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Windmill sail

A windmill sail is a specialized blade or wing mounted on the rotating shaft of a windmill, engineered to harness wind energy and convert it into mechanical rotational power for applications such as grinding grain, pumping water, or sawing timber.^[1] These sails typically consist of a framework covered in canvas, reed matting, or wooden slats, arranged in sets of four to twelve on horizontal-axis windmills, with their angle or twist optimized to divide wind force into lift and drag components for efficient operation.^[1] Originating in Persia around 644 AD with vertical-axis designs using reed sails, the technology spread to Europe by the 12th century, where horizontal-axis mills with cloth-covered common sails became prevalent for agricultural and industrial uses.^[1] In the Netherlands during the Golden Age (late 16th to 17th centuries), sails powered up to 9,000 windmills, enabling land reclamation through polder drainage and supporting economic growth in trade and manufacturing.^[2] Key types of windmill sails evolved to improve efficiency and control in varying winds. Common sails, the earliest European form, feature a wooden frame with adjustable canvas covers that can be reefed manually to reduce surface area.^[1] Spring sails, invented in 1772 by Scottish engineer Andrew Meikle, incorporate spring-loaded shutters that automatically open or close along the sail's leading edge to regulate speed without stopping the mill.^[1] Patent sails, developed in 1807 by Sir William Cubitt, advanced this further with a chain mechanism allowing remote control of all shutters simultaneously from the ground, enhancing operational ease in 19th-century industrial windmills.^[1] In American contexts from the mid-19th century, traditional cloth sails were largely supplanted by solid wooden blades on multi-bladed wheels, ideal for water-pumping on the Great Plains due to their durability and self-regulating features in high winds.^[3] Historically, windmill sails represented a pinnacle of pre-industrial engineering, with designs like those on Dutch tower and smock mills featuring asymmetrical profiles and twisted leading edges for better aerodynamics.^[2] For instance, the 1870 Victoria Grist Windmill in Texas utilized four 15-foot sails to drive grain-grinding machinery at a rate of up to 500 pounds per week, illustrating their role in rural economies.^[4] While steam and electric power diminished their prominence by the early 20th century, preserved examples and restorations highlight sails' enduring legacy in sustainable energy harnessing.^[5]

History and Development

Origins and early sails

The earliest known windmills utilizing sails originated in Persia around the 7th century CE, where vertical-axis designs featured multiple sails arranged around a vertical shaft to harness wind for grinding grain and pumping water. These panemone-style mills, with sails rotating in a horizontal plane, were documented in regions like Sistan (modern-day eastern Iran and Afghanistan) by the 9th century, though evidence suggests their use as early as AD 644. Persian innovations in wind-sail technology subsequently spread westward to the Islamic world and eastward to China. Persian millwrights, taken prisoner by the forces of Genghis Khan, were sent to China to instruct in the building of windmills, with their use for irrigation dating from the 13th century.^[6] By the medieval period in Europe, windmill technology evolved from these vertical-axis precursors to horizontal-axis designs, where sails were mounted on a horizontal shaft to drive millstones more efficiently through right-angle gearing derived from Roman water mills. Post mills, the first European iteration, emerged in England during the 12th century, consisting of a wooden body pivoted on a central post to face the wind, with simple sails formed by basic wooden frameworks. Tower mills followed in France by the early 14th century, featuring fixed stone or brick towers with rotatable caps supporting the sails, allowing for larger structures and greater power output.^[6]^[7]^[8] Regional variations in early sail construction reflected climatic and material differences: Mediterranean areas favored cloth sails stretched over lightweight wooden frames for flexibility in milder winds, while Northern European designs often used solid wooden lattices or slats to withstand harsher, colder conditions without relying on fabric. In basic mechanics, these sails were attached to a horizontal windshaft inclined at 5° to 15° to the horizontal, capturing wind force to generate torque that rotated the shaft; this motion was transmitted via gears—such as a brake wheel on the windshaft engaging a wallower on a vertical spindle—to drive millstones for grinding.^[9]^[10]

