COURTESY SWD From the drawing board of Stephens Waring Design (Belfast, Maine) comes Isobel, a 26’6″ (8.5m) 1950s-inspired runabout being built at nearby Belmont Boatworks. The boat was commissioned by a longtime SWD client, who will run it as a lake commuter/ watersport boat and has specified a sustained top speed of 25 mph (22 kts). As shown in renderings, Isobel will have a low sheer; a stern platform for swimming, tubing, and water-skiing; and a minimal draft of 11″ (28cm) for ramp launching. The hull is built from cedar strips sheathed in fiberglass, while a plywood-foam sandwich is spec’d for deck and cockpit sole, resulting in a light displacement of 2,750 lbs (1,250 kg) with two crew aboard. While hull and deck construction are conventional, the propulsion system is fully electric with a new 40-kW (54 hp) electric outboard hidden from sight but worth a closer look.
COURTESY RAD Drivetrain and battery are supplied as a package by RAD Propulsion, a U.K.-based company that has developed electric propulsion systems including rim drives for RIB coach boats (see “Radical RIB,” Professional BoatBuilder No. 186, page 8) and autonomous vessels, among other applications. On Isobel, the newly designed low-profile RAD 40 is housed under a lifting cowl at the stern and can be tilted up without compromising the passenger area as large four-stroke outboards would. Aside from quiet operation and no need for ventilation, this outboard comes with drive-by-wire controls and steers by swiveling the lower unit through 180°, thus effectively doubling as a stern thruster. RAD partnered with Welsh battery manufacturer Fellten to supply a 55-kWh power pack with a nominal output of 350V and peak output of 330 kW. The system reportedly supports CCS (combined charging system), a fast plug-in charging standard for electric vehicles that can bring the battery status from 20% to 80% in less than an hour, as well as solar charging at the owner’s dock. SWD says the boat, which is expected to be launched later this year, will have a top-speed range of 25 miles or approximately 1 hour of operation, while throttling back to half speed could double distance and runtime per charge.
COURTESY RAD Isobel’s sleek classic styling is made possible by her new low-profile RAD 40 outboard and a Fellten 55-kWh power pack with a peak output of 330 kW.
Isobel Specifications
LOA: 26′ 6″ (8.09m)
Length of hull: 24′ 3″ (7.4m)
LWL: 21′ 8″ (6.6m)
Beam: 7′ 11″ (2.42m)
Draft (motor up): 11″ (28cm)
(motor down) 26.5″ (67.5cm)
Displ. (2 crew): 2,750 lbs (1,250 kg)
Belmont Boatworks, 163 Augusta Rd., Belmont, ME 04952, USA, 207–342–2885. Stephens Waring Yacht Design, 92 Main St., Belfast, ME 04915, USA. RAD Propulsion, Unit 2A & 2B, Universal Marina, Crableck Ln., Sarisbury Green, Southampton, SO31 7ZN, +44 (0)23 82 129530.
