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SpiNNaker
SpiNNaker
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SpiNNaker: spiking neural network architecture
The SpiNNaker 1 million core machine assembled at the University of Manchester
DeveloperSteve Furber
Product familyManchester computers
TypeNeuromorphic
Release date2019
CPUARM968E-S @ 200 MHz
Memory7 TB
SuccessorSpiNNaker 2[1]
Websiteapt.cs.manchester.ac.uk/projects/SpiNNaker/

SpiNNaker (spiking neural network architecture) is a massively parallel, manycore supercomputer architecture designed by the Advanced Processor Technologies Research Group (APT) at the Department of Computer Science, University of Manchester.[2] It is composed of 57,600 processing nodes, each with 18 ARM9 processors (specifically ARM968) and 128 MB of mobile DDR SDRAM, totalling 1,036,800 cores and over 7 TB of RAM.[3] The computing platform is based on spiking neural networks, useful in simulating the human brain (see Human Brain Project).[4][5][6][7][8][9][10][11][12]

The completed design is housed in 10 19-inch racks, with each rack holding over 100,000 cores.[13] The cards holding the chips are held in 5 blade enclosures, and each core emulates 1,000 neurons.[13] In total, the goal is to simulate the behaviour of aggregates of up to a billion neurons in real time.[14] This machine requires about 100 kW from a 240 V supply and an air-conditioned environment.[15]

SpiNNaker is being used as one component of the neuromorphic computing platform for the Human Brain Project.[16][17]

On 14 October 2018 the HBP announced that the million core milestone had been achieved.[18][19]

On 24 September 2019 HBP announced that an 8 million euro grant, that will fund construction of the second generation machine, (called SpiNNcloud) has been given to TU Dresden.[20]

References

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SpiNNaker

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A is a large, typically triangular or balloon-shaped sail constructed from lightweight or similar synthetic fabric, designed for sailboats to use when running downwind or on a broad reach, where it is set forward of the on a spinnaker pole to capture wind and propel the vessel at higher speeds. The originated in the mid-19th century as a , with the first recorded use of such a occurring in 1865 on the British Niobe during the Albert Cup regatta near , , , where it was specially built to provide a speed advantage in light winds. The term "spinnaker" first appeared in print in 1866 in a publication describing a similar innovative downwind on the Sphinx, likely derived from the yacht's name or a colloquial reference to how the "spun" or ballooned out. Initially shaped more like a conventional foresail with moderate , the design evolved significantly in the with the advent of synthetic materials, allowing for greater fullness and aerodynamic efficiency. Spinnakers are categorized primarily into two types: symmetrical and asymmetrical. Symmetrical spinnakers are mirror-image sails flown from a extended from the mast, optimized for deep downwind angles (around 135–180 degrees off the wind) where they require two sheets for control and provide maximum power in lighter conditions. In contrast, asymmetrical spinnakers, also known as "asyms" or "A-sails," feature a tack line attached directly to the bow or a sprit, with a shorter luff and designated head, tack, and clew corners; they excel on broader reaching angles (90–150 degrees) without needing a pole, making them easier to handle for cruising and modern . Setting and trimming a spinnaker demands precise coordination, as its large size and sensitivity to wind shifts can lead to if not managed properly, earning it a reputation among sailors as a challenging yet exhilarating to deploy. Both types are governed by rules in competitive , such as girth ratios and sail area limits, to ensure fairness in races, and they remain essential for optimizing performance in off-the- legs of regattas and ocean passages.

Etymology and History

Etymology

The term "" entered English nautical vocabulary in , denoting a large, lightweight used for downwind on . Its remains debated among linguists and historians. One commonly cited theory links it to the yacht Sphinx, owned by Herbert Maudslay, which helped popularize the during a race in ; the sail's expansive size prompted crew members to it "Sphinx's half-acre," a playful reference to its vast area; over time, this phrase was corrupted or abbreviated in speech to "," possibly influenced by the existing term "spanker" for a large after-. An alternative derivation, tied to the first recorded use of the sail on the yacht Niobe in 1865, connects the word to a crew member's remark of "the sail to make her spin," evolving to "spin-maker" and then "spinnaker." Other theories suggest connections to "spin," evoking the rapid forward motion the sail enables, or to a colloquial nautical term like "spena ker," potentially a mishearing of "span a ker" (as in spanning an acre of ) in 19th-century British . This view posits the name arose organically from the sail's impressive, billowing form when deployed, emphasizing its role in accelerating before the wind. The first documented printed use of "" appears in the 1866 edition of the Yachting Calendar and Review, describing its deployment in competitive sailing. By the late , the term had solidified in maritime literature, appearing in design manuals and race reports as the conventional name for such ballooning sails, coinciding with innovations in 19th-century construction for enhanced speed.