Key inventions and inventors

The development of windmill sails in the 18th and 19th centuries marked a shift toward greater adjustability and automation, building on earlier common sails that required manual adjustment and often halting the mill's operation.^[11] In 1772, Scottish millwright Andrew Meikle invented spring sails, featuring spring-loaded shutters that automatically adjusted to wind strength, enhancing control and reducing storm damage compared to canvas designs.^[12]^[13] Seventeen years later, in 1789, English inventor Stephen Hooper patented roller reefing sails, a system that allowed sails to be rolled up or adjusted via a chain from the ground without stopping the mill, improving efficiency during variable winds.^[14]^[15] William Cubitt advanced this further in 1807 with patent sails in England, integrating hinged shutters akin to Meikle's design with Hooper's roller mechanism for simultaneous adjustment of all shutters, enabling full self-regulation.^[16]^[17] On the European continent, French engineer Pierre-Théophile Berton introduced longitudinal shutters in 1842, an early automated system using long wooden slats along the sail length for precise wind regulation without halting operations.^[18]^[19] In 1860, English millwright Catchpole added air brakes to patent sails, consisting of tip-mounted longitudinal shutters that automatically deployed in high winds to slow rotation and prevent damage.^[20]^[21] Spring sails gained adoption across the United Kingdom by the late 18th century, while patent sails became widespread during the 19th century, contributing to a surge in windmill numbers amid industrialization.^[22]^[11]

Basic Sail Types

Jib sails

Jib sails represent one of the simplest forms of cloth-based windmill sails, consisting of a triangular canvas attached to a single spar that is fixed directly to the windshaft. This design allows the sail to be wound around the spar for adjustment, much like the jib sails employed on contemporary sailing vessels in the region. The sails are typically arranged in multiples—often four to eight—radiating from the central shaft, capturing wind to drive the mill's machinery for tasks such as grinding grain or pumping water.^[23]^[24] These sails found widespread use in Mediterranean windmills, particularly in Spain and Portugal, where they were commonly employed starting from the 16th century onward in tower-style mills suited to the region's milder climates and variable winds. In Portugal, such sails characterized many 18th-century designs, influencing replicas like the one at Cann Mills in Dorset, England, built in 1969–1971 to mimic Portuguese prototypes with multiple triangular canvas panels. Though rare in the United Kingdom, jib sails appeared on at least two documented mills: the Buzza Hill tower mill on St Mary's in the Isles of Scilly, where they were fitted to the structure on a stony outcrop, and the aforementioned Cann Mills in Melbury Abbas, Dorset.^[25]^[26] Operationally, jib sails require the windmill to come to a complete stop for reefing or repositioning the canvas, a process akin to handling sails on a boat, which limits their responsiveness to fluctuating wind speeds and reduces overall efficiency in inconsistent conditions. Their lightweight construction using basic canvas and a single spar makes them straightforward and inexpensive to build, particularly in areas with access to maritime sailmaking traditions. However, the exposed cloth is susceptible to tearing under strong gusts, and the design delivers comparatively limited power output compared to more robust sail types, restricting its application to smaller-scale or peripheral milling operations.^[27]^[28]

Common sails

Common sails, also known as traditional or primitive sails, consist of a ladder-like wooden lattice framework covered with canvas, cloth, or sacking to capture wind energy.^[29] The framework, often called the "whip" or "sweep," is constructed from sail bars mortised into cross pieces, forming a grid that supports the fabric covering, with typical spans reaching up to 80 feet across four sails mounted on the wind shaft.^[30] These sails are adjustable in stages—full sail for maximum area, first reef for initial reduction, dagger point for intermediate exposure, and sword point for minimal area—to adapt to varying wind strengths.^[31] The materials used emphasize durability in harsh northern climates, with frames typically made from oak or deal (pine) wood sourced locally or imported, such as Baltic or pitch pine, while the covering employs coarse canvas stretched and tied over the lattice.^[30] In regions like Kent and Sussex, these sails are colloquially termed "sweeps" due to their sweeping motion and rigid construction.^[32] Historically, common sails dominated windmill designs in England and Northern Europe from the 12th century through the 19th century, powering post mills, tower mills, and smock mills for grinding grain and other tasks.^[30] They represented the standard in medieval and early modern Europe, with widespread examples in England's industrial Midlands and coastal areas.^[30] Operation involves manual intervention, requiring the mill to be stopped via brake before reefing, where workers climb the sails to tie down or roll sections of the canvas, often needing two people for safety and control.^[33] For post mills, wind-facing is achieved by pushing a tailpole attached to the rear, rotating the entire mill body around its central post to align the sails with the wind direction.^[34] This labor-intensive process highlights the sails' foundational role as precursors to more automated designs.^[31]

