Size matters. In the open ocean waves are created by swells (traveling long distances from weather
highs to lows) and wind
which stir up a local pattern that can parallel the swell, or cross it at just about any angle. Swells are long and smooth, with periods sometimes exceeding 140 feet. Wind
blown waves have shorter periods, and the combination is responsible for some beaches having a really high 9th wave (or 5th wave) followed by a set of lower waves.
In shore the depth
of the water
has a major impact on the size of the wave: shallower water produces shorter periods. Off shore and off soundings (that means the water is really deep) the size and period of the wave is determined by the force that generated it.
The amount of pitching a catamaran
will do is primarily dependent on the wave period. Hull
form, particularly hull
rocker, is the second strongest influence.
Catamarans under some length of the waterline will pitch
much more that longer waterline boats that "bridge" the local wave period. sailors will notice that different cats seem to hobby-horse worse in a narrow range of water depths. A 32 foot waterline may be uncomfortable passing through 15 to 19 foot depths, where as 36 foot cat will pitch
more in 25 to 35 feet of water.
When the small boat reaches deep water, the ride is smoother. It is smoothest when the wind is less of a factor, and riding over the long swells is pleasant. Barring strong weather patterns, life on the deep blue is nice. But getting to the deep blue, crossing the transition areas, exposes a small boat to wind driven short period waves at a time when nerves are tuned up because of traffic, obstructions, lack of familiarity with the area and more. A longer waterline moderates the motion of the vessel. There is no upper limit to this moderating, so a 150' yacht is hardly affected by waves that make life on a small craft miserable.
The question of what boat is best for a cruising couple with aspirations to circumnavigate is answered simply: bigger is better. But bigger boats present a crew with heavier challenges. Complexity, muscle power required, and knowledge needed all increase geometrically as the boat gets bigger, arriving at a point that exceeds a typical mature couple's capability in the mid forty-foot range. Even then the boat can survive far worse conditions than the crew can handle. This is an arbitrary number arrived at by consensus of those who have tried it. Interestingly, this number has risen through the years. When Steve Black led the first Caribbean 1500
, the average size of participating boats was in the mid thirties. Lately the average size has been more than 48 feet LOA
My advice to new boaters is to buy the biggest boat you can handle. Experience prepares you to handle bigger boats. Age encourages you to get a smaller vessel. Daugherty's Maxim states that nobody buys their last boat first. There are exceptions that prove the rule
, but for most of us, we don't need to buy something that requires hired crew, and two people will have problems raising and reefing sails
as big as those found on boats over that semi-magic LwL. Electric
winches mandate a heavy and complicated electrical
supply, placing considerable strain on a new sailor's technical competence. Many a day has been ruined by not know where to replace a fuse.