What grit for sanding a bus for paint?

[belfert]

I'm thinking I might actually paint my bus next year.  My bus is all aluminum with fiberglass front and rear.  The clear coating is peeling in spots so I plan to sand at least some of the paint.  What grit sandpaper would I start with for aluminum?  For stripping a car they usually recommend 36 grit, but that seems a bit coarse to me for aluminum.

[TomC]

I'd start with 80 grit. Then 220 then 320. Good Luck, TomC

[bevans6]

Are you thinking to strip the paint off down to the bare aluminium, or surface scuff the paint?  I would do almost anything to only surface scuff the paint, so that you don't have to replace the factory undercoat and acid wash later.  I would use maybe 200 grit and do it by hand, after cleaning with wax remover and reducer.  the fiberglass is a different thing altogether, there I would tend to go down to the glass and rebuild it up.  I have had good luck with cracks by grinding out the crack down to the fiberglass and filling with a slurry of resin mixed with micro-bubble fairing filler.  Anytime you need to bond to fiberglass you need to grind with 80 grit to get teeth in the surface.

Brian

[belfert]

I'm not really sure how far down I need to go with the paint.  None of the paint is actually peeling other than the clear coat.  The paint is three different colors and I definitely need to at least remove the transitions between the colors.  It looks like they painted white first and then painted green and gold on top.  There is a definite ridge where the top colors end.

I used Alcuobond panels to cover my windows and those will need to be primed for sure.

[LowTide]

I agree with TomC, I would use 220 and then go to 320. using a DA sander. Good luck

[TomC]

I have a Dewalt 5" diameter palm rotary sander that I swear by. You'd be surprised at how fast 220 will take anything off. Good luck, TomC

[belfert]

Interesting on the 220 grit.  I used 80 grit on my roof with a 1/4 sheet palm sander to prep before applying the elastomeric.  Only in a couple spots did I end up taking all the paint off.  I suppose I really don't want to take all the paint off anyhow.

[chart1]

I just did mine. I used 220 with round palm sander. Just nock the shine off till you have a dull finish then you are ready for some GOOD primer. Then I used a single stage paint. No need for clear coat. $1500 in materials.