First let's get your mind right. Do not prop up your solar panels and use them as sails. Any skipper caught using his solar panels as sails or paddles spends a night in the box. Do not modify your batteries. They've got to be open-source, off-the-shelf, available-to-the-public merchandise. Capacitors may be used so long as they are charged by the allowable 480 watt one-sun solar array. Skippers are required to carry a paddle on board, but if they use it for reasons other than safety or rescue, the team is disqualified. Any skipper violating the regulations spends a night in the box. Now that we've got your mind right, let's have ourselves a boat race.
On the last weekend in May, 2009, the University of Arkansas hosted the Solar Splash solar powered electric boat engineering competition. Hosting duties rotate among participating schools in five year obligations. Fayetteville will host the event once more in 2010 before the event moves to another school.
Referring to the craft as solar boats is accurate, but a little misleading. Their motors are run from batteries or capacitors which may be charged only with solar power. During the 300 yard sprint competition, the solar panels are removed completely; and the solar panels merely augment battery power during the endurance and maneuverability events.
The engineering challenge lies not in pushing the limits of battery or solar cell or watercraft technology. Those elements are held constant by the rules. The challenge lies in the integration of elements available to all teams. So the championship goes to the team that reduces hull drag just a little bit and the team that reduces prop cavitation by a tiny fraction and the team that cycles its batteries slightly less deeply than its nearest competitor and the team that finds a way to use a slightly shorter cable so the voltage drop between the battery and the motor is improved by just a cat hair or the team that gets its boat out of the water quickly and gets its batteries back on the charger a little sooner than the guy next door. It's the little things -- the management of a thousand little things.
The team who managed their way to victory this year came from Cedarvill University in Ohio. This is their visual display, and that's their team's faculty advisor describing to me the way his team developed the propellor they use on their championship boat. Cedarville's victory provides an excellent example of how a team wins by managing resources. They came in second to New Orleans University in workmanship and in the two high scoring events, the sprint and endurance runs. However, they racked up points in several low point categories like technical report and visual display. This year's regatta was the classic tortoise and hare story.
These Cedarville guys are some serious competitors in the world of solar electric boating. Not only did they win this year's regatta, they also won the year before that. And the year before that. They only took second in 2006, but they took first place in 2005 and 2004. Not to make excuses for them, but in 2006 they divided their resources between Solar Splash and solar boat races in Europe.
These guys weren't always a powerhouse, though. Prior to 2004 they never finished higher than 9th. In 1999 they got the dreaded Perseverance Award. But that's how caterpillars become butterflies how ugly ducklings become swans and toads become handsome princes, figuratively speaking.
And then there's these guys, the team from the State University of New York. The Cedarville story should provide encouragement to the faculty advisor of the SUNY team. To give you an idea of where these guys are in their program's development, this boat not only has an agressive shark face painted on the underside of the bow, they've got a stereo built in to the rear deck behind the skipper. That stereo probably seemed like a good idea late one night in the middle of a cold hallucinatory New York winter. Not to mock, just a little good natured ribbing. Remember the multi-world champ Cedarville team was once the Bad News Bears of the solar boating world.
Their boat has a critical technical flaw. Their props are arranged above the bottom of the hull behind the transom. See for yourself. The props are visible in the picture. If you hooked a tow rope to the bow and pulled the boat so that it planed, the props would be 90% out of the water. If anybody tells me this boat ever goes faster than ten miles an hour I'll call him a liar. These guys told me they were both first time boat builders, so I'm going to have to blame that one on their faculty advisor. So they come south to have a learning experience and sample the culture. They'll correct their mistakes and do better next year.
Some modifications are allowed. For instance, most boats remove their solar panels to run the sprints. The props can be changed, depending on the event. Two blades for endurance, five for speed, as shown in this picture on the left. You can even change the number of motors you hang on the transom, but you have to start and finish the five-day meet with the same batteries.
Most of the top competitors use a similar hull configuration, long and thin, sharp and pointy in the front with a rounded hull the first half and a flat bottom on the back half leading to a square transom. A canoe in the front transitioning to a pirogue in the back. I was told this shape was a compromise between sprint and endurance. The sharp bow cuts the water for the endurance runs, and the flat bottom allows the boat to plane more quickly in the sprints.
There were several twin-hull catamaran designs. On the one hand, hydroplanes do have a multi-hull design and they go pretty fast, but they also have a lot of power to get those hulls out of the water and skimming along the surface. At lower speeds two hulls make two bow wakes. The bow wake is the biggest source of drag for any boat. Why make two of them if you don't have to?
You won't see any bass boat trolling motors here. Those would be too underpowered, and the motors used are so big that they'd create too much drag if used in that arrangement, although I did wonder if a trolling motor wouldn't be a good choice for the endurance competition.
Solar Splash is an international competition open to any College or University that wants to put together a team. This year teams from Mexico and England came to compete. They do not accept entries from clubs, nonacademic institutions or businesses. The home teams (two entries are allowed per school) finished fifth and sixth in a field of twenty.
You can visit the event's official website at www.solarsplash.com.
Here are some more pictures.