Thanks for your replies.

The present boat is launched from a Trailer, but it is very solid,
would guess at 100kg, perhaps a touch more.

My father, 72 and not getting younger, finds winding this heavy boat
up by the winch hard work. Electric winch an option I guess. Think the
side rails of the trailer are solid and not rollers, thus more
difficult.

... but anyway..

As to maintenence, would cover with a good lid and only use every now
and then (every couple of months). Yes I guess a 'tinnie' might be OK,
but it has no character and was hoping to get something out of
building it.

Perhaps metal 'tinnie' is the most logical way to go. Will check out
instantboats.com as suggested.

N. Peter Evans