Multihulls / Cruising / Overloading,

There are any number of ways to account for the added weight of crew, personal effects, and stores. And from the literature that you get in brochures, it is nearly impossible to determine what the displacement actually refers to--it is lightship weight (empty boat with no crew or liquids on board), a medium cruising weight (half crew/stores weight and half liquids), or is it full load displacement (all crew/stores and full liquids). Most brochures and design literature don't give that much detail, and you really have to talk to the designers to find out this information.

In general, most designs will accommodate a reasonable amount of crew weight, stores, and full liquids, so I would not agonize too much about this. Obviously, you want to keep most of the weight towards the middle of the boat, and most boats are built to encourage this. Keep the weight out of the ends of the hull. You don't have any control over the placement of the liquids (fuel and water) as that depends on where the builder put the tanks. If the builder is smart, he will keep the tanks near the middle of the boat.

I always recommend that serious cruisers (or those intended to go cruising) read a very good book by C.A. Marchaj (MAR-ki) called "Seaworthiness, the Forgotten Factor." It deals primarily with racing sailboats and why certain types of boats are not particularly seaworthy. What comes out of that book is the realization that wide shallow hulls are not very seaworthy on the open ocean and in large breaking waves. Multihulls are wide and shallow to the extreme, and that is why I usually question their appropriateness for ocean crossings. If you want to do your cruising along coasts and among some islands, however, then multihulls can be ideal.

Cruiseing catermarans

Hi Daiwa ,
Dont overload cats ;thats the rule, but then that also applies to mono hulls aswell. The biggest problem with cruisers is that they tend to collect "things" as they cruise . On my own boat we would take everything off the yacht once a year and I mean everything . We would then clean inspect and paint the bilges before putting some of the things back . This is the hardest part of cruiseing , but after a few times you learn that all the material things dont improve your cruiseing life . Infact they start owning you .The reason most people go sailing is to getaway from all the material trappings and now we start collecting things that own us . so go sailing not collecting.

But this is a technical forum . Ive sailed 50000 miles on mono hulls and 100000 miles on catermarans .and Ive crossed most oceans at all times of the year. The stongest winds Ive encountered was 70 knts and that was on a delivery in a Moorings 400 cat . The boat handled the big waves and strong winds very well . On the same delivery we encountered 8 gales of 45 plus knts from all directions and at all times the boat was under control. Ive also safely delivered Lagoon cats from France to Tortola during the Hurrican season . During christmas 2005 I delivered a new 55 ft mono hull to Tortola and we sailed next to TRS Zeta for 5 days with sustained winds of 45 knts .
If I had my way I would only sail CATS they are more comfortable ,sail level and fast , yes you shouldnt overload them but as I said earlier dont overload any sailing boat . Good luck with your Cat .
Clive

Catamarans Hulls and the LCG

I might suggest you have a look at this article by Malcolm Tennant, "Power Catamarans and the LCG", even though it is 'power oriented'. Loading of the hulls is still applicable.