Sailcloth encompasses a wide variety of materials that span those from natural fibers, such as flax, hemp or cotton in various forms of sail canvas, to synthetic fibers, including nylon, polyester, aramids, and carbon fibers in a variety of woven, spun and molded textiles.

Moody DS54
Sails made with synthetic fibers.


JSJ-volunteer turning
Volunteer wins the America's Cup in 1887 with cotton sails

Western traditions

Doek is Dutch for cloth, which was evolved into the English word "duck" in reference to sail canvas. Duck was typically made from cotton or linen (flax), with some use of hemp. These natural fibers have poor resistance to rot, UV light and water absorption. Linen is stronger, but cotton is lighter. Linen was the traditional fiber of sails until it was supplanted by cotton during the 19th century. At first cotton was used as a matter of necessity in the United States as it was indigenous and the supply of flax was periodically interrupted by wars such as the War of 1812, during which demand for sailcloth for military use was high. As sail size grew linen was too heavy to be practical so cotton became more popular. Cotton did not substantially replace linen worldwide until the end of the age of sail; however, in some cases the strength of linen was preferred for some types of sails. It was not until the late 20th century that natural fibers were replaced by synthetics in mainstream use. Cotton sailcloth is still used for sportswear, upholstery and draperies. The traditional width for carded cotton sailcloth in the US was 23 inches (58 cm) while the British standard was 24 inches (61 cm).[1]

Other traditions

The wa proa of the Caroline Islands traditionally used pandanus matting as sailcloth.[2]

Modern fibers

The characteristics of a sail are due to design, construction and the attributes of the fibers, which are woven together to make the sail cloth. The following sections discuss the attributes of fibers assuming a good design and careful construction. According to Mahr, there are six key factors in evaluating a fiber for suitability in weaving a sail-cloth:[3]

  • Initial modulus – The ability to resist stretching. Higher resistance is better for upwind sails.
  • Breaking strength – Measured as a force per cross sectional area of fiber. Higher is better for sails.
  • Creep – Describes the long term stretch of a fiber or fabric. A material with creep may have a superior modulus, but lose its shape over time.
  • Resistance to ultraviolet light – Strength loss from exposure to the Sun’s UV rays measured by a standardized exposure test.
  • Flex strength – Strength lost due to bending, folding, or flogging, which is frequently measured with an industry standard 50 fold test.
  • Cost-effectiveness –Both the initial cost and its durability of the material define its cost-effectiveness over time.

There is no perfect solution since in most cases the increase of one attribute generally results in the decreased attractiveness of another. Reduced stretch generally also reduces the flexibility causing a trade-off of performance for durability. Solving both problems generally sends the price out of range for most sailors.


Bear of Britain spinnaker
Spinnaker, made of nylon because of its light weight and high strength.

Nylon is used in spinnakers because of its light weight, high tensile strength, superior abrasion resistance and flexibility. However, it has a low modulus allowing too much stretch to be suitable for upwind sails. Nylon is more susceptible to UV and chemical degradation than polyesters and its physical properties can change due to moisture absorption.

Polyester (PET)

Polyethylene terephthalate, the most common type of polyester, is the most common fiber used in sailcloth; it is also commonly referred to by the brand name Dacron. PET has excellent resiliency, high abrasion resistance, high UV resistance, high flex strength and low cost. Low absorbency allows the fiber to dry quickly. PET has been replaced by stronger fibers for most serious racing applications, but remains the most popular sail cloth due to lower price and high durability. Dacron is the brand name of Dupont’s Type 52 high modulus fiber made specifically for sailcloth. Allied Signal has produced a fiber called 1W70 polyester that has a 27% higher tenacity than Dacron. Other trade names include Terylene, Tetoron, Trevira and Diolen.

PEN fiber (Pentex)

PEN (Polyethylene naphthalate), commonly known by Honeywell's trade name "Pentex", is another kind of polyester fiber, which stretches only 40% as much as standard PET fibers, but about twice as much as Kevlar 29. Because it only shrinks about a third as much as a good PET, PEN can not be woven as tightly; thus, woven PEN must be impregnated with resin making sails prone to damage from improper use and handling. PEN is better suited for making laminated sailcloth, where the fibers are laid straight for strength and are bonded to sheets of film for stability (e.g., PET film often called by one of its trade names Mylar), or as a taffeta outer layer of a laminate, protecting a PET film. PEN laminates are an economical alternative for higher performance sail.


