Novembre 2000

The new boundaries imposed on the navigation of competition yachts with regard to water-ballats and canting keelt

Racing yachts are evolving ; gaining in stability, solidity and speed. Until now sea-going racing yachts had a limited speed : the kinetic energy of the boat when sailing was as significant as the energy necessary to capsize. After a sudden rounding-up or bearing-off she would keel-over.



Modern boats with water-ballasts and a mobile keel are much faster and thus the kinetic energy becomes a very important factor. In addition, their stability curve becomes asymmetrical so that when they are rounding-up they stop as before, because both stability and kinetic energy have increased.

On the other hand, when they are bearing-off the situation becomes more dangerous. Their kinetic energy has become much higher but, at the same time, the energy necessary to capsize to leeward is much less (because the stability has decreased on this side).

In the case of the mobile keel the situation is even more delicate because in this position the winward leaning keel becomes vertical to leeward and facilitates capsizing by blocking the movement of the boat.


In most cases, the boat stops after gybing. However, it is important to be aware that if the pilot loses control it causes a sudden reaction which can make the boat capsize under its own speed (this in spite of the increased stability that new technology recently introduced to the boats), like a car when the steering wheel is turned quickly. After such an accident the boat has the capacity to right itself but represents a very dangerous situation for the crew on deck.

Modern boats have new possibilities, they can navigate better and faster but it is important to remain vigilent and be conscious of the new limits and new dangers.





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