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  #11  
Old 05-27-2016, 01:46 AM
Bevan Bevan is offline
 
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My back rivet set can't be more than 1/2" diameter. Pretty sure I got it from Cleaveland aircraft tools. Having said that, I have taken the plastic part off on occasion.

Bevan.
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  #12  
Old 05-27-2016, 07:35 AM
David Paule David Paule is offline
 
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Quote:
Originally Posted by Marc Bourget View Post
....When needing maximum structural strength, it is not an acceptable method....
Incorrect.

If the parts are snugly together and the dimples formed correctly and the rivet head formed per that spec on Van's download page, it's as strong as if it were formed in any other manner.

It's true that the strength of riveted joints varies with the thickness of the metal being riveted, but that's true for the strength of joints with any kind of mechanical fastener in aluminum.

Dave

Last edited by David Paule : 05-27-2016 at 08:45 AM.
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  #13  
Old 05-27-2016, 08:54 AM
RV7ForMe RV7ForMe is offline
 
Join Date: Jul 2015
Location: Europe
Posts: 601
Default Same issue

Mine also came from Brown and is to large for the stiffeners on the practice kits. The rivets came out with a slight angle because as you hammer the rivet down the rivets set would slip a little bit off. I tried to hold it with my fingers.

Haven't done any sniffers on the empennage yet. I was kind of hoping this issues was just on the practice wing because it is very small. Let me know how you solved it.
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  #14  
Old 05-27-2016, 09:20 AM
Tomcat RV4 Tomcat RV4 is offline
 
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I also filed a flat on one side of white p!astic ,did not effect other use Tom
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  #15  
Old 05-27-2016, 11:38 AM
Marc Bourget Marc Bourget is offline
 
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Quote:
Originally Posted by David Paule View Post
Incorrect.Dave
David,

I have a lot of respect for this forum and it's members. I didn't throw that out as an "off-the-cuff" opinion. My foundation in sheet metal and riveting began with a 15 year mentoring relationship with John Thorp - augmented by regular discussions with other Structural Engineers and research related to Forums given at OSH and Sun'nFun. The forums I gave at Sun'nFun qualified for Continuing Education Credit to IA certificate holders.

The following is from a Boeing structural engineer, discussing just this question, posted in an Aerospace Engineering Forum:

"" I suspect that the mechanics want to reverse drive to ensure max gun-energy directed to deform the tail. If this is the reason, then stop the presses... as You indicate there will be hole-fill issues galore.""
They will be mushrooming the tail without swelling the shank.

reinforced in another paragraph:

"IF this is the case, then what has happened is that the shop is circumventing rivet conventional installation protocol in-favor-of "just getting the job done [any-way they can]". This is a shabby way to run an aerospace company."

point expanded by the following:

"Hole (or hole/csk) preparation???

As usual, hole preparation [IE: straightness, perpendicularity, roundness, roughness, deburring, inner-laminar chipping, +plus all countersink issues, etc] can make a BIG difference... grossly affecting installation soundness.

[end quotes]

I will add that last quote went on to estimate up to 10% less strength and much lower fatigue life (most important to RV builders). This shows the problem lies more with the substrate than the means used to form the rivet. The quality of the rivet installation depends on the execution of the maker of the parts to be assembled and the greatest variability lies with dimpling/countersinking for installation of flush rivets. I do not feel the instruction on riveting currently offered in the E/AB community adequate to sufficiently inform a builder.

I'm not acting as the harbinger of doom in making these statements.

My guess is that there is more than enough "margin" in the RV rivet spacing that the 10% loss of strength is of minimal concern. What I do feel is more significant are fatigue life issues - The recent SB on the rear wing spar is not directly related but it shows the consequence of the point I stress.

RV builders expend a tremendous, admirable, level of effort and detail in the construction of their aircraft. Their airframes, more than likely, will be around long enough to manifest these fatigue related problems if the considerations I raise aren't addressed.

FWIW

mjb
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  #16  
Old 05-27-2016, 02:34 PM
rightrudder rightrudder is offline
 
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Quote:
Originally Posted by Warbo View Post
What Wirejock said. Although the one that came with my tool kit from Brown Tools already had one flat side.
+3. I used a disc sander to remove material for clearance. Even so, I found I had to angle the gun a little to get the shop heads to set nice and square.
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  #17  
Old 05-27-2016, 04:33 PM
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byoung byoung is offline
 
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Default Don't give up on back riveting!

I've got the Isham/plane tools spring loaded back rivet set also. It works great. It is maybe 3/8" dia with no plastic. I haven't had any access issues with it yet. I add a bit of duct tape to the edge to avoid marring the surface. It is one of the most consistent and quick ways for me to set rivets. The wife picked it up very quickly as well.
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  #18  
Old 05-27-2016, 10:45 PM
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RV7A Flyer RV7A Flyer is offline
 
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Quote:
Originally Posted by wirejock View Post
How about grinding one side flat till it clears?
Mine has two opposite sides ground flat. Works in twice as many tight spots.
Some back-rivet sets have collars that have a smaller OD, just small enough to fit in these places, but others have thicker material...if you have the thicker material, just grind it down (but smooth the edge that goes against the material being riveted so it's not a sharp 90 degrees, or you'll run the risk of putting a little mark in the aluminum).

Lots of tools will get "modified" during the build. I'd rather grind away on a tool than mess up a part, any day.
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  #19  
Old 05-28-2016, 07:06 AM
JDA_BTR JDA_BTR is offline
 
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I too had a similar problem until I started using a spring-clamp to hold the skin down firmly so it did not move while I held the gun in the right hand and the tip of the set on the rivet. When things didn't move around the rivets set well. I didn't have to worry if the rivet was in the center of the set or not.

For me back-riveting seems to make the skin move on the table every time if I don't hold it somehow.
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Last edited by JDA_BTR : 05-28-2016 at 07:09 AM.
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  #20  
Old 05-28-2016, 08:50 AM
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Snowflake Snowflake is offline
 
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Quote:
Originally Posted by Marc Bourget View Post
The following is from a Boeing structural engineer, discussing just this question, posted in an Aerospace Engineering Forum:

"" I suspect that the mechanics want to reverse drive to ensure max gun-energy directed to deform the tail. If this is the reason, then stop the presses... as You indicate there will be hole-fill issues galore.""
They will be mushrooming the tail without swelling the shank.
I'd love to know how the physics of that works. Hitting the head while backing up the tail with a bucking bar, or hitting the tail while backing the head up with a bucking bar (or large flat plate) should result in the same forces, as far as the rivet is concerned... The rivet is otherwise free to slide in the hole, until you start hitting it and the shank starts to swell. It's not clear to me that it would start swelling differently depending on which way you drive it.

Not saying the Boeing engineer is wrong, but there were a lot of wild statements in those included posts with very little technical explanation to back them up.
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