The genesis of Stephens Warings’ fully electric venture lies in a deep-rooted client relationship, spanning five boat projects over 20+ years. 8.5 m Isobel was motivated by the client’s need to access and maximize enjoyment of a new vacation home located on an island in a remote Maine lake. The client envisioned a mode of transport that reflected the serenity of the pristine lake environment, but with plenty of utility, performance, and reliability- essential for operating far from any marina or fuel dock.
Having test-driven traditional ICE-propelled boats and disliking the noise, exhaust, and appearance of high-profile outboard motors, the choice was clear for a custom electric powered commuter.
Crafting a Vision: Balancing Form and Function
Isobel has an elegant, simple aesthetic. However, she’s not just a visual stunner. The vessel is carefully curated and designed to meet specific performance requirements of the client. The recurring 2-mile commuter distance from her home dock to the mainland necessitates the ability to carry several passengers with endurance and reliability. The client also wanted performance; a boat equipped for recreation and fun, including occasional tubing and waterskiing, with a top speed of 25MPH.
The result… a sleek profile with mid-century modern styling that draws inspiration from the elegance of 1950s Rivas. Isobel has a low sheer allowing comfortable stepping aboard amidships. Her stern platform allows for water access and facilitates fun for swimming and skiing. Her shallow draft makes trailer-launching viable even on a rudimentary ramp.
Beneath the Surface: Technological Marvels
For design of any planing watercraft, weight is the enemy of speed and range. The careful use of wood-composite construction—cedar-strips sheathed in fiberglass for the hull and a plywood/foam/plywood sandwich for the deck and cockpit sole deliver a light displacement of around 1,300 KG (with two persons aboard), as well as a cost-effective custom build.
The RAD 40 electric motor produces 40kW of continuous power (~55HP)
The boat is powered by a 40kW (54 hp) motor from RAD Propulsion, a UK-based company founded in 2018 that has developed cutting-edge electric solutions for the marine industry. It stands as one of the first 100 production versions off their assembly line. This electric outboard motor, concealed under a lifting cowl at the stern, eliminates the need for noisy ventilation. With only the lower unit swiveling for steering, the boat’s sleek profile echoes the quiet elegance of its operation.
Energy storage is provided by Fellten, a UK battery manufacturer with a focus on electrical repowers of classic automobiles. The 55kWh battery power pack abroad outputs a nominal 350 volts and peak output of 330kW. The Fellten (which means “lightning” in Welsh) battery system supports fast charging via CCS standard system, which can jump from a 20% to 80% charge in less than an hour. When charging from the island’s off
The Fellten 55kWh battery power pack outputs a nominal 350 volts and peak output of 330kW
-grid solar infrastructure, the boat has a truly green, zero-carbon, and economical footprint.
At full power the system provides a range of 25 miles or approximately 1 hour of top performance operation. This equates to half a dozen round-trips to the mainland at top speed. But with most commuter trips moderated to a cruise speed of 12-15 knots, her range is doubled.
Proving the Possible: A Silent Revolution
Most exciting about Isobel, is the prospect of showcasing that an electric boat can outperform its traditional ICE counterparts. While Isobel boasts an impressive array of technologically advanced components, the design approach deliberately adheres closely to operational norms and a desire to eliminate unnecessary complexities. The result is an iconic and timeless design that conceals its electric nature, with the only giveaway being the blissful silence as it gracefully glides through the water, leaving nothing but ripples in its wake.
Construction is underway at the Belmont Boatyard in Maine with an expected launch in 2024.
Technical Specs:
- 40kw motor (54 hp) from RAD Propulsion
- 55kwh battery power pack from Fellten
- LOA: 8.09 meters (26’ 6”)
- Length of hull: 7.4 meters (24’ 3”)
- LWL: 6.6 meters (21’ 8”)
- Beam: 2.42 meters (7’ 11”)
- Draft: Motor down: 675mm (26.5”); motor up 280mm (11”)
- Displacement (with two aboard) 1250 kg (2750 lb)
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