A sail is any type of surface intended to move a vessel, vehicle or rotor by being placed in the wind. It is in essence a wing used for propulsion. Sails are can be made from various materials and strengthened using specific liquid mixtures.
Source materials[edit | edit source]
Any type of natural material also used to make textile can be used, knowingly: cotton, wool, kashmere, hemp, sisal, silk, kenaf, jute, ramie, linen, lyocell
Doping[edit | edit source]
Doping, or impregnating the textile with a liquid to make it tougher can also be done. Since most sails are intented for outdoor use, it is often a good idea to this this as it increases the life span of the sail.
Throughout history, a variety of dopes has been developed:
- a popular dope for windmill sails was: 10 liter water, combined with 0,75 liter linseed oil, 0,75 liter grease, and 1 kg of bolus. 
- cellulose acetate butyrate
- certain other lacquers, varnishes, resins ...
Synthetic dopes are often better in toughening the textile, and thus require only treatment or only a few treatments a year. However, the products can be a lot harder to attain, cost more and are environmentally unfriendly. Due to the latter issue, it is also advisable that the textile is burned when it becomes worn.
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References[edit | edit source]
- Werken met molens by Werkgroep West-Vlaamse Molens v.z.w.
- Bolus used for windmill sail