Sail Concepts

by Dave Acree

I have decided to write a short article on what the wind does to sails and how it drives a sail boat forward. The wind does not only push as some might think but the sail has a forward and sideways pull. This causes the airflow to be deflected when it hits the luff of the sail. As the wind passes over the leeward side, it has a longer, faster path than the air on the windward side. This causes a greater pressure on the windward side than on the leeward side. This pressure difference creates the force on the sail and moves the boat forward. Toward the sail's luff has the greatest pressure which shows in the curvature of the sail.

There are several theories on this concept. Hopefully, this article will explain some of this topic. For those who would like more information, there are several books which help in furthering your understanding. It is an important part of sail design and needs to be understood.