Side Skin Conical Bends - Mixed Results...
After spending the late morning and early afternoon assisting my AI with the annual inspection of my 170, I spent a few hours finishing the conical bends in the forward side skins. I had formed the bend in the left side skin earlier in the week, but got a crack so I quit until I could get an answer back from Vans on whether the skin was usable. Tech support said the crack, after being stop drilled, is not a structural issue so I'm going to press on.
Fitting up the left side skin, I found the first iteration of the bend a bit flat at the beginning and end, and a bit sharp in the middle as compared to the aft skin. After removing the skin and taking a guess as to what the final bend should be, it literally fit like a glove.
Not really pleased with the method George Orndorff demonstrates in his video the left skin, I tried the method described in Van's instructions on the right skin. Instead of using an aluminum angle I used a piece of the 1x1x1/8 steel angle I used to keep the trailing edge of the rudder straight. I used a 3/32 drill rather than a #40 to keep the holes as small as possible, as I had heard of at least one builder that had the clecos pull through. Well, when I started the bend, the forward half of the clecos unzipped so loudly, I thought I had torn the corner completely off the skin.
Fortunately, the noise was just the clecos pulling through the steel angle, and there was no damage at all to the skin. After I re-clecoed and added clamps, the bend went pretty much to plan. To finish up, I did have to remove the forward cleco and clamp to eliminate their interference with the clamping plate.
Even though the aft end of the bend on the right skin looked slightly uneven, it fit the aft curve fairly well and pulled in easily as it was clecoed.
I did have a crack in the forward end of this bend as well, although a bit shorter than the one on the left side. I'm thinking about adding an AN470-4 rivet to nowhere on each side just so the holes look like they're supposed to be there...
If I were doing this again, I would radius the edge of clamping plate, and drill the relief hole out to #30 and deburr it well before starting the bend.