Solar Canoe with Wheels
First
a word about solar powered boats: Shown is a canoe with a 100 watt
solar panel and a 300 watt electric trolling motor. So at the highest
setting, the electric motor gets at best 1/3 of its power directly from
the sun. The rest comes from a lead acid battery stored under the solar
panel. The key design factor here is to realize the battery can be
charged when the canoe is idle, say just floating on a river or lake,
or tied to shore. So three hours total in the sun might, at best, get
you one hour motoring at full speed. I say "might" because the solar
panel's output won't be at 100% of rated capacity, due to the angle of
the collector with respect to the sun, or clouds, or other variables. A
more realistic assumption is that this canoe might have to sit in the
sun for 6 hours total to get a 1 hour ride, but then again if you don't
go full speed for that hour, you can motor longer.
Having said that, this solar canoe with wheels works well and is way cool.
One
of the design goals was to be able to move the solar canoe with its
solar collector, electric motor and 60 pound electric battery around on
land. We live near the Stillwater River, so we needed to transport it
down our driveway, across and along the road a ways, and down to the
river. Loading everything on a trailer and launching it like a power
boat using a gas powered vehicle, seems like too much work and defeats
the goal of trying to do everything using solar power. I wanted wheels
for this canoe that were streamlined enough so they could remain on the
canoe when in the water. I didn't want to have to lift the canoe with
its heavy cargo and place it on store-bought wheels to move it and then
remove those wheels at the river side. I also didn't like the idea of
leaving the those store-bought wheels at the launch site, where someone
might take them. So I wanted collapsible wheels that could be either
placed in the canoe or left on when we were on the water.
Here is a sketch of what I came up with. Two straps hold the left and right wheel assemblies tightly to the boat. Two more straps tied to the center thwart of the canoe hold the upper part of the wheel assemblies tightly and in position at the center of the canoe. The two circles on either side are bumper buoys that could be attached when the canoe is in the water if extra stability is desired.
Even
with the wheels on, the canoe has a nice narrow profile. One wheel can
just barely be seen on the left in this picture. The wheels do add a
bit of drag, but they actually turn when the canoe is under way in
the water, like the paddle wheels on an old-time ferry boat. This
turning decreases the drag factor.
Wheel
height is a compromise. These twenty inch plastic wheels are just low
enough that the canoe can be wheeled around easily, but not so low that
they significantly increase the drag factor in the water.
The
wheel assemblies are made out of PVC board. PVC board is waterproof and
can be machined easily. Note that the assemblies are simply tied to the
top center thwart. They can be untied when the canoe is in the water so
that the wheels can be removed. There might be a slight trick to
mounting them again with the canoe in the water, but that seems
do-able.
To keep things simple and light I drilled 1/2" holes for the ribbon strap. I thought about heating the PVC board and bending it to the shape of the canoe, but I opted for something quick for this prototype. I added a 2X2 inch L-shaped angle aluminum on the back of the board, not visible in this picture, to mount the 5/8" galvanized steel bolt that would server as the axle for the plastic wheel. I went with a no-flat solid plastic wheels I purchased from Amazon. A pneumatic tire would have extra buoyancy, but I really don't like getting flats so settled for the extra weight. I wasn't sure if I had accounted for all the possible forces and torques this wheel would face under real world conditions, but I was pleasantly surprised when testing this design. I've done some terribly things to these wheels dragging the canoe across rough terrain and throwing the canoe on its side. This prototype is much more robust than I expected.
To keep things simple and light I drilled 1/2" holes for the ribbon strap. I thought about heating the PVC board and bending it to the shape of the canoe, but I opted for something quick for this prototype. I added a 2X2 inch L-shaped angle aluminum on the back of the board, not visible in this picture, to mount the 5/8" galvanized steel bolt that would server as the axle for the plastic wheel. I went with a no-flat solid plastic wheels I purchased from Amazon. A pneumatic tire would have extra buoyancy, but I really don't like getting flats so settled for the extra weight. I wasn't sure if I had accounted for all the possible forces and torques this wheel would face under real world conditions, but I was pleasantly surprised when testing this design. I've done some terribly things to these wheels dragging the canoe across rough terrain and throwing the canoe on its side. This prototype is much more robust than I expected.
Here
is the bottom of the canoe showing the thin narrow straps that hold the
two wheel assemblies tightly to the canoe.You can also see the aluminum
angle piece of the wheel assembly. I rounded the corners of this piece
and added tape to it so it wouldn't add scratches to the canoe.
Inspecting the area after prototype test revealed no damage or
scratches to this area, so the design is sound. Still a better design
might involve shaping the PVC board to better fit the canoe.
This prototype works so well, that I would like to see solar canoe races become a traditional event on the Stillwater river. This is an ideal design for the river since there are several portages around dams on the river. The river starts on the Penobscot river, circles around the island where the University of Maine is located and ends up back on the Penobscot. So canoe races could start and end at the same place, perhaps the riverside parking lot near the University. These races would draw university students and perhaps do-it-yourselfers from around the world.
This prototype works so well, that I would like to see solar canoe races become a traditional event on the Stillwater river. This is an ideal design for the river since there are several portages around dams on the river. The river starts on the Penobscot river, circles around the island where the University of Maine is located and ends up back on the Penobscot. So canoe races could start and end at the same place, perhaps the riverside parking lot near the University. These races would draw university students and perhaps do-it-yourselfers from around the world.