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  #1  
Old 09-09-2013, 10:31 PM
tegwilym tegwilym is offline
 
Join Date: Feb 2013
Location: Seattle, WA
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Question Elevator stiffener riveting - back-rivet never worked right.

Anyone else have this same problem? I was back-riveting the stiffeners onto my elevator skins, and they -always- bent over a little bit. I didn't have this problem at all with the rudder skin/stiffeners, but then of course that skin was thinner and rivets shorter. That worked out very well.
I tried removing a few of the worst ones, and basically ended up with an uglier hole. I drilled it to #30 and used a -4 rivet in there instead (next size up method).
The elevator was a different story. They just never could go in without leaning or "smearing?" over to the side. Some reason it always leaned toward the leading edge. I was using the backing plate and the spring loaded rivet bit too.

I then tried reversing and simply clekoing the stiffeners with every other hole, and riveting with the "red rubber mushroom" riveter attachment on the skin side and the buck bar on the inside. That all worked out very nicely on the shop side and the factory head worked flush too. I did have a few to remove and re-do, but they turned out pretty well.

Is there any drawback to have done it this way? It seems that my flush heads are in pretty well, and not sure if I would have any more indentation around the skin if I did it correctly with the back-rivet way.

Anyway, just looking for some reassurance that diverting from the plans isn't a problem.

Tom

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  #2  
Old 09-09-2013, 10:37 PM
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bruceh bruceh is offline
 
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The back rivet set requires quite a bit more air pressure than the mushroom set. Every time I have had issues with rivets not setting properly, I have the wrong pressure set (either too low or too high).
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Old 09-09-2013, 10:55 PM
tegwilym tegwilym is offline
 
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It seems that no matter how much or how little pressure I used when back riveting they would always move over to one side. I would try with a very light squeeze and gently tap them in and it would still end up crooked, and when I tried a big blast they would certainly go crooked!

It was almost as if the rivets were too tall but they appeared to be about the right size.
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Old 09-09-2013, 11:03 PM
fatherson fatherson is offline
 
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Quote:
Originally Posted by tegwilym View Post
It seems that no matter how much or how little pressure I used when back riveting they would always move over to one side.
Perhaps a problem with that particular spring-loaded set? I'd try another one. For me, back riveting has definitely proven to be the easiest method for getting consistently excellent results.

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  #5  
Old 09-09-2013, 11:34 PM
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sahrens sahrens is offline
 
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When using the flush or mushroom rivet set it is easier visually to set everything square. The rivet gun is flush against the skin and although the bucking bar is covering the shop end, you can set it up perpendicular to the skin visually as well.

The back rivet set covers the rivet and as you look down at your project it is much more difficult to set it square to the shop end. You can not really see it. Add to that the AN426AD3-3.5 rivets do not take much to set. So a few degrees off of square gets a malformed shop head.

There is nothing wrong using a bucking bar, but you can get really nice results back riveting. I think it is faster too. If you have some scrap, practice back riveting.

I know it is frustrating setting bad rivets. I have drilled out way too many rivets. I wish I had practiced more before starting my tail.
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Old 09-09-2013, 11:57 PM
tegwilym tegwilym is offline
 
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Quote:
Originally Posted by sahrens View Post

There is nothing wrong using a bucking bar, but you can get really nice results back riveting. I think it is faster too. If you have some scrap, practice back riveting.
I did get all my stiffeners set, and I think they look ok on the skin side (see photo above). Yes, it did take a lot longer with the "red rubber mushroom" riveter, but I got nearly perfect looking shop heads with it. None had the tendency to lean over. I think the "spring head" has to really be perfectly perpendicular. Now that I think of it, it may have been tipped slightly toward me every time since they leaned toward the leading edge (where I was standing). But even then, I tried very hard for a perpendicular setting, but just never worked. Anyway, I guess this is why they call it amateur kit building right?

Yes, I have also removed a lot of rivets, but find that the leaning rivets end up with nasty holes even when drilling them out straight!

Tom
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  #7  
Old 09-10-2013, 12:25 AM
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Andrew M Andrew M is offline
 
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Default shadow alignment

Using a light or two to cast shadows to show vertical alignment helps a lot. Not holding the gun square (or drill) is very common mistake for new sheet metal workers. The two light method will help you learn what the tool is supposed to look like from one angle.
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Old 09-10-2013, 05:11 AM
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KMinor KMinor is offline
 
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I had the same problem. I bought a back rivet set with a plastic tip and shaved one side flat. The round set could not set square because of catching the bend in the stiffener. Just place the flat side against the bend and problem solved!
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  #9  
Old 09-10-2013, 06:29 AM
krw5927 krw5927 is offline
 
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I had the same problem with my first back-rivet set. I got it at the Yard Store because I live close to it. In search of a solution to the problem I eventually bought the Avery back-rivet set. Problem gone.
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  #10  
Old 09-10-2013, 07:31 AM
YellowJacket RV9 YellowJacket RV9 is offline
 
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I too ground one side of the plastic guard on the back rivet set down flat, so that it would fit on the stiffener. I also found that I had to angle the set slightly towards the vertical flange to end up with a good shop head. Don't know why, but it worked. Also, press down very firmly.
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