Riveting techniques?

Hi all:

I am at the 'riveting the wing skeleton' stage and for some reason am having a particularly difficult time with some of the AN-4 rivets, on both the main spar and the aft spar, with regard to the ribs.

I think I am using way too much air pressure on my 3x gun and am making a mess of some of the machine heads on these rivets. As a general rule, I put the shop head on the thicker material(spar), and the machine head on the thinner material (the rib flanges). Generally, not too much problem here with the exception of the machine head seems to be taking a pretty good beating as well as the surrounding flange.

To add to my problem, the rivets on the end rib of the -8 wing rear spar need to be flush rivets ( to accomodate an aileron bracket), with the shop head on the thinner flange side. Having a little trouble here keeping the flange from lifting while riveting.

Any thoughts/recommendations on what's going on here and how to smoothly move through this process? Too much air pressure???

1. Secure the work. Then secure the work.

2. Apply more pressure on the gun side than you're applying with the bucking bar. If you're applying pressure to the rivet with the gun, then the rib flange shouldn't be pulling away from the spar.

3. Are you using an offset rivet set? Solo? This can sometimes be problematic. When using a double offset, I personally like to have both hands on the gun & set, while my helper bucks. To avoid using an offset set, you can rivet the main ribs onto the spar prior to the rear spar even being cleco'd on.

4. Don't let up on the gun until all is quiet. Lift up or let up pressure an instant too soon and you'll see the work "smiling" back at you...

5. As you mentioned, try it with lower air pressure.

I had a heck of a time learning to shoot universal head (AN470) rivets. Once I started following the advice I just gave you above (which I got from experienced builders at the time), it all clicked. Hope this helps.

Oh, also...on the rear spar, use a squeezer instead of shooting and bucking. Longeron yoke and a 3" C yoke should get most if not all of those rivets.

I bucked all mine myself without too much trouble... try the following.
What Dan said - secure the work.
Really lean into the gun. This will keep it on the rivet head. I am a small guy ( 5'10 155#) so I just squeezed in between the ribs while riveting.
I used the "snap socs" that Avery sells that fit over the end of the set - these help keep the set on the rivet. I think tape might work too but I didn't try it.

I squeezed all the rivets on the rear spar - no bucking there.

Look over Dan C's site - definitely rivet the ribs to the main spar first, then to the rear spar.

Hope that helps
Thomas

Something I found to be very helpful is to put a small piece of masking tape on the manufactured head, just enough to cover it. I have never had any 'smilies' after doing this, even with a 2X at max pressure. Very handy for longer 1/8" AN470 rivets.

Conor McCarthy
RV-9A 90990 fuselage
QLD, Australia

Those are all good tips, I'll add a few:

- hockey shin tape is another alternative for the rivet set. Seems to hold the set on the rivet better, and the rivet looks picture-perfect afterward assuming no bad things happened. Lasts 10-30 rivets depending on the air pressure, and comes off pretty easily unlike masking tape.

- If I'm doing a difficult rivet, I'll start with a quick burst from the gun just to get everything settled and make sure nothing is going to slip. You can then do a longer burst right away if everything feels good.

- If unable to watch both sides of the work while riveting, be sure to listen and feel for changes that might indicate trouble or incorrect pressure.

Just finished the wing skeletons for my 9A...

...and had the same problem with mangled rivet heads. The basic problem is vibration of the spar by the rivet gun, which causes the rivet set to bounce around on the manufactured head. My solution included most of the tips posted above, except I didn't try tape on the rivet head. My approach:
...Clamped the main spar, clamped it some more, then clecoed about three ribs to 2x4 blocks screwed to the table.
...Tossed the offset rivet set back into the toolbox and put on the short straight set.
...Taped everything - rivet gun, rivet set, around the shop heads, along the spar edges. Used blue painters tape, and lots of it.
...Left off the rear spar while riveting to the main spar.
...Set the rivet set square on the manufactured head by shoving the rib aside as much as necessary. The tape on the gun prevented scratches, and lots of weight on the gun kept the rib flange flush.
...Used the heaviest bucking bar that would fit into the space.
...Leaned into the gun and kept my eye on the rivet set. If I tried to watch the bucking bar, the rivet gun tended to get off square.
...Set the rivets in short bursts - about 3 per rivet, adjusting the bucking bar in between if needed.
...Used a 3x Taylor gun, with pressure set at 10x the rivet length (measured at the inlet to the 6-ft flexible hose).
...Started at the inboard end and worked outward, adding the closely spaced (wing walk) ribs one at a time.
...Squeezed all the rear spar rivets except the flush heads.

The second wing took half the time of the first, after I figured out how to do it.

Joe Lofton
RV-9A wings

Like others have said.

Snap socs worth their weight in gold (and then some) on these anxiety-producing rivets.
Clamp spar down.
Wait to rivet rear spar until all ribs are on main spar.

All this with the 5.5" double offset rivet set where necessary (many could be hit with the straight set since the rear spar had not yet been riveted), a relatively heavy bucking bar, and bucking by myself lead to almost perfect rivets. I give most of the credit to the snap socs, they're that good.