Frers 40
Aramid (Kevlar) sails, showing the typical color of the fabric.

Kevlar, an aramid fiber, has become the predominant fiber for racing sails, since it was introduced by DuPont in 1971. It is stronger, has a higher strength to weight ratio than steel, and has a modulus that is five times greater than PET, and about twice as high as PEN. There are two popular types of Kevlar: Type 29 and Type 49, the latter having a 50% higher initial modulus than Type 29 but a lower flex loss. DuPont has developed higher modulus Types 129, 149 and 159, but these have seen little use in sails, since generally as the modulus increases the flex strength decreases. DuPont has recently introduced Kevlar Edge, a fiber developed specifically for sails with 25% higher flex strength and a higher modulus than Kevlar 49. Kevlar, along with other aramid fibers, have poor UV resistance (Kevlar loses strength roughly twice as quickly in sunlight as PET) and rapid loss of strength with flexing, folding and flogging. Minimal flogging and careful handling can greatly extend the life of a Kevlar sail.


Technora is an aramid, which is produced in Japan by Teijin, has a slightly lower modulus strength than Kevlar 29 but a slightly higher resistance to flex fatigue. The fiber’s lower UV resistance is enhanced by dying the naturally gold fiber black. Technora is most often used as bias support (X-ply) in laminate sailcloth.


Twaron is an aramid, which is produced in The Netherlands by Teijin, is chemically and physically similar to DuPont’s Kevlar. Twaron HM (High modulus) has similar stretch properties to Kevlar 49, greater tensile strength and better UV resistance. Twaron SM is similar to Kevlar 29. Like Kevlar, the fiber is a bright gold color.


Spectra is an ultra-high-molecular-weight polyethylene (UHMWPE) made by Honeywell, which offers superior UV resistance (on par with PET), very high initial modulus numbers (second only to high modulus Carbon Fiber), superior breaking strength, and high flex strength. However, it also exhibits permanent and continuous elongation under a sustained load (AKA: creep). This results in a change in shape as the sail ages. Because of this Spectra is only used in spinnakers on high performance boats where the sails are replaced regularly.


Equivalent to Spectra, Dyneema is an extremely strong fiber produced by the Dutch company DSM. It is often used by European sailcloth manufacturers, is available in a wider variety of yarn sizes than Spectra, and is growing in popularity. Dyneema DSK78 set a new standard combining the typical high strength to weight ratio, excellent low stretch, abrasion, and UV resistance but added three times better creep performance compared to Dyneema SK75 and nearly two times better than Dyneema SK90.


Hoechst Celanese produces Certran polyethylene similar to Spectra, with about one half the modulus rating of Spectra. It has similar properties to Spectra including superior resistance to flex fatigue and UV degradation but also exhibits creep.

Zylon (PBO)

PBO (Poly (p-phenylene-2, 6-benzobisoxazole)) is liquid crystal polymer developed by Japan-based Toyobo under the trade name Zylon. It is a gold fiber with an initial modulus that is significantly higher than other high modulus yarns, including aramids. Among PBO's desirable properties are high thermal stability, low creep, high chemical resistance, high cut and abrasion resistance, and excellent resistance to stretch after repeated folding. PBO is also quite flexible and has a soft feel. But PBOs have poor resistance to both UV and visible light.


Bodacious (sailboat by Farr Yacht Design)
Carbon fiber mainsail, showing grey-scale hues typical of the material.

Vectran is a polyester-based high performance LCP (liquid crystal polymer) produced by Ticona. It is naturally gold in color and has a modulus similar to Kevlar 29, but has less strength loss with flex. This is a benefit in endurance applications and for cruising sails where durability is key. Additional advantages of Vectran fiber has a 0.02% creep at 30% of max load after 10 000 hours, high chemical and abrasion resistance and high tensile strength. The UV endurance is inferior to PET and PEN, but the degradation levels off after roughly 400 hours of exposure, while the Aramids and Spectra continue to degrade.

Carbon fiber

Carbon fiber is a high modulus synthetic fiber made from carbon atoms. It is virtually unaffected by UV exposure and provides exceptionally low stretch. Variants can balance along a continuum from brittle with no-stretch to extreme durability/flexibility with only slightly more stretch than aramid sails.


