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  #1  
Old 01-04-2015, 05:22 PM
berck berck is offline
 
Join Date: Feb 2014
Location: Divide, Colorado
Posts: 20
Default Yet Another Figure 8 Dimple.

Yesterday, I damaged a hole while dimpling the F1073-L side skin.

Outside:


Inside:


Location:


I read through many of the figure 8 fixes here, but none of them were quite as bad as mine. The original hole location dimple was cracked, which meant I couldn't just put the rivet in the hole and add some epoxy when I put it all together. I wrote Van's, but instead of losing an entire day of working on the airplane, I decided to file it out until the cracks were gone, then drill the hole out to #19 (which was close to round, but still not quite), dimple it for a #8 screw and install a nutplate on the F1010. This turns out to have been a terrible decision. The dimpling for a #8 screw caused further cracks, and seems to have enlarged the hole as well. It's now roughly 3/16", and has cracks:


At this point, I see only 3 options:

(1) Buy a new skin. This is what I'm planning to do, absent advice to the contrary.

(2) Fabricate a patch for the skin. Given that from what I've read in my copy of Aircraft Structural Technician, I'd need a huge patch (something big enough for a dozen or so rivets). I'd also have to have the patch match the curve in the skin, which I think would be very difficult. Also very, very ugly. I'm not looking to build a show-quality plane, but a giant patch resulting from a simple mistake with the dimpler is just not very appealing. I'd rather spend the money on the new skin, which I'm sure will be a rather large pile of money. A patch seems like a good option if I'd already built the plane, but at this point I can buy a new 1073 and be as good as new.

(3) Leave out this rivet entirely. Drill out with a unibit until the cracks are gone, fill with epoxy and hope for the best. I'm only willing to do this if someone at Van's thinks this is an acceptable option. It seems like a bad idea to me, but I'm no aeronautical engineer. Note that I cannot add a rivet to either side of the botched one, as this is in a tab on the curve of the F-1010 and doing so will take me way too close to the edge of the tab.

Maybe I'm missing another option. Any advice appreciated.
Berck

Last edited by berck : 01-04-2015 at 05:26 PM.
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  #2  
Old 01-04-2015, 05:38 PM
BobTurner BobTurner is offline
 
Join Date: Dec 2011
Location: Livermore, CA
Posts: 7,851
Default

Is the hole too large for an "opps" rivet?
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  #3  
Old 01-04-2015, 05:41 PM
berck berck is offline
 
Join Date: Feb 2014
Location: Divide, Colorado
Posts: 20
Default

Quote:
Originally Posted by BobTurner View Post
Is the hole too large for an "opps" rivet?
Way too big. It's about 3/16" right now.
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  #4  
Old 01-04-2015, 05:50 PM
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wirejock wirejock is offline
 
Join Date: Oct 2005
Location: Estes Park, CO
Posts: 4,755
Default Bad dimple

Ask Vans first but one solution is another hole on either side with the correct spacing. Fix the bad hole by drilling as you mention but leave it empty for future filling.
Mind if I ask why you scuff the rivet line outside?
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Donated 01/01/2021, plus a little extra.
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I cannot be, nor will I be, held responsible if you try to do the same things I do and it does not work and/or causes you loss, injury, or even death in the process.

Last edited by wirejock : 01-04-2015 at 05:54 PM. Reason: correction
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  #5  
Old 01-04-2015, 06:19 PM
berck berck is offline
 
Join Date: Feb 2014
Location: Divide, Colorado
Posts: 20
Default

Quote:
Originally Posted by wirejock View Post
Ask Vans first but one solution is another hole on either side with the correct spacing. Fix the bad hole by drilling as you mention but leave it empty for future filling.
I think that would be cutting it awfully close? The F1010 tab with a single hole in it is 1". 3/32 rivets need 3/16" spacing. Edge to first rivet is 3/16. +3/32 for the rivet. +3/16 spacing to the original rivet... Leaves me 1/32" too short, not accounting for the fact that the skin hole is 3/16" now. If I want 3/16" spacing from the skin hole... that leaves 1/8" edge distance to the edge of the tab. Maybe if I split the difference?

Quote:
Mind if I ask why you scuff the rivet line outside?
I haven't found a deburring tool that doesn't remove what I consider to be a lot of aluminum. I'm okay with using the tools on thicker material, but on skins I worry that the chamfered holes after deburring are too thin. So I deburr holes in the skins with scotchbrite, because I know that won't remove any real amount of material. I figure the paint shop is going to rough it up way worse than that, anyway. (That's my reasoning... but I'm certainly not going to claim I'm doing it the RIGHT way.)
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  #6  
Old 01-04-2015, 06:31 PM
N427EF N427EF is offline
 
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Posts: 1,563
Default

Hope you find an easy solution for that hole.

A bit of drift but relevant.
I dimpled most everything upside down. Having the dimple die with the mandrel on the bottom and the female die on top allows you to visually ensure the dies are in the right place before setting the dimple.
This works very well in a C frame dimpler and enabled me to dimple at about
1 dimple every 2 seconds. Most of the time was taken up to reposition the work piece.

On the bright side you have a lot of company with holes like that
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  #7  
Old 01-04-2015, 06:38 PM
berck berck is offline
 
Join Date: Feb 2014
Location: Divide, Colorado
Posts: 20
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Quote:
Originally Posted by N427EF View Post
Having the dimple die with the mandrel on the bottom and the female die on top allows you to visually ensure the dies are in the right place before setting the dimple.
Amusingly, this is exactly what I did with the DRDT in the problem hole. For big sheets like this, I usually dimple with the male end on top to avoid the scratches on the bottom side. But, I wasn't thrilled with the first hole I did on the curve like this (scratches and dents on the curve), so I swapped the dies and did it like you're suggesting. The mandrel was sticking through the hole when I pulled the lever. Unfortunately, rather than slightly straightening out the curve to make the dimple, it pulled the material sideways, cracking/destroying/figure-eighting the hole. I wish I knew what I did wrong. I did the rest of the holes (and the other skin) with the male die on top and it worked fine.
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  #8  
Old 01-04-2015, 06:55 PM
N427EF N427EF is offline
 
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Posts: 1,563
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I should have noticed the curved part in your skin and my advice was a bit off
on that part.

http://www.skygeek.com/aircraft-tool...FRFhfgodTFMAmA

Here is the tool I used on all skins that I considered too difficult to dimple on the C frame.
Wing leading edge and other curved skins.
You cannot fail using the pop rivet dimple die. It is a slow process but is only needed in a few places.
Hope that helps.
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RV-8 finished (sold)
RV-10 IO-540 8.5:1
Running on 91 Octane E10 mogas since 2011
Don't believe everything you know.
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  #9  
Old 01-04-2015, 07:01 PM
berck berck is offline
 
Join Date: Feb 2014
Location: Divide, Colorado
Posts: 20
Default

Yes, I absolutely should have used that pop rivet tool. I completely forgot about it. I had a few of them, but I think I managed to "pop" most of them, while barely making a dimple in the stronger material. Perhaps the version I had was not-so-good. I'll definitely get more...
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  #10  
Old 01-05-2015, 11:19 AM
rocketman1988 rocketman1988 is offline
 
Join Date: Jun 2010
Location: Sunman, IN
Posts: 2,718
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I found that using a smaller diameter die worked much better on the curves. The set of dies that I got when I purchased my used DRDT included a normal sized one and a 3/8" diameter one. The smaller one worked great...
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