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Back riveting wing skins...what am I doing wrong?

N546RV

Well Known Member
OK, after doing plenty of research, I decided to back rivet my top skins. Got the looooooong offset back rivet set from Avery along with Andre the Giant's mushroom bucking bar. We went out tonight intending to shoot at least a few rivets to get the hang of the technique, but what actually happened is that I set precisely zero acceptable rivets in three tries.

I turned up the pressure at the rivet gun, but it still seems like I'm hitting the rivets forever and they're not deforming. And despite me holding the plastic collar on the set with my left hand, the heads are still tending to fold over instead of driving nice and square.

I've barely even started and I'm already about ready to chuck this stuff and just use a regular mushroom set and bucking bar. The back rivet technique sure doesn't seem to be the easier/more foolproof solution that some folks seem to think it is.

In fairness though, I probably should have practiced on some scrap first. Somehow I just didn't expect this to be so much of a challenge.

Side note: After a few drill outs, I'm pretty sure my first top skin rivet is going to be an oops rivet. :mad:
 
I am not familiar with that bucking bar, but you want one that is truly massive, unmoving. Most people use a steel plate on a massive rigid bench, or even on a concrete floor.
 
Just a guess, but with any offset rivet set you must secure it with tape/hand pressure etc to make sure it doesn't rotate and is perpendicular to the rivet shank. I borrowed a friends back rivet set that had a small metal lip instead of the plastic collar and 1 45* bend. Not sure where the back rivet set came from but it was one of my favorites.
 
Long offset

I'm pretty sure that long offset back rivet set was made by the devil himself. Fortunately, we borrowed one and didn't have to suffer the humiliation of buying that thing :rolleyes:. We used a mushroom set and a tungsten bar and never looked back.
 
Hi Philip
I also tried the long offset backrivet set ,luckily on some scrap aluminum. This was done on the bench with the normal backrivet plate ,and tried many times to set an acceptable rivet. They all looked like cr@p. I then decided that if I cant even set a good rivet with the backriveting plate ,there is no way that it is going to work for me on the skins with soneone holding the big bucking bar against the skin. I used the rivet gun with a flush set and bucked them as normal, and it came out looking great. I have since bought a long straight backriveting set from Cleaveland and used it on some scrap to test it out, this worked out perfect.
Regards
Arie
 
I'm pretty sure that long offset back rivet set was made by the devil himself. Fortunately, we borrowed one and didn't have to suffer the humiliation of buying that thing :rolleyes:. We used a mushroom set and a tungsten bar and never looked back.

Yeah, that's the way I've been leaning. It was a pleasure shooting the leading edge and tank rivets with a mini tungsten bucking bar, I dunno how I ever survived without this thing.

I think I'll Arie's approach and try some scrap/sample pieces with the back rivet plate tomorrow night, and if I can't even manage to set good rivet that way, then this back rivet set will join the annals of Tools I Bought And Ended Up Hating.

Thanks all!
 
Like most all things in building an RV, there are processes or techniques that need to be learned, and if we try something new, it wont necessarily work the same way as other ways we were doing it.

Personally, I use back riveting in all instances that it is possible. A lot of others have done it also and got very good results.
So what is my point? If something that others have done is not working for you, it is far more likely to be the technique than it is the tools fault.

Back riveting with a long back rivet set requires a lot more rivet gun energy than traditional riveting. There are two reasons for this.
The gun is working against the mass of a much heavier rivet set, and the offset shape absorbs some of the energy.

When everything is adjusted correctly, the rivet should set in about the same amount of time they do using a back riveting plate on a table, or a mushroom set and a bucking bar.

The very first hit needs to be swelling the rivet shank and reducing the length. That is what prevents it from beginning to lean over. If the gun is set too low, it will sit there and tap tap tap, and start to lean the rivet over

I suggest you clamp some scrap in a bench vice. Turn up the gun quite a bit more, and try to get an adjustment that will fully set a rivet in about 2 seconds (3 seconds at the most). Do some practicing on the scrap before going back to the wing (The tip I have been telling people for years.... Never, ever, try something new that you have never done before, on actual parts. It is a sure way to need to order replacements, or worse)
This should give you a good starting point for the wing, then make slight adjustments as needed.
Keep in mind that back riveting is very sensitive to rivet set alignment. You must keep the rivet set very close to parallel with the rivet or you will lean them over, but having the gun set correctly, so that the rivet sets quickly, will go a long ways towards mitigating that.
Also, only push just hard enough on the rivet set to keep it in contact with the rivet. Any more than that, you risk overcoming the person with the bucking bar and it reduces the driving action, requiring you to turn the gun up even higher still.
 