Combed singles yarn sailcloth in high counts is used for spinnaker and head sails. The count often is 148 by 160 and the fabric is finished at 100 cm (40 in) wide with a length-to-mass ratio of about 13.10 m/kg (6​12 yd/lb).[4] The quality and weight of the weave can be more critical than the choice of fibers, since a poor weave can lead to high stretch and poor sail form. Weight is described in ounces, for example "an 8 oz. cloth". This means that an area of 72 cm × 91 cm (28 12 in × 36 in) weighs 230 g (8 oz).

Sailcloth is woven in two forms: balanced and unbalanced. The yarns in balanced cloth are the same diameter and weight in lengthwise (the "warp") and across the width of the cloth (the "fill"). Unbalanced means a heavier yarn is used in one direction. Most moderns sails are "crosscut", which is an unbalanced technique where the heavier yarns is in the fill. This allows greater loads to radiate up from the clew (back lower corner) along the leech (back edge). This is especially true of mainsails and high aspect jibs.

Woven sail cloths have an inherent problem with stretch resistance. In a weave the warp and fill yarns pass over and under one another. As load is applied the yarns attempt to straighten out, this results in the fabric stretching, commonly referred to as "crimp". Fibers which are resistant to stretching cannot be woven as tightly as more flexible fibers such as PET, thus the cloth is more affected by crimp.


Films are thin sheet material extruded from synthetic polymers and are typically used along with woven cloth in a laminate (see laminates below).


PET film is the most common film used in laminated sailcloth. It is an extruded and biaxially oriented version of PET fiber. In the US and Britain, the most well-known trade names are Mylar and Melinex.

PEN Film

PEN film is extruded and biaxially oriented version of PEN fiber. Just as PEN fiber is stronger than PET fiber, PEN film is stronger than PET film. However, PEN film is rarely used in standard sailcloth styles because it shrinks more rapidly than PET, is less resistant to abuse, and reduces the working life of the sail.

Scrim and strands

Strands are combined from fibers; these are frequently narrow flat bands or ribbons of high strength material. Scrim is a loose weave or lattice of strands, typically bonded where they cross to maintain the grid pattern. Strands and scrims are used to strengthen or reinforce sailcloth (see laminates below).

Laminated sailcloth

In the 1970s sailmakers began to laminate multiple materials with different characteristics to synergize the qualities of each. Using sheets of PET or PEN reduces stretch in all directions, where weaves are most efficient in the direction of the threadlines. Lamination also allow fibers to be placed in a straight, uninterrupted paths. There are four main construction styles:


Film is sandwiched in between two layers of woven taffeta, the film provides most of the stretch resistance and the taffeta enhances tear and abrasion resistance. The high-end versions of this method use a woven Spectra or Kevlar taffeta. In some newer styles, off threadline aramid yarns, are also laid into the laminate. In some cases the second layer of taffeta is eliminated for cost and weight savings

Film-scrim-film or film-insert-film (film-on-film)

In this construction, a scrim or strands (inserts) are sandwiched between layers of film. Thus load-bearing members are laid straight, which maximizes the high modulus of the fibers, where a woven material will have some inherent stretch to the weave. Laminating film to film around the strands creates a very strong and dependable bond reducing the amount of adhesive needed. In high quality cloth, the strands or scrim are tensioned during the lamination process.

The drawbacks are: film is not as abrasion or flex resistant as a weave, it does not protect the structural fibers from UV rays. In some cases UV protection is added.


Woven fabric with high UV and abrasion protection is added to the film-on-film. This combines the best of the above, but is costly, heavy, and stiff. This is an attractive method to combine high modulus fibers with poor UV resistance.


Wovens on both sides of a scrim without the film layer. The problem is getting enough high modulus yarn into the sandwich, and still being able to get a good bond, because, dissimilar fabrics don’t often bond well. This technique is more experimental than practical, but may yield results in time.


