Escaping a flipped Vendee yacht
Organizers of the Vendée Globe round-the-world race now require vessels to prove they can recover from a complete capsize. One entrant, Josh Hall, performed flip-trials in France on his carbon hull and successfully righted the vessel after 90 minutes upside-down spent messing around with electric pumps and water-ballast tanks. The open 60 class vessels are allowed to produce no more than 10° of lateral heel in sailing conditions. Some are fitted with canting keels, which can be made to cant 35° in an emergency, thus popping the vessel back to an even keel in a hurry.
Hall's vessel, Gartmore Investments, is not fitted with a canting keel, however. The yacht's designers, Group Finot, specified that the vessel needed at least 18° of heel to recover from a turtled position. The vessel's water ballast system was then fiddled with to come up with a workable system for the trial flip.
"With our water ballast we can induce 10° of lateral heel. So what happens is the crane flips the boat over; Josh Hall and I are in the thing, now upside down-quite creepy. Kind of like a big, black, empty carbon tomb," said Brian Harris, the race team's shore-side support chief. "The water ballast is usually pumped around the boat with a big, belt-driven pump off the main engine. But since the boat is upside-down, we can't use the motor. So, we have an emergency high-volume, 24-volt pump with an inlet in the top of the boat, which is now the bottom. Ever see the cult movie Brazil, with the terrorist plumbers? That's what I feel like.
"So we use this pump to fill one side of the lateral ballast tanks, about three tons of water. This inclines the boat about 10°-upside-down, mind you. Here we are, upside-down, with only 10° of incline. We have four watertight bulkheads forward. On deck, centered above each of the four compartments, is a hole, attached to a valve on the underside of the deck. So, we go through the series of watertight doors and open all the valves, which begin to flood the forward third of the boat. Remember that the boat is already heeling 10°, so all the water that is coming in flows to the low side. What happens now is that, naturally, these compartments only fill so far because the waterline inside the upside-down boat will only fill up so far-to meet the water level outside."
Harris and Hall then turned to their next set of tasks: "We have a series of fittings in the bottom of the bulkheads, which are now at the top. We hook our pump up to the fittings and pump, pump, pump. In total, between the natural flooding and the pumping, the designers figured we'd have about seven tons of water in the forward sections of the boat, plus the three tons of lateral water ballast, for a total of 10 tons. (The boat only weighs eight tons.) Then, all of a sudden, with a neck-snapping jerk the bloody thing pops back up-Bob's your uncle!"
Once righted, the hull had approximately 28 inches forward freeboard and 20 at the stern: "Not so bad, but still, in a seaway, a rather unstable condition. So, using the quick-disconnect fittings on the watertight bulkheads, which are now at the bottom, and the pump system, you pump all the water out, compartment by compartment. The trick will be to pump the water out before the next great-Jesus, Southern Ocean wave rolls along and capsizes the boat again."
The Vendée Globe, round the world against prevailing winds and currents, with its 20 entrants, begins Nov. 5 at Sables d'Olonnes, France.