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Why do my rivets suck?

s10sakota

s10sakota

Well Known Member
I am so frustrated right now I'd like to beat this airplane with a sledge hammer!!

I'm trying to rivet the seat pan ribs and baggage compartment ribs to the aft spar. I can't figure out why my rivets are folding over.

In one hole, the rivet cracked and broke right as I started squeezing it. They are very difficult to drill out because the head is on the inside of a rib. I drilled it out, put another rivet in, and it folded over. Drilled that rivet out, made such a mess of the hole, that I had to put a bolt in it.

Now I have two others that folded over and I have to figure out how to drill them out without messing up the holes.

Here's one...



Same one...



And look at this one-it's folded and maybe cracked.



I am squeezing these with a high quality squeezer. I'm trying to keep everything square and the squeezer 90 degrees to the surface.

So why are these dang rivets folding? I'm using the proper rivets per the plans, and they don't appear to be too long. Should I use shorter ones anyway?

What am I doing wrong??? Why does no one else have any of these issues? Every blog I read they all say "riveted the ribs in. Pretty easy...no problems, etc..." :mad:
 
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When the head bends over and the rivet is the correct length that simply means the squeezer wasn't straight.

If I use a very long yoke on my Tatco I notice it bends and can cause this, especially on -4 rivets.
 
I'd get out the 3x gun and tungsten bucking bar and see how it goes the old fashioned way.
 
Those rivets are a real challenge to set right. I ended up drilling out about a dozen of them, and even that is a challenge because of the angles involved. I ended up having to use an electric drill and a 12" bit to get them out. I finally got everything together, in good shape and done to standards, but I will be the first to admit it's not my finest looking work and there may have been some judicious use of profanity involved at some point.

I had no luck at all with a squeezer, had to set them with a gun & bucking bar. And of course the gun was a challenge (as you well know by now) because of the tight quarters. I believe I used a double-offset for most of them, taped to the gun, and it took some contortion.

It might help to get an experienced riveting partner. Especially helpful would be someone who has built an RV before and knows what you're up against.
 
I'm thinking of just wrapping everything really good with duct tape. That should work, right?

Seriously, thanks for the replies. I think I'll just wait now until I can sucker a riveting partner here to help.

(the ones I did drill out, I did use a 12" bit. But naturally, the bit wandered because of the angles involved and drilled the head completely off center...)
 
Idea

I am heading to the same place in a few days.
I know the manual says to start at the 704 bulkhead but...
Is there any reason why these can't be set before the seat ribs are set to the 704 aft bulkhead?
That would allow both ribs to flex out of the way a little.
 
Is it a pneumatic squeezer? Make sure you're not just smashing them if it is. Feather the trigger just enough to where it closes on the rivet, then Depress the trigger until it sets the rivet. Adjust air pressure as needed and make sure you're using the right size dies.
 
Rivet length

Working from the first photo, the top rivet looks a little long. Double check to make sure you have the correct length. Could just be the angle of the photo but it they are too long it is much easier to bend the rivet. It the distance needed is less than the call out, cut the longer rivet down. Or order some half sizes like 426-3-4.5

Sometimes a pneumatic squeezer yoke will fit well enough to get over the rivet, but when you squeeze the rivet the yoke will hang up on a flange. This will change the angle of the set just enough to damage the rivet.

There is enough difficulty getting an offset rivet gun on these you might want to get a bucking partner. That way you can concentrate on keeping the rivet gun over the head while someone else manages the tail. It lowers the frustration level a lot. My wife is a much better riveter than I am.

Also on over sized holes there are larger rivets than 426-4. If you have edge distance for an AN-3 bolt you have edge distance for an 426-5 rivet so you might consider those. I struggled with those ribs as well. I was glad when I finished that work.
 
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Shorter Rivets...

I used shorter rivets. It does not take much of a shop head to hold a rivet in there. Plenty strong. Should not have to fight it or stand on one foot to squish a rivet, IMO. If you are worried about small-ish shop heads, you can do a test on some scrap material. Rivet 2 scrap pieces together with various shop head sizes then rip em apart and see what happens. I've seen relatively small rivet shop heads on a 747 wing spar. Drilling out a less-than-perfect rivet is prolly worse than leaving it there.
 
Rosie & Tuppergal sitting around the pool in St. Lucia, waiting for Sharkbait/Crystal to show up so we can leave for St. Kitts.

I showed Tuppergal the rivet picture, and she has bucked MANY A RIVET. Her response (as were my thoughts) were "It's not pretty but I'd leave it alone". If it REALLY bothers you, put two more in; one on either side. Remember that it's always just FINE to add MORE! Rosie & Tuppergal
 
Same advice

+1 for Scott advice!

Sometimes a pneumatic squeezer yoke will fit well enough to get over the rivet, but when you squeeze the rivet the yoke will hang up on a flange. This will change the angle of the set just enough to damage the rivet.
 
Rosie said:
Remember that it's always just FINE to add MORE! Rosie & Tuppergal
Click to expand...

I don't mean to argue with you Rosie, but perhaps to clarify that your statement is generally true only when minimum edge distance and spacing requirements are satisfied.
 
I find myself using a rivet cutter to start the shop head with a shorter rivet. Its not so important to start with 1.5 diameter tall before setting, as it is to have a nice square shop head that is 1.5 dia wide and 0.5 dia tall. You can achieve this with a slightly short rivet to begin with.

Also, the gun and bucking bar seems to give me more control than a squeezer. You can also start the drive lightly, then pull the gun and bar to see how the start is going and adjust your bucking bar position to fight the impending fold before it goes too far.
 
Oh, one more suggestion. I had problems with the rib flanges wanting to lift a little off of the bulkhead when I drove the rivets. I got perfect rivets that I still had to drill out because there was a gap between the flange and bulkhead. THAT sucked.

I found some lawn mower fuel line, or windshield washer hose, whatever in my garage. Black rubber hose. I cut a chunk just about the length of the rivet tails and used that when bucking the rivets. It holds the rib flange tight against the bulkhead while driving them. It's a hint I saw here first.
 
I don't think the cracking in the rivets is normal. I had a whole bunch of rivets crack like that (10 in a row). I ordered new rivets, problem fixed. Maybe the problem is rivet quality.
I had purchased the rivets initially from Aircraft Spruce. I called them and told them about the problem and they overnighted me new rivets and requested that I send all the old ones back. Turned out the rivets were too "hard." I'm not a metallurgist so I wasn't sure what that meant. I do know that I didn't have a problem with the new rivets.
 
Thanks for all the replies. The task is complete and it certainly is a PITA.

I did start using slightly shorter rivets with fantastic results. There's probably a couple of rivets that aren't perfect, but like someone mentioned, sometimes having a less that perfect (but acceptable) rivet is far better than the mess it creates by trying to drill it out.

The rivet that was cracked was removed. That I couldn't live with! Moving on...
 
Just a short response,
I had to use a rivet cutter several times as the rivets that were called to be used were in fact too long. Getting the right length sometime only resulted in a shave off the rivets length but it did make a huge difference. As was stated earlier if I ran into a problem of a bent rivet I would end up using the old fashion method of a gun and bucking bar..it always worked the best.

Smilin' Jack
 
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