Editing Proa (section)

===Foils===
While a proa is fairly efficient at minimizing the amount of wave drag and maximizing stability, there is at least one way to go even further. The use of underwater [[foil (fluid mechanics)|foils]] to provide lift or downforce has been a popular idea recently in cutting-edge yacht building, and the proa is not immune to this influence.

The [[Bruce foil]] is a foil that provides a lateral resistance with zero heeling moment by placing the foil to either or both of the leeward and the windward sides, angled so the direction of the force passes through the center of effort of the sail. Since proas already have an outrigger to the windward side, a simple angled foil mounted on the ama becomes a Bruce foil, making the already stable proa even more stable. Bruce foils are often combined with inclined rigs, which results in a total cancellation of heeling forces. Inclined rigs are also well suited to the proa, as the direction of incline remains constant during shunting.

Another use of foils is to provide lift, turning the boat into a [[hydrofoil]]. Hydrofoils require significant speeds to work, but once the hull is lifted out of the water, the drag is significantly reduced. Many speed sailing designs have been based on a proa type configuration equipped with lifting foils.