You might do a search on this topic. I know I've seen many good ideas before.

Good luck on the second wing.

How timely!

I'm having the same difficulties, but with the aileron brackets on my QB wings. I tried putting them on using the double-offset by myself. I managed to get so far out of alignment that the manufactured head sheared off! I'm going to take these tips, and a friend, and try it again. So very frustrating!

Great ideas all!!

Great ideas guys! The only thing is that for this first wing, most of the ribs are riveted already to the rear spar. Perhaps I can flex the two spars apart sideways a bit to get a little angle on those flanges and rib webs. Just enough to try and get a straight set in there.

I will try these ideas and let you all know how they work out.

I had the same problem with ANY 470AD4 rivets. I found I can turn the air pressure down with a heavier bucking bar, and I don't mangle the factory heads.

Good luck.

What's heavy?

What would qualify as a heavier bucking bar? Are we talking 2 or 3 lbs?

-Rick

Heavier than the lighter one of course!

Seriously, I'll check when I get home and get back to you.

If I would add anything, it would be TAKE YOUR TIME. Too often I found myself in a hurry, which is when I made mistakes. When you feel like you're pushing yourself, back off a bit. A minute lost here and there, will save you hours recovering from mistakes made in haste.

Dan_E_Root said:

If I would add anything, it would be TAKE YOUR TIME. Too often I found myself in a hurry, which is when I made mistakes. When you feel like you're pushing yourself, back off a bit. A minute lost here and there, will save you hours recovering from mistakes made in haste.

Click to expand...

Amen Brother! I can testify to that!
It bears repeating:

Dan_E_Root said:

If I would add anything, it would be TAKE YOUR TIME. Too often I found myself in a hurry, which is when I made mistakes. When you feel like you're pushing yourself, back off a bit. A minute lost here and there, will save you hours recovering from mistakes made in haste.

Click to expand...

Rick,

I weighed the bucking bars. The lighter one that gave me fits was 1.5 lbs. and the heavier one that worked better was 2.5 lbs. I think 2.5 - 3 lbs. would be just about right.

Hope this helps.

Size matters

Alright ... the one I was using is 1.5lbs. I'll give a 3 pounder a go.

Thanks!

back riveting??

Ok.... I've tried some new techniques on the main spar which seem to work quite well. However, I am still having problems with the wingtip end rib on my -8 wing. Where it attaches to the rear spar, flush rivets going the opposite direction are required. The flush side(the back side of the rear spar) is where the aileron attach bracket goes, therefore the reason for the flush rivet. This puts the shop head on the forward side of the rear spar right where the end rib flange meets and is attached with it. My problem continues to be trying to keep the flange from lifting when I rivet.

I do not have a longeron yoke (yet?), because they are quite expensive, but I am beginning to wonder if it would be money well spent. I also don't have a double offset back rivet set, but have been trying to make do with my straight back rivet set. Hard to keep the shop head straight with this set. Has anyone used back riveting techniques on this part of the airplane? I've heard folks talking about back riveting for the wing skins, but not specifically about this area I'm on.

Also, would a nice flush cherry max rivet(structural) work in these locations as a way to get through this? It seems that the cherry max rivet would also pull the flange down as it was setting.

How has everyone else handled this particular rib?

jdmunzell said:

I do not have a longeron yoke (yet?), because they are quite expensive, but I am beginning to wonder if it would be money well spent.

Click to expand...

Ahyup...I'd spend the bucks. You can always sell it when you're done with it (yeah, right!!!).

Also, if the flange is lifting while you're riveting, either you don't have enough clecos in there while you're riveting, or the flange itself is bent, or something of that nature. You can possibly use C clamps to hold it down. I've also seen some people use rubber O-rings on their bucking bars to push against the flange while forming a shop head. Lots of tricks of the trade.

I called Vans this afternoon to see what they would say about it. They too mentioned the rubber O-ring idea. That's a great idea Dan. This "tech" fellow said I was probably being a little too anal about the flange lifting up. I do understand that with all the other pieces riveted together, (rib,spar,skins) that you do wind up with a really strong piece. I understand all that, however, isn't the strength of a given riveted piece in the sheer strength, meaning both mated pieces need to be as flush with each other as you can make it?

This fellow suggested not to worry about it and go ahead and finish that section without it. He said after adding the aileron bracket, I could back drill through the bracket and add an appropriate universal rivet at that point.

...seems logical, because the result is the same. ...strength! So you have a shop head on the "exposed" side of the aileron bracket. So what? It's not like anyone would even see it once the skin, aileron, and fiberglass wingtip are installed.

I also still wonder about using an appropriate flush cherry max blind rivet here...which I already have some of. Dan, what's your opinion about that idea?

Follow up....

I used the rubber donut method of holding down the flange while I bucked the flush rivet on that offending end rib. In fact, I did two of them (the two corner ones), and I am satisfied with the results. I think Cherry Max rivets would've worked in there, but ultimately chose to try this method first and guess what.....it worked!!!

NEXT???.....!