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chintangent

Member
Hello, I am currently working on the Empenage, specifically the Horizontal Stabilizer. I am riveting the skin to the rib/spar assembly. I am having a real tough time riveting the inboard section with the nose rib, forward spar, doubler plate, shim, and main rib come together. I was originally supposed to use AN470AD4, but after setting some really bad rivets, I ended up enlarging the hole trying to drill them out. Every time I use the rivet gun with the bucking bar on these rivets, the rivet always ends up bending or warping on the shop side. I am using a 3x rivet gun, set at 40psi. I've tried all different types of bucking bars, but am unable to set these rivets perfectly. I've also tried to use the Cleaveland Tools Hand Squeezer, but it doesn't seem to have enough leverage or reach to squeeze these things tight. All three holes are now different sizes: AD4, AD5, and AD6. I have not been able to work on the project for well over six months due to this roadblock. Please help!
 
I'm sure someone else will beat me to help, but if not I'll stop by next time I'm back home in the area.

I know there is a lot of help over at Poplar Grove...for example: http://www.motorcyclepilot.com/ or 'David Shelton' here on VAF.

Six months is tooo long...you'll get back on the horse in a jiffy.

Best,

-Jim
 
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I don't claim to be an expert at riveting but I've driven most of the rivets in the airframe of my 9a, so I will claim to be an experienced amateur.

When I've bent a rivet it's usually because I picked one that was too long or the hole was too big (as a result of drilling out an earlier ooops). If you don't hold the bucking bar square to the rivet in both vertical axis, you tend to 'smoosh' the rivet. That is, drive it so it expands but the head is not symmetrically round. It is more oval and not parallel with the surface.

About the only two recommendations I'd have for you are to first, find someone in your area that can show you proper riveting techniques. There's nothing like seeing someone do it right and then have them watch you and tell you what you're doing wrong. The second thing is to practice. Van's sells two practice kits (one is a hypothetical airplane part, the other a tool box). It might be a good idea to get one or the other of these to practice on AFTER you get some one-on-one help. It might not be a bad idea to take one of the many workshops that are available.

As for 40 pounds of pressure, about all I can say is it sounds about right if you're measuring at the gun but...and it's a big but...pressure gauges differ. I've used 3 or 4 gauges during my build and I've used pressure readings from the low 30's to about 80 psi to drive rivets. In reality, 80 psi is way too much pressure but that's what my current gauge reads when I'm driving #4 rivets. I think it also depends on where you're taking the reading. That 80# is at the compressor. The rivet gun is about 75' away and I'm sure there are friction losses.

I'm not sure what to say about your parts - if some of the holes have been opened up to take a #6 rivet, frankly, I'd be inclined to buy new parts and use the old parts for practice. This may not be what you want to hear - again, I'm just an amateur and don't give my opinion more weight than it deserves. If your edge distances are okay, I'd call Van's and get their opinion.
 
I found these are the hardest rivets to set on the empennage. Here's what I did and they came out OK.

I used an offset rivet set with a little masking tape on the tip to keep the set from slipping. The manufactured head was placed on the forward side of the assembly.

Since the skin intersects the spar at an angle, there was some kind of optical illusion going on that made it hard for me to get the gun perpendicular to the rivet. I held a plastic drafting square against the spar and used it to see what 90 degrees looked like. I was way off without the square.

I used a tungsten bucking bar that had about a 10 degree angle on one end. This allowed me to get the bucking bar perpendicular to the spar. Also, lots of tape on the bucking bare kept things from getting dinged.

Most important, I had my ace rivet gunner drive the rivets while I held the bucking bar. Someone with a lot more skill than I have could drive these alone, but for me it was a lot easier with two people. It looks like you have a couple of offers to help. That's terrific.

If you end up sending for a few new parts, you have a lot of company.
 
HI-LOKs, CherryMax or a good structural screw!

When its hard to rivet and you need it to be structural, you still have some good options beside a more expensive tool you will rareley use.

Any of these fasteners will work, with the proper head, Diameter, and Grip Length. Determine what will work best for the situation.

The Cherrymax is the easiest. (It will also expand and fill):)

The Structural Screw is the cheapest.

The Hi-lok is the strongest.

Both the screw and the hi-lok should have a snug fitting close lolerance hole and a structural locknut or collar.
 
Awesome help

Thanks for the support fellas. Jim, I sent a PM to David Shelton, so hopefully someones able to swing by the garage.

Don, I've already the RV builders course, and have already set other rivets successfully. As sledog mentioned, its just a really akward angle. I have 120 psi showing on my compressor and 40 showing at my regulator right before the gun.

I hve ordered the 4" yoke from cleaveland to be able to get more reach, so we'll see how that turns out.

Ill keep you posted. Thanks guys!
 
chintangent said:
Thanks for the support fellas. Jim, I sent a PM to David Shelton, so hopefully someones able to swing by the garage.

Don, I've already the RV builders course, and have already set other rivets successfully. As sledog mentioned, its just a really akward angle. I have 120 psi showing on my compressor and 40 showing at my regulator right before the gun.

