Question Re sanding damaged area before painting

[elwynevenstar]

Hi.....I have a 41 year old fiberglass motorhome I am trying to sell and it has a large black spot which manifested from the water heater thingie being turned up too high and no one knew how to turn it down. It looks like smut but I think it could be a burned area. My question is how much can it be sanded down...or can it be sanded at all...before going too deep so that I damage it. And it should be sanded before painting obviously right? I hope you guys can help because I really need to sell it and several people are quite interested but this spot really looks terrible! Thanx.

[Rusty01]

Diane, perhaps you could try to clean it first with Bartender's Friend{from Home Depot}. The oxcylic acid in the product may be enough to bleach it out a bit and at the very least you may be able to tell how deep it goes. rb

[Joe Z]

Before sanding it with a wet type black sandpaper of 360 grit followed by 500 grit which is dunked in water every minute or so to keep it wet...... before you even try this get a can of barkeepers friend in any supermarket next to the cleanser and try that first to see how it works out ....If that doesn't work try regular cleanser before painting but don't go too far out as this is going to scratch up your gel coat so only do it where you intend to paint.
If neither works then you have to do the wet sandpaper.
Joe

Rusty.... we must have been typing at the same time but we both had the same opinion of barkeepers friend....LOL

[floyd]

Originally Posted by elwynevenstar

Hi.....I have a 41 year old fiberglass motorhome I am trying to sell and it has a large black spot which manifested from the water heater thingie being turned up too high and no one knew how to turn it down. It looks like smut but I think it could be a burned area. My question is how much can it be sanded down...or can it be sanded at all...before going too deep so that I damage it. And it should be sanded before painting obviously right? I hope you guys can help because I really need to sell it and several people are quite interested but this spot really looks terrible! Thanx.

Graghics? Or maybe a faux access door?

[elwynevenstar]

Originally Posted by Rusty Baker

Diane, perhaps you could try to clean it first with Bartender's Friend{from Home Depot}. The oxcylic acid in the product may be enough to bleach it out a bit and at the very least you may be able to tell how deep it goes. rb

Thanks Rusty---I am trying to sell this so I'm worried that it is too deep so if that is the case and Bartender's Friend isn't enough what I'm wondering is what is too deep? Can it be so deep that sanding won't work so that no one will want to buy it for fear they can't restore that part of it? Because it really does look burned in--to me- more than simple smut.

[Night Sailor]

Which side was the heat? The outside or inside. If it was the inside then it gies all the way through probably. If the burn mark came from the outside then you might be able to sand it off. If you are painting, then it is a non issue--sand off anything loose, prime and paint.