The fabric attached to the mast to convert wind energy into propulsion power in a nautical craft is called a sail. Obviously, the choice of sail is extremely important, but at the same time very difficult.
In the elementary concept, a sail is a piece of matter called a canvas of a certain area. The canvases are shaped so that when filled with wind, the sail is streamlined and can develop the greatest useful force. Synthetic materials are used in the manufacture of modern sails. The sail is secured with a spar and rigging.
Types of sails
There are many types of sails. Straight sails - are installed across the vessel and look like a trapezoid. Latin sail - in the form of a right-angled triangle, the larger side is attached to the rail. Bermuda sail - has the form of a triangle and stretches along the mast and boom. Luger sail - is an irregular trapezoid, attached to the rail and boom.
When choosing a sail, it is necessary to take into account the type of vessel and the specific operating conditions. Both oblique and straight sails can be used on boats. A straight sail is used as an additional sail, because it works well only with a tailwind, if the gusts of wind do not correspond to the course, the sail unfolds. Oblique sails allow you to sail at an angle to the wind, but when using them, it is necessary to use elements to reduce drift, as well as controls.
The sail area depends on the underwater part of the vessel, or rather on its shape, and the area also determines the freeboard and stability. When using a sailing structure, the vessel must comply with the following parameters:
L: B = no more than 4
B: T = at least 4-5
B: H = at least 3
H: T = at least 2
Where L - length, B - width, T - draft, H - depth from keel to gunwale.
Precision is the key to success
In order to find out the exact dimensions of the sails, it is necessary to use the data indicated in the reference books, for example, in the reference book on small vessels by Yu. V. Emelyanova and N. A. Krysova.
If the ship deviates from these ratios for the worse, then the area of its sails should be less than the tabular by about 25%.
The sail is an indispensable and very important part of any small vessel. So, it creates a traction force, so it must be easy to adjust, withstand heavy loads, and quickly install and retract. For all this, auxiliary equipment is used: the luff is strengthened with cables, the corners of the sails are additionally stitched and additional pieces of hard canvas are inserted, the corners are reinforced with metal plates, and the lat pockets are sewn.
It should be borne in mind that it is impossible to sew a sail for all types of winds (weak or stormy). In order to expand the range of application of sails, sailors invented several techniques, such as bending the mast (backwards in light winds and forward in strong ones), reducing the sail area by winding it on the rigging, etc. Such techniques are also necessary to know and be able to apply for a successful exit on a ship with a sail.
