Radius question

[jlfernan]

In the, "you learn something new everyday" dept, I did today. I just found out that to make a 1/8" radius requires a 1/4" hole(sometimes mathematically challenged). The reason I bring this up is to educate anyone else out there as dense as me and because that is not how I made the radius required for the F-7108B angle that attaches to the center, front cockpit structure rib which is bent and attached to the firewall. I made only a 1/8" hole with a drill before cutting the angle. It seemed to bend OK. Any reason to do it over?

[Bob Axsom]

"Take it as a lesson learned and move on" was my thinking when something like this came up and I knew there was no safety impact.

Bob Axsom.

[Kevin Horton]

Originally Posted by jlfernan

In the, "you learn something new everyday" dept, I did today. I just found out that to make a 1/8" radius requires a 1/4" hole(sometimes mathematically challenged). The reason I bring this up is to educate anyone else out there as dense as me and because that is not how I made the radius required for the F-7108B angle that attaches to the center, front cockpit structure rib which is bent and attached to the firewall. I made only a 1/8" hole with a drill before cutting the angle. It seemed to bend OK. Any reason to do it over?

The smaller radius you used may slightly increase the odds of a crack starting in service. I'm not familiar with the RV-7. What would be the consequences if that part failed due to a crack starting at that radius? How hard would it be to replace that part once the aircraft is in service, if it cracks?

[dan]

Jorge,

If you're really concerned about it, you could always expand the radius to the full 1/8". It looks like that wouldn't even come close to impacting edge distance to the nearest rivet.

On DWG 24 SECT A-A, it looks like that angle is intended to transmit loads from the slider canopy windshield bar (the one that goes down diagonally in the center) to the firewall. I'm no engineer, but it looks like that angle is only "working" when the plane is flipped over on its back...i.e. supporting the windshield bow.

Put it this way -- imho, enlarging the radius to spec and removing a tiny bit of material from the angle in doing so doesn't seem like it would do much harm. But on the flip side, angle stock is pretty cheap. If you'd sleep better at night knowing the part is 100% to spec, just make a new one!

[airguy]

Originally Posted by dan

it looks like that angle is only "working" when the plane is flipped over on its back...i.e. supporting the windshield bow.

That sounds like a fairly critical safety item - I wouldn't fly with a frayed seatbelt simply because it's only used during a crash, or a dead ELT because it's only used during a crash. Likewise with that angle - if its purpose is to protect my noggin when Plan A goes out the window, it's going to be correct. Angle stock is cheap.

[jlfernan]

I agree and made another this morning, correctly. It took all of 40 minutes(I'm a little anal) and now I feel better. Thanks to all!