Design and Construction
The 105M’s defining structural feature is its one-piece molded hull and deck, which form a rigid bridgedeck. The two sections meet at a flange and are through-bolted every four inches, with a PVC rubbing strake masking the seam.
Smith rejected cored hulls, opting instead for solid, hand-laid fiberglass for strength and simplicity. A barrier coat and vinylester resin protect against osmotic blistering. Only the deck is cored, using half-inch end-grain balsa on its horizontal surfaces.
Bridgedeck clearance tapers from 39 inches at the bow to 24 inches at the maststep and 15 inches beneath the helm, then rises again toward the engine. This profile preserves cabin volume without requiring a wider footprint. The boat’s length-to-beam ratio is near 9 to 1, and its narrow hulls and retractable centerboards give it a boards-up draft of just 18 inches.
Rig, Steering, and Performance
The 105M has a double-spreader masthead rig and a 45-foot air draft. A long aft traveler provides end-boom mainsheeting, while the genoa tracks running the cabintrunk. Two self-tailing winches sit at the aft end of the trunkhouse, and the halyards lead aft. The standard mainsail is slab-reefed rather than full-battened.
The wheel is mounted on the starboard bulkhead. Teleflex push-pull cables connect it to a pair of kick-up rudders.
Test sailors found the boat quick. Under full main and a small genoa in 15 knots, it made better than 8 knots. It held 7.5 knots at 50 degrees apparent and 7 knots at 45 degrees, then reached 10 to 11 knots on a beam reach and touched 12 knots in a gust. The boat tacked easily and accelerated quickly, although speed dropped sharply when it was pinned below 40 degrees apparent. Smith claimed the hull shape all but eliminates a bow wave, contributing to that efficiency.
The main handling drawback is that the helmsman can’t reach either the mainsheet or the genoa winches from the wheel. Crew must therefore manage sail trim from the trunkhouse rather than the wheel.
Accommodations
Smith arranged the 105M for a liveaboard couple, with berths for six when needed. The bright saloon centers on a U-shaped dinette and includes a stand-alone refrigerator. It can run on propane under way because the boat never heels beyond 5 degrees.
Gray-tinted Lexan saloon ports resist leaking and crazing, while the large aft windows slide open like household sash. Molded cabin soles have teak-and-holly inserts. The hull interiors are finished in foam-backed vinyl, and the headliner combines molded fiberglass with foam fabric.
The centerline master stateroom faces forward. In the port hull, a molded head and shower occupy the forward section, a large navigation station sits amidships, and a double cabin is aft. The starboard hull has another double cabin aft and an amidships galley fitted with a two-burner propane stove and double sinks. Two 30-gallon water tanks are located under each aft berth.
Outside, the side decks are narrow by necessity. A hard dodger extends more than four feet aft over the cockpit, and each hull has molded swim steps.
Verdict
The Gemini 105M is a thoughtfully arranged cruising catamaran: narrow enough for ordinary marina slips, yet stable and quick. It’s solidly built where it counts and laid out for practical liveaboard use. Its compromises are few and specific.
Pros
- Fits conventional marina slips with its 14-foot beam and 18-inch boards-up draft
- Solid, hand-laid hull with a blister-resistant resin system
- Redesigned hull provides a 15-percent stability gain without additional beam
- Lively performance, with better than 8 knots upwind and double-digit speeds when reaching
- Propane refrigerator remains viable under way because the boat heels very little
Cons
- Helmsman can’t reach the sheet winches from the wheel
- Poor close-winded speed below 40 degrees apparent
- Narrow side decks limit working room
