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Sailing Robots To Attempt Atlantic Crossing
Roland Piquepaille writes "The Times of London reports that seven robotic craft will compete in a race across the Atlantic Ocean in October 2008. One of them, 'Pinta the robot sailing boat,' has been designed at Aberystwyth University in Wales. Pinta is expected to sail for three months at a maximum speed of four knots (about 7.4 kph). Its designers hope the Pinta will become the first robot to cross an ocean using only wind power. This 150-kilogram sailing robot costs only $4,900. The transatlantic race will start between September 29 and October 5, 2008 from Portugal. The winner will be the first boat to reach a finishing line between the northern tip of St. Lucia and the southern tip of Martinique in the Caribbean. Here are additional details and links."
Like a robot that builds a house or so. A bit more useful too...
Robotics challenges are usually somehow tied to military objectives such as navigating a certain terrain, rarely do they focus on something constructive and creative.
Oh wait, another RP post...
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Actually, building self-righting / uncapsizable boats is pretty straightforward. Remember that the keel needs to be heavy enough to offset the tipping moment of the sails; normally this means they're really, really heavy. Also remember that the keel is submerged in water, which means that its effective weight is rather lower than it would be in air.
With a bit of forethought, you end up with a boat which will tip over until the keel starts coming out of the water, and then it'll just stop --- any additional heel will cause more keel to emerge, which will cause the effective weight of the keel to increase hugely, which will prevent any further heeling.
Even if by some miracle you do end up with the boat upside down, it's unstable in that attitude and will right itself. Yes, the sails will cause huge water resistance, but that resistance is proportional to the speed of motion through the water; it won't stop the self-righting, it'll just cause it to happen slowly. (Also, the sails will act to prevent the capsize in the first place, for exactly the same reason.)
What tends to happen these days on decently designed boats is knock-down; a gust of wind causes the boat to be knocked onto its side, up to the point where the keel's righting moment offsets the tipping moment of the wind against the sail. This can be very hazardous to the crew, but hey, no crew! When the gust passes, the boat will right itself (usually even if it's filled with water).
The biggest risk is that all this process is extremely violent; the boat's being slammed about hugely. You run a very real risk of bits of the boat actually breaking. The tension at the base of the mast is huge at the best of times, and if the mast breaks under strain and doesn't come completely free of the boat it can very easily smash through the bottom of the hull. Which Would Be Bad. That's one of the reasons why people like unstayed masts these days; if you get dismasted, you don't end up with a huge, heavy, sodden and very dangerous lump of stuff smashing about on top of your boat --- you're much more likely to lose it completely overboard. Much safer.
While this does tend to apply to yachts rather than dinghies, which as you say largely use humans for ballast, you really do get yachts that size --- the difference is largely design rather than size. My father designed, built and sailed a highly successful yacht only a little bigger --- 15 feet, I believe. It was a bilge keel gaff rig with two monster lumps of concrete for the keel, and slept three. It would heel comfortably to about 45 degrees and then just stop. My father tried quite hard on several occasions to get the cabin windows in the water (much to my horror) and failed every time...