Spar flange bend radius

[Frank]

My spar flange bend radius is a little too large (main and rear spars).
This affects the inside dimensions of the spar components.
I want the cap strip center-to-center distance to match the plans.
(and maintain the option of buying factory parts, if I need to)
This means I need to reclaim 1/8 inch inside the spar (1/16 each cap strip).
I proposed a solution to Bob by email and he approved it.

[NSLaw]

Thanks frank for sharing this. Ironically I’ve just been thinking about this issue recently as I’ve been working on my flap spars. I bent them and their bend radius is bigger then the plans, which reduces the attach angle height, and to some extent the front part of the trailing flap ribs ability to snug up into the flange of the flap spar.

I was able to round the corners enough where I felt comfortable with the amount of material left to make the slightly bigger bend radius work.

I’ve been thinking about bending main and rear spares for the wings later this month and how to find the right balance between the radius being unacceptably small, or too large. I know the plans call for .10 R. Need to perhaps sharpen my hold down piece on my break slightly to get a snugger R.

Thanks again for sharing your solution.

[Frank]

I ground the bending edge of my Dave's brake to .10 radius. Small test pieces to get the proper dimensions (fit to ribs) bend very easily and look great. But an eight foot piece of .032 is very different: there is a great deal of resistance. I had to over-bend quite a bit more than the ten degrees I was expecting. No doubt a heavy commercial brake would do a better job of maintaining the radius.

[NSLaw]

Agreed - I’ve considered trying to find a local shop and giving them the dimensions and blanks.

[sjt]

shoe.jpgshoe3.jpg
I found some steel strapping material that I bent up in various length shoes.
If the shoe made a small radius I added another 2024 strip to make a shoe over the shoe.

I found this video helpful:

https://www.youtube.com/watch?v=h9fxo95D4Ik

Also lots of test strips and I brought the mylar template
coupons.jpg

I wanted the green steel shoes in various lengths for different brakes.


p.s.
Do not forget to bend the false spar behind the gas tank:
false.jpg