Thompson 31 Information, Review, Specs

Sailing Performance & Handling

The Thompson 31 is widely regarded as a "stiff" boat, a characteristic derived from its healthy ballast ratio of approximately 41%. With a displacement of roughly 8,500 lbs and a 22-foot waterline, the design falls into the category of heavy-displacement cruisers by modern standards, providing a motion comfort ratio of 27.47. This translates to a predictable and sea-kindly motion in a seaway, making it less prone to the "hobby-horsing" seen in lighter, flatter-bottomed designs.

According to owner experiences documented on technical exchanges like the YBW Forum, the boat excels in heavy air, where it "digs in" and tracks exceptionally well. Owners have reported reaching speeds near 9 knots in Force 6 or 7 conditions, though such speeds exceed the theoretical hull speed of 6.29 knots and typically involve surfing on reaching legs. The masthead rig is simple and robust, though it can feel underpowered in very light winds due to the high displacement-to-length ratio of 356. In these conditions, a large overlapping genoa is essential. One notable technical feature found on some early hulls was a trim tab on the trailing edge of the keel, intended to reduce leeway on the wind, though many of these mechanisms have been glassed over or removed by subsequent owners.

Interior Comfort & Variations

The interior of the Thompson 31 was ambitious for its era, offering a layout that remains functional for a small family or a cruising couple. The standard configuration includes a V-berth forward, a central saloon with a folding table, a compact galley, and a dedicated navigation station. Headroom is generally sufficient for sailors up to 6 feet, a significant selling point during its 1970s heyday.

The "Long Cabin" variant is the most sought-after version for liveaboard or extended cruising, as the extended coachroof significantly increases the perceived space in the main cabin and allows for improved storage lockers. The construction often utilized a mix of materials; while the hull is solid GRP, many Thompson 31s were finished with plywood decks and coachroofs sheathed in GRP. This hybrid construction provided a warm, traditional aesthetic below decks, with high-quality timber joinery that outshines the "all-plastic" interiors of later mass-production boats.

Known Issues & Buyer’s Checklist

Prospective buyers should approach the Thompson 31 with a focus on its hybrid construction methods, as the longevity of the vessel is closely tied to the integrity of its timber-to-fiberglass joints.

• Deck and Coachroof Core: Because many T31s utilize GRP-sheathed plywood for the decks and coachroof, freshwater ingress is a primary concern. Potential buyers should inspect for soft spots around stanchion bases, chainplates, and the main hatch. Delamination in these areas often necessitates a labor-intensive "peel and replace" repair.
• Keel-to-Hull Joint: The fin keel is a substantial casting. Ensure there is no evidence of "weeping" at the joint or rust staining from the keel bolts, which may indicate a need for re-bedding or bolt replacement.
• Trim Tab Mechanism: If the vessel retains its original trim tab on the keel, the linkage in the bilge should be inspected. These are frequently seized or have developed play, leading to an audible "clunk" while sailing or at anchor.
• Chainplate Anchors: The chainplates are under significant load on this stiff hull. Inspect the internal mounting points for signs of timber rot or structural stress in the bulkheads where the rods are secured.

Community & Resources

The legacy of Guy Thompson's designs is preserved through a dedicated community of owners, primarily based in the UK and Northern Europe. While no standalone international association exists specifically for the 31, the Guy Thompson Owners group and the broader Clyde Cruising Club technical archives provide a wealth of documentation on the T24, T27, and T31 models. Technical discussions and historical brochures are frequently shared within the YBW technical forums, which serve as the de facto registry for the class.

The Verdict

The Thompson 31 remains a compelling choice for the traditionalist who values sea-kindliness and structural heft over modern planing performance. It is a "sailor's boat" that rewards those willing to put in the maintenance required of its vintage construction.

Pros:

• Exceptional stability and heavy-weather tracking.
• Classic "yacht" aesthetic with high-quality interior joinery.
• Reliable skeg-hung rudder configuration for offshore peace of mind.

Cons:

• Maintenance-heavy GRP-sheathed plywood decks on many hulls.
• Slow performance in light air and downwind compared to modern designs.
• Aging original systems (engines and wiring) often require a refit.