The International Tempest is a 22-foot, two-man, high-performance keelboat equipped with spinnaker and trapeze. It weighs little more than 1000 lbs.; its fiberglass hull weighs less than 500 lbs., its fin keel weighs about the same, and its 30-ft. aluminum mast adds about 30 lbs. On its trailer, its towing weight is normally less than 2000 lbs.

The Tempest’s main and jib total 247 sq.ft., and its spinnaker adds 225 sq.ft. more. Its powerful, high aspect ratio rig and efficient hull enable it to sail upwind at almost seven knots and tack through less than 90 degrees. It’s best known for its offwind speed, however—it can plane in as little as 13 knots of wind and surf in much less—and its heavy air performance once led an editor of Yachting to call it "the fastest one-design keelboat, period!"

Ian Proctor designed the prototype for a competition in 1960, and redesigned the boat in 1990 based on 25 years of lessons learned. During this time, about a dozen builders produced more than 800 boats. But today, the Mader family in southeastern Germany is the only active builder. Until 1990, the Maders’ monopoly stemmed from the quality of their boats: in the 1976 Olympics, for example, all teams except one sailed Mader boats. Subsequently, no buyers ordered boats from any other builder, fearing that they might be second-best. Today, only Mader’s molds incorporate the 1990 design changes, so it’s unlikely that other builders will resume construction in the near future.

The word "International" in International Tempest identifies the Tempest Class as an "international class" controlled by the International Yacht Racing Union (IYRU). This means, among other things, that the IYRU must approve all design changes or measurement procedures—the class cannot do so on its own—to ensure that the class carefully considers its proposed rules changes.

In all other respects, the class is governed by the International Tempest Association (ITA) and National Tempest Associations (e.g., USITA).

The ITA conducts an annual World Championship, publishes a yearbook and international regatta schedules, and serves as the source for proposed rules changes to the IYRU.

The National Tempest Associations schedule their own championships, maintain mailing lists, and publish newsletters.

In May 1965, the International Yacht Racing Union (IYRU) conducted trials in Medemblik, Holland to select a new two-man keelboat for "international status."

Ian Proctor was one of ten people who designed boats for this event. Ian is a British yachting journalist who had tried his hand at dinghy design a dozen years before, and also owned a company that manufactured metal masts. By the mid 60s, his dinghy designs were well known.

The objective for the trials was to select a boat that—it was understood—would supplant the Star in the Olympics. The IYRU specified a boat with a trapeze and spinnaker that would plane in moderate wind. Ian, unlike the other entrants, design a boat with watertight compartments like many centerboarders, but unlike any previous keelboat.

Strong winds and shallow water can cause a very short chop on the IJsselmeer, where the competition was to be held. So Ian designed Tempest to be very sharp forward (see 1), based on his previous experience in dinghy designs.

Ian had Tempest built in plywood, and it completely met his expectations. He rigged it, John Oakeley and Cliff Norbury practiced in it for a month, and then they shipped it to Holland.

There, Ian’s idea worked brilliantly. Tempest won every race except one, in which she broke her rudder while leading. In an extra heavy air race (15–25 knots), she finished half a mile ahead of the nearest competitor. Bob Bavier of Yachting and a member of the IYRU selection committee wrote, "Quite frankly, we fell in love with Tempest ... our decision was unanimous and enthusiastic. I suspect ... we have given yachtsmen of the world a great new boat to rally around." (His description of the trials appears in Appendix A.)

Selection committee members wanted to be sure mass production in fiberglass would be feasible before class rules and Building Specifications were developed, however, and they perceived it might not be possible to mass-produce such a boat at the prototype’s light hull weigh. How would such a boat perform? To find out, Tempest’s team filled two bags with sand, stuck them in the cockpit, and went out to race again. And again they won.

Tempest’s victory attracted immediate worldwide attention. The International Yacht Racing Union granted the Tempest Class international status, prompting boat shows in Europe and America to ask to put boats on display (see Ian’s story in Appendix B). There were teething problems, of course, and while Ian, Beecher Moore, and many others worked on into 1966 to resolve them, production couldn’t keep pace with demand. But that year, enough boats were already sailing for the class to hold a European Championship.

With growth seemingly assured, owners turned their attention from promotion to experimentation. In the U.S., for example, jib sheeting angles among top boats varied between eight and the "original" fourteen degrees, and there was little agreement on the correct rake angle for the mast. 1968 World Champion Billy Kelly remarked that he wasn’t "at all sure that we ... don’t have a lot of unnecessary gadgets."

In November 1969, the IYRU selected Tempest to be used in the 1972 Olympics, prompting many people to buy new boats, and activity reached a peak during the next three years. But after the ’72 Olympics, many people stopped sailing their boats. The emphasis on competition had inhibited growth and the number of active fleets dropped. Magazine articles that featured some of the most gear-laden boats left an impression that complexity and expense were necessary, and that only tall, heavy people could be competitive crews.

The 1976 Olympics temporarily spawned some fresh interest, but did not reverse the declining trend in worldwide popularity. In 1977, the IYRU decided to re-substitute the Star for the Tempest in the Olympics. By 1981, the class had become so weak in North America that it canceled a World Championship scheduled for Newport, Rhode Island.

But new boats now had simplified, standardized rig and hardware layouts that incorporated the lessons learned from the Olympic experience. So, for perhaps the first time, class leaders could begin to focus on promotion.

Today, people sail Tempests because they are remarkable boats, unsurpassed by many newer designs. Worldwide competition in the class isn’t as intense as in the Olympic years, but Mader continues to build new boats, North and Vogel+Meier are developing new sails, and there is an active regatta schedule with events throughout Germany, Austria, Switzerland, Holland, and England, and in America at Annapolis. It seems that old boats don’t deteriorate more quickly than the people who sail them. So while the average age of Tempest sailors is increasing, worldwide membership is stable at more than 200 members.