Georgs: What a good question!! There really is no one good answer but here goes. To me the optimum size depends on the ability of the crew to maintain all the systems that are on and in the boat. Usually the lager the boat the more systems there are as well as redundancies and spare parts. The larger the boat would require more expertise of the crew members who may have specific chores in each of the systems. The larger the boat the less options for the KISS principles. Before going on an ocean passage a boat and crew shakedown should be done so all the routines are worked out and all systems deployed to ensure that everyone can do what is planned and not planned. On our boat (44 ft) our crew was my wife and I and so we had to keep the boat simple in order to be able to manage all that could happen in the shift plan. It would be a potential disaster if the number of systems overwhelmed us. I am concerned now with the more modern equipment that requires an in depth knowledge, e.g. electronic controlled engines and other systems. In this case the crew would have to have taken specialized courses to maintain and repair/replace. What modules do you carry as spares and how to do you determine which modules that are defective are detected. This list can go on and on. I am concerned that the owners/crew of such craft have not got the time to learn all this and still have time left to go long distance cruising. I sure you get the point of my comments. The fluid (fuel,water,supplies,etc.) capacities for the longest leg (plus a reserve) will dictate the smallest boat and that appears to be (40 to 50 ft). The design should also include as much ballast as practical. This last statement is made because some passagemakers being built do not actually have real ballast and depend only the weight of the boat. Having said all of the above and if you take on crew (4 or more) then the most optimum size will approach 70 ft. Beyond that you have to think about full time professional crew. Now you get out of pleasure boating and passagemaking. This is definitely not the route I would take even if I had the wherewithal to do it. Regards. Leonard Stern, Indifference. PS: I have not even touched on the medical aspects. Even on the NAR rally there was a medical doctor who definitely was not redundant (from the tape). CONCLUSION: Unless you are a gambler you best be prepared for self sufficiency and the size of the boat will be dictated by your ability to be self sufficient.