Rib dimple micro cracking

[Induna]

Hi

My S2L was built in the 90’s. When i bought it recently I decided to completely refurbish the aircraft.

I opened the wings to do a thorough inspection and to check if the upgrade had been installed.

So, the top skins are riveted with solid rivets, while the bottom skins had pop rivets. What i found was that there are micro cracks around the dimpled holes of the ribs. My guess is that the holes wasn’t properly deburred when dimpled. Also, the solid rivets of the top skins wasn’t properly set, so i am working my way through the wings and resetting all the solid rivets of the skins to have the correct amount of deformation.

The question now: does this micro cracks have a major effect on the structural integrity of the wings or any other associated risks? If so it will basically mean i have to build new wings.

I thoroughly checked the main spar and it rivets and all are in good shape.

Regards

Jacques

 

[Elviar]

Jacques,

I haven't seen any response to your question, so I'll offer my thoughts on the subject. I'm not an expert in the field, but I am a retired research engineer with some experience with various aluminum alloys.

When you use the term "micro cracks" I assume you mean cracks that can be seen with magnification. Larger cracks that can be seen without magnification are generally referred to as "macro cracks." In any case, my experience tells me that once a crack is initiated it will continue to propagate, especially where cyclic loads are applied. In the case of your wing ribs, I would think that any attempt to install new rivets would apply an additional stress on the cracked area. Cracking of any type can also expose the aluminum to corrosion. I don't like being the bearer of bad news, but I would only feel comfortable if the cracked ribs were replaced. Others may have a different opinion, but you may want to check with a technical adviser before deciding a course of action. Forming new wing ribs may seem like a daunting challenge, but it can be a rewarding one and will certainly give you a sense of accomplishment in the end.

Best of luck with your project! You're a lot closer to a finished airplane than many of us who started building years ago!

Larry

 

[Induna]

Thanks Larry.

I have also been in contact with Fred and i elected to replace all the ribs.

I have disassembled the one wing completely and the other one will follow soon. I have also found some other issues that the original builder created and i now have the chance to make sure i have perfectly safe wings by rebuilding them.