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How to make an outie and innie?

missile29

Member
Hi,

I did something stupid on my rudder. I slipped while riveting the shear clips to the stiffeners and made a tiny little pimple (opposite of a dent, facing out) on my skin. Accidents happen, and I should have left it alone, but being a noob, I thought "I can fix that!" So I placed the skin face down and a back rivet plate and proceeded to try to tap the pimple flat by tapping all around with a hammer / bucking bar, etc.

Now I have a lump about the diameter of a golf ball. It's not terribly tall, but will oil can in and out when I push on it. I'm wondering if anyone has any suggestions on how to turn this particular outie into an innie so that I can fill it later. I have already riveted the skins together and the spar in place, but have not closed up the leading edje yet, so I can still sortof reach some fingers up inside if needed. Anything I do just seems to make matters worse.

Thanks!
 
Sorry I don't know how to make the "outie" into an "innie", since the skin is likely now stretched from the tapping.

But the next time there is another pimple or ding, just use a dinner spoon from the kitchen and slowly work around and around the bump to smooth it out. Try practising on some scrap first, it works!
 
The real problem is that when you started tapping steel to aluminum, you stretch the aluminum sheet where you hit it. You also work harden the sheet in the area you are hitting. That causes the oil canning effect you see. No good way to get rid of that that I know of. Next time, use a firm but softer material as backup, like hdpe, and a leather or rubber hammer to gently reform the damage. It is important to note that when you dinged the metal you stretched the skin locally. The skin will work harden over a couple of minutes. If you can attempt to fix the ding immediately you aren’t fighting the work hardening and will get a better result.
 
Those were the answers I was afraid of, but I appreciate the tips! Definitely learned a lesson on this one. I didn't realize work hardening was a process that took place over time. I assumed it happened at the moment of impact. Does that apply to rivets, as well? i.e. if you under-squeeze a rivet and you want to squeeze it further, you should do it right away?

As for my rudder, I guess I just live with it for now and chaulk it up to experience. I've heard oil-canning can lead to fatigue and cracking, but this should be an easily inspected location.
 
Those were the answers I was afraid of, but I appreciate the tips! Definitely learned a lesson on this one. I didn't realize work hardening was a process that took place over time. I assumed it happened at the moment of impact. Does that apply to rivets, as well? i.e. if you under-squeeze a rivet and you want to squeeze it further, you should do it right away?

As for my rudder, I guess I just live with it for now and chaulk it up to experience. I've heard oil-canning can lead to fatigue and cracking, but this should be an easily inspected location.

Basically, the rivet will get harder with some time, so while not as critical (different alloy), you would want to finish if off in a relatively short period of time.
 
There are companies that do paintless dent removal. Dentless Touch is local to me and has a great rep. You can look up on YT his channel. I know there are people nationwide using these principles and may be able to assist you.

Mark
 
... The skin will work harden over a couple of minutes. If you can attempt to fix the ding immediately you aren’t fighting the work hardening and will get a better result....

Sorry, but that is not true. Age hardening takes place over time as the hardening element precipitates out of a metastable crystal matrix.

Work hardening happens during the deformation process, as dislocations in the crystal matrix move and are created during active yielding.

Working the material will not trigger additional age hardening any time after the yielding process is complete.
 
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