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  #1  
Old 11-24-2017, 01:48 PM
Mort04 Mort04 is offline
 
Join Date: Oct 2017
Location: Michigan
Posts: 15
Default Over countersinking?

Ok, I’m not sure why I feel like I’m struggling with the Front Spar on my Empennage, but here it is.

I countersunk HS-710 and HS-714. I think I may have gone a little too deep in an attempt to make the dimples on HS-702 fit into the countersunk hole. I know section 5 says 7 clicks past flush is the proper depth, however it didn’t seem like the dimple fit properly. Attached is a link to a picture with a AN426AD4 rivet inserted into the hole for reference. I’m worried I’ll need to order new reinforcement angles. What are your thoughts?


https://flic.kr/p/GUigan

Last edited by Mort04 : 11-24-2017 at 01:53 PM.
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  #2  
Old 11-24-2017, 02:14 PM
wirejock's Avatar
wirejock wirejock is offline
 
Join Date: Oct 2005
Location: Estes Park, CO
Posts: 2,726
Default Countersink

Quote:
Originally Posted by Mort04 View Post
Ok, I’m not sure why I feel like I’m struggling with the Front Spar on my Empennage, but here it is.

I countersunk HS-710 and HS-714. I think I may have gone a little too deep in an attempt to make the dimples on HS-702 fit into the countersunk hole. I know section 5 says 7 clicks past flush is the proper depth, however it didn’t seem like the dimple fit properly. Attached is a link to a picture with a AN426AD4 rivet inserted into the hole for reference. I’m worried I’ll need to order new reinforcement angles. What are your thoughts?


https://flic.kr/p/GUigan
That's a close one Kyle. Send it to Vans to be certain. If you send it now and call this afternoon, they may be able to advise by phone and avoid waiting all weekend. I suspect they will say it's ok provided the dimple rests in the countersink and not so deep it doesn't touch bottom.
I suggest fabricating a set of dimple tokens. Tip is on my blog.
Also, never trust a cutter. Test before use on a hunk of scrap drilled full of holes.
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Last edited by wirejock : 11-24-2017 at 02:16 PM.
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  #3  
Old 11-24-2017, 02:31 PM
Mort04 Mort04 is offline
 
Join Date: Oct 2017
Location: Michigan
Posts: 15
Default

Quote:
Originally Posted by wirejock View Post
That's a close one Kyle. Send it to Vans to be certain. If you send it now and call this afternoon, they may be able to advise by phone and avoid waiting all weekend. I suspect they will say it's ok provided the dimple rests in the countersink and not so deep it doesn't touch bottom.
I suggest fabricating a set of dimple tokens. Tip is on my blog.
Also, never trust a cutter. Test before use on a hunk of scrap drilled full of holes.

Thanks for the input, and very good info on your blog. Iíll give vans a call and see what they say. Iím half tempted to just order and start fresh with the reinforcement angles.
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  #4  
Old 11-24-2017, 02:50 PM
E28POWER E28POWER is offline
 
Join Date: Jul 2016
Location: Hillsboro, OR
Posts: 13
Default

Unfortunately, Vans is closed today.
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  #5  
Old 11-24-2017, 03:34 PM
Mort04 Mort04 is offline
 
Join Date: Oct 2017
Location: Michigan
Posts: 15
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Quote:
Originally Posted by E28POWER View Post
Unfortunately, Vans is closed today.
Haha I figured, but called anyway. Iím out of town and away from the project till Monday so either way Iíd be thinking about it all weekend............
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  #6  
Old 11-24-2017, 04:50 PM
Robin8er Robin8er is offline
 
Join Date: Sep 2015
Location: Oahu HI
Posts: 173
Default

I did this on purpose on my cowling so that i could fill in the void with filler that way you cant see the rivets.

I set them by taking a very large dimple die, grinding the male part flat and using that to set the rivet. It works perfect. Hopefully vans blesses off on it in your case. Yours is a structural component, mine is not.
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  #7  
Old 11-24-2017, 05:03 PM
tims88 tims88 is offline
 
Join Date: Jul 2016
Location: Arvada, CO
Posts: 43
Default

I obsessed over the proper counter sink depth for a while. It really bugged me that chapter 5's recommendation of seven clicks past flush wasn't deep enough to allow the dimpled part to fit perfectly flush into the countersink. After a ton of searching and reading about countersink depth on these forums I came across this post:

http://www.vansairforce.com/communit...82&postcount=5

That, along with another post from the same person where he pointed out that the RV-14 prototype was built entirely using 7 clicks past flush was enough to convince me that 7 clicks was adequate. I'd rather have a tiny sliver of light visible between the parts than risk countersinking too deep and decreasing the strength of the joint. I've also heard that once the parts are riveted together that small gap usually disappears anyway. However, I can't remember ever holding two riveted parts up to a light to see if I can still see light between them or not.
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  #8  
Old 11-25-2017, 09:54 AM
Marc Bourget Marc Bourget is offline
 
Join Date: Apr 2009
Location: Stockton, California
Posts: 143
Default

I'd do some dimples in a piece of scrap and see how they "fit" in the CS.

Should be less than .002" between the skin and spar. (If more, too shallow of a C/S. If it "slides" or "wiggles" C/S is too deep).
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  #9  
Old 11-25-2017, 12:52 PM
PilotjohnS PilotjohnS is offline
 
Join Date: Jan 2016
Location: Los Angeles
Posts: 346
Default Looks too deep

The picture looks too deep in my opinion. I religiously followed Vans advice and use the depth gauge part of a dial caliper to get the .007.
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  #10  
Old 11-27-2017, 03:45 PM
Mort04 Mort04 is offline
 
Join Date: Oct 2017
Location: Michigan
Posts: 15
Default

The verdict is in, time to order new HS-710 and 714 reinforcement angles. Vans got back to me and as a couple people mentioned earlier in this thread 7 clicks past flush is what I should have done, regardless of the two peices not mating completely tight. Not sure why I would question that as a first time builder......

Anyway, one thing Vans pointed out to me that I didnít think about is the shape of the dimple vs the countersink. It is slightly different. Below is Vans response to me. Thanks for everybodyís input.


That does look substantially deep. I would probably start over.

The concern is that if you go too deep, you wonít have a solid interface between the skin and the underlying structure. You will almost always have some gap showing between the skin and underlying structure. The edge on that countersink is pretty sharp whereas the edge on the dimple is rounded. 7 clicks beyond flush is safe.
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