OSTAC, Ltd. initially oversaw production in Australia. Corsair purchased the American production rights in 1994, and 50 hulls had been built at the Chula Vista, California, facility by the time Practical Sailor surveyed the boat.
Design and Construction
The F-31 has a pleasing profile, with a fine entry, fine lines, and low, 27-inch freeboard. A flat aft section prevents the stern from burying when the bow rises in heavier breezes.
The hulls are hand laid in a foam sandwich. The lamination schedule begins with NPG gelcoat and a skin of .75-ounce chopped-strand mat bonded with vinylester resin to prevent blistering. Corsair warrants the hull against blisters for five years. Five to eight layers of unidirectional and bidirectional fiberglass follow, with Kevlar reinforcement in high-stress areas; all are bonded with polyester isophthalic resin. Vacuum bagging is used to ensure the proper mix of resins and catalysts.
Rather than a conventional shoebox joint, the hull-to-deck connection uses Farrier’s “top hat” method. Special foam inserts are glassed throughout the hull wherever shrouds, bulkheads, and hardware are installed. The amas contain marine-plywood bulkheads tabbed to the hull in as many as seven places.
The aka beams are carbon fiber filled with foam. Aluminum struts support them, with fiberglass-reinforced acetal bushings and stainless-steel-alloy pivot points. The boat has nine watertight compartments and is unsinkable. Most importantly, Farrier says no owners have reported a failure of the folding system.
Rig and Handling
The standard rig has a 40-foot-tall, fractionally rigged Sparcraft mast with swept-back double spreaders. Standing rigging is 1 x 19 stainless steel, with three shrouds and two cap shrouds. There’s no permanent backstay; the cap shrouds are led outboard to the amas.
The F-31 carries 599 square feet of sail in a fully battened, large-roach mainsail and jib. Running rigging includes a main halyard, two jib halyards, and a spinnaker halyard, all internal and led aft. A racing rig is available, while the optional 42-foot-tall rig increases the bowsprit-mounted asymmetrical spinnaker from 1,004 to 1,112 square feet.
Sailing World’s testers found the foam-cored, vacuum-bagged hulls and rotating aluminum spar well built and rigged for speed. The mainsail roller-furls around the boom.
At the launch ramp, two moderately experienced people can rig the F-31 within 15 minutes. On the water, test sailors reached 18 knots on a tight reach in only 12 knots of wind. Changing from the jib to a 180-percent genoa “screecher” increased tight-reaching speed by 30 percent. Even under full power, the boat hardly heels, though it has a quick motion in a breeze and needs a conservative hand for the crew.
Accommodations
The main hull is narrow but flares above the waterline to make room for settee berths and a forward V-berth. The main cabin has 6 feet 2 inches of standing headroom.
Practical Sailor notes that the cabin is only 7 feet wide, making it narrow compared with a typical 32-foot monohull. Even so, the F-31 has an enclosed head to port with a small stainless-steel sink, a toilet, and a handheld shower that drains into a pumped sump. The sanitation system also includes a 22-gallon holding tank and a Y-valve.
All cushions are upholstered in Sunbrella in owner-selected patterns, while interior surfaces are covered in Frontrunner fabric. Gray polycarbonate windows run the length of the cabin.
The galley is utilitarian, with an Origo two-burner alcohol stove and a small, single stainless-steel sink supplied by a hand pump. There are also two small cockpit stowage areas, one for a 5-gallon fuel tank.
Aft-cabin versions placed a wide double berth behind the cockpit, accessed through a hatch. The aft-cockpit model became so popular, however, that aft-cabin production was discontinued before a redesigned aft-cabin version was scheduled to resume.
Known Issues
Several defects have emerged in the F-31’s service history. Practical Sailor’s survey found that wiring from the mast aft was exposed along the overhead, while running-light wiring ran along the hull beneath the galley without drip loops.
The halyards exit the mast too close to the deck for easy hoisting, particularly when racing. Testers also noticed the deck moving beneath a jib winch in 15-knot winds and recommended double-checking those backing areas, although all winches and hardware are backed with aluminum plates.
The Foss Foam rudder’s trailing edges were too wide and needed fairing. Several owners have experienced bearing failures, and water spouts appear in the cockpit at high speeds. At least one owner saw fore-and-aft daggerboard movement from too much play in the trunk.
Some owners have reported water entering the amas through hatches or fittings after extended heavy-air sailing above 15 knots. The mesh forward of the beams deflects spray but won’t support the weight of an average crew member. Corsair also changed from tanks made in-house to Ronco Manufacturing roto-molded plastic water tanks after experiencing leaks.
Refits and Ownership
For adventurous builders, Farrier offered a kit version called the F9A.
Ownership includes the routine maintenance of a folding trimaran’s aka beams and pivots. Sailing World nevertheless found the well-engineered folding mechanism and trailering systems remarkable. Farrier says the prototype weighed 5,600 pounds, compared with 3,800 pounds for the standard boat. That light displacement underpins both the F-31’s speed and its easy rigging behavior at the ramp.
The Verdict
The F-31 is a genuinely fast, trailerable trimaran, with serious engineering behind its folding system and unsinkable hull. Its narrow main cabin and a cluster of wiring and hardware-backing details, however, call for a careful owner.
Pros
- Won the 1992 Multihull Offshore Championship and Australian Sailboat of the Year
- Unsinkable, with nine watertight compartments; no owner-reported failures of the folding system
- Reached 18 knots on a tight reach in 12 knots of wind
- Can be rigged in 15 minutes by two moderately experienced people
- Foam-sandwich, vacuum-bagged hull with Kevlar reinforcement and a five-year blister warranty
Cons
- Exposed wiring from the mast aft and running-light wiring without drip loops
- Deck movement beneath a jib winch; rudder trailing edges required fairing
- Reported ama water ingress above 15 knots and daggerboard-trunk play
- Main cabin is only 7 feet wide
- Mesh forward of the beams won’t support an average crew member’s weight
