FlyBoy8

FlyBoy8

Active Member
My first attempt at the rivet shown on the top of this pic resulted in a nice smile on the universal head, and the rib flange was not tight against the spar (looked like the rivet below the top one) bit I think the rib flange and spar were tight right around the rivet area itself.

I drilled out the top rivet (should have left it).

The rivet hole after drilling out the rivet was slightly enlarged but I thought it would be OK.

But, the result after riveting again was worse than the first one as can be seen in this pic. I can see the rivet shaft between the rib flange and spar.

I'm pretty frustrated, questioning my ability to build a structurally sound airplane, and wondering how to fix this and prevent similar issues in the future with ribs and spars.

IMG_1657.jpg


This is a view from the other side. Its hard to see but there is a small gap between the rib and spar at the top.

IMG_1658.jpg
 
When you buck a river, the first couple of hits swell the rivet to fill the hole, then the shop head sets. If you have a gap that you can't close otherwise, you can hit it a couple of times to swell the river, then put the bucking bar on the skin and hit the rivet head gently to close the gap, then back to bucking. Ideally, you want to find a way to hold the gap closed from the start. If you are seeing River shaft between the parts, it needs to be removed and replaced. The strength will be much lower that way.
 
One trick is to glue the right size O ring to the bucking bar, so it pushes the pieces together before you drive the rivet.
 
There are things called "oops rivets". They have the same size head but a fatter body. ACS has them and probably the other suppliers do to.

What you need to do is get some scrap material and rivet a bunch of times until you get the feeling on how to use the squeezer or hammer correctly. Practice is what you need and buying some cheap sheet aluminum and angle pieces at HD will give you something to try without having to order new parts.

If you can't find the oops rivets, let me know and I will send you a few.
 
Thanks Jessy. I hadn't heard of that technique before. I will order some an470ad5-5 rivets and try it.
 
opps rivets are for where you do not want a larger factory head, e.g., on a dimpled skin. For the ribs, just go oversize if needed (assuming edge distances are okay).
 
Rivet

It looks like the rib flange is a bit deformed. I would drill the rivets, remove and straighten it before moving on.
470AD4 rivets are tricky to drill. First center punch the head. Drill to just the head depth with a #40. Next drill #30 staying clear of the part edges. Pop off the head then center punch the rivet core and drill #40 all the way through. Place something behind to support while you drive it. I use a small socket.
One trick to keep parts tight is small pieces of rubber tubing over the shop side. They hold tension when pressed and compress with the shop head as you drive the rivet. Your pressure may be too high causing the shank to expand and separate parts.
 
rockwoodrv9 said:
There are things called "oops rivets". They have the same size head but a fatter body. ACS has them and probably the other suppliers do to.

What you need to do is get some scrap material and rivet a bunch of times until you get the feeling on how to use the squeezer or hammer correctly. Practice is what you need and buying some cheap sheet aluminum and angle pieces at HD will give you something to try without having to order new parts.

If you can't find the oops rivets, let me know and I will send you a few.
Click to expand...

I've done quite a bit of riveting. Just don't understand why the rib flanges are curling up like that. Maybe I should put the shop head on the spar side and the universal head on the rib flange. Thanks for offering to send me some rivets. I'm 10 miles from aircraft spruce though.
 
FlyBoy8 said:
I've done quite a bit of riveting. Just don't understand why the rib flanges are curling up like that. Maybe I should put the shop head on the spar side and the universal head on the rib flange. Thanks for offering to send me some rivets. I'm 10 miles from aircraft spruce though.
Click to expand...

Yes, when you have a choice it's better to put the factory head on the thinner material. Then the gun pushes the sheets together.
 
Someone posted a picture very much like this a week or two ago. If you search back a little bit you can read those responses as well.
 
Squeezer

On light structures like this I have found that a hand or pneumatic squeezer will set the rivets very well with little chance of damage to the machine head. Of course you can, and many people have, set rivets beautifully with a rivet gun. But you can not beat the consistency of a properly adjusted squeezer.

Using a cleco clamp through the lightening hole to hold the ribs together during riveting will also help. The more you make the structure unmovable the easier it is to set the rivet regardless of which tool you use to set it.

Just my experience, YMMV
 
FlyBoy8 said:
I've done quite a bit of riveting. Just don't understand why the rib flanges are curling up like that. Maybe I should put the shop head on the spar side and the universal head on the rib flange. Thanks for offering to send me some rivets. I'm 10 miles from aircraft spruce though.
Click to expand...

Yes, you should get an assortment of NAS1097 rivets -3 and -4 countersink. You should get a lot of -3-3.5's for mounting nut plates. Universal rivets just use the next size.

The o-ring or other method to hold the pieces together will eliminate the buckling/curling. The root cause of this, curling, is because the pieces are separated, not held together during the rivet setting/swelling process.
 
I like the o-ring suggestion. On loose parts, I hold the bucking bar with tension between my thumb and forefinger and use the tips of those two fingers to press the parts tight. The pressure is against the rivet gun head on the opposite side. Unorthodox possibly, but it works.

Good luck,

Larry
 
One suggestion I can offer is to make sure that you clamp all parts down to your bench top when riveting. Any movement of the parts while riveting will increase the chances for gaps between the structure, smiles, bent rivets etc.
Also, when starting, try to set the rivet with a series of small hits, make a couple of hits, stop and look at the rivet to see how it is going and then proceed with a few more, etc. When you get comfortable you can move on to setting with one longer pull.
I am not sure what gun you are using but a 3X gun will set -4 rivets much easier then a 2X gun.
 
Flanges

Those small, unrestrained flanges will want to curl a bit if the shop head is installed on the flange. Turn your rivets around and most of your problems will go away.
 
Bucking bar

Not mentioned yet is the bucking bar you are using. My goto bar is a relatively small tungsten bar that fits in the palm of my hand - ala http://www.tungstenbuckingbars.com/images/more_pics/etbb13.html

Its at least 3 times heavier than my next steel bar, but it bucks rivets like a mofo. And because its small, it anchors in the base of your palm and allows you to do the finger-thumb method to hold pressure on the skins - same way you use a small self centering punch.

You might baulk at the price, but once you use a T bar, you won't want to use anything else - like trying your first Guinness off tap in Dublin vs that PBR you been drinking at tailgates....

All that said, I squeeze rivets anytime I can.
 
Thanks to everyone for the tips. I'm going to put down my PBR :)
now and have a go with some scraps to try some of these suggestions.
 
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