The OP already said he wants a cat (not a dog, nor half a boat). However it is very difficult to resist taking the piss once someone starts up the old debate.
Ok, so his original question is about length, not the number of hulls.
A really general answer would be:
20´ is doable but too uncomfortable, difficult and dangerous
30´ is doable and cheap
but probably only sitting headroom
in main cabin
40´ is a decent compromise for a tradewind RTW
50´ is better but more expensive
60´ is even better but much more expensive. Ring Alwoplast in Valdivia, Chile
, and ask about the Atlantic 57. US$1.6M, but the US$ is going down the tubes, so maybe you can afford it this year, but not next year. If so, go for it! A true world cruiser.
It is difficult to give a better answer due to the sheer number of variables involved, which all seem to be interrelated - overall beam, individual hull
waterline beam, waterline L:B ratio, b/deck clearance and length, inboards/outboards, single/twin engines, daggerboards/fixed keels, etc etc. The OP must do some more research
on his own and then ask a more specific question.
Most of my cruising since I was a kid was on steel
monos, so I spent years looking at this feline stuff and came down to the following, which ONLY APPLIES TO US:
Minimum waterline L:B ratio of 12
Minimum length of 40´
Minimum 3´ b/deck clearance
and kick up rudders
A-frame rig with r/f main and jibs
But hey that doesn´t exist unless we build it ourselves!
So, since our time on this planet is too short for building, and considering that used boats are cheap
, we looked around and decided we better make a compromise. So then we looked at Outremers, Kelsalls, Catanas, Atlantics, Wharrams, FPs. Ended up with:
correct L:B ratio
incorrect b/deck clearance
but no kick-up rudders
material (FG, not alum)
, not A-frame
So you take what you can get. Such is life!
The most important things are to:
Minimise your time in the rat race
Minimise your time in a boatyard
Maximise your time cruising