Evaluating Modern Catamarans
Ocean Navigator|March/April 2020
Evaluating Modern Catamarans
A multihull voyager examines the of key elements offshore cruising cats.

Catamarans have been around, especially in the Pacific, for several thousand years. Early islanders sailed large twin-hulled canoes many thousands of miles, generally from Southeast Asia eastward to discover new island homes.

Modern multihull production started with the catamarans of Hawaiian Rudy Choy in 1947. The first cruising catamaran to circumnavigate was his World Cat in 1965. During the 1960s, Prout and Catalac of Great Britain were also starting to produce catamarans. Catamaran production took off in the late 1970s and early 1980s with French builders Fountaine Pajot, Catana, Lagoon and several others producing catamarans for the charter industry. Gemini also started building boats in the U.S. Soon afterward, South African builder St. Francis got started with a 43-foot cat in about 1990, and now a dozen others in South Africa produce about 30 percent of the world’s cruising cats.

After considerable research looking at a number of boats and more than four years aboard, full time cruising in Southeast Asia, here are our thoughts on some important features to look for in a bluewater cruising catamaran.

Size vs. cost: As with all boats, as size increases, so does cost. We think a 42- to 48-foot cat makes a great cruising home. Any shorter, and sufficient load-carrying capacity for full-time cruising suffers; longer, and the hull and equipment costs skyrocket.

Bridge deck clearance (BDC): BDC affects the amount of noise in the boat from wave slap, especially while going upwind. We think a catamaran with about 30 inches of clearance is ideal. Increasing the BDC means more windage, which is a negative. Much less than 30 inches, and wave slap becomes a problem in rowdy sea conditions. Longitudinal under-bridge deck fins reduce wave impacts and strengthen the bridge deck. Reducing speed and falling off can also help minimize the problem. Consider how often you actually go close upwind in heavy conditions when cruising versus how much time you spend on other points of sail and in port. The St. Francis 44 has about 24 inches of BDC and it has completed many circumnavigations. However, that does not mean its BDC is ideal.

Load carrying capacity (LCC): Larger boats have more LCC for fuel, water, stores and equipment. Boats with finer hulls are faster than boats with fat hulls, but they will have less LCC. Most full-time cruisers will need at least 5,000 pounds of LCC. When asking this question, make sure you know the hull weight facts and what is included or not. Overloading a cat adversely affects speed, stability and BDC.

Beam-to-length (B/L) ratio and stability: For boats in the 42- to 48-foot range, the B/L ratio should be around 50 percent. Less than that will adversely affect stability in heavy beam winds, but larger boats can be okay with slightly less. A higher ratio adversely affects sailing characteristics. Most modern cats are in that range; older cats are somewhat narrower but also have shorter rigs. For more on this important characteristic, search the Internet for “catamaran stability.” Integrity and quality of build:

There is a big difference in build quality across manufacturers of catamarans. Things to look for include builder reputation, hardware quality and strength, use of lightweight construction materials, anodizing vs. painting of aluminum extrusions, interior woodwork finish, exterior design, and equipment quality and installation technique. If water enters older cats made of cored balsa or plywood, there are often maintenance problems. A good construction practice is to make the underwater hulls of solid fiberglass, and the topsides and decks of foam-cored fiberglass. Solid underwater sections are more impact resistant and easier to repair; they also make adding thru-hulls less of a problem. But they do add weight. If enough of the boat is made with lightweight cored fiberglass, the hull will not sink in case of a major collision or capsizing. This is a major catamaran safety feature, as it is always better to be upsidedown on the surface than rightside up on the bottom.


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March/April 2020