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Bad blind rivet - forgotten

skelrad

Well Known Member
Friend
Half way through riveting on the rear spar of my horizontal stabilizer, it hit me. I had forgotten to drill out and replace one of the blind rivets for the middle main rib and front spar connection. I even had it written down on my "to do" list! I didn't get one of the three blind rivets seated well against the rib flange/spar when it popped, so there was a small gap under the head, which according to the manual fits under the "replace" category. I had to get more rivets, so couldn't do it right away and wrote it down in the plans so I wouldn't forget. Then I forgot.

So my options are to drill out a bunch of rivets to remove the rear spar and take it all apart so I can access that one rivet again, or just leave it since it's unlikely one blind rivet that isn't seated is going to break anything given the number of other rivets holding that main rib in place to the two spars and skin. I will disassemble the rear spar if necessary, but I'm afraid I'll damage more than help. Forge ahead or drill out a ton of rivets to get access?
 
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I'm an engineer, mechanical and worked for Boeing as a stress engineer (doing structural analysis and supporting certification and manufacturing. I signed off drawings for new airplanes and came up with repairs for aircraft in production when mistakes were made. You'd be surprised how production could damage new planes.

I can't comment on you situation because I don't know what rivet you are talking about. You talk of drilling rivets out?

"inboard main rib and front spar connection."
It has been awhile since I built my Stab, but you don't have access to the rivet?

You talk of drilling out how many rivets? Which ones?
You are correct drilling out many rivets risks worse damage.

You installed a blind rivet? Why? Is that per drawing? What kind of blind rivet and what defect, a gap under head. How big of a gap.

So don't take this as approval but one blind rivet (per drawing) with a gap under manufacturers head is not going to appreciatively change the strength if all other rivets are sound.Can you say all other rivets are within specs?

The gap under rivet head is undesirable but it is filling hole and will take some shear load. In tension blinds are not great with no gap, even if seated. With a gap it is more likely to get loose, but may stay tight and effective. Can't say with info provided.

Is it where you can inspect it?

Is it in a row of rivets? How many? Is it an end rivet or middle rivet.

Please provide more information, photos of location and defect, marked up building drawing with location of rivet indicated.
 
Sleeping Dog ... let it lie

My opinion tho, you gotta sleep at night!

I just dug out an inspection mirror and took another look at it through one of the small lightening holes in the rear spar. I'm a perfectionist, but after looking at it again, you're probably right. It's nowhere near bad enough to justify ripping things apart to get to it. It's not as bad as I remember. Not ideal, but with what that rivet needs to do, I can't see it ever contributing to a problem.

Funny how bad things always look at first. After a break, not so bad.
 
"inboard main rib and front spar connection."
It has been awhile since I built my Stab, but you don't have access to the rivet?

You talk of drilling out how many rivets? Which ones?
You are correct drilling out many rivets risks worse damage.

You installed a blind rivet? Why? Is that per drawing? What kind of blind rivet and what defect, a gap under head. How big of a gap.

So don't take this as approval but one blind rivet (per drawing) with a gap under manufacturers head is not going to appreciatively change the strength if all other rivets are sound.Can you say all other rivets are within specs?

The gap under rivet head is undesirable but it is filling hole and will take some shear load. In tension blinds are not great with no gap, even if seated. With a gap it is more likely to get loose, but may stay tight and effective. Can't say with info provided.

Is it where you can inspect it?

Is it in a row of rivets? How many? Is it an end rivet or middle rivet.

Please provide more information, photos of location and defect, marked up building drawing with location of rivet indicated.

Thanks for thinking this through with me George. These are blind rivets per the plans. There are three blind rivets that connect the middle main rib to the front spar (the rib that has a nose rib associated with it, and given the order Van's has you assemble, can't install a solid rivet since the nose rib and front spar are already in place). The bad rivet is an end rivet. There's no way to access it after the rear spar is on, but I did take a look with a mirror. I'd say it's a 1/16" gap under the head (probably less really) - not sticking up into nowhere, but not seated against the material. I can definitely say that all other rivets holding the main rib to the front spar, skin and to the rear spar are to spec. I'm a bit anal in that regard, which is why this one bugged me to forget.
 

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wrote it down in the plans so I wouldn't forget. Then I forgot.

I used a Sharpie to write notes like that directly on the aluminum of the work as needed. You won't miss it that way, and it wipes off with a rag and acetone. I didn't paint my plane until after first flight, and the bare fuselage made an excellent blackboard for various notes and lists, especially while doing the wiring.
 
I used a Sharpie to write notes like that directly on the aluminum of the work as needed. You won't miss it that way, and it wipes off with a rag and acetone. I didn't paint my plane until after first flight, and the bare fuselage made an excellent blackboard for various notes and lists, especially while doing the wiring.

Great suggestion. I will give that a shot.
 
Leave it alone...just my opinion

These wonderful airplanes are well-designed and somewhat over-engineered for amateur builders. Depending on the model, there are 10-20K rivets. If one slightly "not perfect" rivet causes it to fall from the sky, I'm a dead man........
 
These wonderful airplanes are well-designed and somewhat over-engineered for amateur builders. Depending on the model, there are 10-20K rivets. If one slightly "not perfect" rivet causes it to fall from the sky, I'm a dead man........

You are of course correct. This airplane is going to do wonders for my life long issue with perfectionism! :D This was more a moment of disbelief of how I forgot something that was written down for the express purpose of not forgetting. As I thought about the actual "issue," I realized exactly what you're saying.
 
Thanks for thinking this through with me George. These are blind rivets per the plans. There are three blind rivets that connect the middle main rib to the front spar (the rib that has a nose rib associated with it, and given the order Van's has you assemble, can't install a solid rivet since the nose rib and front spar are already in place). The bad rivet is an end rivet. There's no way to access it after the rar spar is on, but I did take a look with a mirror. I'd say it's a 1/16" gap under the head (probably less really) - not sticking up into nowhere, but not seated against the material. I can definitely say that all other rivets holding the main rib to the front spar, skin and to the rear spar are to spec. I'm a bit anal in that regard, which is why this one bugged me to forget.
So it is all skinned and you have no access.... Hummm.

Leave it. If you had some access you could drill out that one blind and re-set a new blind. That's not an option now. it's skinned. To drill out many rivets will likely cause more details that are less than perfect. One rivet of three and the one is set with a small head gap.... Don't worry. Drive on.

If you want to be super anal about it when you do you condition inspections gain access with mirror or remote bore scope and look at it. If you can push on it with a probe to see if its loose even better. I am guessing after doing this for a few years, you will stop because it will be firm and set. I doubt it will get loose. You have 2 good ones and one good but gapped.
 
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