Solar Power

A solar propelled micro-cruiser on Puget Sound

[Article by Rick Retzlaff ]

It began last fall, like many of my projects begin, sitting with my logbook and a pencil. I needed a project for the long, cold Canadian winter, something technically challenging that would lead to some kind of further purpose. From a long list of possibilities, one idea rose to the top—design and build a solar micro-cruiser and head off on a trip next summer.

I had a starting place. Last spring, my daughter and I had built a wooden rowing boat we called Newt from an excellent Chester Yawl kit by Chesapeake Light Craft. We had done a little bit of camp cruising with it, but it was really a day boat. Could Newt be converted to a self-contained solar micro-cruiser? Having previously designed and built several electric vehicles and boats, I figured the answer was “probably.”

However, the winter project needed a purpose, an intended cruise to keep the design focused. A few destinations came to mind; the Thousand Islands of Ontario where we used to spend summers sailing our family boat, Saphira. Or maybe cruise down the Mississippi just like Huckleberry Finn. But the Thousand Islands were well trodden ground, and the Mississippi is a little different than it was 150 years ago, now with 24 locks where I would like to cruise. Puget Sound was the next obvious choice. It has protected waters, a lot of nooks and crannies to explore, is somewhat populated, but somewhat isolated. There were some challenges —saltwater, tides and currents, but I believed I could deal with that. But first, I had some design and fabrication to do.

Engineering design normally starts with a problem. I teach engineering at the University of Saskatchewan, where we encourage students to carefully define the problem and summarize it in a single sentence. However, in my case the summary was a bit lame: “Rick is bored and wants some adventure next summer.” This is not exactly the open-ended problem summary that we encourage in our students. However, it would do for a start.

The biggest issue was the nature of Newt. It was an excellent recreational rowing boat, but it needed significant modification to transform it into a solar propelled micro-cruiser. Compounding the problem was my desire to have all of the cruising gear removable so I could still use it as a day boat. I needed some kind of a living space, solar cells, and an electric drive system.

Launched and ready to hit the big city—grey and somber

I began with some conceptual sketches and calculations to ensure that I had enough plan area for the solar cells and interior volume to live in. I estimated I needed approximately 300W of electrical power to propel the boat close to its 10 km/hr hull speed. I planned for enough solar cell area to provide 100% of the power needed for cruising on a sunny day. This meant covering almost the entire deck area with cells, leaving a small cockpit area for me to live in, covered by a small tent at night. To deal with cloudy days and early morning starts, I needed lithium phosphate batteries, chosen primarily because they were left over from a previous project (an electric Jet-Ski) and they are lightweight, safe and durable.

An important part of the design was a set of foam pontoons mounted on the sides of the hull. These served three purposes: first, they provided storage for the oars, which were to be used only occasionally; second, they provided reserve buoyancy and stability (I could actually stand on the gunwale); and third, they provided some protection against banging into docks.

Working out the rest of the design details was an iterative process, with problem summary sentences more in line with what we teach our undergraduate engineering students. How do I cook and sleep? How do I keep splashing waves out of the boat, how can I re-enter after a capsize? How do I steer? Where do I store the oars? The list went on and on. In time, all of these were worked out, filling in all of the nooks and crannies of the design space.

Newt at the dock, with the tent set up

One special detail was the VMS or “Vessel Management System.” This was a custom microprocessor with an LCD screen that monitored the power system, including the state of charge of the batteries, indicating power coming in from the solar cells and being used by the motor, as well as boat speed (via GPS). This would help plan daily trips, and ensure I had enough energy to get there, since I hoped to avoid rowing.

Fabrication began with the arched deck panels. These needed to be rigid, strong and lightweight. I used a PVC foam/fiberglass/epoxy sandwich. This has the advantage of not requiring any molds; the PVC foam sheet can be easily bent into the right shape, and fiberglass applied to both sides. These turned out very well, keeping me dry and secure throughout the entire trip. They were made to clip onto the gunwales of the boat, to be removed when not needed.

Custom solar panels were required to accommodate the special shape and curvature of the decks. I used high-efficiency 5" x 5" flexible cells (SunPower Maxeon—22% efficiency). These were soldered together in an array and then vacuum laminated in an oven. This produced durable, flexible panels that could be draped over the curved decks. It took about 10 failed test laminations to get things right, but I was very happy with the result. In full sun, the array produced 300W via a high efficiency charge controller to the batteries.

The Bridges! Moving at twice my normal cruise speed. Oars ready just in case.

The motor was a modified Minnkota Endura 30 with a custom high-efficiency variable speed controller. I tested many propellers and settled on a model airplane 10 x 7inch unit, which gave me 2 km/h more speed than the standard Minnkota propeller. This power system resulted in a cruising speed of 8 km/h. This could be maintained indefinitely in full sun, and about four hours under battery alone. In practice during the trip, I never had a shortage of energy. The batteries spent most of their time with more than 90% charge. In retrospect, I had too much battery and solar energy and not enough motor power. Next time, I would certainly consider a 400-500 watt motor.

Once I had finished the power system, I did some testing on the river in Saskatoon. I found the ride to be just like a magic carpet, perfectly silent with very little wake. This tended to mask the speed of the boat, which became evident only when you put your hand in the water or saw something pass by.

The rest of the fabrication was the bits and pieces, including the motor mount, electronics rack, the tent, the seat and miscellaneous living amenities. These seemed to take up the most time, and I was certainly still building things the day before I left on my planned three week trip in mid-June.

Unfortunately, I live about as far from any ocean as you can possibly get on the North American continent. Saskatoon, Saskatchewan. I put the boat on its trailer, jumped into the reliable Honda, and said goodbye to my wife. The last thing she said to me was “Rick, I’m glad you’re going on this trip, but I’m glad I’m staying here.” I took that as a good sendoff.