Historical Development

The spinnaker's origins are subject to some debate, but the first recorded use in competitive occurred in 1865 during a match race under the Royal London Yacht Club in , , where the Niobe, owned by William Gordon, employed a large, ballooning to gain speed downwind. In 1866, the Sphinx used a similar in a race at , , initially referred to as a "spinker" by . This addressed the need for additional downwind power in handicap races, where lighter yachts often struggled against heavier competitors. The sail's early use helped these yachts outperform rivals, marking the spinnaker's role in transforming downwind performance. By the 1880s, the spinnaker had crossed the Atlantic and become integral to American racing, notably during the 1885 challenge between the defender Puritan and challenger Genesta. Crews on both deployed spinnakers to maximize speed in light winds, demonstrating the sail's value in high-stakes international competition and its rapid adoption among U.S. . This period solidified the spinnaker's use in handicap events, where it provided a tactical edge for underpowered boats without altering overall ratings. Post-World War II advancements in synthetic materials revolutionized spinnaker design, with lightweight fabrics—originally developed for parachutes—replacing heavier cotton and silk for greater durability and efficiency. Introduced widely in the late 1940s, nylon allowed for larger, more resilient sails that performed better in variable winds, enhancing downwind speeds across racing fleets. The 1958 between Columbia and Sceptre highlighted this evolution, as both 12-meter yachts relied on optimized nylon spinnakers for key maneuvers, contributing to tactical innovations in the event. The saw the rise of asymmetric spinnakers, designed for easier handling and broader wind angles without a traditional pole, first popularized in high-performance to simplify crew operations downwind. By the , these sails integrated into Olympic classes like the Tornado catamaran, boosting speeds and media appeal in events such as the 1996 Atlanta Games, while influencing where large spinnakers became essential for planing performance.

Design and Types

Symmetric Spinnakers

Symmetric spinnakers exhibit a distinctive parachute-like with a full, rounded belly that provides a balanced, symmetrical form across the sail's centerline. This design features equal clews at the lower corners, with the head hoisted to the masthead and one clew attached to the forward end of a spinnaker pole projecting from the mast, stabilized by sheets and guys attached to the clews. The pole is positioned dynamically to keep the sail filled and optimized for the apparent . Sizing conventions for symmetric spinnakers account for varying wind conditions, with dedicated versions for light, medium, and heavy air to match performance needs. Light air sails, such as the S1 designation, are suited for winds of 0-7 knots at apparent wind angles (AWA) of 60-120 degrees, while medium air options like the S2 handle 6-18 knots at 115-170 degrees AWA, and heavy air variants such as the S4 perform in 14-30 knots at 120-170 degrees AWA. These sails ensure appropriate power without overwhelming the boat's rig. In traditional applications, symmetric spinnakers excel in downwind and cruising scenarios, particularly on broad reaching courses where the guy foresees the pole's windward position and the sheet controls the leeward clew for precise adjustment. This setup maximizes the sail's spherical profile and broad-shouldered girth, capturing more than tacked alternatives. Their inherent stability benefits larger boats by reducing collapse risk in gusts, contributing to their historical dominance in offshore before the rise of easier-to-handle designs.

