Design Brief & Intent
The Searunner 31 was engineered specifically as a self-built, blue-water capable cruising pocket-yacht. Unlike its contemporaries from Arthur Piver—which were simpler to build but suffered from a lack of windward ability and structural refinement—or the flat-out racing designs of Lock Crowther, the Searunner was balanced. It was built for sailors who valued passage-making speed but refused to compromise on safety.
Crucial to this design philosophy is the center-cockpit configuration, an unconventional layout for a 31-foot boat. By positioning the cockpit directly over the centerboard trunk amidships, Jim Brown placed the helmsman at the boat’s center of gravity. This central placement significantly reduces the pitch and roll experienced by the crew, making watch-keeping far less fatiguing. Furthermore, keeping the mast step and all primary halyards and sheets within arm's reach of the cockpit allowed for exceptionally safe, short-handed sail handling.
This layout naturally splits the interior accommodation into two distinct cabins separated by the cockpit, connected below only by a low passageway or "crawl-through." The forward cabin serves as the primary living saloon, featuring a dinette, a functional galley, and a V-berth, while the aft cabin (often called the "sterncastle") provides a separate double berth or two single berths. While this split configuration ensures excellent privacy for two couples or a cruising family, it does require stepping up into the cockpit to move between the cabins, which can feel exposed in cold or wet weather. The interior joinery on these boats is entirely dependent on the skill of the original builder, ranging from utilitarian painted marine plywood to highly detailed teak or mahogany finishes.
Variations & Configurations
While early blueprints designated a standard format, the Searunner 31 was offered in two primary build configurations: the "Fixed-Wing" and the "A-Frame" (or wishbone) models.
- Fixed-Wing: This version features solid, enclosed wing fairings connecting the main hull (vaka) to the outer hulls (amas). These wings dramatically expand the boat's interior feel, providing massive dry-storage lockers and deep wing berths that feel incredibly secure when underway. However, this configuration presents a large surface area to the sea, leading to occasional "underwing pounding" when sailing into short, steep head waves.
- A-Frame: The A-frame configuration utilizes open trampoline netting laced between heavy tubular aluminum or steel "A-frames". This setup sheds water instantly, eliminates underwing pounding, reduces wind resistance, and shaves significant weight off the platform.
A common misconception—often repeated in amateur databases—is that the Searunner 31 has a folding mechanism similar to modern Farrier or Corsair trimarans. In reality, the fixed-wing version is completely rigid. Only the A-frame version can be disassembled (demounted) by unbolting the structural frames for trailering or long-term storage, a labor-intensive process that cannot be done dynamically on the water.
The sail plan is overwhelmingly configured as a cutter rig. By splitting the sail area between a mainsail, a staysail, and a jib, the cutter rig allows the skipper to easily downshift the sail area in climbing winds without losing the boat's balanced helm. Underwater, the boat relies on a pivoting centerboard housed in a central trunk rather than a deep fixed keel or a delicate daggerboard.
Sailing Performance & Handling
The physical numbers behind the Searunner 31 paint a picture of a highly responsive, easily driven cruiser. With a light-ship displacement of 7,000 lbs and a generous sail area, the boat boasts a Sail Area to Displacement (SA/Disp) ratio of 24.13. This high ratio translates to immediate acceleration in light air, allowing the boat to ghost along at wind speed when monohulls of the same era are forced to turn on their engines. Its Displacement to Waterline Length (Disp/LWL) ratio of 141.14 places it firmly in the light-displacement category, enabling the hulls to slip through the water with minimal resistance and easily achieve double-digit speeds off the wind.
At the helm, the Searunner 31 behaves more like a large sailing dinghy than a traditional keelboat. Dynamic stability is derived from its wide 18.67-foot beam. The boat heels only a few degrees before the leeward ama submerges its buoyant hull, creating a solid, upright sailing platform that reduces crew fatigue. The Comfort Ratio of 7.57 is low by monohull standards, reflecting the quick, active motion typical of light multihulls in a seaway. It does not roll in the agonizing manner of a heavy-displacement boat, but it does follow the contour of the waves quickly.
Its Capsize Screening Formula of 3.9 is technically high, but this is a mathematical artifact of the formula's design, which assumes a monohull's ballasted geometry; in practice, the wide-stance trimaran is extremely resistant to capsize under working sail. The windward performance is surprisingly efficient for a 1960s design, provided the centerboard is fully deployed to its 5.75-foot draft. When running downwind or entering shallow anchorages, raising the board reduces the draft to just 1.92 feet, allowing the boat to slide over sandbars or be safely run right up onto a beach.
One handling quirk characteristic of the design is "hobby-horsing". Because of the relatively short waterline (LWL of approximately 28 feet) and the concentration of accommodation weight amidships, the boat can develop a pitching motion when driving directly into a short, steep chop. Active weight management—keeping the bow and stern compartments as light as possible—is essential to mitigating this behavior.