Personally, I tried to do the same, with the wing laying flat on top of a padded table with my large back riveting plate underneath. It worked out miserably, mainly for one reason - the taper of the top wing surface from front to aft. Never made for a properly flat surface against the back riveting plate, even with other people weighing down the wing at the front to try and keep it "rotated" flat against the plate.

I resorted to hanging the wing back on my wing stand and back riveting a few rivets at a time, with my dad using my tungsten bar (my go-to bucking bar for anything in general). That way the bar always remained flat against the rivet.
 
I wouldn't back rivet again.

I used the same tools and technique you describe with a builder/friend to back rivet the top skins of my first RV7 wings. It was a challenge, but we eventually got acceptable results. It was especially difficult to get the corners where the ribs meet the spars properly set.

If I did it again....I would use low pressure, mushroom set, and the tungsten bar. IMHO, you do not gain anything but frustration back riveting the wing skins. They can come out just as smooth if done with light pressure and traditional methods. Anywhere else...yes, back rivet.

Another thought...if riveting using a traditional method...lay down some heavy padding just below the area where you are working, on the main spar...in case you drop the bucking bar.
 
I'm pretty sure that long offset back rivet set was made by the devil himself. Fortunately, we borrowed one and didn't have to suffer the humiliation of buying that thing :rolleyes:. We used a mushroom set and a tungsten bar and never looked back.

+1 on the Devil Mfg. Inc. I had the same problem and never could really get a consistent product out of it. I, too, went back to the mushroom set and tungsten bucking bar and was happy every since.
 
IMHO, you do not gain anything but frustration back riveting the wing skins. They can come out just as smooth if done with light pressure and traditional methods. Anywhere else...yes, back rivet.

My response to that is that just because someone doesn't get good results with something (a tool, process, etc.), doesn't mean it is of no value (see my other post above).
I assure you that there is a reason that years ago when builder training classes were being taught at Van's (yes, Van's used to teach their own class), back riveting with a large bucking bar and long back rivet sets were a major part of the curriculum.

Is it necessary? No. With good technique and good tools, a good quality job can be done with the more conventional method.
Is it for everyone? Apparently not.
But I guarantee it is superior to any other method (in finish quality, and the speed at which you can work).
 
Wing skin rivets

+1 on the Devil Mfg. Inc. I had the same problem and never could really get a consistent product out of it. I, too, went back to the mushroom set and tungsten bucking bar and was happy every since.

+1
Same here. Swivel mushroom set and tungsten bar.
You may want to get really good at the swivel mushroom set and tungsten bar so you're ready for the bottom skin.
 
I had the same experience as the OP when I started - using the long offset back rivet set and the mondo bucking bar. RVBuilder's advice is right on, based on my experience. Using a 2x gun (3x would likely be better here), I had to increase gun pressure from 40-45 to 70 psi - it made a huge difference and I'm very pleased with the results. In fact, I'm doing the second wing skin today using this method.
 
I used an Avery double offset backrivet set up to about 70-80 lbs pressure until it broke. I could not get consistent rivets even with the set taped to the gun. I drilled out about 1 in 10 rivets completing one wing. I tried everything I could think of and was getting very frustrated...

While waiting for a replacement set (kudos to Avery) we started using a swivel mushroom set and tungsten bucking bar. Immediately we started getting consistent rivets. We drilled out about 4 on the second wing!

The replacement set arrived during the second wing. It's never set a rivet...

Keep in mind that you're going to have to rivet the bottom skins "blind" for most of the rivets. Practice when you can see what's happening helps prepare you for bucking by feel only...
 
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Learned something new

I assure you that there is a reason that years ago when builder training classes were being taught at Van's (yes, Van's used to teach their own class), back riveting with a large bucking bar and long back rivet sets were a major part of the curriculum.