Asymmetric Spinnakers

Asymmetric spinnakers feature a non-symmetrical shape with a defined luff and , distinguishing them from traditional designs by allowing attachment via a tack line to the bow or a retractable sprit, secured by a single sheet led aft from the clew to the stern quarters. This configuration eliminates the need for a spinnaker pole, enabling simpler gybing maneuvers where the sheet is eased and the new sheet trimmed without repositioning hardware. Evolving from symmetric , this tacked setup provides greater stability in reaching conditions by projecting the forward of the . The foretriangle area, used for area comparisons, is calculated as (I × J)/2, where I is the height from deck to masthead attachment and J is the distance from mast to bow along deck. Development of asymmetric spinnakers accelerated in the early , initially as a means to optimize performance under the International Offshore Rule (IOR), which influenced yacht design toward lighter, more agile hulls and rigs. Early examples emerged in high-performance classes like the Australian 18-foot skiffs, where retractable bowsprits facilitated their use for downwind speed. By the 1990s, advancements in and furling systems made them viable for cruising, with sailmakers like Neil Pryde producing initial versions tailored for IOR-era boats. In modern racing under the International Measurement System (IMS) and Offshore Racing Congress () rules, asymmetric spinnakers have become standard, with provisions for their and rating based on girth and luff dimensions to ensure fair . Sizing is typically smaller than that of symmetric spinnakers, often 75-85% of their area, with maximums up to about 1.5-1.8 times the foretriangle area under rating rules (e.g., 160-180% of the J for the foot ), allowing for enhanced power in light airs. They are optimized for apparent wind speeds of 0-12 knots and angles from 50° to 130° off the wind, providing lift where genoas lose efficiency. Key advantages include streamlined handling for crews, as the pole-free design reduces setup time and the number of lines to manage, often requiring just two to three people for hoists and douses. Additionally, the forward tack minimizes chafe against bow pulpits or lifelines common on production cruisers, preserving integrity during prolonged use.

Specialized Variants

The Parasailor is a specialized symmetric spinnaker variant featuring a horizontal wing that spans the 's widest point, combined with a full-length along the luff, designed to enhance self-stabilization and minimize collapse in light winds, particularly for cruising crews. This wing creates a parafoil-like effect, allowing the to maintain shape without a pole in winds as low as 4 knots, while the facilitates easier deployment and gybing from the . Cruising asymmetric spinnakers often incorporate torsion lines integrated into the luff for reinforced and simplified handling in non-racing scenarios, enabling top-down furling without specialized hardware. These variants use heavier fabrics and anti-twist ropes to withstand repeated use in variable offshore conditions, prioritizing longevity over racing performance. The Code Zero represents a flat asymmetric spinnaker subtype with a straight luff and minimal camber, optimized for close-reaching in winds of 8 to 18 knots, and typically deployed on continuous-line furling systems for quick adjustment. Its design, with a mid-girth limited to 60-75% of the foot length under rating rules, bridges and functions while allowing roller from the . Other specialized variants include wing-on-wing setups, where an asymmetric spinnaker is poled out opposite the for deep downwind angles, and hybrids that blend genoa-like luff tension with spinnaker fullness for versatile light-air use. Under Offshore Racing Congress () rules, these sails must maintain a half-width of at least 75% of the foot length to qualify as spinnakers, while (PHRF) limits girth and foot to 1.8 times the J measurement to avoid penalties.

Materials and Construction

Fabrics and Materials

Traditional spinnakers have primarily utilized nylon fabrics, typically ranging from 0.75 to 1.5 ounces per (oz/yd²), valued for their elasticity, which allows the to inflate fully under pressure, and inherent UV resistance that prolongs usability in prolonged exposure. This material, derived from post-World War II advancements in synthetic textiles originally developed for parachutes, became standard for spinnaker construction in the , enabling lighter and more durable downwind sails compared to earlier or alternatives. Key properties include moderate air permeability to allow the to fill with while reducing heeling, and high tear resistance provided by the weave to withstand rigging contact and gusts. Additionally, coatings such as or enhance water repellency, minimizing weight gain in wet conditions while maintaining . In modern applications, particularly racing, fabrics have emerged as low-stretch alternatives to , offering superior shape retention and reduced elongation under load for asymmetric spinnakers in high-performance scenarios. For grand prix events, specialized Superkote fabrics provide enhanced stability and zero through coatings, allowing lighter sails to handle stronger winds without compromising power. Eco-friendly options, including recycled or derived from upcycled sails, are increasingly adopted for cruising spinnakers, promoting without sacrificing core performance attributes like and . As of 2025, recycled from post-consumer sails is gaining traction in sustainable production. Fabric selection involves inherent trade-offs: ultralightweight options (e.g., 0.75 oz/yd² ) maximize speed in light airs but may wear faster, whereas heavier variants (1.5 oz/yd² or coated) prioritize longevity in demanding trade wind conditions, balancing velocity against endurance.

