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-   -   Vans say replace main spar (https://vansairforce.net/community/showthread.php?t=117935)

RV7A Flyer 09-27-2014 02:28 PM

Quote:

Originally Posted by Yen (Post 919996)
With the top of the rivet being so far below the surface of the spar, I doubt you would be able to fully drive a rivet, there would be no firm contact between rivet head and rivetting tool.

Quote:

There is no way you will effectively set those rivets with them sitting so far below the surface and going to a larger rivet will not satisfy the edge distance requirements necessary for those components.
Isn't there skin that goes on top of this area, and the rivet goes into the dimple on the skin? :)

These holes are countersunk to accept a dimpled skin, not a rivet...right?

Jerry Cochran 09-27-2014 03:10 PM

Replace, pls...
 
Some day in the future this RV will be sold. If you do a repair counter to Van's advice you might sell it, but for a reduced price far exceeding the cost of a new spar. That is assuming the repair is properly documented. Replace the spar, it's the right thing to do, and you will sleep much better.

BTW, I would not rely on Phlogiston over Van's. Van designed the spar not them.

Be safe,

Jerry

sglynn 09-27-2014 03:34 PM

countersink is for dimple
 
Your photo of rivet in the countersink looks terrible, but the countersink accepts the dimple of a skin. I'm with RV7aFlyer that you might want to further clarify and make sure you didn't communicate with Vans. How does a dimple and a rivet fit into this countersink?

lr172 09-27-2014 04:16 PM

Quote:

Originally Posted by sglynn (Post 920120)
Your photo of rivet in the countersink looks terrible, but the countersink accepts the dimple of a skin. I'm with RV7aFlyer that you might want to further clarify and make sure you didn't communicate with Vans. How does a dimple and a rivet fit into this countersink?

I agree. Dimple a piece of scrap .023 and put it in the countersunk hole and see if it fits. Put a little playdoh to check the clearance between the dimple and the countersink. I wonder if there was something lost in the communication of the problem.

Larry

N427EF 09-27-2014 04:16 PM

Exactly right
 
Quote:

Isn't there skin that goes on top of this area, and the rivet goes into the dimple on the skin?

These holes are countersunk to accept a dimpled skin, not a rivet...right?
Your countersinks may be spot on.
Hard to tell from the picture though.

Are your countersinks painted, is that why the look so bad in the picture?

ChiefPilot 09-27-2014 05:32 PM

There are plenty of instances where folks have had problems, called Van's, and been told "You're building an airplane, not a swiss watch - continue and build on."

This is not one of those times. Do the right thing - replace the spar.

rvbuilder2002 09-27-2014 05:49 PM

Quote:

Originally Posted by lr172 (Post 920125)
I wonder if there was something lost in the communication of the problem.

From my understanding the OP is aware (now anyway, possibly not when the countersinking was done) that when countersinking for insertion of a dimple instead of a rivet, that you go approx. .006" - .007 deeper (approx. because it varys slightly depending on the rivet size and the thickness of the skin).

He has stated that with a rivet inserted in the hole (as shown in his attached photo), the measurement to the top of a rivet head, below the surface of the spar web is .015". This means that the countersink is about .009" too deep (2.5 times what it should be).

The wing could be built as is, and would probably not have a catastrophic failure because of it. But what would happen over time (many load cycles) is the rivets that attach the wing skins to the spar would start working/smoking.
This would happen because the skin dimples wouldn't fit tightly within the countersinks. There would be clearance that would allow lateral movement of the dimple within the countersink. Because of this minute movement of the skin on the spar, the holes and the rivets would slowly be effected dimensionally. It may even take quite a few years, but the wing would eventually become un-airworthy.

BillL 09-27-2014 06:08 PM

Quote:

Originally Posted by rvbuilder2002 (Post 920135)
From my understanding the OP is aware (now anyway, possibly not when the countersinking was done) that when countersinking for insertion of a dimple instead of a rivet, that you go approx. .006" - .007 deeper (approx. because it varys slightly depending on the rivet size and the thickness of the skin).

He has stated that with a rivet inserted in the hole (as shown in his attached photo), the measurement to the top of a rivet head, below the surface of the spar web is .015". This means that the countersink is about .009" too deep (2.5 times what it should be).

The wing could be built as is, and would probably not have a catastrophic failure because of it. But what would happen over time (many load cycles) is the rivets that attach the wing skins to the spar would start working/smoking.
This would happen because the skin dimples wouldn't fit tightly within the countersinks. There would be clearance that would allow lateral movement of the dimple within the countersink. Because of this minute movement of the skin on the spar, the holes and the rivets would slowly be effected dimensionally. It may even take quite a few years, but the wing would eventually become un-airworthy.

Not arguing with the result, just trying understand the "why". So, I assume the thickness of this flange is insufficient to simply step up to the next size rivet due to the knife edge at the bottom of the countersink affecting the structural integrity of this rivet (these rivets) joint? I am also assuming that the nesting nature of the countersink gives this joint its significant shear strength.

Thanks,

Vbug 09-27-2014 06:10 PM

Thanks for the responses. Yes the dimpled leading and main skins are riveted to the spar flange. The countersinks are primed with a qtip that's why the look so bad but are indeed uniform and smooth. I inserted a rivet to show depth.
Yes I have a dimpled test piece which nests nicely into the countersink with no play.
I am going to call tech support just to confirm the understanding of the issue since communication has been completely via email.
New spar is $1625. Its not the money just can't believe what I did. I have built a lot of things in my life and never destroyed anything in the process.
Like they say if your gonna be dumb you gotta be tough!

blueflyer 09-27-2014 06:18 PM

I'll be honest, I was thinking a new spar would be way more than $1,625. I would have that sucker ordered tomorrow and forget about the whole thing.


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