It is clear to me that back riveting produces great results and when this technique is used in the right place such as thin skinned control surfaces or other small flat assemblies that can be riveted on a solid table, superior results are achieved.
Even back riveting on a structure where parts interfere with a rivet gun and mushroom set I would choose back riveting.
However, I would not agree that one of those long "Devil's canes" rivet sets and a bucking bar produces superior results on a wing surface when unobstructed access with a mushroom set is assured and a tungsten bucking bar fits in just about any part of the backside.

You may choose your own weapons but I save that offset piece of riveting gear
if absolutely nothing else works and nowhere on the wing is one of those necessary.

Keep in mind that you're going to have to rivet the bottom skins "blind" for most of the rivets. Practice when you can see what's happening helps prepare you for bucking by feel only..
Excellent point.
 
Bucking

When I got to the bottom skins, I made a shim for the tungsten bar so when it was laying flat on the rear spar, the surface of the bar would be perpendicular to the rivet without looking. Totally blind as other mention. I also taped a lanyard to the bar so it wouldn't fall.
 
When I got to the bottom skins, I made a shim for the tungsten bar so when it was laying flat on the rear spar, the surface of the bar would be perpendicular to the rivet without looking. Totally blind as other mention. I also taped a lanyard to the bar so it wouldn't fall.

And grow long, skinny arms .. I did my bottom skins solo, and some of those corners are quite a stretch! Doable though! (I did develop a bit of tennis elbow after; I suggest phone a friend if you can)
 
Appreciate all the tips. I didn't have a ton of time tonight, but I went out and used a couple pieces of scrap to practice technique (should have done this in the first place). Back riveting against the plate on the bench went nicely, though even with the pressure cranked up around 80 PSI I still have to hit the tail for several seconds to get a good shop head. Then we clamped the scrap assembly in the vise and shot a few more practice rivets there. Those weren't perfect, but I think the instability of the work contributed quite a bit.

Tomorrow night we'll try again, and I think the results will be far better.
 
Scrap - where does it come from?

That is always the suggestion, learn and practice on some scrap - well, that comes from practicing on good parts until they become scrap. Or spelled without the leading "s"

Anyway, I absolutely drooled over the huge amount of material I saw on the Vans Factory Tour for the scrap bin where the tailings were stacked from the punch machine.

I may suggest to Vans, that they package some of that "scrap" and sell it for the newbies to practice bending, drilling and riveting on. Surely the labor would be more than recovered, or practice kits. This saves the recipt of new parts, degrading status, and re-catagorizing as scrap along, with the associated costs shipping cost and time delays of replacement as skills degrade and the process is possibly repeated. Horse ahead of the cart!

Would you buy it, or say it won't happen to me?
 
I may suggest to Vans, that they package some of that "scrap" and sell it for the newbies to practice bending, drilling and riveting on. Surely the labor would be more than recovered, or practice kits. This saves the recipt of new parts, degrading status, and re-catagorizing as scrap along, with the associated costs shipping cost and time delays of replacement as skills degrade and the process is possibly repeated. Horse ahead of the cart!

Next time you order from Van's pick up some "trim bundles." I found a set in my Emp kit and and didn't know it was for .. I found it was the leftovers! Mine came in a bundle about 6" x 12" in various thicknesses (all 2024-T3). Super useful around the shop to practice on, make fittings, etc. I bought 3 and am slowly using it up.
 
I had a wing skin and a leading edge skin get ruined during a cross-country move a year ago. To say that I have an overabundance of scrap material would be a serious understatement.

:)
 
Does the long straight back rivet set work for riveting the top skins? The angle looks so small against the shop head.
 
Leading edges

Does the long straight back rivet set work for riveting the top skins? The angle looks so small against the shop head.

I used the same swivel mushroom set and tungsten bar. Also on the tanks. I trued back riveting and didn't like the results.
 
I guess I am the weird one here, I love back riveting and also have one of those big back rivet sets. I like the small one better but have used both with good results. As far as the tungsten bucking bar, I have used one several times helping a friend with his 7 but never much liked it. To me it seems to small to hold accurately. My favorite bar is a great big thing about 2 3/4 lbs item #12-01302 from Aircraft Spruce.
I guess if we all liked the same thing there would not be much variety.
 
