Thu May 13 2010

Canopy frame work

This morning I fabricated this F-732D angle. Simple stuff...just cut it to length, clamp it in the vise and pound it down with a mallet to achieve the required 88 degrees. Note that I've located and drilled the first of four holes which will mount it to the canopy frame (temporarily drilled #40). The bracket was then clecoed to the aft doubler plate and the other three holes were transfer drilled.

When fabricating the heavy brackets on the outside of the canopy frame, the plans show that some of the vertical flange must be filed / sanded away to allow for the curvature of the skin. I decided to make a template to simplify transferring the correct curvature to the angles. Here's a template to transfer the plan-view curvature (made from a scrap of 0.025).

...and here's a template for transferring front-view curvature. This is pretty close to 90 degrees, but not quite. Now that I think about it, I wonder if it's supposed to be 90 degrees. I'll have to do some more investigation. The skin is quite flexible, so it could certainly accomodate the angle being 90 degrees at the canopy frame.

Next, I decided to get to work on the F-631C angle brackets. These are made of 3/16 thick aluminum angle.

When I was still working at ATS, I revovered a piece of angle from the scrap bin which had 3/16 thick flanges, but the flanges were longer. You can see the material with the longer flanges underneath the piece supplied by Vans. I'm going to use the material with the longer flanges to fabricate these brackets because I don't like having the top edge of the completed bracket show the flange radius from the stock material. Once I'm all done, the top edge of the brackets will be nice and square.

After transferring the angle from the skin (rather than using the dimensions in the plans), I did a bit of trigonometry to determine how wide the angled flange is supposed to be. Turns out it's exactly 1 17/64 inch wide.

After a few hours, I had these two brackets completed, but when I set them side by side to take this photo noticed that the angles weren't square (notice the gap). Also notice that I chose to radius the upper corners. I did this because I believe the plexiglass for both the main canopy and the rear window will need to be notched to fit around these brackets. Instead of having a sharp corner notch, I thought a radiused notch would be less prone to cracking.

A bit of tweaking in the vise had them nice and square.