Moth (dinghy)

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International Moth
Moth red.svg
Class symbol
Moth Kiel2008.jpg
An International Moth Class sailing hydrofoil flying over the water.
Design Development class
Crew 1
Type Monohull
Construction Carbon Fiber or Fiberglass
Hull weight Unrestricted
LOA 11 ft (3.4 m)
RYA PN 600

The Moth Class is the name for a small development class of sailing dinghy. Originally a cheap home built sailing boat designed to plane, now it is an expensive largely commercially produced boat designed to hydroplane on foils.

The pre hydrofoil design Moths are still sailed and raced but are far slower than their foiled counterparts.


The Moth types have been (not all may still exist):

  • the International Moth, a fast sailing hydrofoil dinghy with liberal restrictions;
  • the Classic Moth, a traditional dinghy with tighter restrictions
  • the British Moth, a one design sailboat similar to those sailed in the 1930s
  • the New Zealand Mark 2 scow moth which became abundant in the 1970s.
  • the earlier Restricted Moth of the 1960s and 70s which had fewer restrictions allowing for class development. Confusingly, this nomenclature was sometimes used interchangeably with the term International Moth in Australia and NZ.



The current International Moth is a result of merging two separate but similar historical developments. The first occurred in Australia in 1928 when Len Morris built a cat rigged (single sail) flat bottomed scow (horizontal bow rather than the "normal" vertical bow) to sail on Andersons' Inlet at Inverloch, a seaside resort 130 kilometres (81 mi) from Melbourne. The scow was hard chined, 11 feet (3.4 m) long, with a single 80 square feet (7.4 m2) mainsail. The craft was named "Olive" after his wife. The construction was timber with an internal construction somewhat like Hargreave's box kite. "Olive's" performance was so outstanding, that a similar boat "Whoopee" was built. Len Morris then sold "Olive", and built another boat called "Flutterby", and with those three boats, the Inverloch Yacht Club was formed. Restrictions for the class known as the Inverloch Eleven Footer class were then drawn up, with the distinguishing characteristic that of being not a one-design boat but rather that of a boat permitting development within the set of design parameters.

At much the same time, 1929 in fact, halfway around the world another development class, the American Moth Boat was started by Captain Joel Van Sant of Elizabeth City, North Carolina[1] with his boat “Jumping Juniper” built of Atlantic White Cedar from the Great Dismal Swamp. The major difference between the Australian and American boats early on was that the American boat used only 72 square feet (6.7 m2) of sail on a somewhat shorter mast. The US development class was formally organized in 1932 as the "National Moth Boat Association" and in 1935, due to increasing overseas interest, changed its name to the "International Moth Class Association" or IMCA.

In 1933, an American magazine, The Rudder, published an article dealing with the Moth Boat scene in the US. The Australians noted the similarities between the two groups of boats and intuitively realized that the name "Moth Boat" rolled more easily from the tongue than "Inverlock Eleven Footer Class", and changed the name of their class to Moth. The Australians also noted the differences, particularly in sail plan between the two boats, but since this was in the middle of the great depression, and the two groups were 13,000 miles apart, no attempt was made to reconcile these differences. Thus two large Moth classes developed separately for over 30 years.

Early growth[edit]

Also, in the early 1930s a small group of sailors in Great Britain formed a British Moth Class. The British Moth class was restricted to a particular hull shape of a 1930s Vintage American Moth Boat, and is thus a one-design boat, not a development class which allows experimental development with shapes and materials. Meanwhile, in Australia, in 1936 the Victorian Moth Class Association was formed, but it was not until after WWII, that the NSW Moth Class Sailing Association was formed with foundation members coming from Seaforth Moth Club and Woolahra Sailing Club. During this time Australian Moths were using pre-bent and wing masts in the 1950s. From 1956 to 1961 all other states formed Moth Associations and in 1962 the Australian Yachting Federation (AYF) recognized the Australian Moth class as a national class, the FIRST small boat class in Australia to be granted national status.

After the second world war, more and more European interest in the Moth Boat was expressed. The European Moth clubs subscribed, more or less, to the US class rules. One European Moth design from the early 1960s, the "Europa Moth", broke away from the IMCA and formed the one-design Europe dinghy class and became the woman's single-hander used in the Olympic games from 1992-2004. Also in the 1960s, the Australian Moth sailors began campaigning for rules changes that would permit the Australian Moths to compete in the IMCA's "World Championships".

International Moth Class[edit]

In 1971 the US-based IMCA completed a phase-in of new rules which attempted a "marriage" of the IMCA and the Australian Moth. This amalgamation process had started at the annual IMCA meeting in 1965. New rules embraced the larger, more powerful high aspect, loose footed, fully battened rig of the Australian Moth. The new rules also permitted controversial hiking wings first seen on Moths from Switzerland. Finally, the rule change abolished the US centralized organization of the class in favor of an independent world body with equal-partner national associations. Each national association elected its own officers and world body representatives. The culmination of these changes was the recognition in 1972 of the IMCA by the International Yacht Racing Union (the forerunner of today’s ISAF) bound by the agreed upon new restrictions of the class (with metric measurement conversions) operating today. The moth class association that had originated in the US was now truly an international organization.

Being a development class, the Moth has evolved from a hull in the 1930s that could best be described as a heavy, narrow scow or a blunt nosed skiff, (weighing about 50 kg) to today’s remarkable foilers with hull weights of under 10 kg. Designs have run the gamut from wide skiffs without wings, to lightweight scows, to wedge-shaped hulls characterized with narrow waterlines and hiking wings out to the maximum permitted beam. Likewise, the sail plan has evolved from cotton sails on wooden spars, through the fully battened Dacron sails on aluminum spars, to the windsurfer inspired sleeved film sails on carbon masts seen today.

