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The author, in the foreground, racing a Marstrom A-Cat.

International A-Class Catamaran By Dave Ellis


n the 1960s, the then international sailing governing body undertook to quantify and encourage development of multihulls. They divided the genre by size and sail area, with the D-Cat, at 32-feet and 500 square feet of sail, the largest. Few were built, of course, the most famous being Beowolf, Steve Dashew’s Tornado cat on steroids. The C-Cat is up to 25 feet long with 300 square feet of sail. There are few of these very fast and expensive craft, but they are followed with interest partly because of their early embrace of wing sails starting in the early 1970s. The B-Cat was deemed to be up to 20 feet with up to 235 square feet of sail. The Hobie 16 actually falls within this rule. But the Tornado was so much faster than other offerings that the B-Class disappeared. Then there was the A-Class. At 18 feet long and no more than 7-1/2 feet wide, it was to have no more than 150 square feet of actual sail area. Here was a boat that could be built in the shop, tweaked, cut up and started over, all by the average sailing nut. The first A-Cats were home-built. But soon, the Unicorn, similar to a skinny Tornado, and the Australis, a hull that came to a point at both ends with a faired rudder, could be purchased. They weighed about 200-pounds. By the mid-1980s there was a good fleet at the Gulfport Yacht Club in Florida. Twenty boats raced at the selfdescribed “Nationals” in 1989. Most of the hulls looked alike, pretty conventional with normal bows and flat decks, connected by trampolines, aluminum spars with rather tall, 48

January 2011


fully battened sails, pointy at the head. But, since the A-Cat is a development class, innovation is welcomed within the basic box rule. It was not long before fertile minds went to work. As the saying goes, “This is not your grandpa’s A-Cat.” Imagine an 18-foot sailing craft with very little extra hull above the waterline when one hull is flying; with a reverse bow to punch through, not over, the waves; with a mast approaching nearly 30 feet in height; that in total only weighs 165 pounds. Yes, that is including hulls, sails, foils, spars, everything but the skipper. With so little weight to support, the hulls are now quite narrow, especially at the bow and stern. The foredeck is not designed to ever feel the feet of a human, so it is designed to shed water and go through lumpy stuff. To get the maximum beam, narrow by catamaran standards, there is often a small ledge built into the side of the deck where the range of the skipper’s feet would be. This is to make up for the loss of beam there by the tumblehome or canting of the hulls. Details, details. Dagger boards are evolving. But the jury is still out among conventional high aspect boards, high aspect canted boards and “banana boards” that curve underwater. The rule states that the boards must be inserted from the deck. Otherwise somebody would put an “L” board under there for foils. Nothing but the skipper can extend beyond the maximum beam. Sails and rigs have also evolved. Besides being taller, they are also shorter on the boom and have a “square top,” making the sails almost a skinny rectangle. Masts are now a