The term foil indicates a specific type of appendage that does not exist in “traditional” boats, which can increase the straightening force and counteract gravity and friction in the water.
Sailboats with foils can counteract friction by lightening themselves with the vertical thrust of the foils. We put “wings” in the water to lift and fly the sailboats with foils and we will progressively avoid the friction of the water until the friction of the hull is eliminated. The friction of the foils remains, which is not zero, but is much less than that of the hull.
It may seem incredible to you, but the first experiments in this direction date back to the twentieth century. These were motor boats that accelerated and exploited submerged wings to lift the hull from the water. Today there are many hydrofoils around that use this principle to navigate at high speeds. There is a very famous foil sailboat that introduced this type of V-shaped foil to lift out of the water. This is the Hydroptere, a flying V-foil trimaran that has set many speed records.
For the full story, see: https://globalsolochallenge.com/sailboats-with-foils/
