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  #1  
Old 10-28-2018, 07:04 PM
Girraf Girraf is offline
 
Join Date: Dec 2017
Location: Great Mills, MD
Posts: 17
Default Feedback on Rivets Please!

I set the rivets on the left side HS-707 tonight. They look acceptable in my opinion, despite the fact that I expected them to seat in the dimple slightly deeper. After a booboo working the same parts for the right side and still struggling to drill a rivet out, I'm really convinced I should leave these be.





Despite my uncertainty on those rivets, I pressed on with the left side, blind riveting the HS-708 mid rib and set the tip rib rivets that attach to the front spar. The rivets set well but the fwd spar flange bent away from the rib during the final strikes of the rivet gun. I can slip a .013 feeler gauge in there but just a little ways before the material cinches up around the rivet itself. Did I do something wrong here? I didn't anticipate this happening. Here's a photo of the manufactured heads and shop heads.



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Last edited by Girraf : 10-28-2018 at 07:11 PM. Reason: fix images
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  #2  
Old 10-29-2018, 09:26 AM
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Raymo Raymo is offline
 
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Location: Richmond Hill, GA (KLHW)
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Default

I see no issues with the skin rivets. The flange that pulled away is not a problem either but you could use a couple light taps with the bar on the flange between the rivets to push it back down.

From the marks in the corner of the flange, it appears you may have inadvertently hit that area while bucking the rivets, which caused the gap.
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  #3  
Old 10-29-2018, 09:50 AM
Girraf Girraf is offline
 
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Location: Great Mills, MD
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Something else that may be affecting my performance is gun pressure. I've been using 90 psi on my 3X gun at the compressor and using the flow rate control knob that I installed at the gun to slow the rate of fire. After som elight reading I see that thats not the optimal pressure. Maybe I'd get better results instead by putting the total pressure down to 35 psi (for 3/32 rivets) and 45 psi (for 1/8 rivets), and then readjusting that flow control valve at the gun...
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  #4  
Old 10-29-2018, 10:27 AM
PilotjohnS PilotjohnS is offline
 
Join Date: Jan 2016
Location: Los Angeles
Posts: 550
Default no expert but

I am no expert on riveting but here are some observations.

The final rivet should have a 3:1 aspect ration width to height (.5 tall x 1.5 wide) the one in the picture looks like it is under driven; I suggest you check with rivet gauge any that don't have that aspect ratio.

I think the flange separating from other flange is technically OK if the feeler gauge doesn't hit the rivet shank, but I would work on improving that for next time. Some things that worked for me: make sure the holes are deburred, when the rivet swells it could tweak the flanges up if there are burrs. Also, use a piece of tubing, faucet washer or whatever to keep the pieces together when initial riveting thin pieces; You want the rivet to swell on the outside not between the two pieces. Lastly put the manufactured head on the side of the thinness material.

I am not expert, but I found these things helped.
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  #5  
Old 10-29-2018, 10:54 AM
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wirejock wirejock is offline
 
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Location: Estes Park, CO
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Default Regulator

Quote:
Originally Posted by Girraf View Post
Something else that may be affecting my performance is gun pressure. I've been using 90 psi on my 3X gun at the compressor and using the flow rate control knob that I installed at the gun to slow the rate of fire. After som elight reading I see that thats not the optimal pressure. Maybe I'd get better results instead by putting the total pressure down to 35 psi (for 3/32 rivets) and 45 psi (for 1/8 rivets), and then readjusting that flow control valve at the gun...
I recommend a regulator instead of flow valve. HF mini regulator works but tends to drift. RTI is pricey but never drifts. I keep it on a 6' pigtail with a quick connect. Main line has a three way manifold. One low pressure regulator, one high pressure regulator, one unregulated.

Find a local builder and ask for a Mentor visit. A little time with an experienced builder will correct issues early in the build.
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  #6  
Old 10-29-2018, 11:29 AM
Mlidzct Mlidzct is offline
 
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Location: Southington, Ct
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I would say the skin looks like it could be a little under dimpled. Its always hard to tell from pics but the light distortion suggests it, as well as just a scuff ring at the OD of the die vs a scuff over the whole face of the die contact area.

Personally I don't like to see a gap on the flush rivet head. I was getting a small gap around my flush rivet heads which were due to a manufacturing defect in my dimple dies. I went to a different set of dies and the gap went away.

I can see the tool marks on the edges of the skins, the inside corners near the spar flange look like they may have burrs too. Deburring & edge prep is important.

You should get the metal chips out of the area before you rivet. If some of the larger chips get sandwiched between the skin and sub structure you could end up with bumps in the skin, plus you don't want chips in there anyway.

Google MIL-R-74196A and read it over if you haven't. Section 4 talks about defects. The flange gap you have is ok if you cant reach the rivet shank with a .002 feeler gage.
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Last edited by Mlidzct : 10-29-2018 at 11:35 AM.
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  #7  
Old 10-29-2018, 11:44 PM
sblack sblack is offline
 
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Location: Montreal
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I had this same thing where one of my vertical stab ribs attached to the spar and my inspector snagged it. I sent vans a picture and they said that those rivets were not really taking that much load. They were only there to hold the rib in place. Most of the load goes through the skin. I agree with the statement that you kight have better luck with different dimple dies and make sure you dimple deep enough. The die should leave a ring the width of the die. A friend had an issue and switched dies and it was fixed.
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  #8  
Old 10-30-2018, 06:33 AM
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steve murray steve murray is offline
 
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I have had better luck on the ribs with putting the shop head of the rivet on the thicker side (spar side). Not always possible, but this seems to prevent lifting of the rib flange.
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  #9  
Old 10-30-2018, 07:04 AM
BillL BillL is offline
 
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Default YMMV

Mark has some good advice above.

I have the Avery dimple dies ( excellent tool ) and still got a few rivets that showed gap under the perimeter. Although they are not a structural issue, there remained a desire to understand and correct the condition.

Finally, I would check each rivet in place before setting, if one looked this way, a couple light turns of the deburring tool solved the problem. This might be a hot button for some, and hotly contested, so do some experiments and make your own decision.

If there is another sure way to solve this, hopefully it won't be kept a trade secret.
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  #10  
Old 10-30-2018, 05:02 PM
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Debovsky Debovsky is offline
 
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Location: Val-d'Or (Quebec), CANADA
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Default

Hi Girraf,

Based on the photos only, its hard to tell but it looks like the dimples aren't deep enough. If you are using the DRDT-2, make sure to set the adjustment screw to exert enough pressure to get a very positive detent on the tool handle.

As for the curling flanges, it generally happens with AN470D4-x rivets. They exert a lot of pressure. I solved the problem using a rubber washer that I slip between the squeezer die and the rivet shop head. When I can't use a squeezer then I simply tape off an AN3 washer on the face of the bucking bar and line up the washer around the shop head before firing the rivet gun. In either case, it makes for a true flat flange that fully contact the spar.

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