Semi-Automatic Sails

Spring sails

Spring sails represent an early innovation in windmill technology, building upon the lattice framework of common sails by incorporating automated shutter mechanisms. These sails consist of a series of parallel wooden shutters arranged in a venetian blind-like configuration across the sail's surface, each connected to a system of springs and rods that respond to variations in wind pressure.^[20]^[6] Invented by Scottish millwright Andrew Meikle in 1772, spring sails marked a significant advancement in semi-automatic sail design, allowing for greater operational efficiency without constant manual intervention.^[6]^[20] They were widely adopted on British tower mills and post mills, particularly in England, and remained in use through the 19th century and into the early 20th century before being largely superseded by more advanced systems.^[20]^[12] In operation, the shutters automatically open to spill excess wind in gusty conditions, maintaining a consistent rotational speed, while closing to capture more power in lighter winds—all without requiring the mill to stop.^[20] However, reefing, or reducing the overall sail area for very high winds, still necessitated halting the mill to manually adjust the spring tension via a ground-level rope or brake.^[20] This partial automation proved particularly effective in variable British weather, enabling mills to run unattended for longer periods compared to fully manual common sails.^[35]^[20] Despite their advantages, spring sails had notable limitations, as the springs required pre-setting for expected wind conditions and inevitably weakened over time, necessitating periodic replacement.^[20] Preserved examples include those at Nutley Windmill in East Sussex, which features two spring sails alongside common sails, and Wrawby Windmill in Lincolnshire, a post mill retaining its original spring sail configuration.^[36]^[37]

Roller reefing sails

Roller reefing sails feature a design in which canvas is stretched across a series of rollers attached along the length of each main spar, forming bays that can be individually adjusted to vary the sail area exposed to the wind.^[20] The canvas rolls up from the outer end toward the mill, allowing the miller to reduce sail exposure progressively in response to increasing wind speeds.^[38] This system integrates elements of traditional common sails, such as fixed spars, but replaces rigid cloth panels with flexible, rollable sections for easier management.^[39] The roller reefing sail was invented and patented by Captain Stephen Hooper of Margate, Kent, in 1789, marking a significant advancement in windmill sail technology by enabling adjustments without halting mill operations.^[20] It gained popularity particularly in Yorkshire, England, where mills like Holgate Windmill were originally equipped with five such sails before later modifications.^[39] An intact example of Hooper's original roller reefing system survives at Ballycopeland Windmill in Northern Ireland, the only known remaining instance worldwide, where it was installed as part of 19th-century upgrades and used for animal feed production until 1915.^[40]^[38] In operation, the sails permit partial reefing while the mill is running, achieved by pulling a chain from the ground to roll up the canvas sections and spill wind, thus maintaining power output in moderate gusts without full stops.^[20] However, complete furling for storage or high storms requires stopping the mill to secure the rolled canvas fully.^[39] This manual yet remote control mechanism provided millers with greater flexibility over wind capture compared to earlier fixed-sail designs. The primary advantages of roller reefing sails include their relative simplicity over more complex shutter-based systems, allowing precise regulation of wind power to prevent structural damage during storms and extend operational hours in variable conditions.^[39] A notable drawback is the potential for uneven wind distribution across partially rolled bays, which could reduce efficiency in certain configurations.^[20] Hooper's design served as a precursor to later combined systems in patent sails, influencing subsequent innovations in adjustable windmill technology.^[39]

Advanced Adjustable Sails

Patent sails

Patent sails represent an advanced design in British windmill technology, featuring a framework with a series of linked pivoted shutters or vanes along each sail, connected to a striking rod and regulated by counterweights via a chain, allowing automatic adjustment to wind speed without halting the mill's operation, building on earlier innovations in sail regulation.^[20] The patent sail was developed and patented in 1807 by William Cubitt, a millwright from Norfolk, England, who combined elements of shuttered and roller mechanisms to create a self-regulating system. By the mid-19th century, this design had become the standard for many windmills in East Anglia, particularly in Norfolk and Suffolk, due to its reliability and ease of control.^[16]^[39]^[41] Operation of patent sails is facilitated through remote control using chains that extend from the ground level to the mill's cap, allowing operators to adjust the shutters without climbing the structure. In high winds, an additional feature known as air brakes, introduced by millwright R. Catchpole in 1860, consists of longitudinal shutters at the outer tips of the sails that automatically deploy to increase drag and prevent overspeeding. These brakes, typically two per sail positioned at the leading edge of the outboard section, enhance safety and control during gusts.^[42]^[43]^[20] Patent sails provide higher power output in variable wind conditions compared to earlier fixed or manual designs, as their automatic adjustment minimizes downtime and optimizes energy capture over extended periods. For instance, at Thurne Dyke Drainage Mill in Norfolk, the installation of longer patent sails in 1835 significantly increased the mill's pumping capacity for marshland drainage, demonstrating the design's practical impact on efficiency.^[20]^[44]

