Full Rib Lightening Hole

[Bucky]

Trying to finish up my ribs so I can get to building up the spars. I started to cut out the lightening holes on the full ribs that go on the outboard end of the wings. On the hole that corresponds to the aft lightening hole on the center ribs...should these be round holes or can they be oval like the rest of the .025 center ribs? The plans do not seem to specify but Newtons book seems to show that he did round holes at this location. Maybe I'm just being, but if it is not a big deal, I don't want to waste time building the flanging die for the round one for only two applications. Whats your thoughts??

[sjt]

I am working on a patrol. Are you referring to the location aft of the rear spar? For my full size ribs , I did not place any holes there. If you do, then weather will get into the wing tips. Just did not see any reason to do it.

patrol 284
austin tx

[Bucky]

It is the lightening hole just forward of the Aft Spar. Reading Eric Newtons manual, the holes are called for. Since it is .025 aluminum it adds strength once the hole is flanged. I get what you are saying about the holes aft of the aft spar allowing weather to get in, I had just planned on putting fabric patches over them.

[Gary Wallace]

i just cut my full ribs out with a router, and i went with the oval holes the same as the center 025 rib lightening hole.

[sjt]

As I recall, the oval hole is the worst case. On some of the inboard ribs there is a hole for the flap control tube. If it was not for the flap control tube they would all be round. That said, I do not think it matters.