Antifouling | risk of damaging gelcoat when sanding?

[AleCiotti]

Hi guys, my boat currently has about 4-5 layers of antifouling on it and I've never (myself) removed all the antifouling on it to bring it back to bare gelcoat.

This year I will be doing antifouling and I can get away with scraping the big chunks of fouling / paint and then wet sanding with 80 git to make it smooth.

The problem is that in some places the paint is almost all the way gone and i can almost see the gelcoat so I'm worried that if i start sanding I'll damage the gelcoat..

Do i just try to not go too heavy with the sanding where i see the gelcoat?

Should i scrape all the paint off to bare gelcoat and go from there?

Thanks

[AleCiotti]

I was thinking of doing copper coat next year, so I was trying to leave the work of removing all the paint for that moment instead of having to do it again next year if I do it this year. (copper coat requires the removal of all previous bottom paint)

[dougweibel]

I am no expert in this area but I'd expect that if you have antifouling right on top of your gelcoat and you are going to sand the antifouling off then you will want to apply a few coats of an epoxy barrier coat before applying new antifouling, be that Copper Coat or something else.

[SailingHarmonie]

Generally, hand sanding--done well--is unlikely to damage the gelcoat. If you are recoating with a compatible paint, you do not need to remove every spot of old paint. So you stop whenever you see gelcoat, and call it good.

Other removal methods are much more likely to damage any existing barrier coat, especially sand blasting. If I was not going to re-barrier coat, I would never do that.

[AleCiotti]

Originally Posted by SailingHarmonie

Generally, hand sanding--done well--is unlikely to damage the gelcoat. If you are recoating with a compatible paint, you do not need to remove every spot of old paint. So you stop whenever you see gelcoat, and call it good.

Other removal methods are much more likely to damage any existing barrier coat, especially sand blasting. If I was not going to re-barrier coat, I would never do that.

How do I know if there is already barrier coat under my antifouling? my boat is made of wood and the hull is protected with gelcoat, but I don't know if someone has ever put a barrier coat before antifouling..

i personally have never stripped the boat of all the bottom paint so I don't know what there is under there.

do you think I should do it?
Thanks