We have a carferry that puts out black soot that blows over the marina twice a day all summer. It has left black steaks on our furling jib. The rain must wash it down inside when it is rolled up or at least that is what it looks like. I've tried washing it with a Woolite & vinegar solution in water but it didn't touch it. Also have problems with spider excrement on the sails. The sail is brand new last year so don't want to damage it with harsh chemicals. Any ideas how to clean these two things off the sails?