I know it's possible to blow a canopy bubble and I intended to do this
for a while. However, I found a source of canopies that makes this
effort mostly worthless. I bought it from Todd Canopies. Todd
is a very nice guy who makes canopies for various aircrafts. Not only does
he sell perfect canopies, but he is very easy to deal with (very
accommodating). His prices include crating. I ordered my
canopy at the same time a friend ordered five canopies for another type of
aircraft. That allowed me to share a crate and thus, save
significantly on the shipping cost. While Todd's prices are already
very competitive, he may make special deals for batches of canopies
ordered at the same time.
The following picture shows an optically perfect canopy with no
deformations. Please take note that the canopy is mis-positioned on
the fuselage (front should be the back) on the picture dated May 28th.
First thing we did (my wife's father was helping me for the canopy
installation) was to check the canopy for fit. I felt comfortable
sitting in the airplane with a pair of headset... GOOD!
Next, after centering the canopy, we marked its position on the
fuselage. A second positioning line may be noticed on some
pictures. This is because at one point, we decided to move the
canopy back a little bit. The purpose of the yellow tape pieces with
the alignment marks was to ensure exact positioning of the canopy each
time we moved it.
Fitting the tube frame with the canopy has been a simpler job than
expected. For minute adjustments, I used two pieces of
2"X4" with 3/4" holes drilled. I also used a heavy
gauge steel tube to straighten the first two inches of the tube so it fits
in the canopy arm rear tube.
This is the fit of the bubble with the rear canopy tube installed and
drilled. For a reason, I have a pretty large gap on the rear left
side of the canopy between the bubble and the fuselage. The right
side is just perfect. I thought of various ways to correct
this. One would be to cut the canopy and make a fiberglass frame
(suggestion of Todd). Another approach would be to split the canopy
and have the rear portion fixed on the fuselage. This would allow me
to correct this and to hide any defect. Gerald Kelley (see Other
Projects on this web site) has a split canopy. I also tried on a
scrap piece of acrylic to reform the material using a heat gun. Todd
and others are very nervous about using this method, but it worked well on
my test pieces. I'll check with a plastic expert before doing this
July 3rd update: I modified the shape of the rear
left portion of the canopy using a heat gun. I'm satisfied with the
result. You may notice the advanced acrylic forming tools being used.
:-) During the heating session, the heat gun was actually held
further from the acrylic in order to avoid concentrated hot spots.
To install the front tube frame, it is required that a
"volunteer" sits in the plane and hold the tube in place while
"I" drill it. I would have volunteered, but frankly, it's
pretty hot in there and I had a good excuse not to take that job... I want
to be the one risking my canopy when it is getting drilled. So, my
father in law took seat!
Next, we tried opening the canopy to see that everything goes well...
IT DOES NOT! The canopy cannot be raised to the specified 67 degree
opening angle because it pushes the cowling past 50-something
degrees. The maximum practical angle I can obtain is about 50
I modified a gas spring to see how the canopy is at a reduced
angle. For this, I just clamped the spring shaft in a lathe (which
has jaws that don't damage the shaft) and I tapped more threads.
Then, I cut 1-3/8" of the shaft. At that reduced length, the
canopy opens to 45 degrees, but the springs are nowhere strong enough to
hold the canopy open. I ordered two 80 lbs springs from McMaster to
replace the original ones (that are 40 lb springs).
I made a special tool for dimpling the 6-32 screw holes. I used a
screw from which I removed the threads (on a mini lathe). Then, I
drilled and countersunk a piece of 1/4" aluminum. The holes
need to be drilled to 7/64" and they come just fine for the 6-32
screws once dimpled.