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Vans say replace main spar

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ountersink dimple

I recall a Convair 580 referance that specs acceptable gaps for dimpled joints. Every DC-6 joint I ever worked or reworked had gaps. I believe this idea of having the parts nest perfectly together is false. Follow Vans instructiins. I suspect.removing more material to get it to nest gains little for the joint and costs strength for the base part.
 
miko38, that is what I am saying. I think RV6_flyer may not have followed what I was suggesting. That is, for a thicker skin you would want a deeper countersink. Perhaps the OP's countersinks would be acceptable for a thicker skin if he went up to an 0.040 skin thickness from the current 0.032.
 
My intent with this post was not to be persuaded to build on but to only better understand dimple to countersink engineering.
In my RV8 build manual there is one sentence buried in I believe section 5 about countersinking for dimples. When I talked to Vans yesterday they said the reason for countersinking .005 beyond flush is due to no accurate way for average builders to gage depth. But they also said to make a test piece out of .020 sheet drilled #40 and dimpled for -3 and it should fit flush with no play. That's where I got into trouble using the test piece.
I will be replacing the spar as recommended.
 
Vbug said:
But they also said to make a test piece out of .020 sheet drilled #40 and dimpled for -3 and it should fit flush with no play.
Click to expand...

The instructions in the wing section said to make a "test patch" dimple on .032, and adjust the countersink until the dimple fits snug in the hole.
Click to expand...

There must be *thousands* of airplanes flying out there with wings that are about to fall off...all built by people who did exactly this.

I sure hope mine stay on next time I go up...
 
Vbug said:
My intent with this post was not to be persuaded to build on but to only better understand dimple to countersink engineering.
In my RV8 build manual there is one sentence buried in I believe section 5 about countersinking for dimples. When I talked to Vans yesterday they said the reason for countersinking .005 beyond flush is due to no accurate way for average builders to gage depth. But they also said to make a test piece out of .020 sheet drilled #40 and dimpled for -3 and it should fit flush with no play. That's where I got into trouble using the test piece.
I will be replacing the spar as recommended.
Click to expand...

Glad to see you went with Van's recommendation. I believe the updated chapter 5 now states .007 past flush for machine countersinking. Regardless, this was a frustrating skill (CS for skin dimples) for me when I began my build, and I see posts on here again and again - what is enough?

I think Andrew M hit the key to the problem talking about gaps and removing so much material so there is absolutely no gap before riveting - which I believe most times would be too much. Some of the confusion may come from the MILSPEC about sheet gaps:

"Sheet separation after riveting which allows a 0.002 inch feeler gage to be inserted between sheets from any direction far enough to touch rivet shank"

I initially questioned that spec (even though it clearly says rivet shank) whether that meant actual rivet or hitting the dimple. You'd have to have a serious gap between dimpled sheets to be hitting the rivet shank exposed from between the dimples. Start with scrap, test with dimple of same skin thickness, and sneek up on it. Slow and steady wins the race here. I count clicks past flush as I go through this process and if I feel the need to go past approximately .005-.007, I seriously take a step back to analyze what I'm doing.
 
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