Spring patent sails

Spring patent sails emerged as a mid-19th-century refinement of William Cubitt's 1807 patent sail design, integrating individual spring controls to enhance adaptability in variable wind conditions.^[45] These sails build on the core shuttered structure of standard patent sails but incorporate separate spring mechanisms for the shutters on each individual sail, enabling asymmetric adjustments that allow millers to tailor tension independently across the four-sail configuration.^[45] The key design feature involves springs positioned between the head of the striking rod and the rein irons connected to the triangles, which permit each sail to maintain its own spring tension setting without affecting the others.^[45] This independent operation facilitates precise balancing, particularly useful in gusty or uneven winds common to exposed locations. In the United Kingdom, spring patent sails saw limited use, appearing rarely in specialized applications such as some Norfolk drainage mills, where they improved overall balance and operational stability. Examples include the Denton Great Green post mill, equipped with one pair of spring patent sails alongside common sails by 1862, and the Cawston smock mill, which featured two pairs driving French burr stones until its destruction by fire in 1875.^[46]^[47] This configuration offered advantages in storm resistance by distributing wind loads more evenly and reducing the risk of sail overload or mill imbalance during high winds.^[45] However, the added complexity of multiple independent spring systems resulted in elevated maintenance demands, including frequent inspections and adjustments, which likely contributed to their scarcity compared to simpler sail types.^[48]

Specialized Sail Designs

Annular sails

Annular sails consist of a ring-shaped configuration of adjustable shutters or vanes arranged radially around the windmill's central shaft, forming a continuous circular structure that significantly reduces the overall diameter of the sail assembly compared to conventional designs. This annular arrangement adapts the principles of patent sails by distributing numerous small, louver-like elements in a symmetrical pattern, often supported by spokes, to create a fan-like appearance. The design originated in England, with the first implementation credited to Henry Chopping and Richard Ruffle in 1838, followed by Ruffle's installation on his own mill in Haverhill, Suffolk, in 1860, where it was inspired by an observed French prototype.^[49]^[50] Notable examples include the post mill at Feltwell, Norfolk, which received annular sails with 8 spokes and 120 vanes sometime after 1860 as a replacement for common sails, and the Titt-type wind engine at Crux Easton, Hampshire, a wind engine constructed circa 1891 featuring 48 canvas sails, each approximately 5 feet long, mounted on a 20-foot diameter wheel atop a 35-foot hexagonal steel tower. These 19th-century installations highlight the sails' application on both post and tower mills for pumping or light grinding tasks in rural settings.^[50]^[51] In operation, annular sails operate akin to patent sails through the collective adjustment of their shutters or vanes to optimize aerodynamic efficiency, but their rotational symmetry allows for uniform wind exposure across the full circle, facilitating smoother rotation and easier alignment via a fantail on compatible mills. This setup enables the sails to harness wind effectively in varying conditions by altering vane angles without halting the mechanism, making them suitable for smaller-scale or space-constrained windmills.^[50]^[51] The primary advantages of annular sails lie in their compact footprint, which enhances space efficiency and wind capture in limited areas, rendering them particularly apt for ornamental mills or installations where larger sails would be impractical. However, their reduced size and distributed load result in lower torque output, restricting them to lighter-duty operations and making them less suitable for heavy milling compared to expansive traditional sails.^[51]

Berton sails

Berton sails, also known as ailes Berton, are a type of adjustable windmill sail featuring a system of longitudinal wooden shutters that run the full length of each sail. These shutters, typically numbering around 11 per sail, are mounted on a framework of spars and can open and close along the leading edge, resembling the pages of a book unfolding. Invented in 1842 by French engineer Pierre-Théophile Berton (1803–1861), this design replaced traditional cloth sails with a rigid, wooden mechanism to improve control and efficiency in wind-powered milling.^[18]^[52] The sails operate through a linkage system connected to rods that extend into the mill's interior, allowing the miller to adjust the shutter angle from inside without halting rotation. This adjustment regulates the sail's surface area and pitch to capture optimal wind power, making the system particularly effective in steady, consistent winds where fine-tuning is needed for sustained operation. Developed as a continental European innovation, Berton sails paralleled British patent sails by enabling semi-automatic regulation but differed in their linear shutter orientation along the sail's length.^[18]^[53] Berton sails were primarily adopted in French windmills during the mid-19th century, and they remained in service until the early 20th century as wind power declined. Notable preserved examples include the Moulin du Cotentin in Fierville-les-Mines, Normandy, a restored 18th-century tower mill equipped with Berton sails that demonstrates the mechanism to visitors; and the Moulin de Rairé in Sallertaine, Vendée, operational since 1555 and retrofitted with Berton sails in 1842, continuing to grind flour today. These restorations highlight the sails' enduring mechanical ingenuity in regional milling heritage.^[54]^[18]

