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-   -   Strange crack in skin. Why would this happen? (https://vansairforce.net/community/showthread.php?t=96834)

543TB 02-24-2013 10:17 AM

Strange crack in skin. Why would this happen?
 
Okay, friends. We've been building for awhile, and completed the leading edge (outboard) section on the left wing back in November. While out in the garage this week, we noticed what appears to be a crack in the skin, top-side, right along the rivet line where the bracket for the stall warning assembly lies. As you can see, however, the crack does not extend to the rivet hole. Why on earth would this occur, and what can be done about it? (We are sending Van's the same question, but wondering what the collective knowledge of the Van's-verse would say.)




curtis 02-24-2013 11:16 AM

Is this a crack or is it something that has been smashed onto the skin during riveting?

543TB 02-24-2013 01:17 PM

Quote:

Originally Posted by curtis (Post 747248)
Is this a crack or is it something that has been smashed onto the skin during riveting?

It appears to be a small stress crack, but the weird thing is that it didn't show up until recently. It was definitely not there when and right after we installed the stall warning kit, and it isn't raised, which would indicate something between the skin and bracket. The wing has been on the stand the whole winter, and there is no damage around it, so it doesn't appear to have had something hit it. I'm mystified by it.

az_gila 02-24-2013 02:18 PM

Is it truly a crack?

Could it have been a sliver of something hard getting in the way during dimpling or riveting?

RV10inOz 02-24-2013 02:22 PM

Get all that plastic off. If you have been building for a while it may already be a nightmare to remove.

And you can get corrosion growing under it. You are not doing yourself any favours, trust me.

rgmwa 02-24-2013 02:39 PM

It may just be the lighting, but you appear to have creases in the skin.

RVbySDI 02-24-2013 09:23 PM

Quote:

Originally Posted by RV10inOz (Post 747290)
Get all that plastic off. If you have been building for a while it may already be a nightmare to remove.

And you can get corrosion growing under it. You are not doing yourself any favours, trust me.

+1 with this statement! It is hard to tell what the dis coloring is on the plastic but leaving the plastic on the metal for any length of time is not good at all.

Frank Smidler 02-25-2013 09:18 AM

Not a crack
 
I doubt it is a crack. A crack can only be formed by repetative or extreme bending of the metal. Since this is a new assembly that has not seen either of these it is most likely a scratch or coining from debris when riveting. You can burnish most of this out if you want to with a scotch bright pad. I would not worrie about it though. Work towards good quality not perfect quality. The latter will never result in a finished airplane.

TerryWighs 02-25-2013 09:26 AM

There may be a "drill shaving" contaminate under the skin that is sandwiched under the skin, between skin and rib.

pa38112 02-25-2013 09:54 AM

Do you have kids/wife ? Never underestimate their ability to damage something in a way you could not ever imagine - and then deny it no matter how much supporting evidence you have. Most of the time they don?t even realize or remember what the did.

aarvig 02-25-2013 10:24 AM

Quote:

Originally Posted by TerryWighs (Post 747539)
There may be a "drill shaving" contaminate under the skin that is sandwiched under the skin, between skin and rib.

+1 for this opinion. The stress riser appears to be pushed outward which would seem to indicate there is something between the skin and the rib stressing the metal. Regardless, you need to check it out. :(

ccrawford 02-25-2013 09:25 PM

The dimples seem a bit oversized too, but maybe that's the camera angle.

Where in Denver is your project? I'm sure I or someone else would be happy to stop by and check things out in person.

bobmarkert 02-26-2013 03:51 AM

Denver Builders
 
Andrew,
Give me a call if you want to plug in to a great group of builders in the denver area.
Bob Markert
303 882-7410


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