[Craig Coffin]

I just purchased a used tail kit for a 4, very little has been done. When I finally got a look at the parts, I was concerned with the number of scratches in the skins. There are areas where the skins were rubbing together in shipping and from other sources. I plan on priming interior surfaces with a self-ethcing primer for aluminum and also painting the plane when finished. Do I need to completly sand out/ polish the scratches or just remove rough surfaces and prime? I do not want to remove more material than I need to. The plane will be in So Cal so it will be in a dry environment, but I do want to make sure that I don't leave areas that will lead to corrosion in the future.

Craig

 

[cytoxin]

edge scratches

edge sratches are the ones i sand smooth, as a general rule remove no more than 10 % sheet thickness.as far as scratches in the center (away from the edges and holes) i would just smooth them out. when you begin to sand a scratch out you will see the alclad open up and the real deal under neath.the all clad provides 0 strength and is about .002 thick. so on a .025 skin you can go to around 4-5 thou. YMMV good luck.smaple the worst one. then just wait till your finished to do the rest before you paint.

 

[MrNomad]

self etching primer

When some self etching primers get hard, they don't adhere to the paint to follow. Read the label on your primer. If it says "paint within 7 days or scuff sand to promote adhesion" that implies the paint won't stick after 7 days.

Believe the label. Scuff sanding does not promote adhesion as well as fresh primer. Once upon a time we primered a 55 chev with PPG self etching primer but waited 3 weeks before paint (due to a major problem). Yes, we scuff sanded before painting, no, it didn't adhere properly.