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  #1  
Old 10-14-2018, 11:44 AM
galt1074 galt1074 is offline
 
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Location: Lakenheath, UK
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Default VS808PP Countersink

This may not be a problem...

I'm countersinking the mating surface of VS808PP to accept the dimples at the bottom of the VS803PP Rear Spar. I made a test piece of .032 aluminium with a #30 hole and a dimple. When I check with the test piece it appears that I'm pretty close to getting the surfaces flush, but I'm starting to get the dimple to slide around inside the countersink.
When I cleco the parts together, I can see a sliver of light (maybe 1/64" or less) between the two pieces which leads me to believe I need to countersink deeper...but the fact that my test piece is starting to slide around in the countersink makes me nervous to keep hogging out material.
It feels like I've countersunk pretty deeply already.
I'm not sure if a picture would help but I don't think the gap between the two surfaces will show in a picture.
Any advice would be awesome.
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  #2  
Old 10-14-2018, 12:04 PM
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Mark H Mark H is offline
 
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Default

This is a very common question and there are lots of previous posts on the subject. Here is a link to one:

http://www.vansairforce.com/communit...d.php?t=155478

Section 5 of the builder's manual details this. The bottom line is don't go too deep. It is acceptable to have a slight gap between the materials being joined, as it doesn't compromise the strength of the rivets. If it's too deep then the structural integrity may be compromised.
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  #3  
Old 10-14-2018, 12:56 PM
rv7charlie rv7charlie is offline
 
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Location: Pocahontas MS
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Try re- dimpling in the 'skin' piece, using a lot heavier hand on the mallet. If you don't have nice crisp 'corners' on the dimple, the underside will have a rounded corner at the top of the dimple that won't nest properly in the underlying structure, and the skin around the dimple won't be flat. Another byproduct is that the rivet won't sit flush, and you'll be able to catch a fingernail on the head after it's set.
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  #4  
Old 10-14-2018, 01:08 PM
galt1074 galt1074 is offline
 
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Default Thank you

Thank you both for your inputs.
I read through that thread and that clears up a lot of confusion. I'll rivet it as-is.
I will also try re-dimpling though I have the DRDT2 so I'll just try to squeeze them one more time.
Thanks again.
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  #5  
Old 10-14-2018, 01:43 PM
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jcarne jcarne is offline
 
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Default

Yep very common question indeed. I like to countersink to flush then go 0.007 thousandths deeper as section 5 mentions. Usually leaves a little gap between the pieces that will pretty much always close up while riveting. I also check quite a few rivets (test rivet sitting in the countersink) while countersinking with calipers to make sure they are coming out 0.007 deeper.
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  #6  
Old 10-14-2018, 03:53 PM
rv7charlie rv7charlie is offline
 
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Quote:
Originally Posted by galt1074 View Post
Thank you both for your inputs.
I read through that thread and that clears up a lot of confusion. I'll rivet it as-is.
I will also try re-dimpling though I have the DRDT2 so I'll just try to squeeze them one more time.
Thanks again.
The DDRT2 is no guarantee of a proper dimple. Have you done the 'straightedge' test on the skin after dimpling? If it's underdimpled, the skin won't be flat around the dimple after dimpling. Fully dimpled leaves the skin perfectly flat (no light under the straightedge outside the dimple.

Another test is to drop a rivet in the dimple, and while holding the stem with one hand, drag your fingernail across the head. Should be hard to catch your nail on the head.
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  #7  
Old 10-21-2018, 01:44 PM
galt1074 galt1074 is offline
 
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Default Thank you

Thank you everyone for the help.

I tried searching for this answer but I must have not put in the magic search string to find that post.

I checked my dimples and they pass all the tests. I was just approaching too deep a countersink and not seeing the parts coming together and I expected them to be perfect.

Lesson learned.
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  #8  
Old 10-21-2018, 03:04 PM
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wirejock wirejock is offline
 
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Default Dimple tokens

You might consider fabricating a set of dimple tokens. There's a link on my blog. Look under the Shop Tips links.
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Last edited by wirejock : 10-21-2018 at 08:31 PM.
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  #9  
Old 10-21-2018, 07:37 PM
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Brantel Brantel is offline
 
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Quote:
Originally Posted by wirejock View Post
You might consider fabricating a set of simple tokens. There's a link on my blog. Look under the Shop Tips links.
If you countersink deep enough that the dimple token will fit flush, it will not meet the current spec provided by Vans....it will be too deep.
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  #10  
Old 10-21-2018, 08:30 PM
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Default Deleted

Disregard my recommendation. Wouldn't want you to mess up your airplane.
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