Does the long straight back rivet set work for riveting the top skins? The angle looks so small against the shop head.

I'd be very skeptical myself. But the real answer I'd give would be to learn from my mistake here - if you're trying something new, do it on scrap. Even though I've probably read every stinking thread on VAF about back riveting, I still screwed up the first time.
 
Update: We tried again to back rivet the wings today. The gun worked a lot better with the pressure up, and I set several acceptable rivets, but they were really on the fence in terms of quality. Despite being very attentive with the set's orientation and such, all of the heads ended up somewhat asymmetrical.

My final opinion - for me - is that while back riveting produced OK results, I don't feel that it's conducive to maintaining good quality. I imagine it would me more difficult to keep up the good work over a long work session.

So we switched to using a normal mushroom set and proceeded to set lots and lots of beautiful rivets. About the only real challenge is working between the wing walk ribs, which is just a bit of a contortion game.
 
Update: We tried again to back rivet the wings today. The gun worked a lot better with the pressure up, and I set several acceptable rivets, but they were really on the fence in terms of quality. Despite being very attentive with the set's orientation and such, all of the heads ended up somewhat asymmetrical.

My final opinion - for me - is that while back riveting produced OK results, I don't feel that it's conducive to maintaining good quality. I imagine it would me more difficult to keep up the good work over a long work session.

So we switched to using a normal mushroom set and proceeded to set lots and lots of beautiful rivets. About the only real challenge is working between the wing walk ribs, which is just a bit of a contortion game.

My finding exactly...
 
Glad you saw the the light before you ruined another wing skin.
I hope you have a tungsten bucking bar and most of your tight spot challenges become a thing of the past.
 
I hope you have a tungsten bucking bar and most of your tight spot challenges become a thing of the past.

I sure do. I was skeptical of the thing at first- I felt more "stable" holding those big steel bucking bars - but now that I've used the mini tungsten quite a bit, I love it. You can hold the thing almost with your fingertips and shoot great rivets. I've barely touched my steel bucking bars in months - in fact, I think the only time I've used one recently was when shooting skin rivets on the bottoms of the tanks. The rivets that sit next to the stiffeners don't have a lot of room, so I used a steel bucking bar with a narrow face.

Anyway, back into the skin riveting breach today - hopefully we can finish those up and I'll still have time to build the wing cart. It's gonna be weird to not have the wings on stands taking up half the garage!
 
Thread Revival - Back Rivet Wings

Just throwing my $.02 into an old topic. I was nervous about trying back riveting of the top skins based on reading this thread. I gave it a shot, and I'm glad I did. I did not try the offset back rivet set, since I haven't really liked working with the universal head offset. I bought the long, straight back rivet set from Cleaveland and just used that. It's long enough that the gun can be positioned beyond the rib itself, and the angle at the rivet is pretty minimal (the set does hit the opposing rib flange). Plus, the ribs are flexible enough to push slightly out of the way for the vast majority of rivets. I probably back riveted 95% of the wing. The only rivets I bucked were the skin to main spar and a few of the tightest areas at the aft end of the ribs where I couldn't move the opposite flange out of the way enough to get the gun relatively perpendicular to the rivet.
 

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Just throwing my $.02 into an old topic. I was nervous about trying back riveting of the top skins based on reading this thread. I gave it a shot, and I'm glad I did. I did not try the offset back rivet set, since I haven't really liked working with the universal head offset. I bought the long, straight back rivet set from Cleaveland and just used that. It's long enough that the gun can be positioned beyond the rib itself, and the angle at the rivet is pretty minimal (the set does hit the opposing rib flange). Plus, the ribs are flexible enough to push slightly out of the way for the vast majority of rivets. I probably back riveted 95% of the wing. The only rivets I bucked were the skin to main spar and a few of the tightest areas at the aft end of the ribs where I couldn't move the opposite flange out of the way enough to get the gun relatively perpendicular to the rivet.

this is absolutely my intention as well...same tools and the big polished mushroom head buck bar for the skin side. I also invested in the offset long back rivet set as well....might try that on scrap as i understand it needs more pressure to work well....Ill probably shoot 100 or so test rivets before getting near the wing with it though...as a backup i have my swivel mushroom and tungsten bars
 
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