  1. ^ Fairchild's dictionary of textiles, 7th edition, NY, 1996, pg. 484
  2. ^ McCoy, Michael (1973). "A Renaissance in Carolinian-Marianas Voyaging". Journal of the Polynesian Society. Auckland University. As of 1973, all canoes on Satawal were using dacron sails sewn by the men themselves. Most Carolinian canoes had used canvas acquired during the Japanese presence in the islands. The people of Satawal, however, were reluctant to switch from the cumbersome pandanus-mat sails, probably because canoes and voyaging were included in the elaborate pre-Christian taboo system. Christianity took hold on Satawal during the decades after World War II, and the islanders then used canvas. When I and Gary Mount, as Peace Corps volunteers, demonstrated the obvious superiority of dacron over canvas with only a 4-inch square sample, the men agreed to purchase sails for the canoes of the island. As word of the superiority of dacron spread, the people of Ifalik, Elato, Woleai, Pulusuk, Pulap and Puluwat have equipped at least one canoe on each island with dacron.
  3. ^ Textor, Ken (1995). The New Book of Sail Trim. Sheridan House, Inc. p. 228. ISBN 0924486813.
  4. ^ Fairchild's Dictionary of Textiles, 7th edition, NY 1996, pg. 484

See also

American Aerolights

American Aerolights Inc. was an American aircraft manufacturer founded by Larry Newman. The company specialized in the design and manufacture of ultralight aircraft in the form of kits for amateur construction and ready-to-fly aircraft under the US FAR 103 Ultralight Vehicles rules.Newman was well known for his 1978 flight across the Atlantic Ocean in the balloon Double Eagle II with Ben Abruzzo and Maxie Anderson. As a result of that flight Newman received the Congressional Gold Medal from the United States Congress. He died of pancreatic cancer on 20 December 2010 in Scottsdale, Arizona at the age of 63.The company produced the simple flex-wing single-seat ultralight American Aerolights Eagle and the two-seat American Aerolights Double Eagle as well as the advanced, enclosed cockpit American Aerolights Falcon.The Eagle design sold in large numbers, but suffered many wing failures that resulted in several fatalities as a result of the deterioration of the unreinforced Dacron sailcloth trailing edge design. The lawsuits, as a result of the design defects, put the company out of business in about 1984, just as the market for ultralight aircraft in the United States collapsed.The company is most noted as the first manufacturer of ultralight aircraft to have one of their designs used by a police service. The Monterey Park, California Police Department flew a Double Eagle for six months in 1982, becoming the first police department to fly an ultralight aircraft for patrols. The program was ended after seven engine failures in flight. An example of the police service aircraft is on display in the Smithsonian Air and Space Museum's Steven F. Udvar-Hazy Center and one was at one time in the EAA AirVenture Museum in Oshkosh, Wisconsin.

American Aerolights Eagle

The American Aerolights Eagle is an American ultralight aircraft that was produced by American Aerolights, introduced in 1975. The aircraft was supplied as a kit for amateur construction.Different sources attribute the design to Larry Hair or Larry Newman.

Ballycopeland Windmill

Ballycopeland Windmill is a functioning windmill located one mile west of Millisle, County Down, Northern Ireland. It is managed by The Historic Environment Division of The Department for Communities and is open to the public. It is known in Irish as Muileann gaoithe Bhaile Chóplainn and in Ulster-Scots as Ballycopelann Wun-mäll.

Birdwell (clothing)

Birdwell, makers of Birdwell Beach Britches, is an American surf clothing company headquartered in Santa Ana, California,. Founded by Carrie Birdwell Mann in 1961, the company manufactures and sells customized heavy-duty swimsuits, which are sold internationally. With four basic models, various fabrics, including Surfnyl, Tectyl, heavy nylon, sailcloth, and canvas, more than 40 colors, and various other options, the combinations that can be created are nearly endless. The company's motto is "We don't build 1000 things. We build one thing 1000 ways."

The swimsuits themselves, which resemble board shorts, are paneled swimsuits, with waistbands resembling those of boxing trunks, always double-stitched, always with two layers of fabric. These shorts are known and favored among surfers, lifeguards, and paddleboarders, because of their quick-drying design and extreme durability; with an estimated 10 years for average use, and 2–5 for more strenuous use.

On all of the trunks there is a 2 square inch (50 mm2) logo, of a stylized anthropomorphic surfboard, wearing, of course, Birdwell Beach Britches, nicknamed "Birdie".

Burial at sea

Burial at sea is the disposal of human remains in the ocean, normally from a ship or boat. It is regularly performed by navies, and is done by private citizens in many countries.

Burial-at-sea services are conducted at many different locations and with many different customs, either by ship or by aircraft. Usually, either the captain of the ship or aircraft or a religious representative (of the decedent's religion or the state religion) performs the ceremony.

