In which I venture into giving advice … (with all the usual caveats, of course)
In the end I had both Andante’s hull and cabin gritblasted, although not at the same time. From that experience, and from talking to the bloke that did it, I offer the following pearls of wisdom.
1. Having your hull gritblasted is probably on balance less trouble than scraping all the weed, crap, rust and old blacking off with a scraper and a wire brush.
2. It is of course more expensive – unless you could use the three days that it would take you doing it yourself to earn some money doing something else.
3. Stuff something (removable) up your sink waste outlets, and stick (with gaffer tape) the plug in at the other end. Otherwise you will get a sink full of grit at the very least, and if you have a u-bend, its contents will be sprayed up the walls.
The cabin is more trouble – but might also be of greater benefit if you want a really good start to repainting.
4. Grit will get in everywhere if you let it. Tape up all vents on both sides; tape round the inside of all opening windows and window drain holes. Tape round the doors after you leave. Don’t light the fire and sleep in the boat after doing this. Don’t forget the gaps at the top of the rear doors (voice of bitter experience and a gritty engine room).
5. Handy hint I thought of all by myself: remove the grilles from ceiling vents or they will just act as a receptacle for grit that will fall out over the next few months. Instead of taping or masking over the holes in the ceiling, tape small tubs underneath And seal round them. That way it won’t all fall on your head when you unmask it.
6. The main reason for masking the windows (on the outside) is to protect the glass. Start by running a line of gaffer tape all round the outer edge of each pane. Tape your heavy duty polythene to this or to the glass itself. Cover any gaps with more tape. Finish with a line of tape on the window frame. Don’t let this extend onto the paintwork – the whole point of the gritblasting is to get under the paint so it would lift the tape too. Make sure there are no loose edges, ditto.
7. If it’s cold or damp the tape won’t stick and you’ll be wasting your time. So try not to run out of tape at six pm with the nearest B&Q half an hour away.
8. If it’s cold and damp (see above) lighting the stove and ramping it up like a blast furnace helps. (Unless, presumably, you have exceptionally good insulation) As you have already taped up all the windows and vents, best leave the doors open while doing this. This also works following the heavy two minute downpour that will happen while you’re putting the primer on.