29' Light Cruising Launch (2004) - WHIO, now Electric

A Light Classic Launch on a Trailer

The overall dimensions is less than those which would incur the necessity of an oversize permit for towing on a trailer.
In the interest of fuel economy and towing on the road Whio is built light, and wherever practicable, the lightest materials possible were used.
Whio is capable of making coastal passages safely and at speed and be able to cope comfortably with adverse sea conditions.

The propeller diameter is large (24.5 X 21.5 ins.) and narrow blades to enable slow revving which results in a much higher efficiency than smaller high revving props. The propeller had to be specially constructed to mount on four studs for easy and quick removal when on the trailer. To further assist the efficiency of the prop careful attention was paid to the fairing of the deadwood and skeg (which is removable for going on the road.

Whio is now Electric with a 50 volt 640 Ahr battery. This is made up of 32 x 320 Ahr LiFePo4 cells.
There is 600W of solar on the cabin top.

The range at 6kn is over 200 NM on the battery alone. The range at 8 kn is 80 NM on the battery. In good sun at 6kn half the power is coming from the solar, so the range is considerably extended.

Of note is that I have tried about 6 different propellers. When using a standard prop recommended by a local supplier, which runs at twice the rpm of mine, the range is only 125 NM at 6 kn, instead of 200 NM. The drop is way worse at 8 kn with the standard prop. And the top speed is only 11.5kn instead of 19kn with my best prop for speed. Both those speeds use the full 20kW of the motor.

With the most efficient prop, 24 1/2 inch dai, two blade, I’m limited to 9 kn because of the motor torque limit. ( 180 Newton Meters ) At 9 kn the motor is doing 500 rpm, it is direct drive. In a 25kn wind, the speed only changes by a very small amount between going up wind in to a sea or down wind.