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Back riveting problem.

AboveMSL

AboveMSL

Well Known Member
Hello,

I've been experiencing a problem while trying to back rivet the elevator stiffeners to the skin. The rivets are being driven with a slight offset, as though the back rivet set is slipping or at an angle. I have taken precautions to ensure that neither of those things occur during bucking and I'm still ending up with offset shop heads. I'm now speculating that perhaps the dimpling process made the holes slightly too large, there is a very small amount of play when the rivet is positioned into the hole and taped down.

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I would love suggestions from this experienced group as to what I'm doing wrong and suggested remedies.

And dogonit, my rudder turned out great and I started the elevators with the notion that I was starting to get the hang of things.

As always, thanks,

Greg
 
The light/shadow trick

Being that we are built with our eyes to close together, it can be hard to tell if one is holding the tool square. Position a light so the shadow cast by the tool is 90 degrees from where you are looking. Looking at the tool for square from your vantage, and again at the shadow, will let you know if you are straight "both ways" . I have been drilling and riveting for years, and sometimes I still use this trick.
 
Causes

Hi

the most likely cause is that you dont have the gun square to the rivet. It takes a lot of practice and it is easy to deceive yourself that its square when its not.

Its also possible the rivets are a little long.

If I were you I would get some scrap and practice on that and get it right before trying more on these stiffeners. What I do when setting these rivets is a short burst on the gun to get the rivet to thicken up and make sure its square, then another short burst to set it.
 
Build on!

I am sure you'll get a lot of advice, since all of us started where you are at this time.
I am quite sure the front side looks good except maybe for one of those rivets that are leaned over.
The angle of the shop heads indicate that you are not holding the back rivetset straight. You may have used rivets that are too long, 3.5 instead of 3s.
I hold the rivet set in place with one hand and squeeze the trigger with the other.
For back riveting you'll need much less pressure than conventional bucking/riveting, maybe 40 psi. or less.
Keep going, it'll get better.
 
Hey Tilford, are you using one of those "spring loaded" back riveting sets? If you are, I would be really surprised that your shop heads look like that...the white plastic "cup" on the riveting set makes it pretty easy to verify that you're lined up straight.

Throughout my build I found that back riveting was by far the easiest way to get nice looking rivets. Regular bucking was next, and the squeezer came in last. Actually, holding the squeezer with my left hand gave good results...holding with my right they always came out slightly ugly (but acceptable).

Anyway, my point is, the spring loaded rivet set makes it pretty easy.
 
Thanks for the quick responses

Wow! Thanks everyone for the fast responses.

I love the light trick suggestion, I'll give it a try.

I am using 3.5 length rivets, which is what the plans call for and the length extending beyond the material is 9/64, 1.5 X the diameter. So I think that's the correct length.

Also, I am using the back rivet set with the spring collar, which, I too, thought was stupid proof :roll eyes:, however, once again, I prove there is no such thing :eek:

Thanks everyone, I'll go drill out my bad ones, practice some more, then give it another go.
 
Rivet set?

Where did you get your back rivet set?

I started with a cheap set thinking that any back rivet set ought to work. Wrong. I bought a good set and all my problems went away.
 
1. Use the rivet length call out in the plans, &
2. Practice on some scrap till you have it figured out.

I found I needed a lot less air pressure and a lot fewer hits to set these rivets. On .016" skins I used -3 rivets, I'd be interested to know what is called out tor .020" skins.

As others have said having the gun normal ( perpendicular) to the surface is also critical.
 
This is the simplest thing in the world once you learn how to do it. I built a couple of the practice kits before I started on the real thing. You might think about this since you are having trouble.

A couple of thoughts about your set. I have two back rivet sets. One has a thicker colar than the other. The one with the thick colar doesn't work very well for what you are doing since the thick colar goes up onto the bend of the stiffener. The other set which I think I bought from Cleaveland Tool works great.

As has been mentioned you don't need much air pressure to back rivet. Make sure you don't have too much air pressure. Then hold the colar down with one hand and keep the end flat on the stiffener. Pull the trigger with the other hand. It should be a sound like rat-a-tat-tat. With the pressure set correctly you should be able to control it easily. One of your rivets looks over driven. If you had your air pressure too high this is very easy to do.

I hope this helps. I'm not an expert yet, but I'm getting better.
 
A couple more pointers from my experience

Body/Arm/Eye positioning
I have found that doing any kind of riveting with the gun works better for me if I know that my line if sight is as straight in line with the rivet head and the center of the rivet set of the gun as possible. As others have stated previously, sometimes this is just not possible, like when you are back riveting close to the bent trailing edge. ALso try to be aware of what is happening with your arm as you press the trigger of the gun. If your arm length is not fairly close to your body or in an awkward position, the tendency is to tilt the gun slightly to one side.

I don't think you have a rivet length problem, but I do think that the rivet gun and set are getting slightly cocked to one side. I have had the same problem at times, so you are not alone.

Air Pressure:
Make sure you turn your air pressure down when back riveting. A couple of prior posts mentioned this and I personally think that too much air pressure is one of the most common reasons that back riveted shop heads end up similar to some of yours.

Technique:
Are you holding the rivet set with one hand at the base and running the gun with the other hand? I found that this helps not only position the back rivet set squarely over the rivet shank before you begin, but also helps you keep it there when the gun is activated.

Someone else also mentioned performing an initial set following by a final set. I do this sometimes as well. You can bang on it a couple of times, then check to see if it is straight, and then finish it up. If it is not straight you can sometimes adjust the rivet set or your positioning of the gun so that it will straighten itself out once you finished setting the rivet.

If these are elevator skins, I think these are bent TEs for the RV-7 just as they are for the RV-8. Are you trying to back rivet the most rearward TE rivets solo, or do you have a helper than can hold the upper skins back while you back rivet the stiffeners in place. Having a helper made a huge difference for me.

Clamping:
Are you clamping or firmly holding the skins securely so they do not move and so you can keep two hands on the riveting?

Tools:
Someone mentioned the wider back rivet set vs. the smaller diameter one from Cleaveland Tools. I am a devout Cleaveland Tool user, so I have the smaller set which works well on small the stiffener flanges. which one are you using?

Metal Anamolies:
Sometimes I have encountered what I will refer to as a soft dimple, which looks just the same as a series of other dimples in the same part, but for some reason the metal is softer in that area than it might be in other areas of the part. This, in my opinion, also causes the occassional lop-sided shop head. I have had a couple of dimples cave in on me while using the same gun at the same pressure with the same technique and same rivet set. And no, it did not slide off the back rivet plate. :eek:

Good luck and hope this helps.
 
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Thanks

Thanks everyone,

I've been using a 3X rivet gun with the air pressure at approx. 30psi. with my work clamped. One hand on the gun and trigger, the other holding the collar of the back rivet set.

My back rivet set is from Avery's and I had not considered that the collar may be resting on the radius of the stiffener. I'll check this out today.

Thanks again for the great suggestions,

Greg
 
Just echoing Bryan above.....

Keep the collar of the back rivet set/tool between your thumb and index finger, to help keep it square to your work and also limit the lateral movement of your set during the riveting.

Keep at it, you'll be a pro in very short order.
 
This is why I donate to VAF.
Had problems with consistency on my first stiffener.
Problems were pretty much dead on what OP had.
Turned down the pressure from 55 to 40 and it worked like a charm.
 
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