What to do, what to do??
I'm about to start wing construction for my BD-4 using John Steere's wing building methods as found on the BD-4 website here: http://www.old.bd-4.org/wings_steere00.html
After forming and shrinking some practice ribs on some 032 5052 scrap (much easier to work than the heat treated alloys, I must say!), 2 issues have emerged about which the knowledge here at OK365 will be highly valued. Thanks in advance for ringing in.
The shrinker literally grabs the metal edge and compresses it together, leaving several marks per squeeze. Does this cause an acceptable amount of stress compared to fluting? Seems like fluting would cause less but I already have a shrinker and stretcher and am familiar with their use. I'm thinking the stretcher probably causes more stress by pulling the metal in the opposite direction but that is not what is needed for this operation fortunately.
For the real rib, I originally intended to use .025 2024 T3 but am now considering going to 6061 T6 for it's easier formability and greater resistance (I hope) to cracking from the shrinking operation. I've planned to use an .020 rib with .032 skin in the wet wing area which is the first 4 feet of the wing from the root as John Steere did; then changing to .025 ribs and skin both outward from there. I could save a bit of weight by using .025 skin on the whole wing but in the tank area, the skin is also the tank wall, thoughts on this?
Finally, given that the modulus of elasticity is about the same for different alloys, which alloy would offer the greatest resistance to hail denting? We've just had a BUNCH of cars at local car lots get peppered here in north TX and that's been on my mind too and I'm not sure whether denting would be more related to the tensile strength or modulus.
BTW, a .032 "scrap" rib weighs 9.2 oz if anyone cares! I haven't built any out of .025 or .020 yet.
Thought on these issues before I jump in??