Aluminum Overcast Update

aerovin · **Posted:** Sat Jan 29, 2022 9:38 am

I just posted information from an update I received from the EAA about the status of B-17G Aluminum Overcast (44-85740, N5017N). Not a whole lot of new information but it does provide an authoritative update.

https://www.aerovintage.com/home/blog/

Kyleb · **Posted:** Sat Jan 29, 2022 9:45 am

Interesting wing attach. I didn't realize there was a "middle" attachment point. It has been a long, long time since I took statics, but doesn't that middle attach point make the entire structure indeterminate, where it becomes extremely hard (impossible?) to know the load path?

Chuck Giese · **Posted:** Sat Jan 29, 2022 4:50 pm

Kyleb wrote:

Interesting wing attach. I didn't realize there was a "middle" attachment point. It has been a long, long time since I took statics, but doesn't that middle attach point make the entire structure indeterminate, where it becomes extremely hard (impossible?) to know the load path?

Almost 50 years removed from Statics and Dynamics classes, and I'm not sure that I understood it even then. I still haven't figured out in what plane it is trying to prevent shear. (Yeah, yeah, I know, B-17. Other definition of plane.)

All I know is that the shear web is not anywhere near as strong of a connection as the upper or lower. Smaller diameter single taper pin, relatively thin steel fittings riveted to 0.180" aluminum.

Cvairwerks · **Posted:** Sat Jan 29, 2022 5:41 pm

I'm wondering if the "D" connection was added to prevent some kind of twisting of the wing attachment frame. The plates are only .180" thick there, so it can't have a lot of load on it.

Kyleb · **Posted:** Sat Jan 29, 2022 5:52 pm

Cvairwerks wrote:

I'm wondering if the "D" connection was added to prevent some kind of twisting of the wing attachment frame. The plates are only .180" thick there, so it can't have a lot of load on it.

Another thought (not mine) was that it is there to prevent the shear web from buckling. You've effectively reduced the column height of the shear web by 50% at that point by attaching it to something to keep it from buckling fore or aft.

TimAPNY · **Posted:** Tue Feb 01, 2022 12:52 pm

"As we removed the wing, our teams noticed other things that would be best served by repairing them at the same time. Such is life with vintage aircraft. Thus, we put a plan together during the last few months of 2021 to take care of all the discrepancies at once during this project."

I own a 100 year old house, that is how I live my life as I repair things, my wife asks me how long it will take and I respond "depends on what we find".

Great updates!

Tim

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