Originally Posted by Petar
If removing the paint what is the best way of doing it? What are pros and cons of self polishing and / or hard bottom paint?
It is not necessary to remove an ablative (self-polishing) paint before applying a modified epoxy (hard) paint over it. Generally, a good sanding and then paint will do. But if a pressure washer will remove most of the old paint, why not try that?
The pros and cons of one type over another will vary depending on where you sail and who you ask. I clean hulls for a living in the San Francisco Bay Area and have seen virtually every type of anti fouling available in this country. In my opinion, ablatives have only two advantages over other types; 1.- Ablatives do not build up successive layers of old paint each time the the bottom is painted. 2.- Ablatives can withstand extended periods exposed to air, making them a good choice for trailerable boats.
All that being said, I think modified epoxies are a better choice in almost all cases. A good epoxy paint (like Petit Trinidad SR) will have excellent anti fouling characteristics. Ablatives are not superior to epoxies in this regard and in regions of moderate-to-high fouling, ablatives are certainly not "self-polishing". Modified epoxies are durable and easily withstand several years of repeated in-water cleanings, something that ablatives have trouble claiming. Modified epoxies can be burnished to an ultra-smooth finish (although a sprayed-on ablative is very smooth as well.) But maybe most important, ablatives are tougher on the environment than epoxies, in that they shed much of their matrix along with their biocide. Epoxies do not do this. The argument can be made that the chemicals being shed by ablatives are inert and do not harm the environment, but I don't buy into this. Many state and local water quality regualtory agencies have stated that ablative paints should not be cleaned in-water. In fact, the State of Washington has banned the practice.
Your best bet is to ask other sailors in your area what products work for them and why. But I hope you'll keep in mind the points I made when making a final decision on what to paint with.