, etc. So
any small tidbits of info on what you did would
help. I save
everything pertaining to glass layups but, so far,
most want to show
off their excellent work but not reveal how they
did it. Also, I
would like to know the general dimensions and
weight of the completed
cowl if possible.
Thank you,
Randy
Thank you. I'm art work until monday, so I'll get you
the weight of the
cowl at that time. The cowl is 44 inches from firewall
to spinner. I
wrapped the engine in a couple of rolls of saran wrap,
then rolled some
screen material over that to hold the two part foam
that I slathered
over the engine. Here's a tip- bulk out the whole thing
by putting
newspapers or hunks of styrofoam around the engine to
get it near the
size of what you want the plug to be.(The foam isn't
too cheap, and
there's no advantage to useing lots of it.) Then wrap
the whole thing in
saran wrap & screen. after you get the foam slathered
on and it expands
and hardens(you'll have to do it in small batches and
keep filling until
you get enough size) then you can sculpt it down to
close to where you
want it.
I used a surfoam tool and 50 grit sandpaper glued to a
piece
of 1/4" plywood. I then got a bucket of drywall
compound and coated the
whole thing and then sanded it down to a very smooth
finish. You'll have
to sand and add drywall compound a few times. You want
a nice smooth
contour. I checked the contour from side to side with a
template cut
from cardboard. I then painted two or three coats of
ordinary latex
paint onto the the plug and then waxed it. I had a
problem with the
resin making some of the foam underneath shrink a bit,
so I had to fill
in with some more dry wall compound. In retrospect, I
think that I
shouild have had a much thicker coat of drywall
compound, it remains
stable when in contact with the polyester resin., and
It's way cheaper
than the expanding foam. If you have layer of drywall
compound that was
1/2 inch thick, I think that you would avoid any
stability problems.
When you have the plug the way you want it, wax it and
lay up from 4-5
layers of plain weave 5.8 oz cloth. Your probably
better off laying no
more than two layers at a time. I had no problem laying
whole sheets
over the top part of the cowl, but found it much easier
to use smaller
pieces around 1 foot square. After you have all your
layups done, you
can fill low spots with resin mixed with microballons,
sand and repeat
until you have the finish that you can paint. I used a
2 x4 kerfed so
it would bend and clamped it on the side of the cowl to
use as a guide
to cut the cowl off. It made nice straight cuts using
a die grinder
with a 3" wheel. Lots of gentle, loving prying was
required to remove
the cowl from the plug, with a lot of the plug
remaining stuck to the
cowl. I borrowed my neighbor's pressure washer and
cleaned that crap off.
One tip- I have a flange riveted to my firewall that
the cowl fastens to
with piano hinges. Before you cut off your cowl. drill
a couple of
holes though the cowl into whatever you are mounting it
to so you have
reference points, and can cleco the cowl to the
airplane. Also, drill
and cleco a few pieces of aluminum sheet between the
top and bottom
halves of the cowl to use as a reference.
The forward bulkhead was cut out of 1/2" hexcell and
bonded in.
I'm sure that this whole procedure raises a lot of
questions, feel free
to contact me if you think I can be of assistance.
bktrub@aol.com <mailto:bktrub@aol.com>
For ease of parting, consider spray application of
P.V.A. (polyvinyl alcohol) to plug prior to laying
glass. It's water soluble and cheap. Available from
Fiberglass Coatings in St. Petersburg, Fl.
Will James
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