Global Solo Challenge: Knock-downs, capsizes, 360s, dismastings
by Global Solo Challenge 10 Oct 2021 04:01 NZDT
Fastnet 2011 - Class40 dismasting © Global Solo Challenge
Everyone who has gone by boat has certainly wondered what would happen if the boat overturned. Just think about how many times I have asked myself this before leaving for the Global Ocean Race.
With a boat of just 12 meters, a Class40 the possibility is far from remote. In fact the probability of an overturning or capsize is proportional to the wave height. It usually occurs with a breaking wave.
A rule of thumb say that a capsize is likely with a wave of height proportional but even less than the length of the boat. A breaker taken sideways can not only lay us down with a knock-down but also makes us roll or capsize. Mini 650 sailors know something about this as a Mini 6.50s has a higher chance of meeting a wave of dangerous height. My co-skipper at the Global Ocean Race, Paul Peggs on two occasions in two editions of the Mini Transat has suffered an a full 360.
The first time he abandone the boat by helicopter, the second he managed to sail it under jury rig to Spain. Once ashore, he replaced the mast with that of a friend with an identical boat and set off again and concluded the race. However, I can only imagine his memory of those two episodes was still alive at the Global Ocean Race. After seeing the stormy sea of the roaring forties, I could sense a bit of gloom in his mood. He later decided not to carry on and Hugo Ramon of Spain replaced him for the following two legs.
What would happen in the event of a rollover
First, I make a brief digression knock-downs, which is when you are completely laid flat at 90 degrees by the wind. At the moment of the knock-down, the boat is in a very precarious situation of stability. If a wave hit us right then it would be easy to go over. Knock-down usually occurs in very gusty wind situations or when you are hit by a squall.
In fact, a thunderstorm cloud can produce very dangerous situations. The movement of air inside a large cumulonimbus can become our real enemy. The hot and humid air that rises in altitude feeding a cumulonimbus falls to the sides of it with violence. The wind is not horizontal but vertical, and has all the characteristics of the katabatic wind falling from the mountains.
Kock-down
To give you a sense of how a sudden burst can actually lay us down completely I recovered this video. We are in winter in the Gulf of Spezia in Italy. The wind is gusty, a north-westerly after a cold front. Moreover, the wind accelerates down from the mountain sides, so-called katabatic wind. On the boat we were with a full mainsail and jib with canvas for an average wind of 10-15 knots. Suddenly we were hit by gusts of 30-40 or maybe even more knots of wind. The sea was flat and apart from the fear there were no consequences.
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