BOTTOM PAINT GUIDE PART 4: REMOVING OLD BOTTOM PAINT
One of the big deals is that the dust from sanding anti-fouling paint is toxic – you don’t want it in your lungs or in your eyes. Experts recommend wet sanding old anti-fouling paint, capturing the residue, and then disposing of it as hazardous waste. Some boatyards, such as Independence in St. Thomas, have installed dustless sanders; they are loud, but they capture the poisoned dust.
You can use chemical paint removers to do the job, but they, too, are hazardous to your health; proper care must be taken during use and clean up. Sand-blasting is yet another way to remove old anti-fouling paint, but it requires special equipment and practice – it is a job for professionals.
The other big deal is that if you remove all of your old anti-fouling paint, you will have a chance to carefully inspect the bottom of your boat. Sure, you can loosely sand, then prime and paint over the old stuff, but why miss an opportunity to take a close look at a part of your boat you rarely get to see? You don’t want to miss a chance to fix small problems before they become large ones.
Inspect your hull for cracks in your gelcoat; cracks can allow water to seep in and eventually cause blisters. You want to look for blisters, too, and deal with them before you re-paint. Blisters should be ground out, dried, and then filled with epoxy – generally a job for professionals or experienced do-it-yourselfers.
Grinding and filling blisters addresses only one part of the problem. Blisters can be a warning sign of osmosis. If you have fluid behind a blister, you’ve got to find out where the water is coming from and take action in order to prevent more damage to your hull. Your best option is to consult your boatyard professional or a surveyor; they will help you accurately track the water source.
Once your blister problems have been solved, whatever the cause, and the blisters have been filled, you will need to apply a coating of epoxy to the hull. (For boats that have not yet been launched, Interlux recommends applying a layer of epoxy to the gelcoat as a way to help prevent osmosis.)Yacht paint manufacturers and distributors will be able to guide you to the correct choice for the epoxy you will need to seal your hull before applying the anti-fouling paint.
You should also inspect and clean your out-drive and props, centerboard, keel, and any other part of your boat that is normally underwater. As with everything else on a boat, these parts are subject to wear and may need to be repaired or replaced before you launch your boat.
As with any painting project, the most crucial part of the job is the preparation. It is worth it to take the time to thoroughly sand, repair and clean your hull before applying your anti-fouling paint. Your anti-fouling paint will adhere better and last longer on a clean, well-prepped hull, and you will have the peace of mind that comes from knowing that the underwater portion of your boat is in good condition.