My first solar electric boat came from an old faded blue 20 foot Gruman aluminum canoe. The boat was slow in the water and noisy. By adding some photovoltaic panels, batteries and an electric trolling motor it became quiet and fun water transportation. A combination battery box and seat along with new paint made it look okay too and gave it the name Teal.
Teal is a canoe and the PV panels raised the center of gravity making the boat a little more tippy. People who know how to handle canoes have no trouble, but Teal is not a freight boat.
I came across two 14 foot aluminum outboard boats that had been in the rental trade for many years. They were heeded for recycling because of leaking rivets and dents so I got them for a good price. They were designed for planing with a moderate horsepower gasoline engine. I needed a displacement hull pointed at both ends, like canoes and most sailboats.
Using a circular saw with a carbide tipped blade, I cut the transoms off both boats at slightly different distances from the transom. The asymmetry allowed one bow end to slide inside the other bow end making a 20 foot double ended boat. Pop rivets mechanically joined the hulls and Gorilla glue sealed the joint. Structural strength came by overlapping the gunnels and three keels and adding a marine plywood frame for torsional strength. The battery box and seatback provided seating for 4 with 4 other seats available from the original boats.
This boat got more PV panels, more battery and a larger electric trolling motor as well as new paint. It has been up the Hudson River 4 locks from Troy and out the Erie Canal to Utica. It is now called Sirius Sun and is currently a fun and freight boat on an Adirondack Lake.
The two boats proved the concept and serviceability for my use. However, neither boat has a good, efficient, hull shape and neither can comfortably carry 4x8 sheets of plywood, for example. My son suggested a specific boat design which I had lofted with 50% more stability for the photovoltaic roof. So I have started a multi-year project to build Sol, a 25 foot wooden boat, designed to be solar electric, and able to carry heavy loads of people and freight including 4x8 plywood.
Boat Teal Sun Sol
Hull (ft) material 20 AL 20 AL 25 Wood
PV (Watts) 250 600 1200
System Volts 12 12 24
Battery (AH) 300 400 400
Motor (Watts) 360 600 2000
Note: 1000 W will get Sol close to hull speed, 5.5 knots (about 6.3 MPH).