Design and Construction
The Sigma 38 OOD rests on robust fiberglass construction, with a solid hull and a balsa-cored deck. Below the waterline the elliptical fin keel carries a lead bulb on a cast iron stub, delivering a 41% ballast ratio and a draft just over two metres elliptical fin keel with lead bulb. There is enough forefoot to avoid slamming yet a flat enough aft section to surf, and the spade rudder under a 42-inch wheel gives a beautifully light helm. Shroud load is taken by a large stainless steel T-piece laminated into the hull, while inboard chainplates and a swept-back double-spreader rig keep the decks clear. A cruising version was offered but only a handful were built, with minimal differences from the standard OOD.
Rig and Handling
The 7/8ths fractional rig concentrates sail area in the mainsail, serving a 691-square-foot total sail plan that yields a 19% sail-area-to-displacement ratio. She goes about cleanly, and running backstays — fitted to the 7/8th rig — open the leech of the main and genoa and tension the forestay in over Force 3 conditions, brightening performance when it gets fruity. Primary winches sit at the end of the coachroof with a 52:1 ratio more at home on a 50-footer, and the mainsheet traveller lies just ahead of the helm. Writing in Yachting Monthly, test sailors found her responsive, with good stability and a turning circle of just over a boat length to starboard, and the spade rudder gave a beautifully light helm through the 42-inch wheel light helm; the shaft drive gave only a small kick to port in reverse that she quickly overcame.
Accommodations
Below, the Sigma 38 OOD provides a practical layout for six to eight crew. Two settees make good sea berths at 6ft 8in, with two further pilot berths outboard, and a vee-berth forward whose bunks flip up to reveal a large storage cage. Headroom at the companionway base is 6ft 3in, though the steep steps assume crew agility. A proper nav station to port and a longitudinal starboard galley with a top-loading fridge sit amid limited work surface, while two aft cabins offer equal-length doubles, the port one gaining a small wash basin above the engine bay. The cockpit holds four or five for cruising, with binnacle-mounted throttle and nearby mainsheet controls aiding single-handing, and a deep lazarette beneath the helm seat.
Known Issues
Surveyor Ben Sutcliffe-Davies notes that the balsa-cored decks commonly soften on these boats, and the alloy toerail can guide the eye to prior impact locations. Hull-to-deck joints should be watched for collision damage, and goose neck fittings wear with use. Former class chairman Nigel Goodhew points out that the laminated shroud T-piece has often needed reinforcement — a manageable job within the class's expertise — and the structural matrix around the keel can delaminate in a grounding. Many owners have since upgraded keel security with larger backing plates and added lamination to the internal matrix frame.
Refits and Ownership
Most boats left the factory with 28hp Volvo engines, and many have been re-engined since. Engine access comes through a removable front box and side panels in the aft cabins reaching the gearbox and stern gland. The forehatch is a vast 600mm square by modern measure. The active class association and the boat's one-design discipline make shared knowledge and spares straightforward for an owner, and the minimal cruising-version differences mean most hulls share the same core platform.
The Verdict
The Sigma 38 OOD is a deceptively quick and powerful offshore one-design that remains manageable for smaller crews — a sheep in wolf's clothing, as the phrase goes. Her Thomas-designed hull and rig reward both club racing and shorthanded cruising, and the class's continuity keeps support close at hand, though buyers should budget for deck and structure vigilance.
Pros
- Fast cruiser-racer with proven offshore lineage and active UK/Ireland fleets
- Light helm, clean tacking, and tight turning from the spade rudder and fractional rig
- Practical six-to-eight berth layout with sea berths and a real nav station
Cons
- Balsa-cored decks prone to softening and keel-matrix vulnerability in groundings
- Shroud T-piece often requires reinforcement; goose neck wear is common
- Steep companionway and limited galley surface demand crew agility and compromise