Known Issues & Triage
Because almost all Searunner 31s were owner-built from plans rather than manufactured in a standardized factory, construction quality is the single greatest variable on the market. Potential buyers and current owners must approach these boats with a disciplined triage routine focused on structural woodwork.
- Plywood Rot and Delamination: Early Searunners built in the late 1960s and 1970s often utilized older resorcinol glues and were sheathed in polyester resin and fiberglass cloth over marine plywood. Over decades, polyester resin loses its bond to wood, allowing freshwater to migrate behind the glass skin. The primary areas for rot triage are the cockpit floor, the "scupper-spaces" where water can pool, and the underwing joints where the vaka meets the wing decks. Any soft spots require immediate surgical removal of the damaged plywood, followed by a rebuild using modern marine epoxy and biaxial fiberglass cloth.
- The Centerboard Trunk: The centerboard trunk is a critical structural member that acts as a structural spine for the main hull. It is highly prone to internal rot if the interior surfaces were not thoroughly saturated with epoxy during construction. Furthermore, the pivot pin can wear its housing oval over time, leading to slow, persistent leaks into the bilge. Triage requires hauled inspection, re-bushing the pivot hole with high-density G10 fiberglass tubes, and glassing the trunk’s interior seams.
- A-Frame Corrosion and Lashings: On A-frame models, the metallic frames can suffer from crevice corrosion at the through-bolts where they attach to the ama bulkheads. The trampoline nets and their lashing points also degrade under UV exposure and must be replaced every few years to ensure crew safety when walking on deck.
Modernization & Upgrades
Modern owners are actively refitting these classic platforms to adapt them to contemporary cruising expectations.
- Propulsion Upgrades: The Searunner 31 was originally designed to carry small, heavy inboard engines (such as the Universal Atomic 4 gasoline engine or early raw-water-cooled diesels). Modern refits almost universally discard these heavy, space-consuming inboards in favor of modern, lightweight alternatives. Installing a 9.9 hp high-thrust, long-shaft outboard on a retracting transom bracket or a specialized "sled" in the cockpit well reduces overall weight, eliminates drag when sailing, and frees up massive interior space formerly occupied by the engine box.
- Electrical and LiFePO4 Systems: Because these boats have limited payload capacity, the heavy lead-acid battery banks of the past are being replaced with lightweight Lithium Iron Phosphate (LiFePO4) batteries. This conversion reduces weight while providing the high capacity needed to run modern navigation instruments and refrigeration.
- Solar Arrays: The flat expanse of the fixed wing decks or the custom dodgers over the center cockpit provide ideal mounting surfaces for walk-on, semi-flexible solar panels, allowing owners to achieve complete energy independence without adding aerodynamic drag.
Market Snapshot & Economics
The Searunner 31 occupies a unique niche on the brokerage market, operating as an "evergreen" value proposition. Because they are wooden-composite boats of a certain vintage, they do not command the high prices of modern, production fiberglass catamarans. Instead, they trade at a significant value, making them one of the most accessible pathways to blue-water capable cruising.
However, the economics of buying a Searunner 31 are heavily weighted toward condition. A professionally built or meticulously amateur-constructed example that has been stored under cover, built with West System epoxy, and regularly maintained will command a clear premium. Conversely, neglected or poorly built projects constructed with cheap materials and polyester resin are often financial traps. The cost of materials (epoxy, marine-grade plywood, and safety gear) required to rehabilitate a rotted hull can easily exceed the eventual market value of the boat, making a thorough pre-purchase survey by a surveyor experienced in cold-molded or wood-epoxy multihulls absolutely mandatory.
The Verdict
The Searunner 31 remains a brilliant testament to Jim Brown's forward-thinking design philosophy. For the hands-on sailor who prioritizes sparkling sailing performance, shallow-draft versatility, and the proven safety of a center-cockpit layout over condominium-style interior volume, this classic trimaran remains an exceptional blue-water voyager.
Pros
- Exceptional light-air performance and high top-end speeds off the wind.
- Center-cockpit layout places the helmsman in the area of lowest motion and simplifies single-handed sail handling.
- Pivoting centerboard and kick-up rudder allow for beaching and extremely shallow-draft cruising.
- Highly seaworthy cutter rig provides excellent flexibility in heavy weather.
- High secondary stability provides a level, comfortable platform compared to heeling monohulls.
Cons
- Variable build quality due to its history as an owner-built design.
- Plywood hulls require vigilant maintenance to prevent freshwater intrusion and rot.
- The split-cabin layout requires exiting to the cockpit to transition between the forward saloon and aft cabin.
- Prone to hobby-horsing in short, steep head seas if weight is not carefully managed.
- Strict payload capacity; performance degrades quickly if overloaded with heavy modern cruising gear.
