scraping her bottom

Hi Mike


I guess you do that instead of using antifoul paint, yes?
Sorry, but no. You need to antifoul the boat.
To get a longer span between (expensive ) anti fouling, most people go over the side and scrub with a scotch pad or something similar.
Most modern antfoul paints are "ablative". This means as you sail along very thin layers of the outer surface of the paint wear away and the weed, slime and barnacles leave with the paint. If you don't move so much or so fast or the paint is not as good as it is cracked up to be you will get slime.
The slime then becomes a surface that the weed and other critters can stick to.
A scrub removes the slime.


If so how often do you do it?
That depends on how much, how fast you sail, where you are moored and how good your (expensive ) paint is.
Ask people moored around you, what they do.

Do you still need to paint the hull every couple of years?
If you can get two years out of a coat of antifoul (with scrubbing to help it along) count yourself lucky.

Racers pay very careful attention to the condition of the underwater surfaces, cruisers are a little more laid back, but everyone has to deal with it.
Not to be ignored.

I haven't mentioned antifouling the prop, because it is a subject of much discussion to put it mildly.

To give you an indication of what can happen. My boat had been out of the water for two years when I bought her.
The antifouling was dead (there is probably a more correct word , like deactivated)
First pic . As she was to go in the water.



Second pic exactly one year later. I moor in a very fertile estuary in Japan where aquaculture big.
I mean really fertile

I didn't scrub. I do now!

Gary

Yes during the club racing season we dive and scrub every 2 weeks. We wear a Sharkshield. Annual antifoul.