Ever seen this in a skin sheet?

[thehagg501]

I pulled out my top wing skins and one of W-00002 has this spot beneath the vinyl. I rubbed it off with some 800 grit. It seemed like it was just some dirt. There isn't an indentation in the spot after removing. Build on?

 

[David Paule]

I think if it was mine, I'd call Van's Support in the morning and ask them.

Dave

 

[Snowflake]

Looks like an inclusion in the aluminum, maybe something got on the rollers where it was formed into a sheet in the first place.

 

[RViator60]

Never seen that before. I agree better to give Vans a call in the morning. If me, would ask for a replacement part.

 

[PaulvS]

I don't think it is a problem because it looks like it is on the surface only and it should not be sanded out by more than 10% of the thickness of the sheet (see AC43.13-1B).

If using 800 grit then ensure it is not silicon carbide "wet and dry" because the carbide grit can embed and cause corrosion on aluminum. Scotch brite (aluminum oxide) is a safer bet.

 

[Ralph Inkster]

Being the top skin, I’d give Vans a call.
If it was the bottom, I’d deal with it by dressing it out, or patching it.

 

[thehagg501]

I don't think it is a problem because it looks like it is on the surface only and it should not be sanded out by more than 10% of the thickness of the sheet (see AC43.13-1B).

If using 800 grit then ensure it is not silicon carbide "wet and dry" because the carbide grit can embed and cause corrosion on aluminum. Scotch brite (aluminum oxide) is a safer bet.

Thanks for the heads up on the grit, it's 3M 213Q. I should have been less invasive, think it would of wiped off with water actually.