Thompson 850 Information, Review, Specs

Sailing Performance & Handling

The Thompson 850 is defined by its exceptional power-to-weight ratio. According to technical specifications provided by the designer at T-Boats, the vessel features a deep 2.1-meter (approx. 6' 10") retractable bulb keel, which provides the necessary righting moment to support an expansive sail plan. Under sail, the boat is characterized by its "light" helm and its ability to plane in as little as 12 knots of true wind speed.

Upwind, the 850 tracks with precision, though it requires an active crew to manage the backstay and traveler to keep the boat flat and maximize the efficiency of its high-aspect foils. Downwind, the boat transforms; once the asymmetrical spinnaker is deployed from the retractable pole, the T850 easily reaches speeds in the mid-to-high teens. Handling is described by owners as "nervous but rewarding," typical of a boat with a low displacement-to-length ratio. The use of a large, high-balanced rudder ensures that the boat remains controllable even when pushed hard in a blow, though a skilled hand is required to prevent "wipeouts" during high-speed gybes.

Interior Comfort & Variations

Despite its primary identity as a racer, the Thompson 850 offers a functional, albeit Spartan, interior that classifies it as a "racer-cruiser." The cabin layout typically includes four pipe-cot or cushioned berths—two in the midships area and two aft under the cockpit—providing enough accommodation for a crew during a regatta weekend.

The interior is characterized by its white flow-coated finish and carbon fiber accents, prioritizing weight savings over luxury. Headroom is restricted to sitting height, as is standard for a vessel with such a low-profile coachroof. Variations of the model exist primarily in the construction materials used; while the hull is typically a fiberglass and foam core sandwich, some units were outfitted with full carbon rigs and high-modulus standing rigging. The T850 is a direct sibling to the Thompson 7 and the larger Thompson 980, with the 850 often cited as the "sweet spot" in the range for those who require a trailerable boat that does not sacrifice the waterline length needed for coastal chop.

Known Issues & Buyer’s Checklist

Purchasing a Thompson 850 requires a specialized survey focusing on high-load components and composite integrity. Prospective buyers should prioritize the following areas:

• Keel Trunk and Lifting Mechanism: The retractable keel exerts significant leverage on the hull structure. Inspect the keel box for stress fractures or signs of movement, and ensure the lifting winch and stainless steel pin (which locks the keel in the down position) are in good working order.
• Chainplate Reinforcement: Given the high tension of the rig, the areas where the chainplates meet the hull and deck should be checked for crazing or delamination.
• Rudder Bearings and Gudgeons: The high speeds achieved by the T850 put immense pressure on the steering system. Check for any "slop" or play in the rudder bearings, which can lead to vibration and loss of control at high speeds.
• Mast and Sprit Integrity: Many 850s are equipped with carbon fiber masts and bowsprits. These should be professionally inspected for UV damage, hairline cracks, or compression at the exit blocks and spreaders.
• Deck Core: Like many foam-cored boats, any poorly sealed deck hardware can lead to localized delamination. Use a phenolic hammer to tap out the deck, particularly around winches and the mast step.

Community & Resources

Owners of Steve Thompson’s designs are a dedicated group, often sharing technical data through regional sports boat associations. While no single-model international class association exists, the T-Boats Designer Archive remains the primary source for original sail plans and technical drawings. In Australasia, the boat is a frequent participant in the Australian Sports Boat Association (ASBA) events, where technical parity and handicap adjustments for the 850 are regularly discussed.

The Verdict

The Thompson 850 is a high-octane sports boat that offers a bridge to coastal racing for crews who have outgrown smaller dinghies or sports boats. It is not a vessel for the novice, nor is it a comfortable family cruiser, but for the performance-oriented sailor, it offers a level of excitement that few boats in the 28-foot range can match.

Pros:

• Exceptional downwind performance and early planing capabilities.
• Trailerable design allows for easy transport to various racing circuits.
• High-quality design pedigree from a world-renowned sports boat specialist.
• Effective retractable keel system for shallow water access and transport.

Cons:

• Spartan interior with very limited headroom and amenities.
• Physically demanding to sail at a competitive level.
• Requires a high level of maintenance for the rig and foil systems.
• Sensitivity to crew weight and trim makes it less forgiving than traditional keelboats.