Sun May 9 2010

Working on canopy frame

Well I spent a good part of yesterday cleaning and organizing, so no progress was made on the plane. Today I got back to work on the canopy frame. The aft two canopy frame channel halves need to have a 1 1/2 inch hole cut in them to allow access to the nuts which hold the canopy frame on. When the location was marked, I could see that the tooling hole was going to be very close to where the fly cutter pilot hole needed to go. I had drilled the pilot hole up to #10 at the time of this photo, but the fly cutter pilot is 6mm, so it's going to be close.

Well, although the pilot hole actually did break into the tooling hole, it came out allright.

In order to have a consistent spacing for the rivets around the outside and inside of the canopy frame, I made a drilling jig from a piecd of scrap square corner angle.

I marked out the hole locations around the inside of the curve and started drilling. The jig was working great.

When I was about halfway around the inside of the first curve, I had a nagging feeling I was forgetting something, so I stopped, rechecked the plans, and found this. The bottom most hole is supposed to be 2 1/32 from the end of hte part...

...but using the 1 1/2 hole spacing I had laid out resulted in only about 1 7/8 inch from the end of the part to the first fastener. After studying the plans some more, I decided to stick with the 1 1/2 hole spacing. The mounting bracket that attaches in this area is only 1 1/2 inch high, so my 1 7/8 spacing should be fine.

With the holes drilled in the aft left and right canopy frame segments, I marked a line 1/4 inch from each edge all the way along each edge of the strip and clamped up the center strip. The line was to allow me to see through the pilot holes and determin if the strip was correctly positioned.

Here's the center strip after being match drilled to the aft half of the canopy frame. This took quite a while since I had to remove the center strip several times to clear chips out. Once it was all drilled, I marked the ends and trimmed the excess materrial off. Getting the strip positioned correctly took a lot of clamping, pushing, and pounding with the dead blow mallet. Not an easy job at all.

The fit of the outer strip was even worse. I eneded up having to use a bunch of C-clamps to hold the strip tight to the flanges of the curved sections. I wasn't especially careful about scratches or dents on the outer flanges of since the outer surfaces are going to be buried under about 1/8 inch of Sikaflex adhesive eventually anyway.

After both strips were drilled to the aft half of the canopy frame, I decided to square up the flanges of the curved sections. I had not done this previously because I squaring flanges usually turns parts into a potatochip. This was no exception. Although not terribly bad, these curved sections no longer lay flat on the bench. The good news is that with the flanges squared, the strips fit much better. I'm not sure if I should square the flanges on the other sections before or after drilling to the strip. I'll figure that out tomorrow.