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Section 10-07 dimple cracks

lipper03

Builder RV14A & ZA750SD
Benefactor
Dimple cracks on deburred F-01412A but not B. I've ordered a replacement A and asked Vans, it's worse on #30 and #27 dimples, vs #40, which makes sense, but I don't get why so many when edges were taken care of. It's most of the #30 on A, but none on B. Suggestions?
 

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I did test more #30 holes, and #31, then reamed #30, both deburr and not, no cracks. I wonder if there was a flaw on the hole punch on that piece.
 
I have a theory...

I had the exact same issue on a specific part on the wing. The part seemed to be laser cut, and the dimple cracks always originated from the spot that the laser first penetrated the part to create the hole. This spot was slightly discolored a brownish tint, which is why I believe that was done by the laser.

All of the cracks originated at this brown spot. If I drilled my own hole in the part, no cracking.

https://vansairforce.net/community/showthread.php?t=209650

I don't know this part on the fuse, but do you see any discoloration from the point of the crack? If so that would lend some evidence to my theory.

Regards,
G
 
I went back to your post after it happened to me, and I’m thinking it’s similar, but I don’t think it was laser, I don’t remember any discoloration, but we’ll see on the replacement. I am going to run a reamer in though, I think.
 
Replacement part was laser drilled, and the laser cut is not the greatest. Ran a reamer in all the holes to clean up, probably ever so slightly enlarged to get the rough inside edge out. Dimpling went much better, no cracks except for one and it was filed out fine.
 
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