Perfect Cruising boat?

You mean a 70ft with 2 junk sail will suffice? How much surface area u need?

 

Fred, I am talking only of big sailingboats with small crews.

I thought you liked fast sailing. Who wants to sail at 8 knots in a 70ft sail boat (with inefficient or small sails)?

Make it 16 knots and big sails…and if you think you can control a big fast boat alone without help from a furling boom…maybe you can, if you are young and fit, but if you are over 60 and have a big boat you can do three things: get a crew, sell the boat, have a furling boom.

That has nothing to do with “Different folks , different strokes”, but with big boats, small crews and the possibility of continuing sailing fast in a big boat when you get older.

Lots of performance boats use furling booms, not for racing (big crews) but for cruising with small crews, or no crew.

 

If you plan to sail alone, a reefing system that leads all the cables to the cockpit is the way to go. In bad weather and troubled seas you don't want to be on the deck of a relatively small boat while a not very effective autopilot is trying to control the boat.
Modern systems allow you to have two single line reefing points. I have a third reef running with two lines. No need to go on deck.

 

Welly, as a rough estimate traditional gaff rigged vessels masts height above the deck are about 3 times beam of the hull and length of the boom for offshore boat maximum 2 times beam of the hull. Shorter is safer. (Longer then that would catch waves as the boat rolls).

You have to make detailed calculations of course. Calculate sail area / displacement ratio for indication of the speed in moderate wind strengths and sail area / wet area for indication of speed in light airs. Then draw few versions of desired sail area configuration and compare heeling forces versus righting moment.

You will find excel spread sheets in the attachments which will help you:

Milan