I hve ordered the 4" yoke from cleaveland to be able to get more reach, so we'll see how that turns out.

Ill keep you posted. Thanks guys!
Click to expand...

Hate to see you get hung up like this for six months over one lousy rivet.

ATS http://www.aircraft-tool.com/default.aspx

has a Cherrymax Rivet Assorment and puller for less money than a set of tungsten bars.

Those hard to reach spots can be conquered quickly with Cherrymax if need be. (That won't satisfy a riveting purist but certainly will meet structural requirements.)

The name of the game here is get the airplane built and go fly. :)
 
Riveting

can you take a pic of the area you are working on?

those tight areas are so much easier with a buddy to help out. those extra yokes do help though, i must admit;)
 
Don't get discouraged

I had a very hard time with those rivets too; had to do them several times. I can tell you the masking tape on the machine head helps a lot as does someone else to help you buck. Alignment of the offset rivet tool is critical.

Good luck,

Tom
 
40 psi is too low for those AN470AD4-8 rivets. Try 75 psi.

Whenever I start messing up rivets consistently, it usually is the air pressure settings to blame.
 
EAA workshops?

Have you considered a trip up to EAA Oshkosh? Its probably 2.5 - 3 hours from you and they offer various classes. They setup a demo at AirVenture last year and I played awhile. They are very patient and use the absolute worst tools so you can get the confidence to use your good stuff at home.

Dennis Snyder
Mooney M20J N201HV
 
All material being rivited must be evenly touching - any gaps between the ribs, shims,spars etc and the rivit will not set
 
One more chiming in ....

I agree with several others ... I had more trouble with those rivets than any other encountered in the project. I found structural Cherry rivets (Spruce) that I used after I drilled out my bad driven rivets for the 3rd time. :mad: Since I was a nubie then, I know now I was also using too low air pressure for those big 1/8" rivets ... 75psi and up is needed to "get after" the 1/8" rivets, especially the longer ones.
 
Nobody has said it yet

When I went to the class at Van's in October 1996 (no longer available) during the rivet training including removal (you do just drill off the manufactured head and drive ou the shank with a punch and a plastic mallet right?) we were given some words of wisdom about clenched (bent over) rivets. Most bent over rivets occur because the rivets are too long for the installation. Look at the installation after you have clenched a rivet and evaluate carefully before you remove it. If it is mechanically sound you may want to leave well enough alone and move on.

Since you went to a training class I'm surprised no one told you this exercise of judgement part of the job. When something is difficult you should recognize that going in and you have to exercise caution in doing the job and consider every rivet installation an individual task. I always use a hand squeezer when possible because it seems the risk is less but riveting with a gun and bucking bar is eazy in open areas. Some times you have to get creative with the bucking bar requirement - I have used a flat blade of a screwdriver in an extreme case. When it is not an open area is when you have to step back and evaluate the job ahead.

At one point in building our RV-6A I realized that as careful as I was, some manufacturing defects are going to occur. They do in production aircraft building as well. The trick is evaluate the defect if it is more than standard shop practice (something that you know needs some careful thought) and develop a proper non-degrading repair. Often in the heat of the moment bad decisions are made. Removing and replacing a rivet properly should not increase the size of the hole to the point it requires a larger river and that is just ongoing work but when you have to go up a whole number rivet diameter and then once again there is a serious problem. I'm inspired by your thoughts here. I found that it was a good idea to document the discrepancies that you don't have an immediately implementable solution for in a standard form that requires a disposition and acceptance (closure). Documenting the open problem in a controlled system prevents it from being forgotten. Having to write down a disposition before implementing it forces you to think about what you are about to do before you do it. Accepting the fix closes it out from further concern - you need to focus on the open subset of discrepancies.

My form has a narrow column on the left side of th page for a discrepancy report number (or squawk #); then a wide column extending across to the middle of the page for recording the discrepancy; then another column as wide as the discrepancy column for recording the disposition; and finally another narrow column for initialling and dating your acceptance of the implementation of the disposition. When you are done building the airplane there should be no open squawks.

By the way, one of the most respected mechanical engineers I ever met, Bill Leyman (SP?) once told me and others that it is not desirable to have different size rivets in the same pattern because the loads are not distributed evenly and it can lead to failure. This had to do with the Shuttle RADAR Topography Mission (SRTM, STS-99) canister for the outboard antenna mast so maybe that is an extreme case but I think you should avoid it or at least minimize the practice. I think if you keep going the way you are going you will become quite skilled at this and the education is half of what the EAB category is all about.

I'm glad you came back and I would try to salvage the parts you have if possible - that will reinforce the learning and avoid a deflating set back. Two common discrepancy dospositions are "acceptable as is" and "remove and replace" but of course there are many in between these two extremes. The fact that you are coming back to the task says you have the desire and the fact that you mention different tools is clear evidence that you are thinking carefully about different ways to handle this particularly difficult requirement.


Bob Axsom
 
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Thanks everyone

Thanks to all of your help, I was able to get back off the wagon again.. :)

I am almost done with Horizontal Stabilizer and am looking forward to starting the Vertical Stabilizer in a couple weeks. Thanks again,
 
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