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Cruising America’s Great Loop in a Solar Powered Canal Boat

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Dragonfly at the dock.

In the 36 years since I began to plan our Great Loop cruise I have learned about the variety of boats people use to do the loop. There have been row boats, kayaks, fishing boats, jet skis, kayaks, trailerable cruisers, sailboats, fast cruisers, passagemakers and catamarans, but never an English-style canal boat. At least not until October 2, 2010 when, before my eyes, on the transient dock at Kenlake Marina on the Tennessee River was a 41-foot all steel canal boat. I hurried over and introduced myself to owners Cynthia Berger and Bill Carlsen of the canal boat named Dragonfly.

Bill is an environmental science education professor at Penn State University and Cynthia was writing for Public Radio. They were on a mission to prove that not only can the Great Loop be done in a canal boat, but much of it can be done under solar power. Bill received a one-year sabbatical from his university to show that solar powered boats are both practical and eco-friendly.

The experiment was not a multi-million dollar research project , but rather a very modest undertaking with Bill and Cynthia doing most of the work. They bought a used rental canal boat that had seen 20 years of service on the Erie Canal. The Yanmar diesel engine had 13,000 hours! On our Great Loop trip we had seen a few of these on the Erie Canal.

They renamed the boat Dragonfly, renovated the interior, beautifully painted the exterior, and installed a $6,500 solar power system. Bill engineered the solar power system and installed it himself. Think about this: the cost of a solar system is much less than the cost of a second engine and it has near-complete redundancy with only the shaft, stuffing box and propeller common to both engines. Bill estimates their diesel consumption of 600 gallons of fuel over the course of the trip was a reduction of 40 percent through solar operation.

The canal boat was ideal for solar power because of its long wide flat roof. Bill installed eight 175-watt, 62-inch-by-32-inch panels, a total of 110 square feet of surface area and 1,400 watts of energy with full sun. The 24-volt panels were wired in pairs to get 48 volts. Eight 6-volt lead acid batteries holding 400Ah were installed inside close to the engine room and wired in series to create a 48-volt battery bank.

The sun charges the batteries and the stored power drives a dinner plate sized, 12hp electric motor. What?! Only 12hp to drive a 14-ton boat? Bill says, “After all, if three mules can pull a canal boat, 12 horses should be able to do the job.” The boat came with a 63hp Yanmar diesel engine. Bill retained this engine and figured out a simple mechanical means using an automotive timing belt from the electric motor’s shaft to a gear on the propeller shaft. He also put several spare belts around the shaft just in case one broke. The electric motor is the same one used to power the Zero, the world’s first production electric motorcycle. However, both the Zero and Dragonfly take advantage of the enormous torque electric motors provided at any speed. The Zero uses that torque to go from zero to 30mph in less than 2 seconds; Dragonfly uses it to precisely control its 14 tons in and out of docks.

Bill and Cynthia spent a year getting Dragonfly ready for the trip. They left June 1, 2010 from Midlakes Erie Macedon Landing on the Erie Canal, crossed Lake Ontario and headed up the Trent-Severn Waterway to Georgian Bay. They “crossed their wake” on May 27, 2011. On solar power, Dragonfly typically cruises between 3 and 4mph. On diesel, it can go 6mph or sailboat speed. Bill calculated that with no sun at all the battery would carry the boat 4.8 hours at 3mph or 15 miles.

The life of a lead acid battery is greatly extended by not using more than 50 percent of the charge before recharging. All Bill’s calculations took this into account. With sun, his calculations show they can do 22 miles in 7.4 hours, which makes for a nice cruising day on the loop. To cover the 6,000 miles of the Great Loop it will take 272 days. Since quite a few safe stretches on the loop are longer than 22 miles or require operating at over 4 mph, the diesel engine was used about 60 percent of the time. After a day of 22 miles cruising on solar the battery is half full, so they have to wait the next day at anchor or a dock to let the sun recharge the batteries to full power. Neither the diesel engine nor shorepower was used to charge the batteries.

The big question for me was how Dragonfly would cross the 168-mile Gulf of Mexico. At 3.5mph with 12 hours of sunlight in December, it would take 154 hours or 6 days from Carrabelle to Tarpon Springs, Florida. I didn’t think about the fact that the canal boat only draws 3 feet, so it can go around pretty close to the shore and anchor overnight. They did the first leg of 99 miles from Carrabelle’s Dog Island to Steinhatchee in 17 hours on December 21.

The weather was perfect except for the temperature of 25 degrees Fahrenheit. Since the helm on a canal boat is outside, Bill and Cynthia each took 20-minute shifts at the helm. It was the night of a full lunar eclipse, so there was some entertainment as they cruised. The next 7 days brought horrible weather with 10-foot waves on the gulf so they stayed put. They finally made it to Tarpon Springs on January 1, 2011—12 days to do 168 miles is probably a new record.

The goal of the trip was not to be the first boat to do the loop exclusively on solar power. The goal was to design, build and test a solar hybrid system, and give it a good workout. The solar propulsion system performed perfectly, with the only maintenance washing off the panels occasionally and topping up the batteries. Bill estimates that 95 percent of the service and maintenance was with the diesel engine that required oil changes, filters, impellers, fuel, etc. Another benefit of the solar system is how quiet it is. Check out the video clip on YouTube to hear Dragonfly leaving the transient dock at Kenlake.

To learn more about Bill, Cynthia and Dragonfly visit and for more information on Bob & Mavis Duthie’s boating adventures visit