After what seemed like a straightforward exercise, I quickly ran into some difficulty getting the leaded edges rolled correctly. After carefully reading the instructions and doing some research, I bought two lengths of 3/4 inch steel pipe from Home Depot. I traced the cross section templates onto some cardboard, and rolled the top section. Everything went well on the right side, so I flipped the rudder over and did the left top section. Alignment was good, and I could easily cleco the three holes.
I moved to the middle section, and rolled the right hand side. In hindsight I made the mistake of using the short length of tube, which meant I couldn’t get the torque I needed to make the bend as cleanly as I needed. I didn’t fully realize the issue, so instead of fixing it, I moved to the bottom section on the same side and rolled that section. This made it harder to fix the middle section problem, due to interference, which I didn’t realize until later. I flipped the rudder over and rolled the middle section on the left side, but didn’t match the bend radius or location, and ended up with a gap between the two sides.
Squeezing hard, I could make it work, but there’s too much tension, and I’m concerned that the thin skins will crease at the edge of the spar, which is not good.
I stopped there, and decided I needed to experiment some more before proceeding.
Here’s the one bend side on the bottom section, which is not quite the right shape.
Using some string and the template, I marked out locations for the start and stop of the bottom section bend, and transferred it to a scrap of 0.016 aluminum (same as skins). Then, experimenting with where I place the pipe, I made some bends.
The bend on the right is close to the shape I need on the bottom section. This was made with the pipe about 1 inch from the edge of the skin. The bend I made in the bottom section on the rudder was done with the pipe almost flush with the edge of the skin, which is the bend on the left. It’s easy to see the difference between the bends on this test piece, and there is definitely going to be an alignment problem. A secondary issue is that the bottom section bend radius is larger than at the top. For the bottom section, I probably need a larger diameter pipe, perhaps 1 or 1.25 inch instead of the 3/4 I’m using.
I need to fix the middle section first. The primary issue is that the distance between the spar and the start of the bend radius is too large, on both sides, with the left side being worse than the right side. Since the left side overlaps with the right, I’m planning to fix the right side, then the left. Using a string, I’ll mark on the skin the locations I need the bend radius to start and finish. Then using my test piece, I’ll carefully place and tape the long pipe into position and torque. The edge may end up slightly over-bent, but shouldn’t be a problem. Then I’ll switch to the left side, and repeat. It will be harder since the bent right hand side, and the bent bottom sections will be in the way. Hopefully I’ll be able to get enough of a bend to make it work. Once the middle section is aligned, I’ll worry about the bottom section.
