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After 4 coats of paste wax are applied and buffed out, a
structure is created that will create a flange on the lines where the top
and bottom molds meet. We are making the cowling in two parts for
several reasons: first, the shape is wider at the nose than at the
firewall. There would be no way to remove it if it were one piece.
Second, once it were on the airplane, we would have to take the propeller
off each time we wanted to remove the and that would be problematic.
Third, it will be easier to lay up the fiberglass in an two open molds than
in a one deep hollow mold. Last, we want to be able to quickly remove
the top for maintenance or to check the engine and it should be an easy
thing to do. |
| The advantage to composite construction (fiberglass and
resin) is that one can construct multiple parts of complex shapes with
minimal skill. Rolling this shape out of aluminum on an English Wheel,
welding, and finishing it would result in a lighter piece. But that
would require an expert level of skill in several different disciplines.
These abilities would be wonderful to develop but are currently beyond the
scope of our project. |
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Here's the mold laid over the plug. The raised lines are reinforcing
ribs that help the mold keep the correct shape and not flatten out.
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| Here we're pulling the clay off to reveal the flange build
into the mold.
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Disaster. Well, a little one. The mold stuck on
the plug. When we tried to pull it off, it stuck.
Part of the problem was the oil cooler air intake was a bit 'undercut' and
didn't want to release. We cut the section out and pulled it off
separately. The mold still wouldn't come off! That's when we
found we had missed a spot with the wax or PVA. 6 coats of wax and
there was still a spot that we had missed. Part of the plug came up
with the mold. We will be able to clean up the mold and make a good
cowling part but it won't be quite as effortless as we had hoped. |
| The top part of the plug came apart as we got the mold off.
This looks bad but isn't really a disaster. We don't need the plug,
just the mold. As soon as we are done all of the plug
will be broken off and thrown away anyway. |
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Here the guys are holding the top cowling mold. It is
perfectly useable and will create a fine top cowling piece. The part around the oil cooler intake
will be reattached. |
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We tried to smooth the bottom of the plug with the airplane right-side-up
but it just wasn't worth all the dust we got in our faces. With a
hoist, three mentors, and five students, we raised and rotated the
airframe, and set it gently on some timbers. In this position we
will shape, smooth, wax, and mold the bottom of the cowling.
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