Sport Boat 18 by

[SB18] A trailerable high performance sail boat with lifting keel

Length overall18'5.5 m
Waterline length16' 5"5 m
Beam8'2.44 m
Draft4' 7"1.4 m
Draft (cb up)7"0.18 m
Weight917 lbs416 kg
Centerboard weight397 lbs180 kg
Displacement1459 lbs662 kg
Sail area241 sq. ft.22.40 m2
Engine power2 - 4
Hull construction Stich-n-glue
Gallery 6 photos and 1 video
See also i550



Our second generation stitch and glue is the ideal material for a light and fast sport boat. The plywood cored epoxy-fiberglass composite panels are stronger and stiffer than a plain fiberglass skin and the construction of such a boat is within the reach of any amateur builder.

The 5 panel hull shape is easy to build.It has less wet area than a sharpie hull but still has the flat bottom ideal for good downwind performance and planing.

The powerful fractional rig is based on a keel stepped Al tapered spar, 7/8 rig with swept back single spreaders, no running or mast head backstays.. Spinnakers are set on a retractable pole.

The preferred keel is the vertical drop keel with a 400 lb bulb on the end of the high aspect foil. It is lifted by a tackle made from the main sheet with an extra block. . Fully retracted, the bulb remains below the hull.

Spade rudder, fin bulb keel are described in detail with full size pattern for the bulb and keel fin

While this a Mertens-Goossens design, credit must be given to Evan Gatehouse for his collaboration. Evan designed the rig, appendages and did most of the engineering work. Without Evan, this design would still be an unfinished project.


The cockpit is 110" (280 cm) long, giving plenty of space for working the boat.

The plans show an integral outboard bracket for a motor of 2 to 4 HP, 20" or longer shaft..

The inside is wide open except for the mast and keel trunk. The sole extends under the cockpit. There is plenty of space for two sleeping bags. The max, height under the small cuddy is 34", 19" under the deck. While this is far from the comfort of a cruising boat, there sufficient space to sleep two.


For best performance, we recommend the lifting fin keel. The plans show the construction of the fin and the lead bulb. This is within the reach of an amateur.

For those who prefer a centerboard type keel, the plans show in great detail a swing keel. That CB keel is made of a steel core (2x2 bars) in plywood-epoxy-glass foil. While the CB keel will not deliver the same performance than the fin keel, it is good solution for those who must adjust draft as they sail.

Plans give specs for Al spars and it is easy to extrapolate to carbon fiber.

Stanchions and backrest webbing are an highly recommended option .

The deck plan is detailed. We show specifications and part numbers for all parts but this an area where experts sailors will customize their boat.

The inside sole is an option. It can be replaced by a smaller, lighter structural platform to support the keel trunk and a stringer all around.

Lockers can be built in but racers will prefer canvas pouches.

As with all our boats, buoyancy foam is an option. Around 4 gallons of our tow part foam will make the boat unsinkable. There is plenty of room for that foam under the sole.

Foam core is not an option for the hull but is a good choice for all other parts.

Consult the designer for a super light version using honeycomb for most parts except the hull. Weight gain will be around 80 lbs but material cost will double.

Sailing Rigs

The plans show two main sails, the larger one with a pronounced roach. This is not a boat for a first time sailor and builders will use our sail plan and deck plans as a starting point that they can adapt to their preferences.

Sport Boat 18

Deck plan
Deck plan

Photo gallery

On the trailer
On the trailer

At the dock
At the dock

At the dock
At the dock

Inside. Note the spi pole and the centerboard winch.
Inside. Note the spi pole and the centerboard winch.

On the trailer
On the trailer

On the trailer with mainsail
On the trailer with mainsail

Video gallery

Sportboat 18 - Lady C.
Sportboat 18 - Lady C.
Seatrials #2

See also

Design Length Beam Sail area Engine power Compare
i550 i550 by Watershed Sailboats
Annoyingly fast sport boat
5.5 m
2.45 m
237 sq. ft.
22.00 m2

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A mighty, miniature long range cruiser

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i550   i550
Annoyingly fast sport boat

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Vagabond 18   Vagabond 18
[VG18] A fast day sailor with cabin

LOA: 18' 2"/5.54 m   compare
Daysailer/Pocket Cruiser

LOA: 19' 6"/5.94 m   compare

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