In reply to ebdon:
> I guess you could come down on ascenders, I've never tried it (whilst climbing) but i thought it was meant to be a total arse?
No more than going up! It might depend on the sort of ascender - I've got some old jumars which are very easy to use, you can hold the cam open with your thumb while moving it but a metal piece prevents it opening completely and coming off the rope. I used this method when clearing ivy off an old building inches a long job as the ivy was 8 thick at the bottom and even near the top a couple of inches in place.
On the other hand I was wondering what size of rope he would jumar up? Most sail halyards are thinner than climbing ropes, aren't they?
As said mostly people seem to have themselves winched up and down, which requires a second person. I saw a boat which was regularly used by a lone sailor and he had fixed aluminium rungs up the mast.