Construction Methods

Spinnaker primarily employs radial or cross-cut panel layouts to optimize control and stress distribution while maintaining the sail's profile. Radial layouts, the most common for modern spinnakers, consist of triangular panels or gores radiating from the head, clew, and tack corners, allowing precise alignment of fabric threads with load paths for enhanced and aerodynamic shaping. These designs typically use multiple panels—often dozens in number—to enable three-dimensional contouring and minimize stretch under wind loads. In contrast, cross-cut layouts feature horizontal panels stacked perpendicular to the , offering a simpler, more cost-effective build suitable for smaller or less demanding sails, though they provide less refined load distribution compared to radial methods. Seams in spinnaker construction are engineered to add minimal weight while ensuring seam strength, typically comprising less than a small fraction of the total . Panels are joined using stitching with UV-resistant thread, which creates flexible, durable bonds that resist without excessive bulk. is occasionally applied for specific lightweight applications, fusing panels through high-frequency vibrations to produce flat, seamless joins that reduce disruption. Triple-step patterns are favored for high-stress areas, enhancing tear resistance in the delicate fabrics commonly used. Reinforcements focus on high-load points to protect the sail's integrity during deployment and handling. Corner patches, often radial in design, are sewn or adhered at the head, clew, and tack to distribute forces evenly and prevent tearing. lines reinforce the trailing edge against flutter and abrasion, while asymmetric spinnakers incorporate anti-torsion cables integrated into the luff for stable furling and torsion resistance. Boltropes or continuous tapes along the head facilitate secure hoisting via the , ensuring smooth attachment without adding significant weight. Spinnakers are produced either as stock models for standard boat sizes or custom builds tailored to specific vessels. Custom construction leverages (CAD) software to model precise sail profiles, including camber depths typically ranging from moderate to deep for optimal downwind performance. This digital approach allows sailmakers to simulate load paths and refine panel shapes before cutting, resulting in sails that maintain form under varying conditions. Stock spinnakers, by comparison, follow predefined templates for quicker production and broader availability.

Aerodynamics and Performance

Aerodynamic Principles

Spinnakers generate propulsion primarily downwind by functioning as a parachute-like structure that traps wind, creating forward thrust through form drag rather than the profile lift dominant in upwind sails like mainsails. Their low aspect ratio enhances this drag-based mechanism by maximizing the projected area exposed to the apparent wind while minimizing induced drag inefficiencies associated with higher-aspect-ratio wings. This design contrasts sharply with upwind sails, which depend on attached airflow over cambered surfaces to produce lift via pressure differences, whereas spinnakers tolerate and exploit substantial flow separation to inflate and maintain their bulbous shape. The curved, highly cambered profile of a spinnaker induces pressure differentials across its surfaces, accelerating airflow over the leeward side and reducing pressure there in accordance with , which contributes to both lift and overall generation. These effects are most effective at apparent wind angles between 90 and 150 degrees, where the sail's inflation allows optimal wind capture without excessive collapse or fluttering. Within this regime, careful control of twist and camber ensures partial attachment of the , particularly along the lower sections of the sail, to mitigate risks during gusts and maintain consistent . For symmetric spinnakers, the aerodynamic forces reflect their reliance on a combination of lift and drag components under separated flow conditions. Asymmetric variants exhibit similar principles but with slight variations in optimal trim due to their tacked configuration.

Performance Characteristics

Spinnakers deliver substantial enhancements to downwind performance, particularly in (VMC), with asymmetric variants optimizing reaching angles in winds of 5-15 knots where their operational range typically spans apparent wind angles () of 115-160 degrees. In these conditions, polar diagrams from sail design analyses indicate peak efficiency around 120 degrees , allowing boats to maintain higher speeds compared to alternatives like poled genoas. Symmetric spinnakers, by contrast, excel in deeper running angles beyond 140 degrees , providing superior VMC in moderate to strong winds above 14 knots by enabling courses 10 degrees off square, which translates to gains of 30-60 seconds over asymmetric setups at the bottom mark. Stability characteristics differ markedly between spinnaker types and sea states. Symmetric spinnakers promote greater overall boat stability when trimmed for dead downwind running, reducing through balanced distribution and proving advantageous in choppy or wavy conditions where maintaining course is challenging. Asymmetric spinnakers, while offering faster planing in flat due to their reaching bias, carry a higher of collapse or forestay wrapping in gusty or sustained winds exceeding 20 knots, necessitating precise trimming to mitigate . These factors underscore the importance of matching spinnaker type to expected conditions for optimal control and safety. Efficiency metrics for spinnakers emphasize their role in maximizing thrust over drag minimization, operating at comparatively low lift-to-drag ratios that prioritize power generation in separated airflow downwind. Velocity prediction programs (VPP), such as those employed by the Offshore Racing Congress (ORC), quantify these benefits through simulated polars, with crossover points to spinnaker use evident around 90-120 degrees true wind angle where efficiency gains become pronounced.

