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Free pumping: endurance, acrobatics and horsepower

he Finn has always been the most physical of the Olympic classes. In the old days, the physicality used to be associated more with upwind sailing, hiking out and playing the waves with leg kicks for leech flicking. With free pumping in more than 10 knots of wind, introduced in 2010, downwind has become the most physical part of sailing. And maybe interestingly, the physically most demanding conditions in Finn sailing are now in the range of 10-12 knots, rather than in truly heavy air, at least when it comes to aerobic exertion. Finn sailors are tall, 185-200 cm, and heavy, with a bodyweight ranging from 90 to 110 kg. To master the 10.8 sq.m sail they need to be strong, fit and tolerant of long periods of concentration and physical exertion. Sailing the Finn is probably the purest athletic experience in world class sailing, equaled perhaps by only the windsurfers. We attempt here to understand downwind sailing better with the help of aerodynamic computer simulation, as well as taking a look at the physical demands of free pumping. For this, we have picked the motions of the boat and the rig from video footage. In addition to actually pumping the sail one to one, the mainsheet coming straight from the boom to the hand, the sailor rocks the boat through body movement. The enforced motion is said have 4 degrees of freedom (4DOF), around the longitudinal axes of the boat as well as the vertical. Ideally you have synchronised videos from different angles, to capture the

Upwind, the sailor's pulse is around 80% of max, but hiking and leech flicking with the thighs require maximum strength and endurance. Upwind work is more static than the extremely dynamic downwind free pumping.

motion. In 10 knots, at the limit of free pumping, the boatspeed is totally dominated by the action of the sailor, who is literally rowing the boat through the water, with the sail as his oar or paddle in the air. So you need to be fit, but the crucial thing is not fitness alone, but the timing and rhythm of the pumps and rocking. There's an optimum roll and pumping rate for any given windspeed, associated with a periodic shedding of vortices, alternately from the luff and the leech. This relates loosely to a quantity called the Strouhal number (St), a dimensionless number describing oscillating flow mechanisms. Simulating

Tapio Nirkko's heart rate, from a training session on the Medal race course in Rio. Note the 12 min run, with and average heart rate of 172, rising to 194 towards the end.

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FINNFARE NOVEMBER 2016

“Sailing the Finn is probably the purest athletic experience in world class sailing...”