I arrived in Seattle late in the afternoon three days later with a plan. It was my birthday the next day, and I had a reservation in a downtown Seattle Marina. I envisioned spending my birthday relaxing on the boat and enjoying all that Seattle had to offer. All I had to do was get across Elliott Bay from the Don Armeni public boat launch, about a 5 km trip. How bad could that be?

After getting the boat in the water and the car parked, I jumped in and left the dock with some trepidation. There was a lot of traffic, ferry wake and a huge city on the other side of the bay. This was certainly different than the river back home.

All seemed well until I got about a third of the way across the bay. Looking down, I noticed water above the floor boards. That means that there was about three-inches of water in the boat. That is bad. The water is supposed to be on the other side of the hull. Well, I got busy with the bailer, and did a quick U-turn back to the launch. It seemed 1,000,000 miles away. All I could think of during that agonizingly slow trip was a line from the famous Stan Rogers song—Barrett’s Privateers—Bailing like madmen all the way! I could feel the boat heavy in the water when I finally made it back to the launch. I frantically backed the trailer and got the boat safely back on the hard. Whew…. Looking underneath, I could see water pouring from a 4 foot crack between two of the hull panels. It made perfect sense now. It was a bad idea to load the boat with batteries and camping gear, put it on my very stiff-sprung trailer and drive 2300 km across the country. The bouncing had opened up a seam and almost put an end to the trip before it began.

My birthday turned out a little bit differently than planned. I spent the day at the local Econolodge parking lot in the rain, fixing. Luckily, the owner took pity on me and let me work underneath the front canopy of the hotel. After a quick trip to West Marine for supplies, and an afternoon prepping and mooking epoxy, it was stronger than new.

Although I knew I had to get back to Seattle at some point, I could not face Elliott Bay again right away. I needed a place where I could launch and stay at the dock for a bit to make sure that all was well. Point Defiance, near Tacoma, fit the bill. So began my soggy life as a homeless person. In the rainy days that I spent there, I had all the symptoms of vagrancy. The local officials knew me by name, I knew the cheap places to get hot tea, I frequented all the free bathrooms, and I had a favourite bench out of the rain. I was the “weird guy in the teeny boat at the end of the dock.” However, this was where the nature of Washington boaters came to the fore. Everybody, from crabbers in camouflage, SeaRay owners in polo shirts, to aging hippies on bicycles all showed sincere interest and support for my odd boat and my solo trip. This was to become the norm for the next three weeks, as I spent almost all of my time at the dock trying to explain myself.

A particular example of this character was demonstrated one late-night in Gig Harbor. I have a very special custom seat that clicks into slots in the bottom of my boat. It is the center of my existence, and I’m not sure how I could do the trip without it. One night, I had left it folded on the dock to save space below. Getting up late that night for the bathroom, I noticed it missing. Walking in despondency towards shore, I ran into two newly made friends—Scott and Brandi— holding my beloved seat. They had noticed a young kid carrying it away and endeavored to get it back for me. Thank You!

In my experience, Tacoma Narrows is not a real place. It’s a shaky video of a galloping bridge, and a classic case study in aeroelastic self-induced oscillation. So it seemed surreal when I found myself being swept with the current through the Narrows underneath the two graceful spans. I was a bit apprehensive because all of the good boaters at Point Defiance had told me horror stories about being caught up on the bridge piers, spun around in circles in the eddies, and generally having bad things happen. However, sticking right to the middle of the channel brought me safe and sound to the entrance of Hale Passage and so on to Penrose Point State Park, where I spent a few relaxing and memorable days in such a beautiful spot. It was during this stay where the trip really began to hit its stride. The sun was out, the solar cells were pumping out energy, and I was beginning to get over “crisis mode” and begin to enjoy myself.

However, the challenge of Elliott Bay and Seattle was still hanging over my head. A ridiculously early morning start brought me back through the Narrows at the right time for the tide, and so back to Point Defiance where I pulled the boat and (as the name suggests) defiantly drove back to the Don Armeni boat launch. This time, it was “second time lucky” and I arrived at Bell Harbor Marina in downtown Seattle safe and sound with hardly any sinking at all.

I must admit, this was my kind of cruising. Deep down, I am a “Glamper”. Nominally, I was staying on the boat (at least I was sleeping there) but the rest of the time was restaurants and museums. I had my own little waterfront hotel room, for only $25 per night. My days in Seattle were fantastic. However, this kind of cruising is not what this boat was built for. Last winter back home in the dark and cold, I had envisioned a kind of running cruise through the Sound—every day travelling to new place, and taking full advantage of the independent nature of solar power. Therefore, with some reluctance, I pulled the boat out of the water again and headed south.

3D CAD model of the seat, to be laser cut from 1/4” birch plywood and ready for weaving.

The remainder of the trip was spent poking around the southern Sound. Every day, I had a new place to go, lots of sun, and great people to talk to on the dock. I visited almost all of the Washington State Parks that had docks, as well as a few commercial marinas. Certainly, it was not without some challenges; a very uncomfortable and rolly night in Joemma Beach State Park, a cold and wet passage to Boston Harbor, and logistical difficulties because of the impending state budget crisis that was threatening to shut down all of the State Parks. What an odd thing.

My three weeks had come and gone. It was time to put the boat back on the trailer and head to the airport to pick up my wife. The two of us planned to camp through British Columbia for a week or so. However, this part of the trip was over. I had done what I set out to do, the boat had performed just like I hoped it would, and the trip ended with a fully charged battery. •SCA•

Rick Retzlaff is an Engineer, teacher, maker, and frustrated sailor living on the bald prairie of Canada. He can be reached at Rick.Retzlaff@usask.ca

First appeared in issue #110