Usage and Handling

Setting the Spinnaker

Setting the spinnaker requires careful preparation and coordinated crew action to ensure a smooth deployment, minimizing risks such as twists or uncontrolled inflation. Prerequisites include rigging the necessary lines—sheets and guys for both types, plus the pole for symmetric spinnakers—and attaching the , with the often pre-fed into a or bag for controlled hoisting. For symmetric spinnakers, preparation involves positioning the bag on the leeward side and securing it to the guardwires, while rigging the pole to the mast at shoulder height with jaws facing upwards and attaching the uphaul and downhaul. The guy is threaded through the pole end and clipped to the windward clew, with the leeward sheet attached to the other clew; all lines must be checked for free runs and coiled neatly. The is attached to the head, and the is flaked with and luff separated to avoid tangles. The hoisting sequence for a symmetric spinnaker begins on a broad reach from the leeward side: with sheets eased, the halyard is hoisted swiftly to prevent partial inflation, the pole is raised to square the sail, and then the sheets are trimmed as the sail fills. For smaller sails up to 50 m², a team of three (helmsman plus two) rigs the pole, hoists the halyard, and hauls in the sheet or guy, calling "top" when fully raised. Larger sails require more crew to guide the sail and adjust lines during the hoist. Asymmetric spinnakers differ primarily in lacking a pole, with the tack attached to a bow line led through a block outside the pulpit. Preparation mirrors the symmetric process but positions the bag leeward, attaches the sheet to the clew with a bowline or shackle, and ensures the halyard and tack line are ready. The hoisting sequence involves bearing away to about 160° off the wind, easing the mainsail for shadow, attaching the halyard, and hoisting quickly with the sheet slack before luffing slightly to fill the sail with apparent wind; if using a sock, it is pulled up post-hoist to deploy. Crew roles scale with team size from 2 to 6 persons: in a minimal 2-person setup, one handles foredeck and hoisting while the other manages the cockpit lines and helm; larger teams divide tasks with dedicated roles for pole adjustment, pull, and sheet control to achieve a coordinated lift. In racing, the hoist should be completed swiftly, ideally under 1 minute, to maintain speed. Beginners should limit attempts to winds under 12 knots true wind speed to reduce handling difficulties. Common errors include over-sheeting before full hoist, which causes twists or halts deployment, and failing to check line leads, potentially leading to jams. Safety checks are essential: verify all attachments are secure, lines run freely without stopper knots, and the pole is properly tensioned to prevent injuries.

Trimming and Control

Trimming a spinnaker involves fine adjustments to its shape, angle, and tension to maintain optimal airflow, maximize boat speed, and prevent collapses or instability while downwind. For symmetric spinnakers, the spinnaker pole's position and sheet tension are primary controls, with the pole typically set to the apparent in reaching conditions and slightly aft for running to avoid the mainsail's shadow. The pole height is adjusted via the and downhaul so the tack is slightly lower than the clew on reaches, promoting even luff tension, while on runs it is set parallel to the for . Fore-aft positioning of the pole is often fine-tuned relative to the mast in moderate conditions to balance the sail's projection without excessive twist. Sheet tension on symmetric spinnakers is adjusted to induce a slight twist at the , ensuring the upper sections fill without stalling, typically by trimming until a small, consistent curl forms at the luff—about 6 inches in light to moderate winds. Gybing is commonly performed end-for-end for smaller boats, where the bears away, releases the working guy, detaches the pole from the mast and , swings it across the foredeck suspended by the uphaul, reattaches it to the new guy, and trims the new sheet as the boat turns through the wind. This technique minimizes collapse and allows quick transitions, with the pole jaws kept upward throughout. Asymmetric spinnakers, flown from a or tack line without a pole, rely on sheet leads and downhaul adjustments for control, with the sheet angled at 45-60 degrees to the centerline on reaches—closer to 50 degrees apparent in winds under 10 knots—to optimize lift and reduce drag. A barber hauler or twing line is used to tension the luff and prevent the clew from rising or the from dumping on broader angles, pulling the sheet lead forward while easing the downhaul to let the tack float 4-6 feet off the deck for running. Over-trimming in puffs is avoided by monitoring the luff for excessive curl, instead bearing off slightly to keep the sail full. In gusts, both symmetric and asymmetric spinnakers are depowered by easing the sheets to spill excess , combined with down to maintain stability and monitoring the boat's heel to prevent excessive weather helm or broaching. For symmetric kites, the pole is eased forward in lulls and aft in puffs to adjust projected area, while asymmetric sails benefit from lowering the tack in stronger winds. is kept moderate—ideally 5-10 degrees to windward on runs—to enhance righting moment without stalling the . Key tools for precise control include telltales attached along the luff to visualize airflow, indicating optimal trim when both windward and leeward sets stream evenly with a minor curl on the windward side. Winches are employed for fine sheet adjustments, with slow, incremental cranks to avoid shocking the sail into collapse, and pre-marked sheets help replicate ideal positions across wind shifts. Masthead wind indicators further aid in aligning the pole or sheet to the apparent wind direction.

