Design and Hull Form
Bill Dixon's brief for the S31 was to squeeze genuine offshore capability and coastal-cruiser habitability into a hull measuring just under ten metres overall. The result is a beamy, twin-keel-capable design with a beam of three-point-three metres that maximises interior volume without overreaching in displacement. Twin-keel and fin-keel variants were offered simultaneously, the shoal-draft bilge-keel option drawing only three feet nine inches, which opens drying harbours and tidal creeks that a fin-keel yacht could never enter. The fin-keel version deepens the draft to five feet six inches and sheds roughly 180 kilograms of displacement, favouring those who prioritise windward performance over tidal flexibility. Both versions share the same deck moulding and interior, so the choice is essentially one of sailing territory rather than accommodation.
A detail that sets the S31 apart from contemporary rivals is the centre section of the transom which folds down entirely to form steps to the water — a genuinely useful feature for swimmers and dinghy handling, and one that was unusual at this price point in the mid-1990s. The cockpit access to the aft cabin via its own hatchway further reflects Dixon's intention to make the boat feel larger than its overall length suggests.
Rig and Sail Plan
The S31 was offered in two rig configurations: a masthead arrangement and a fractional sloop. The masthead rig carries a mainsail of twenty-one square metres paired with a working jib of fourteen-point-eight square metres and an optional furling genoa of twenty-seven square metres, while the fractional version steps a slightly taller mainsail at twenty-three-and-a-half square metres that compensates for a shorter foretriangle. Both arrangements suit short-handed sailing, and the modest sail areas are consistent with a boat designed to be handled by a couple without the need for powered winches in ordinary conditions. The I measurement of twelve-point-two metres gives the rig a clean, uncluttered profile well suited to coastal passages and estuary sailing, though the fractional version's emphasis on the mainsail rewards owners who invest in a good furling main or stack-pack for single-handed operation.
The standard engine is a Volvo MD2020 nineteen-horsepower diesel driving through a saildrive — a reliable and widely-serviced unit that pairs sensibly with the displacement of the bilge-keel variant at just under five tonnes. Fuel capacity of ninety litres offers reasonable motoring range for a boat of this size.
Accommodations
Interior volume is the S31's most discussed attribute. The aft cabin stretches right across the full width of the boat, an arrangement that is genuinely unusual in a thirty-one footer — most competitors of the era consigned the aft accommodation to a cramped quarterberth or a narrow double accessible only from the saloon. Here the full-beam aft cabin contains a full-size double berth with headroom and stowage to match, accessed independently from the cockpit via its own hatch. Forward, the forecabin sleeps two in a conventional V-berth arrangement, and the saloon settees provide two additional berths if needed, bringing total sleeping capacity to six — a number more commonly found on thirty-five footers. Tankage is sensibly scaled: a hundred and eighty litres of water supports extended coastal passages without the anxiety of rationing.
Known Limitations
With only 145 boats built over four years, the S31 never achieved the production volume that drives down component costs or generates a dense network of owners' associations. Prospective buyers should be aware that trim parts, mouldings, and deck hardware specific to the model may require fabrication or adaptation from other Moody series. The bilge-keel variant's twin-keel arrangement, while invaluable for drying harbours, typically yields noticeably inferior windward performance compared to the fin version — a trade-off inherent to the configuration rather than a flaw in the design, but one worth understanding before committing. The displacement-to-length ratio of the bilge-keel boat reflects her weight, and hull speed under sail in light airs will expose this. Buyers who plan to sail competitively or passage-make predominantly offshore should weigh the fin-keel variant seriously.
Refit Considerations
The Volvo MD2020 saildrive unit is well into its decades-long service life on most surviving examples, and saildrive bellows replacement is a standard interval item that should be surveyed carefully — a failed bellows floods the bilge rapidly and is an easy item to defer. The saildrive installation is otherwise a clean and accessible arrangement that simplifies engine access compared to shaft-drive equivalents. The optional furling genoa was not standard equipment, so rigs should be inspected for the forestay arrangement actually fitted. The transom swim platform mechanism should be checked for its hinge integrity and drainage, as standing water in the fold-down section can accelerate osmotic exposure on boats that have not been maintained to a rigorous antifoul schedule. Given the full-beam aft cabin's proximity to the waterline, the hull-to-deck joint in that area merits close survey attention.
The Verdict
The Moody S31 is a thoughtfully engineered family cruiser that punches well above its waterline in interior space and accommodation quality, thanks largely to Bill Dixon's decision to prioritise volume and the distinctive full-beam aft cabin. The bilge-keel option gives access to shallow tidal waters that a conventional fin-keel yacht cannot reach, making the S31 particularly well suited to the cruising grounds of the British Isles and similarly tide-governed coastlines. Her production run of 145 boats means she is not a common sight, which sustains a degree of exclusivity but also limits the support network available to owners.
Pros
- Full-beam aft cabin with double berth and independent cockpit access is genuinely unusual at this length
- Bilge-keel option enables drying harbours and very shallow anchorages
- Folding transom swim platform adds practicality ahead of its era
- Reliable and widely-serviced Volvo MD2020 saildrive engine
- Six-berth capacity in a manageable thirty-one-foot hull
Cons
- Small production run limits availability of model-specific parts and owner community support
- Bilge-keel variant carries a meaningful windward performance penalty versus the fin-keel version
- Saildrive bellows require diligent inspection on aging examples
- Light-air performance will feel pedestrian in the heavier bilge-keel configuration
- Furling genoa was optional, so rig specification varies between boats
