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  #1  
Old 05-12-2020, 03:22 PM
Coaltowngarage Coaltowngarage is offline
 
Join Date: Aug 2019
Location: Altoona,AL
Posts: 49
Default What would you do? countersink vs dimple

ok, so the kit I bought had the tailfeathers mostly complete and the wings about 75% done. The top wing skins and the tailfeather skins were all countersunk rivets. The surfaces are flawless. I'm at the point now to begin preparing the fuse skins for riveting. If it were you, would you complete the airplane countersinking rivets to match the previous work or dimple? I was told the plane is a show winner if the workmanship is completed as well as the wings and tail had been done. Is the difference something that will be very noticeable on the finished product?
I know this is subjective I guess, and folks will have different opinions. I want the hear them.
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  #2  
Old 05-12-2020, 03:37 PM
Raymo's Avatar
Raymo Raymo is offline
 
Join Date: Nov 2014
Location: Richmond Hill, GA (KLHW)
Posts: 2,306
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Only countersink if the skin is at least .032 thick. Thinner sheets must be dimpled, else the countersink will open the hole before achieving the necessary depth for the rivet head. Rivet size also matters, so the above rule requires modification for larger diameter rivet.
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RV-7A - Slider - N495KL - First flt 27 Jan 17
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  #3  
Old 05-12-2020, 03:47 PM
dwranda dwranda is offline
 
Join Date: Jan 2015
Location: Jamestown,NY
Posts: 644
Default

I'm not done yet with my 9A yet so am no expert on building planes but this question scares me. The wing and tail skins were countersunk?? Is that even airworthy? Did the kit come with instructions? The instructions tell you what to do and what thickness to start countersinks. You don't have to countersink to get flawless results. What model is this anyway?
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  #4  
Old 05-12-2020, 03:56 PM
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Ed_Wischmeyer Ed_Wischmeyer is offline
 
Join Date: May 2005
Location: Savannah, GA
Posts: 1,411
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Easy call - my countersinking skills aren't nearly as good as my dimpling skills. I'd probably end up buying new skins several times over...
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  #5  
Old 05-12-2020, 03:57 PM
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Raymo Raymo is offline
 
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I wonder if you are referring to the builder dimpling the skin, then lightly countersinking for a better rivet fit? IMO, not needed. What might be needed are better dimple dies.
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RV-7A - Slider - N495KL - First flt 27 Jan 17
O-360-A4M w/ AFP FM-150 FI, Dual PMags, Vetterman Trombone Exh, SkyTech starter, BandC Alt (PP failed after 226 hrs)
Catto 3 blade NLE, FlightLines Interior, James cowl, plenum & intake, Anti-Splat -14 seat mod and nose gear support
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  #6  
Old 05-12-2020, 04:19 PM
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wirejock wirejock is offline
 
Join Date: Oct 2005
Location: Estes Park, CO
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Default Dimple

I think you need to provide more information and some photos because the skins should not be countersinked. Maybe you mean flush riveted? You're scaring us!
The manual is very specific about what is dimpled vs countersinked.
The fuse skins are dimpled.
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Donated 01/01/2021, plus a little extra.
RV-7A #73391, N511RV reserved (2,000+ hours)
HS SB, empennage, tanks, wings, fuse, working finishing kit
Disclaimer
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.
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  #7  
Old 05-12-2020, 05:11 PM
Coaltowngarage Coaltowngarage is offline
 
Join Date: Aug 2019
Location: Altoona,AL
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Its an early 6, the skins are riveted with flush rivets and the holes are countersunk. The plans say that countersinking is acceptable on panels .032 or over. Ive read of a few others doing it this way. When I say flawless. I mean glass smooth, absolutely zero deformation around any rivet, the tank skins and bottom skins are dimpled. This isn't a question of airworthiness, its a question of aesthetics, would it bother you if the rivets on the top of the wings looked different that on the fuselage?

Last edited by Coaltowngarage : 05-12-2020 at 05:30 PM.
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  #8  
Old 05-12-2020, 05:59 PM
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wirejock wirejock is offline
 
Join Date: Oct 2005
Location: Estes Park, CO
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Default Countersinked

Bother? Nope. Only that it was buillt in compliance with 43.13 and it's safe.
Maybe a 6 builder will comment. Seems odd to contersink .032 but I'm no Engineer and mine is a 7A.
I do know it is totally possible to dimple a skin perfectly. I've seen many an airplane with perfect dimpled skins.
If it's not an airworthiness question then as they say, it's your bird.
I would ask Vans.
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Estes Park, CO
http://wirejockrv7a.blogspot.com
wirejock at yahoo dot com
Donated 01/01/2021, plus a little extra.
RV-7A #73391, N511RV reserved (2,000+ hours)
HS SB, empennage, tanks, wings, fuse, working finishing kit
Disclaimer
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 : 05-12-2020 at 06:01 PM.
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  #9  
Old 05-12-2020, 06:38 PM
Desert Rat Desert Rat is offline
 
Join Date: Aug 2018
Location: 50-50 Wichita KS & Scottsdale AZ
Posts: 538
Default

Guys, you can countersink .032 for -3 rivets. Even Vans says so in section 5.

If you do the math, you'll see that .032 is the absolute thinnest sheet that you can get away with countersinking without enlarging the hole. a perfectly countersunk hole will leave a -3 rivet a couple of thousandths proud.

Having said that, If you ever botch one to a point that you have to go up to a -4, you're screwed, because then you absolutely don't have enough material thickness to countersink for a -4. For that reason, I would dimple the fuselage if it were me. But then again, I'm not building a show plane.
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Last edited by Desert Rat : 05-12-2020 at 06:42 PM.
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  #10  
Old 05-12-2020, 06:47 PM
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PaulvS PaulvS is offline
 
Join Date: Aug 2019
Location: Western Australia
Posts: 558
Default Comments

I'm a -6A builder and for me safety comes first, performance second and aesthetics is third.
I prefer to dimple wherever possible and only countersink if I cannot dimple e.g. .040 is difficult to dimple well.
The best dimple dies for a smooth finish came from Avery but I'm not sure if they are available any more after Avery retired.
It's obviously also equally important to be able to set rivets for a good finish and some builders make the effort to back rivet wherever possible.

On a -6 the wing top skins are mainly .025, apart from the area behind the tanks (.032), so should be dimpled and not countersunk. It is possible though that the previous builder might have put on non-standard thicker skins for countersinking.

The fuselage skins are generally .025, so must be dimpled and not countersunk.
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Building RV-6A #22320 O-320 FP. Wings and tail complete, working on fuselage
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Last edited by PaulvS : 05-12-2020 at 06:56 PM.
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