Dutch and Continental Variations

Dutch sail types overview

Dutch windmill sails emerged as a key innovation in the Netherlands during the late 19th and early 20th centuries, building on earlier windmill traditions to support extensive polder drainage efforts that reclaimed vast low-lying lands from the sea. These sails were specifically engineered for efficiency in the region's characteristic low and steady winds, enabling consistent operation of pumps and Archimedean screws to manage water levels across expansive flat terrains. Unlike earlier common sails, late 19th- and early 20th-century Dutch designs emphasized aerodynamic optimization to maximize lift and torque under moderate wind conditions, reflecting the Netherlands' urgent need for reliable land reclamation amid ongoing flooding risks.^[43]^[32] Central to Dutch sail designs are their airfoil-like profiles, which generate lift similar to an aircraft wing by directing airflow over a cambered leading edge. These sails typically incorporate leading-edge slats or plates—thin boards or vanes positioned to create a high-lift slot that enhances performance at low wind speeds and large angles of attack, allowing the mill to start and operate effectively without excessive drag. Most Dutch sails are fixed or semi-fixed in configuration, with minimal adjustability required during operation, as the lattice framework covered in canvas or boards provides inherent stability and reduces the need for frequent reconfiguration. This approach contrasts sharply with British systems, where adjustments often necessitated stopping the mill entirely, highlighting Dutch priorities for low-maintenance reliability in continuous drainage tasks.^[43]^[32] As of 2023, approximately 1,200 traditional windmills equipped with these sail types survive across the Netherlands, many preserved as cultural heritage sites that continue to demonstrate their enduring functionality.^[55] The fixed or semi-fixed nature of Dutch sails minimizes mechanical complexity and maintenance demands, aligning with the practical needs of rural polder operations where wind consistency allows for prolonged, unattended runs. While influenced by British patent sail concepts, Dutch adaptations focused on streamlined aerodynamics suited to the country's level landscapes, eschewing elaborate automation in favor of robust, wind-responsive simplicity.^[56]^[43]

Specific Dutch systems

The Dekker system, developed by A.J. Dekker from Leiden and patented in 1929, features aerodynamic cladding made of zinc, steel, or aluminum sheets applied to the sails, creating an airfoil profile with near-zero camber and optional airbrakes for control.^[57] This design drew from aeronautical principles to enhance wind capture, achieving efficiencies of 34-52% compared to the 9-12% of traditional Dutch sails.^[57] Initially tested in 1927 on a poldermolen at Waardenburg, it proved non-adjustable in surface area but significantly boosted power output, doubling it from around 50 to 100 horsepower in late 1920s applications.^[20] By 1933, over 83 mills had adopted Dekker sails, starting with drainage mills and expanding to corn mills.^[57] The Van Bussel system, invented by Chris van Bussel in Weert and introduced before 1934, refines the airfoil approach with a spoon-shaped profile featuring a rounded nose and wider rear, reducing sail flapping and material use by 60% compared to Dekker designs.^[57] Optional airbrakes allow for better performance in varying winds, while the streamlined leading edge enhances lift, particularly in low-wind conditions below 4 m/s.^[57] This system provided excellent torque for industrial tasks, leading to its installation on 146 mills by 1946 and over 300 total, with about 80 still in use today.^[57] The Ten Have system, created by G.J. Ten Have from Vorden as a post-Van Bussel development, employs a streamlined nose profile that is wider and sharper than its predecessor, reinforced with hemlath for structural integrity.^[57] It incorporates wide shutters adjustable via centrifugal weights for automatic surface area regulation, improving efficiency in moderate winds.^[58] The related Beckers system uses a similar series of centrifugal weights to dynamically adjust sail surface, but remains rare with only two known installations.^[58] The Fauël or Fok system, patented in 1944 by engineer P.L. Fauël (1891-1993) and inspired by jib sail aerodynamics, utilizes slotted airfoils formed by bent redwood boards that create a foresail-like structure.^[57] This design excels in light winds by optimizing airflow through the slots, often paired with centrifugal airbrakes for speed control and storm resistance.^[57] Tested in 1946 at the De Vooruitgang mill, it suits low-power operations and saw adoption on approximately 150 mills.^[57] The Bilau Ventisails and Van Riet systems represent German-Dutch hybrids focused on advanced profiling. Kurt Bilau (1872-1941) developed Ventisails between 1935 and 1938, featuring airplane-wing-like shapes with centrifugal weights and reefing tackle for automatic adjustment, though its high cost and weight limited it to 13 mills, with only one surviving today at De Hoop in Norg.^[57] In contrast, the Van Riet system from Goes uses a streamlined wooden nose with shutters regulated by springs and weights, forming a more complete airfoil but lacking full storm-proofing; its adoption was limited, primarily in Zeeland.^[57] These systems built on broader Dutch aerodynamic principles to revive wind power amid competition from engines, achieving widespread adoption post-1920s, especially on industrial mills, where power outputs reached 125 horsepower by 1940 and operating hours doubled to over 4,400 annually at lower wind thresholds of 3.5-4 m/s.^[20]

