WB No. 248: The 22′ power catamaran SEAHORSE is meant to carry six people—and their kayaks—on excursions to distant paddling grounds. She’s also adaptable to other uses, such as a support boat for waterfront parks or a power launch for rowing clubs.
In flat water and lightly loaded, SEAHORSE will reach her cruising speed of 5 knots with just 10 hp. But because the boat will carry a heavy load and much windage in her cargo of kayaks, a 30-hp motor is specified.
SEAHORSE’s two hulls take the simplest of forms: straight-sided and flat-bottomed. They’re built of commonly available lauan marine plywood. The loaded kayak rack and bimini top will make steering a challenge in a crosswind; this challenge is partially addressed with a bow board, the equivalent of a sailboat’s centerboard.
The boat’s construction is simple: Chines, stringers, and sheer clamps are sprung to plywood bulkheads, and the boat is planked in sheet plywood. The cockpit layout is adaptable to a number of configurations; the concept shown here uses tiller steering for the outboard motor.
- LOA: 22′ (6.71 m)
- Beam: 8′ 51/2″ (2.58 m)
- Draft (1/2 load)
Bow board up: 10″ (25 cm)
Bow board down: 2′3″ (68 cm)
- Boat weight: 680 lbs (295kg) approx.
- Half-load displacement: 1,455 lbs (599 kg)
- Full-load displacement: 2,020 lbs (916 kg)
- Power: 30-hp outboard
See more details in Designs: Sketchbook, WoodenBoat issue 248.
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