Square sail

The square sail, which is in fact trapezoid, is the oldest and simplest form and fulfils the need to set up a screen against the wind in order to capture its energy. This the type of sail was used on longships and large traditional sailing ships. It is a powerful sail whose efficiency is limited when manoeuvring in strong winds. The solution to moving forward facing the wind is to zigzag – a long and complicated manoeuvre with this type of sail.