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  #1  
Old 12-29-2020, 11:50 AM
allenthoe allenthoe is offline
 
Join Date: Jul 2020
Location: Redlands
Posts: 7
Default Counter-Sink Longerons and Side Skins (Aft fuselage)

Hey guys-
This is a specific question that I didn't get a clear answer from Vans. In the end, I already decided to countersink the skins but wanted to know if other managed to avoid this, did the same or just went with truss head screws.
On page 10-14 there are some specifics for an (optional) set of directions for people who prefer flush screws for the access panels. This lead to some additional dimpling of the #27 holes (for the #6 screw) and different set of nutplates to receive the dimnple.
There are also some places where you need to dimple the stiffeners (namely F-01486A-L&R). However, they do not address the two nutplates at the top (which get riveted to the longerons on page 20).
The even provide a fairly detailed image (attached below) for you to clearly see the holes you need to prep if you are priming (like me) and want to do all your prep first.
I decided to do an entire side first but when I got the nutplates (page 10-20) step 3 (optional) says to machine countersink the #27 holes common to the skins and the longerons. I assume they mean to countersink both the skins and the longerons at the same time as they are already riveted? It seems like it would have been easier to just dimple the skins and counter sink the longerons BEFORE installing the skins (when I countersunk all the #40 holes). Is this how other people did it or did they catch it ahead of time and countersink just the longeron and dimple the skin?
It does appear that I have ample edge distance but I sure didn't like countersinking the skin.

Thanks for your feedback. Curious if this is how others managed this part or if they caught it ahead of time and just countersunk the longeron.

Allen
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  #2  
Old 12-29-2020, 12:38 PM
BravoAlphaRomeo BravoAlphaRomeo is offline
 
Join Date: Jan 2020
Location: Edgewood, KY
Posts: 17
Default

I just did this a week or so ago. Like you I was hesitant to CS the skin but after over analyzing it for a couple of days I did it, and it turned out perfectly fine. Just be cautious to not go to deep.

I donít know how to post pictures here but if you PM me I can send a pic of
what mine looks like.

Best of luck
BAR
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  #3  
Old 12-29-2020, 05:06 PM
BoydBirchler BoydBirchler is offline
 
Join Date: Jul 2020
Location: Indianapolis
Posts: 71
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While you are there; there is a service letter/bulletin on tailwheel planes to place a diagonal aluminum angle under the opening on each side. If you do not, there will be wrinkles in the side skins when weight is on the tailwheel.
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  #4  
Old 12-29-2020, 07:22 PM
SabreFlyr SabreFlyr is offline
 
Join Date: Sep 2015
Location: Marion, IN
Posts: 268
Default

I countersunk the skin, as well. Don't think I had planned to but got the side skin riveted on and suddenly realized that I hadn't countersunk the longeron. Checked with the mothership because I hadn't countersunk skin before. Came out just fine. You'll be doing it again when you get to the root edge of the wing skins.

Quote:
Originally Posted by BoydBirchler View Post
While you are there; there is a service letter/bulletin on tailwheel planes to place a diagonal aluminum angle under the opening on each side. If you do not, there will be wrinkles in the side skins when weight is on the tailwheel.
The RV-14 includes the diagonal brace as part of the original design, I believe because of it being heavier to begin with.
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  #5  
Old 12-29-2020, 08:31 PM
Allan Stern Allan Stern is offline
 
Join Date: Jan 2006
Location: Cape Coral, Florida
Posts: 277
Default Counter sinking longerons

There are two ways you can do this. 1. You can just use your standard k1000-6 nutplates and use standard truss head screws to attatch inspection plates. 2. You can use countersunk screws if you want a flush surface.

The way I read those instructions you machine counter sink the longerons for the #40 rivets and countersunk #6 screws and then use your dimple dies to dimple the skins to fit into the counter sunk holes. The inspection plates also get dimpled to fit into the screw holes.

Thin metal skins are generally dimpled not machined countersunk. There are times when you machine countersink both the skin and a piece of aluminum angle that eill be riveted.



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  #6  
Old 12-30-2020, 06:43 AM
mturnerb mturnerb is offline
 
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Location: Ponte Vedra, FL
Posts: 1,546
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If I were doing it again I'd not countersink or dimple. The plate is tucked away under the HS and a few screw heads don't really create much drag.
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  #7  
Old 12-30-2020, 09:00 AM
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flion flion is offline
 
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Location: Flagstaff, AZ
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Countersinking through the skin will result in less material removed from the longeron (as it doesn't have to accommodate a skin dimple), but I'm not sure if it makes that much difference. Either way, it will be hidden under the screw head. For my RV-6, I have pan-head screws and was planning on same for the -10.
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  #8  
Old 01-04-2021, 01:28 PM
Ender Ender is offline
 
Join Date: Dec 2017
Location: Marion, IA
Posts: 77
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I countersunk the skin and longeron.

I wish I hadn't done any countersinking, because my c/s's weren't very pretty. It doesn't hurt anything, but its just annoying that they chattered.

I used the same tolerances/measurements as the wing spar countersinks (same screw size).

If I could do it over again, I'd do all of the dimpled ones as flush screws, and the top two as non-flush. Nobody will see the top two under the HS.
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  #9  
Old 01-04-2021, 02:15 PM
TASEsq TASEsq is offline
 
Join Date: Aug 2017
Location: Melbourne, Australia
Posts: 303
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Quote:
Originally Posted by mturnerb View Post
If I were doing it again I'd not countersink or dimple. The plate is tucked away under the HS and a few screw heads don't really create much drag.
I agree! I went to all that trouble of making them flush then right above them is the HS gap fairing with pan head screws. #headslap
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