Operation and Symbolism

Adjustment and communication

In traditional British windmills equipped with patent sails, adjustment is achieved remotely via chains or levers connected to the shutters, enabling the miller to vary the sail area and optimize performance without halting rotation.^[59] In contrast, Dutch windmills typically employ fixed or weighted mechanisms for sail adjustment; common sails rely on manual repositioning of the canvas on the lattice framework, often while stationary, whereas weighted systems in more advanced designs maintain tension for stability during operation.^[60] To prevent overspeed in gusty conditions, some patent sail configurations incorporate air brakes—longitudinal tip shutters that automatically deploy to increase drag and regulate velocity.^[61] For safety in high winds, millers apply brakes via the internal brake wheel, a friction mechanism operated by ropes or chains to slow or stop the windshaft, often combined with reefing sails or reorienting the cap away from the wind direction.^[62] In Dutch tradition, sail positions serve as a form of passive communication, conveying messages visible from afar without verbal or written means; for instance, a "+" configuration signals a short operational break, while an "X" indicates a longer halt. These positions are standardized by organizations like De Hollandsche Molen. Symbolic uses include the 11 o'clock position for mourning, as seen nationwide following Queen Wilhelmina's death in 1962 and the arrival of MH17 victims' remains in 2014.^[63]^[64] Regional practices highlight these differences: English windmills emphasize functional reefing of sails to precisely control power and adapt to wind strength for efficient milling, whereas Dutch operations integrate symbolic sail codes into daily and ceremonial life, blending mechanics with cultural expression.^[65]

Modern restorations and uses

In the United Kingdom, organizations such as the Norfolk Windmills Trust have led extensive preservation efforts since the late 20th century, focusing on restoring traditional windmill sails to maintain historical integrity and operational capability. For instance, the sails of Billingford Windmill were hoisted back in 2020 following a five-year restoration project that included fitting new shutters, enabling periodic demonstrations of milling. Similarly, in 2025, Haddiscoe Island's drainage windpump received its first set of sails in over a century, marking a significant revival of functional sail systems in Norfolk's marshlands. These projects emphasize the repair and replacement of sail components using treated traditional timbers to withstand weather exposure, though widespread adoption of synthetic composites remains limited in heritage contexts.^[66]^[67] In the Netherlands, the UNESCO World Heritage site of Kinderdijk exemplifies continental preservation, where one of the 19 mills with Dutch-style common sails was damaged by fire in 1997 and underwent major restoration, with full operational sails reinstated by 2000 to support water management demonstrations. Recent initiatives, such as the training of a record number of new millers as of February 2025, have bolstered ongoing maintenance, ensuring sails can turn for educational purposes amid rising interest in sustainable heritage. While post-2000 efforts have incorporated modern preservatives for sail durability, the focus remains on replicating original designs rather than innovative materials. No significant post-1960s advancements in sail technology have emerged, reflecting a commitment to authenticity over modernization.^[68]^[69] Contemporary uses of windmill sails are primarily heritage-oriented, with operational examples limited to demonstrations rather than industrial production. Ballycopeland Windmill in Northern Ireland stands out as one of the few fully functional sites, where roller-reefing sails enable occasional grain grinding into flour, attracting visitors to experience traditional processes. Across Europe, sails at restored sites like Chesterton Windmill in Warwickshire, reinstalled in March 2025, serve educational and touristic roles without contributing to commercial output. As of November 2025, there has been no widespread industrial revival of sail-equipped windmills, overshadowed by modern renewables.^[38]^[70] Adaptations in recent decades have explored sail efficiency for niche applications in heritage settings to promote sustainability education, such as at restored mills integrated into green heritage trails. The 2020s have seen heightened restoration activity driven by broader green energy interests, positioning windmill sails as symbols of low-impact renewable history without displacing contemporary turbine technologies.