The ceremony may include burial in a casket, burial sewn in sailcloth, burial in an urn, or scattering of the cremated remains from a ship. Burial at sea by aircraft is usually done only with cremated remains. Other types of burial at sea include the mixing of the ashes with concrete and dropping the concrete block to form an artificial reef such as the Atlantis Reef.

Below is a list of religions that allow burial at sea, with some details of the burial.

Fractional rig

A fractional rig on a sailing vessel consists of a foresail, such as a jib or genoa sail, that does not reach all the way to the top of the mast.

In the adjacent picture, the forestay that secures the mast at the front of the boat is attached to the mast at a lower point and the fore sail (jib or genoa) is rigged to this stay. The mast is farther forward on the boat than on a masthead rig and so it has a larger main sail. Masthead rigs are most common on larger keel boats or cruisers.

A fractional rig is typically used on dinghy sailing boats and racing oriented keel boats, such as the J/24.

Fractional rigs were introduced on race boats in order to allow more controllability of the surface of the main sail and also less drag during tacking. According to one manufacturer, "a key to making fast boats easier to sail than slow boats is the fractional rig".Usually a fractional rig features a larger main sail and a smaller non-overlapping jib. This configuration is optimized for up-wind sailing efficiency. For downwind sailing, a larger jib is more desirable but in the case of many high-performance fractional rig sailboats, the smaller jib is substituted by a spinnaker or gennaker. On many modern skiffs and race dinghies, the jib is relatively small compared to the size of the main and it is normally left in place when the spinnaker or gennaker is used due to this type of jib's minimal aerodynamic interference.

A major advantage of the fractional rig, especially the '3/4' rig (where the fore stay goes 3/4 the way up the mast), is that the jib can be taken in without the boat rounding up into the wind like a weather vane. With the masthead sloop, both the main and the jib must be reefed, when shortening sail, to keep this from happening.

Since jibs need considerable fore stay tension to set properly and the amount of tension needed increases with wind speed, being able to drop the jib first in windy conditions puts less strain on the rig and hull. Fractional rigs are used on lightly built multi-hulls for this reason.

Hang gliding

Hang gliding is an air sport or recreational activity in which a pilot flies a light, non-motorised foot-launched heavier-than-air aircraft called a hang glider. Most modern hang gliders are made of an aluminium alloy or composite frame covered with synthetic sailcloth to form a wing. Typically the pilot is in a harness suspended from the airframe, and controls the aircraft by shifting body weight in opposition to a control frame.

Early hang gliders had a low lift-to-drag ratio, so pilots were restricted to gliding down small hills. By the 1980s this ratio significantly improved, and since then pilots can soar for hours, gain thousands of feet of altitude in thermal updrafts, perform aerobatics, and glide cross-country for hundreds of kilometers. The Fédération Aéronautique Internationale and national airspace governing organisations control some regulatory aspects of hang gliding. Obtaining the safety benefits of being instructed is highly recommended.


A headsail is any sail forward of the foremost mast on a sailboat.

Junk rig

The junk rig, also known as the Chinese lugsail or sampan rig, is a type of sail rig in which rigid members, called battens, span the full width of the sail and extend the sail forward of the mast.While relatively uncommon in use among modern production sailboats, the rig's potential advantages of easier use and lower cost for blue-water cruisers have been explored by individuals such as trans-Atlantic racer Herbert "Blondie" Hasler and author Annie Hill.

M-Squared Breese

The M-Squared Breese is a large family of high-wing, strut-braced, pusher configuration, tricycle gear, ultralight aircraft produced by M-Squared Aircraft of St. Elmo, Alabama in kit form, for amateur construction.


A mainsail ("mains'l") is a sail rigged on the main mast of a sailing vessel.On a square rigged vessel, it is the lowest and largest sail on the main mast.

On a fore-and-aft rigged vessel, it is the lowest and largest and often the only sail rigged aft of the main mast, and is controlled along its foot by a spar known as the boom. A sail rigged in this position without a boom is generally called a trysail, and is used in extremely heavy weather.

Traditional fore-and-aft rigs used a four-sided gaff rigged mainsail, sometimes setting a gaff topsail above it.