In New Zealand the class reached its maximum popularity in the late 1960s and early 70s. The NZ Moth was standardized as a 90 lb flat bottom scow type known as the Mk2 using an alloy spars and a Dacron sail. The measured sail area was nominally 80 square feet but the actual area grew to about 90 square feet by 1970. Many hundreds were home made by amateurs. In addition there were a smaller number of International Moths of both scow and skiff type. Hulls were noticeably lighter -down to 50 lbs for skiffs using plywood by 1970. The international yacht designer Bruce Farr built Moths to his own design in the 1967-1971 period when still a young school boy.


In the United States in the late 1970s participation in the International Moth class died and the class growth and interest moved to Europe and Australia. After ten years of little Moth activity in the US, several sailors started looking for old Moth Boats with the original US rig to restore and race. A newsletter was started to aid communication between like-minded Mothists. Racing of "Classic Moths" resumed in 1989 and in 1990 a new club was formed to govern racing and construction of Classic Moths. This club, the Classic Moth Boat Association or CMBA is the current governing body for the original US type of Moth Boat. The intent of the CMBA is to revive the original US version of the boat and update the rules so that development is permitted without allowing the boats to become too freakish. The IMCA rules from 1965, the final year prior to the phase-in of the Australian rig and wings were consulted as a starting point for reviving the US Moth. Those rules have been revised where necessary. Interest in Classic Moths has grown internationally, with new activity in Europe, primarily France.

Moth firsts[edit]

The International Moth has fostered a number of achievements. In 1966-67, The King of Siam was involved in the building of three Moths and sailed them on the pond at Chitrlada Palace. The King raced for almost 20 years on his second moth called 'Super Mod' until his design and construction efforts were cut short by the 'press of royal duties'. [2] In 1957 Patricia Duane became the first woman to win the moth world championship in her Cates-Florida design.[citation needed] In 1968 Marie Claude Fauroux became the first woman skipper to win a World dinghy racing title from an IYRU sanctioned international class - in her Duflos designed moth.[citation needed] The International Moth was selected[when?] as an official training class for the Japanese Olympic sailing team, to hone their balance skills.[citation needed]

Recent years have seen the International Moth literally take flight with the advent of lifting hydrofoils on daggerboard and rudder, which lift the entire hull and skipper above the water surface, dramatically reducing drag and increasing speed. Top speeds achieved are above 30 knots, the highest 10 second average of 30.7 knots[3] (56.9 km/h) was recorded on 2 May 2010. This high speed is reflected in the International Moth's RYA Portsmouth Yardstick of 600, the fastest (As of 2012) of any sailing dinghy or multihull.[4]

Class growth[edit]

Since the addition of hydrofoils to the boat, the International Moth Class has experienced worldwide growth, including a resurgence in the United States. The moth has become the standard of a successful hydrofoiling class[citation needed], with most foils and control systems based on developments by John Ilett of Fastacraft in Australia.[citation needed] It is currently, on April 2014 one of only two practical foiling monohulls, the second being the foiling version of the RS600, though recently[when?] the R-class skiff in New Zealand has seen some boats add hydrofoils as well. There are now several manufacturers supporting Moth fleet growth, including Mach 2 boats (Australia/China), Fastacraft (Australia), Aardvark Boats (UK), and Maguire Boats (UK). New boats cost around $22,000 USD,[when?] though used hydrofoil boats can be had in most active countries for less than half that.[citation needed]

As of 2009, areas of rapid development in the class, include rigid sails,[5] wing masts,[6] hydrofoils[citation needed], and foil control systems[citation needed].

Skills needed[edit]

Moths are sailed by young, agile, and athletic sailors from the mid teens upwards. They are not regarded as a beginner's sailboat. They are not suited to sailors under 55kg and performance drops with heavy sailors. The class emphasizes light hull weight to promote quick planing or foiling. Older designs are extremely variable and because of the emphasis on light weight, need careful transportation and storage indoors when not in use. They are designed for one person. Because of their short length they are best suited to sheltered waters, light to moderate wind speeds, and smaller waves. They are primarily a fast racing boat not suited to load carrying.

Recent events[edit]

The 2011 International Moth World Championships was in Belmont, Australia on 8–14 January 2011.[7] This event was the biggest Moth Worlds in a long time, with 109 boats mostly foilers but including several scow and skiff Moths. The winner was Nathan Outteridge of Australia in a Mach 2. A solid wing sail although not strictly allowed by the class rules was allowed to sail by virtue of a vote of the class membership. The wing was not sailed by its developers Bora Gulari and George Peet as it was clear to them that it was not yet developed enough to take the championship. Charlie McKee sailed with the wing and came 23rd despite a number of breakages.

The winner of the 2010 PUMA International Moth World Championships, sailed in Dubai in March, was Simon Payne[8] (GBR) in a Mach 2 over Andrew McDougall (AUS) - also in a Mach 2. The series was noted for its light air, with last year's champion Bora Gulari (USA - 6th) using the race with the strongest breeze to record his only win of the series.

The 2009 International Moth World Championship was won by Bora Gulari on a Mach 2 over 2009 World 49er champion Nathan Outteridge sailing a Bladerider (2009, Columbia River, Oregon, USA). This regatta was notable for the caliber of the competitors it attracted, including many full-time professionals, Olympic champions, and World Champions in various fleets. Gulari's victory was a remarkable achievement and spoke volumes about how learning to push the boat very hard and optimizing control systems can pay dividends against very smart but less foiling-savvy competition.


External links[edit]