Some people keep very little on the roof of their boat, maybe just the gang plank and a pole or two and some rope. Other keep bikes, logs and bags of coal for the stove, TV ariels, pot plants, mops, brooms, buckby cans and general junk. We're somewhere in between, but the roof gets a fair bit of wear and tear and is of course exposed to the sun and all manner of stuff dropping from trees. So we really need to repaint Herbie's top.
The painting is the easy bit, its the unpainting that's the problem. Getting off all the old stuff and rubbing away the dozens of little rust spots. Here you can see where I've rubbed down and treated lots of little spots. (Picture taken as we cruised through Little Venice)
They'll all have to be done again because I wasn't able to get them overpainted quickly enough. Unless you get back to the bare metal and treat any rust before the applying primer, the undercoats and the top coats of paint, then you're wasting your time. The question is, how do you get it all off in a reasonable time? (We're talking about 250 square feet on Herbie).
I've been doing some research. Chemicals are out because of the environmental damage of washing them off into the canal. The commonly used belt sander doesn't appeal because it takes forever and clogs up the abrasive paper in no time. People who have done it this way claim to have used a mountain of the paper.
The best options seem to be heavyish industrial kit, either a needle gun which jabs at the paint with a bunch of spikes, or a scabbler which rasps it off at high speed. I can hire either of these by the day locally, so that's easy. However, because they are used on building sites etc, they are restricted by Health and Safety rules to running off either compressed air or 110 volt power supplies. No good off the boat's power then. I can get the loan of a 110v transformer though.
Then there's the problem of the weather. Once the bare metal is exposed it needs treating and painting at least as far as the undercoat before it might rain. This takes two or three days at best. So the best answer (if you can afford it) is to do it indoors by hiring a wet dock for a few days, which is probably what we'll do. Actually, the best answer if you can afford it, is to pay someone else to do it!