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Dimpled wrong direction

jls32

Member
I'm an idiot - I dimpled half my rudder stiffeners in the wrong direction. Can I simply turn them over and dimple in the correct direction? I did a few and didn't notice any cracking around the hole.
 
I've flattened a few dimples and maybe even reversed one. But once is all you are probably going to get. If you were doing one or two holes I might try that and see if there were any cracking, but since this is for a control surface I would order new parts and specify cheapest available shipping. You'll have plenty to do on other things while you wait for the new parts. They won't cost that much. You should probably ask the Vans guys.
 
This question is directly addressed in the manual for my ATI professional riveter.

I have a small library of Military Sheet Metal instruction books, along with the AC 43. None mention this predicament, maybe because it is considered "obvious."

Reversing a dimple scraps a structural part.
 
I'm no structural engineer. Heck, I didn't even stay at a Holiday Inn last night. But, I think the rule of thumb is that you can flatten a dimple and reverse it one time without issue. With that being said, if you did half of the stiffeners, I would probably order new ones. It's really not expensive and won't take long to make some new ones. Just part of the process.
 
Stiffeners

I recommend buying new stiffeners. Stiffeners are cheap.
That's a pretty important component.
 
Thanks for replies. Vans said: “It is an accepted practice to reverse dimples one time, keep an eye out for cracks but this should be fine.”

There’s no structural load going through these.
 
P-38 Story

Used to work with a man who’s Dad worked for Lockheed during the Big War. He’d dimpled a skin when he realized he’d dimpled it the wrong way. He was halfway thru reversing the dimples when the shop Lead wandered by and saw what was going on. He said that if he’d known they would have just used the part on the other side, but reversing the dimples made the part into scrap. Respect to Van, but I’ve squashed a dimple or two the wrong way my own self and it never occurred to me to go ahead and use the part. Just my 2 cents, worth one of those pennies.
 
There’s no structural load going through these.[/QUOTE]

So, they install the stiffeners as eye candy? :rolleyes:

I submit they are structural because they "preserve" the airfoil.

Stiffener drops off, skin starts oil canning, all sorts of mischief might result.

YMMV

:D
 
I'm leaning hard with the "replace 'em" guys. If it were just an odd dimple here and there, you could probably get away with it with minimal risk. But inside the rudder will be hidden forever and ever, and it's every hole on those stiffeners. Stiffener stock is cheap, and Van's can likely send you a replacement pretty quickly.

If Van's tells you otherwise about reversing a row of dimples, I wouldn't want to question their collective knowledge and experience. But I know which route would let me sleep at night.
 
Nobody ever dimples in the wrong direction!

Or drills the wrong size hole.

Or.....
 
Are you also using proseal or something when fastening these particular stiffeners? If so I wouldn't worry about it.
That said, stiffeners are cheap.
 
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