References

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### Summary of Windmill Sails: Definition, Types, History, Function, Key Developments
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[28]
[PDF] THE GRAIN CYCLE AND A WINDMILL AT A VILLAGE ON THE ...
Veranzio*s windmill can be taken as one of the antecedents of Mediterranean windmills. ... For the beginning of the use of jib-sails in the. Mediterranean region ...
[29]
Common Sails - The Mills Archive
Traditional northern Europe windmill sails, where cloth, sacking or canvas is spread on a lattice framework, each sail being set separately to suit the wind ...Missing: materials | Show results with:materials
[30]
[PDF] windmill sails and stocks. - Archives Hub
Windmills first appeared in England in the Middle Ages, probably during the 12th. Century. These early mills were quite small, with sails spanning 30-40 feet.
[31]
[PDF] Dictionary of Molinology Wörterbuch der Molinologie Dictionnaire de ...
a full sail volles Segel n, 'mit ... c sword point, long point langes halbes Segel n à demi et sur long lange halve (zeilen) d dagger point, short point.<|control11|><|separator|>
[32]
Windmill sails - why they go round
Early windmill designs used simple canvas sails mounted on wooden frames, attached radially to a shaft which pointed directly into the wind. They worked - when ...Missing: definition | Show results with:definition
[33]
iii. how a windmill works - Tring Local History
In the case of the windmill, wind striking its sails exerts a force upon them that causes the shaft to which the sails are attached to rotate.Missing: definition | Show results with:definition
[34]
Windmills and Their Story - Wonders of World Engineering
Invented in 1809 by Sir William Cubitt, patent sails have all their shutters controlled simultaneously by means of an endless chain hanging down to the ground ...<|control11|><|separator|>
[35]
https://www.heidorn.info/keith/weather/life/windmills.htm
[36]
Nutley Windmill - Uckfield Heritage
This magnificent structure, dating back over 300 years, stands as the sole surviving and operational open-trestle post mill in the entire country.
[37]
Wrawby Windmill | John Bangay
Wrawby Windmill is the most northerly preserved Post type windmill in Great Britain. It uses a combination of Spring and Common sails.
[38]
Ballycopeland Windmill - Atlas Obscura
Jul 27, 2022 · The system was invented by captain Stephen Hooper in 1789 and the Ballycopeland Windmill is the last working windmill with the Roller Reefing ...
[39]
Major Developments in Milling History - Holgate Windmill
... England. 1700-1800 cast iron introduced in windmill gears, wheels, racks ... sails engineered by John Smeeton. 1768 rotating grain cleaner patented by ...
[40]
Ballycopeland Windmill featured on special Royal Mail stamp
Jun 20, 2017 · And we've learnt that Ballycopeland is the last known windmill in the world to still retain the patented Hooper Roller Reefing Gear, which ...
[41]
Guide - Stansted Windmill
This system, the cubitt patent sail, was invented in 1807 by William Cubitt and was first installed in Stansted Mill in 1848. Previously, the shutters, or ...Missing: England | Show results with:England
[42]
Outside the mill | Brixton Windmill & Education Centre
In 1807 a man called William Cubitt invented patent sails, which are more expensive but much easier to adjust. Patent sails are made up of shutters that can ...
[43]
[PDF] Contractor Repo_'_;_ _7..........
The European windmill's four sails, possibly fiat boards in the earliest instances, were mounted on a horizontal shaft, with each sail set at a small angle with ...
[44]
Thurne dyke drainage windmill - Norfolk Mills
The mill was built with common sails to power its scoop wheel and these were uprated to the longer patent sails in 1835 after the additional storey was built..Missing: efficiency | Show results with:efficiency
[45]
Spring Patent Sails - A-Z glossary – The Mills Archive
A sail incorporating the principles of both the SPRING SAIL and PATENT SAIL. Springs being incorporated between the head of the striking rod and the REIN IRONS ...
[46]
Denton Great Green post windmill - Norfolk Mills
Also, the Post WINDMILL with Spring Patent sails, 2 pairs of French Stones, Flour Mill & all going Gears & now in full trade, with Dwelling house, Garden & one ...
[47]
Cawston smock mill - Norfolk Mills
A Capital Wood Smock Self Winding WINDMILL with two spring patent sails, driving two pair of French Stones with Flour Mill & Jumper & every requisite for ...
[48]
Dilham post wind mill - Norfolk Mills
