Design and Construction
Most J/105s were built by Tillotson Pearson International, which pioneered the SCRIMP resin-infusion process for the hull, laying up the fiberglass and core dry before infusion. Vinylester resin is used throughout the boat. The deck is cored with balsa, with the builder favoring Baltek end-grain AL600.
The hull and deck are joined with Plexus, creating a chemical bond rated stronger than the laminate itself. Fore-and-aft and transverse solid-glass hat sections, molded during the initial lay-up, stiffen the hull. A matrix of robust floors supports the keel bolts, while an aluminum I-beam maststep keeps the spar out of the bilge and is through-bolted across two floors. The bulkheads have six-inch tabbing through 360 degrees. A substantial bridgedeck adds structural support and helps defend the cabin against green water.
The narrow keel foil carries a torpedo bulb, placing the ballast low while limiting wetted surface. The boat carries 3,400 pounds of lead in a 7,750-pound hull. Its 44 percent ballast-displacement ratio allows it to carry sail while other boats are reefed, and the deep fin with its raked leading edge provides a limit of positive stability near 130 degrees. A 5-foot-6 shoal keel was offered for thin water, at the cost of some ultimate stability.
Rig and Handling
The fractional rig allows the mast to bend for sail shape. Many boats carry a Hall Spars double-spreader mast with Navtec rod rigging, a Quick Vang, and a Sailtech hydraulic backstay. Harken roller furling is typical on the headstay.
The mainsheet traveler sits forward of the helm, recessed into the T-shaped cockpit. A single pair of primary winches keeps the controls manageable from the seats. Strict class rules limit the sail inventory to a main, jib, and asymmetrical chute. The spinnaker is usually flown from a carbon sprit with under-deck launch and retraction, and it is snuffed so one sailor can handle a jibe. The retractable sprit also eliminates the need to handle a conventional pole aloft.
On an early hull tested off Miami, sailors recorded 12.5 to 13.5 knots in a 20-knot northeasterly and three-foot seas, touching 14.8 knots. The boat worked back upwind at 7.5 knots with the sheets eased. Owners report that carrying a full main and jib is tenable to roughly 22–25 knots, with a reef going in around 30.
The standard tiller and hiking stick were replaced on quite a few boats by an Edson wheel. The straight-shaft drivetrain uses a Martec folding propeller, as required by the class rule.
Accommodations
Below, the J/105 makes no secret of its priorities. Saloon headroom is only 5 feet 4 or 5 inches, except at the open companionway. Port and starboard settees double as 6-1/2-foot berths. A 7-foot V-berth fills the bow and includes a hanging locker, while small quarterberths aft are optional.
The split galley sits just aft of the main bulkhead. The navigation table is to port, with a stainless-steel sink and space for a one-burner Origo stove to starboard. A 54-quart portable cooler fits beneath the ladder, and freshwater comes from a 5-gallon jug.
A private head occupies the space immediately behind the bow berth, with a shower offered as an option. Vinyl covers the overhead and hull sides, while the cushions are upholstered in Sunbrella.
Known Issues
Owners have reported problems with the bulkhead that supports the chainplates. On early boats, the balsa deck core was left intact where the chainplates pass through, allowing moisture to reach the structure; later hulls used solid glass in this area.
The Bomar foredeck hatch has also caused frustration. Its frame welds can crack where the hatch lies flat on deck, and a bumper and weld kit were later offered.
The shallow bilge wets the ends of the floorboards when the boat heels. The original plywood boards rotted, while later plastic-faced boards still suffered from delamination. Sealing the floorboards’ end grain is a common catch-up job.
The rudder turns in aluminum bearings, which corrode where they encounter copper in antifouling paint. Jeff Johnstone cites a service life of three to five years, and some owners now install Harken plastic bearings instead.
Soft engine mounts allow the diesel to move, in some cases causing dripless seals to leak. Water has also entered the forward cabin through the sprit tube. Some emergency tillers reportedly didn’t fit at commissioning or sat hard to port when the rudder was centered.
Refits and Ownership
The 10-year transferable hull warranty has long since expired on used boats, but the underlying structure ages well. Common catch-up work includes replacing the rudder bearings with plastic versions, fitting the foredeck-hatch bumper, and sealing the floorboards’ end grain.
The class’s strict three-sail rule helps contain campaign costs, while the retractable sprit removes the need for conventional spinnaker-pole handling.
The Verdict
The J/105 is a purist’s speed machine: light, stiff, and refreshingly simple, with a construction process that still seems advanced. It asks owners to accept low headroom, minimal tankage, and a list of detail defects in return for a boat that planes in a breeze and points without drama.
Pros
- First keelboat with a retractable sprit and pole-free spinnaker
- High ballast ratio allows it to carry sail in strong wind
- Infused vinylester structure with robust floors and an I-beam maststep
- Class rules limit the sail inventory and help hold costs down
Cons
- Shallow bilge can rot floorboards; early boats can admit moisture into the core around the chainplates
- Aluminum rudder bearings corrode and have a short service life
- Low headroom and only a 5-gallon freshwater supply
- Soft engine mounts can contribute to seal leaks; the sprit tube can admit water
