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Step 1 TRIMMING THE FOAM BLOCKS AND
CUTTING THE CORES |
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I started on Chapter 10 by
scanning the canard airfoil templates on my computer. I then printed
the scanned images on some regular printer paper. After checking that
the dimensions were exactly correct (no stretching or distortion had
occurred) I used spray adhesive to glue the printed templates to a scrap
piece of aircraft plywood. You can see the templates here glued to the
plywood and ready to be cut out. Where the plans called for mirror
images, or, left and right versions of a given template, I used my Photoshop
software to create a mirror image of the template with the counting numbers
on the opposite side. |
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I have some sanding belts for
my band saw that work great for this sort of work. After using the
band saw to cut close to the lines, I use the sanding belt to get the
template exactly to shape. It takes a while, but, it's pleasing work
with a stool next to the band saw to sit on. The sanding belt takes of
a very small amount of wood at one time so you can get right to the line. |
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Here are the templates all
sanded to size/shape and ready to be used for hot wiring. |
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I made a hot wire fixture out
of a 2x4 with some holes drilled in it and the edges routed. Turned
out pretty nice, but, I should have spent more time on the hot wire
tensioning. It was very hard to get good tension using this device
that stayed once the wire heated up. |
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After trying a couple of test
hot wire cuts with some cheap styrofoam (not expanded polystyrene!) from the
hardware store, I spoke with a fellow builder and he told me he'd used this
device. I am not sure who made it, but, it's AWESOME! They found
some kind of wire that doesn't stretch when heated, so, it maintains amazing
tension and makes pretty nice cuts. |
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Here's the power supply for the
hot wire device above. Not sure what's inside (does it matter?) but it
provided plenty of juice for hot wiring. The dimmer switch has a mark
on it that all the people who have used it have determined is the right
setting. |
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Here I am hot wiring. All
in all, the cores turned out pretty well. I only had to junk one,
because the nail moved (see the picture below). |
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My nephew Will helped me hot
wire. This frame was a little long for canard sections but should be
just the right length when it comes time to do wings. I think Will's
facial expression helps him do a better job on the hot wiring... |
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We used some scrap plywood for
straight cut templates. I made nail holes every inch in the boards, in
some cases I needed to drill additional holes because the foam we were hot
wiring was only slightly more than an inch thick. Also, two nails in
this sort of fixture had a tendency to try to move around. |
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Here we are using a straight
cut template to cut a canard section to width. |
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I don't think the picture shows
it well but the aft nail moved a bit on this core. This made the
fishtail part of the canard to thin and this core had to be rejected. |
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This one turned out better.
The nail didn't move and the fish tail is the right shape. |
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A nice shot of the top of one
of the sections after hot wiring to shape. |
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It was a little tricky to get
the trough for the spar cap layups hot wired. The aft section seemed
to be the place to put the weights (note the pieces of wood under them to
distribute the weight and avoid foam dings) to allow the trough to be cut
and the wire lifted out without disturbing any of the other cuts. |
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Once all the cuts were done I
taped the sections back together (with the waste foam protecting the canard
sections) and then, just for fun, stuck them together to get a sense for the
size of the thing. It's pretty big! |
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That completes Step 1 - on to Step 2! |