A Valuable Post Windmill in good trade & substantial repair complete with one pair of large French Stones, one pair of spring patent sails, iron wind shaft ...
[49]
[PDF] Renewable Energy for Development - Stockholm Environment Institute
The first use of the annular sail, in which all the shutters are assembled radially, was made by. Henry Chopping and Richard Rufflein in England. 1838, and ...
[50]
Feltwell Wilton Road post mill - Norfolk Mills
Feltwell postmill was very unusual in that it had disinctive annular sails with 8 spokes and 120 vanes. These were a later addition, some time after 1860, ...Missing: Crux Easton Hampshire
[51]
None
**Summary of Annular Sails on Crux Easton Wind Engine:**
[52]
https://www.wiki-anjou.fr/index.php/Pierre-Th%C3%A9ophile_Berton
[53]
Windmills and Their Technology since the Middle Ages - Brewminate
The first practical windmills were panemone windmills, using sails that rotated in a horizontal plane, around a vertical axis. ... The horizontal-axis or vertical ...
[54]
Le moulin de Fierville - Moulin à vent du Cotentin - GuideVoyageur.fr
C'est un moulin à vent équipé du système d'ailes Berton, permettant au menier, de régler la surface des ailes sans arrêter le moulin. La tour est en pierre ...
[55]
Windmill spotting in and around Amsterdam - Iamsterdam.com
May 22, 2025 · Did you know there were once more than 10,000 fully operational windmills in the Netherlands? Windmills are a quaint symbol of Dutch ...
[56]
[PDF] Wing systems in the Netherlands
So he invented a better Dekker system, which a rounder nose profile and a wider backside of the profile, which caused the sails lesser flapping and also the ...Missing: windmill types
[57]
Different Types of Windmill Sails
Jib sails – Very simple type of sail that consists from simple wooden frame and sailcloth in the form of triangle. This triangle can be made in several distinct ...Missing: definition | Show results with:definition
[58]
Dutch Windmills Left Behind | The Inconsequential Diary
Jun 16, 2020 · Wind millers must therefore adjust the sails that cover the latticed blades of the windmill to different extents. They can change the ...
[59]
Windmill sail - Wikipedia
During the nineteenth and twentieth centuries, Dutch millwrights developed the windmill sail to make it more efficient aerodynamically and operation easier in ...Missing: history | Show results with:history
[60]
Meanings of the position of the sails of a windmill | Heavenly Holland
Oct 22, 2014 · Leaving the sails locked in a '+' position means that the miller is taking a rest for a short period of time (image above left) and when the ...<|separator|>
[61]
Dutch mourn as first MH17 bodies arrive in Netherlands - Swissinfo
Jul 24, 2014 · ... mourning since wartime Queen Wilhelmina died in 1962. King Willem ... mourning position – with the topmost sail fixed counter-clockwise from the ...
[62]
How the Dutch Used Windmills for Passive Communication - Core77
Nov 9, 2023 · If the topmost sail was in the 11 o'clock position, it signified "mourning" or "death." It would be placed in this position following a funeral.Missing: modern post- 1920s
[63]
Celebration as 5 year restoration of iconic Billingford Windmill now ...
May 17, 2022 · The stocks and sails were hoisted back onto the mill in September 2020 and work to fit a half set of shutters has recently been completed.
[64]
Haddiscoe Island wind pump gets first set of sails in a century - BBC
Jul 3, 2025 · Windpump sails turn again after 76 years · Windmill mapped with laser technology · Timelapse shows windpump restoration · Two more cases of bird ...
[65]
The Kinderdijk Windmills of The Netherlands - Wanderers Compass
Jan 25, 2022 · Since that day, the windmill has been restored and operational since the spring of 2000. All the Kinderdijk windmills are watermills, which ...
[66]
The Netherlands has a record crop of new millers to keep ... - AP News
Feb 18, 2025 · On the mill's cutting floor, six blades briefly rise and fall, sawing into a rough-hewn plank. But the wind drops and the mill's sails and saws ...Missing: Dekker Van Bussel<|separator|>
[67]
New sails installed on much-loved Warwickshire windmill - BBC
Mar 20, 2025 · Chesterton Windmill has sat on a hill in Warwickshire for nearly 400 years, but its sails were removed in 2021 after cracks appeared in the wood ...
[68]
Mathematical modeling of the aerodynamic coefficients of a sail blade
Apr 11, 2023 · The sail blade modeling was based on the Reynolds-averaged Navier–Stokes equations (RANS) using the ANSYS FLUENT computer program.