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11-25-2009, 07:05 PM
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Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,687
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A clenched rivet is offset or bent over, if you can fit a .002 feeler gauge between the pieces and touch the shank than you have a "shanked" rivet. Some good ways to prevent these have already been given. Here's a link to the spec sheet:
http://www.vansaircraft.com/public/Specs.htm
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Walt Aronow, DFW, TX (52F)
EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
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Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
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11-25-2009, 10:40 PM
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Join Date: Nov 2005
Posts: 452
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Quote:
Originally Posted by Denase
We used to use a thick piece of rubber with a hole punched in it to go over the rivet. We would start to "shoot" the rivet then remove the rubber and complete the shooting. This would draw the two pieces of aluminum very tightly together before the rivet swells as a result of shooting. 
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Out of interest, what kind of thickness did you find works best. I suppose this will be also a function of how compressible the rubber is ?
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EJ
RV7 flying
xp360, CS, All Glass cockpit
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11-26-2009, 06:03 AM
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Join Date: Oct 2008
Location: Schaumburg, IL
Posts: 2,053
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Welcome to the world of sheetmetal.
Lot's of good suggestions on how to help this. To be honest, when working with thin sheet (<.032) you are gonna get gaps and shanked rivets. (rivet set so that you can reach it with a feeler gauge between sheets). Back riveting helps, driving the head on the "thinnest side" also you can use a "draw" technique.
To "draw" takes some real finesse and you use low air pressure.
1. Drive the rivet just a little bit (till it is just barely swollen)
2. Place your bar next to the rivet shank and tap until the gap closes up.
3. Drive it the rest of the way.
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Tony Phillips
N524AP, RV 9 (tail wheel)
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11-26-2009, 06:13 AM
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Join Date: Oct 2009
Location: Colorado
Posts: 40
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What thickness I am not sure, I do remember the neoprene being just thick enough to be even with the top of the rivet before shooting. So you would use slightly thinner material for a number three than a number four or five rivet. The donut also worked when we used a phnuematic squeezer. Looking on a website this am I found a company that sells samples of neoprene cheap. Comes in .063, .092, .125, and heavier. There are alot of guides to tell you how high and wide the finished rivet side should be, but not how much rivet shank should be exposed before shooting. 
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11-26-2009, 09:16 AM
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Join Date: Oct 2009
Location: Colorado
Posts: 40
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Just curious. In the early 80's I worked at the old FRONTIER airlines where I was involved with the replacement of entire belly skins, on a 737 due to corrosion. We used the donut technique to drive all the rivets. Has no one else on this forum heard of this? 
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11-26-2009, 10:29 AM
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Join Date: Mar 2007
Location: Beaverton, OR
Posts: 49
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Use RC airplane fuel line
I use RC airplane fuel line for my "donuts" I think I got this idea from someones build page. I slice off a bunch of these "cushions" from a length of fuel line at a time, as the riveting with destroy a cushion after a dozen rivets or so. I cut the cushion slightly longer than the rivet tail so that the bucking bar will compress the cushion enough to touch the tail of the rivet without requiring excessive force on the bucking bar. If I am having a problem getting the flange to lay flat on its mating surface I will cut a longer cushion. I usually just drive the rivet in one shot and then remove the cushion. I have used this cushion technique on every one of my rivet gun driven rivets except for the fuel tanks. This works pretty good, but after reading others posts on this subject I am going to try the sheet of neoprene technique and see if that works better for drawing flanges tight.
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RV-8A: Flipped fuselage, working on wiring.
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11-26-2009, 10:46 AM
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Join Date: Nov 2007
Location: Keller, TX
Posts: 151
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Old trick
Hit the rivet a couple of taps to start it to swell. Then lay the bar next to the swollen tail and against the sheet and tap it a couple of more times lightly (very). This will bring the two sheets together. Because the rivet is swelled, everything will stay together when you go back finish driving the rivet. I was tought this in A&P school in 1970 and have used it ever since. Much faster that messing with donuts etc. 
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11-26-2009, 10:50 AM
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Join Date: Oct 2009
Location: Colorado
Posts: 40
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Yea I earned my A&P in 1979. The neoprene works much better and faster. 
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