An oilskin is a waterproof garment, typically worn by sailors and by others in wet areas, such as fish-plant workers. The modern oilskin garment was developed by a New Zealander, Edward Le Roy, in 1898. Le Roy used worn-out sailcloth painted with a mixture of linseed oil and wax to produce a waterproof, yet still breathable garment suitable to be worn on deck in foul-weather conditions.

Owen Buckingham (died 1713)

Sir Owen Buckingham (c. 1649 – 20 March 1713) was an English merchant, alderman, MP and Lord Mayor of London.

He was born the son of George Buckingham, an innkeeper of Stanwell, Middlesex. By 1680 he was a liveryman in the Butchers’ Company of the City of London and by 1692 a liveryman of the Salter's Company.

He became involved in local city politics and was a common councilman for London in 1689–90 and 1691–1696 and an alderman from 1696 to his death. He was appointed Sheriff of London for 1695–96, knighted the same year and elected Lord Mayor of London for 1704–05.

As a result of a promise to manufacture sailcloth in the town he was elected MP for Reading in 1698, and again in 1701, 1702 and 1705, giving up the seat in 1708 in favour of his son, also Owen Buckingham.

By virtue of his own enterprise and a succession of favourable marriages he became quite wealthy and by 1706 had purchased the Fettiplace family estates near Reading.

He died in 1713. He had married 6 times but was survived by only the one son and heir Owen and two daughters from his first marriage.


In embroidery, plainweave is a technical category of woven base fabrics that are suitable for working certain varieties of embroidery. Plainweave fabrics have a tight weave and individual threads are not readily visible. Surface embroidery may be performed on plainweave, such as crewel work, goldwork, stumpwork, cutwork, and candlewicking.Embroideries that can be performed on plainweave do not require the crafter to perform stitches at a precise thread count. Most woven fabrics that were not specifically manufactured for the purpose of embroidery qualify as plainweave. Traditionally, linen plainweave is the preferred fabric for crewel embroidery. Other plainweaves suitable for crewel include denim, sailcloth, ticking, and organdy when worked in wool.

Sedna IV

The S/Y Sedna IV is a 51-metre (167 ft) three-masted schooner which has been used for scientific expeditions and the filming of documentaries.

Built by Abeking & Rasmussen in Germany in 1957 as a Sidefishing Trawler, refitted as a sailing vessel in 1992, she was equipped with a film studio in 2001 when a Canadian film crew acquired her. The ship was previously named Saint Kilda. Sedna IV is fitted out with a cutting room and an equipment room containing high-definition filmmaking apparatus. The crew can use the onboard high-precision scientific equipment to gather, compile and analyze data to fulfill the expedition's scientific research program. The schooner is also connected to the internet via satellite, enabling land-based researchers to become virtual mariners.

The schooner has a 78,000 L (17,000 imp gal; 21,000 US gal) diesel reserve giving her a range of 8,500 nautical miles (20,000 km). She is also equipped with 700 square metres (7,500 sq ft) of sailcloth.

Spreader patch

A spreader patch is a fabric reinforcement at a point on a sail where it is likely to rub with the spreader on a mast.

Vox Piscis

Vox Pisces, or The Book-Fish, contayning three treatises which were found in the belly of a cod-fish in Cambridge market, on Midsummer Eve last is a book published in 1627 with a very unusual origin.

The original text of the work was found in the belly of a fish. On June 23, 1626, scholar and theologian Dr. Joseph Mede (or Mead) of Christ's College, Cambridge, was walking through Cambridge's market, when a fishwife found a small thin book (size sextodecimo) wrapped in sailcloth inside the stomach of a codfish caught at King's Lynn.

These texts were attributed to Protestant reformer John Frith, who was imprisoned in a fish-cellar in Oxford and later burned at the stake. The texts were published as a book the next year with a preface written by Thomas Goad. The texts have also been attributed to Richard Tracy of Stanbury Manor, Gloucestershire.

It is not known how the original book got in the fish's stomach.

Waxed cotton

Waxed cotton is cotton impregnated with a paraffin or natural beeswax based wax, woven into or applied to the cloth. Popular from the 1920s to the mid-1950s, the product, which developed from the sailing industry in England and Scotland, became commonly used for waterproofing. It has been replaced by more modern materials but is still used by the country sports community.

The main drawback is that waxed fabric is not very breathable.

Windmill sail

Windmills are powered by their sails. Sails are found in different designs, from primitive common sails to the advanced patent sails.


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