Heavy Duty Awning Cleaner

[jeff]

The awnings from our 83 Avion have not been used in what looks like a decade. The white stripes have yellowed / browned, and using the standard "awning cleaner" from the local RV supply shop helps a little, but they still look downright bad.

Before resorting to removing them and soaking them in oxiclean or bleach for a day - does anyone have experience removing this sort of nastiness without full awning removal?

Thanks!