Glossary · Keels, foils & rudders
Ventilation
Also called: cavitation, décrochage, stall
When air or vapour forms on a foil and makes it suddenly lose lift.
A foil close to the surface can draw air down: ventilation. At very high speed, pressure on its upper side drops so low that the water boils: cavitation. Either way, lift collapses and the boat drops. Designers use foil sections and fences to prevent it.