Sigma sailboats: the one-designs Britain built after Fastnet
"Sigma" on a brokerage listing almost always means one thing: a David Thomas-designed offshore one-design built by Marine Projects of Plymouth — a range whose two pillars, the Sigma 33 and Sigma 38, became fixtures of British offshore racing. It occasionally means something else entirely: a short-lived American 18-footer that shares nothing with the Devon boats but the name. Both stories are told below; the British one is the reason the make matters.
Origins and the Thomas era
The Sigma 33 began as an answer to a brief for the Royal Ocean Racing Club's 1978 Offshore One-Design conference. It was not among the three designs the conference officially chose — and it outlasted that verdict comprehensively. Production started in December 1978 with hull A3001 and ran to December 1991 and hull A3364: 364 boats. The class was initially to be called the Skua 33, renamed Sigma after a Scottish fleet pointed out their boats were already Skuas. David Thomas's association with his design was personal as well as professional: of the two Sigma 33s that survived the 1979 Fastnet Race, one was sailed by Thomas himself, and he won the class's national championship more than once aboard his own boat, Circe. The class went on to set a record described as one that will never be broken — 105 Sigma 33s in a single Round the Island Race start, the largest one-design fleet in the race's history. From 1981 Marine Projects added the 33C, a cruising version with a shorter masthead rig and longer, shallower keel, of which roughly 44 were built.
The Sigma 38 and the Fastnet legacy
The 38 has the range's most consequential origin. In the wake of the 1979 Fastnet disaster, the Royal Ocean Racing Club and the Royal Thames Yacht Club answered the question of what should be done about offshore racing by sponsoring an offshore one-design fleet built to strict standards. Thomas and Rob Humphreys were the two finalists in the 1985 design competition; the finalists' plans were circulated to the RORC membership, and Thomas won on the strength of the Sigma 33's record. Marine Projects built 125 Sigma 38s between 1985 and 1993, and the class association founded in 1988 still organizes the fleet.
Construction and the wider range
Sigma construction is straightforward, strongly built GRP — hand-laid chopped-strand mat and woven rovings on the 33, with foam-cored floors, integral bulkheads, and almost no internal moldings outside the heads, which makes stowage generous and the hull easy to survey. The 38 carries balsa-cored decks. Around 70 Sigma 41s were built at the Plymouth yard, in both masthead and fractional rigs with the masthead marginally more popular, and their interiors are likewise joinery rather than pan moldings. The one boat in the range Thomas did not draw is the Sigma 400, designed by Humphreys Yacht Design in 1990.
Who Sigma is for
A Sigma suits the sailor who wants proven offshore pedigree with living class support — boats conceived for serious racing, built simply enough to maintain, with the 33 and 38 fleets still active. Thomas, who died at 82, was described by his friend, Hunter Boats co-owner Peter Poland, as "the Pied Piper of yacht designers" — and the Sigma fleets, still following him decades on, are the evidence.