Systems and Equipment

Launching Systems

Launching systems for spinnakers enable controlled and efficient deployment, minimizing chaos during hoists and allowing sailors to manage large sails safely, particularly in cruising or scenarios. These systems range from simple fabric enclosures to advanced mechanical furlers, each designed to contain the until can fill it progressively. Common options include systems, launch chutes, and top-down furlers, with setups emphasizing secure attachments and preventive maintenance to ensure reliability. Sock systems, also known as or , provide a straightforward method for controlled deployment. The is packed into a fabric tube that encases the from head to foot, featuring a rigid hoop at the bottom for stability and a separate channel for the to avoid tangling. During launch, the sock is hoisted via the to the masthead, keeping the contained and preventing premature inflation. Once at height, pulling the uphaul line opens the bottom of the sock, allowing wind to progressively fill the from the head down, enabling a smooth and tangle-free deployment suitable for single-handed or crews. Launch chutes, prevalent in setups, consist of rigid or semi-rigid tubes mounted forward near the bow or amidships to facilitate rapid hoists and retrievals. The is packed into the chute with sheets and guys led aft to winches, and a retrieval line threaded through the system for pulling the back in after use. For deployment, the crew haists the directly from the chute using the , with the tube guiding it clear of the to inflate quickly in the apparent . This setup allows for sub-minute launches in regattas, enhancing tactical speed around marks. Top-down furlers are specialized for asymmetric spinnakers, offering automated and cockpit-controlled launching. The system employs an anti-torsion cable (such as Dyneema) wrapped by a continuous furling line from the head swivel down the luff, with the tack attached to a ring above the for even torque distribution. To launch, the furled is hoisted to the masthead and secured, then deployed by easing the furling line while maintaining sheet tension at angles of 120–160 degrees apparent wind, unfurling from the top in approximately 30 seconds without leaving the . This method suits larger yachts, reducing physical effort and enabling quick adjustments in variable conditions. Effective setup of launching systems requires precise attachments, locks, and routine to prevent operational failures. Bridles, typically Dyneema lines with stainless rings, connect the sheets or guys to poles or bowsprits, distributing loads evenly and allowing adjustable positioning during deployment. locks, lightweight mechanisms at the masthead, secure the without clutches, reducing weight aloft and compression on the rig for faster, more reliable hoists. involves flaking rather than coiling to avoid knots, inspecting lines for chafe, and lubricating annually to prevent tangles during critical launches.

Dousing Systems

Dousing systems for spinnakers are essential for safely and efficiently lowering the sail to prevent accidents, reduce drag, and prepare for maneuvers or storage. These methods vary by sail type, crew size, and conditions, with symmetric spinnakers often requiring coordinated crew actions to gather the sail to leeward while easing sheets and hauling down the halyard. Manual dousing of symmetric spinnakers typically involves gathering the sail to leeward by easing the pole forward to the forestay and over-trimming the sheet to tighten the foot, making it accessible for the foredeck crew. The halyard is then released in stages: the initial third is eased quickly to collapse the luff and deflate the sail, followed by full release as crew members pull the leeches aboard, stuffing the sail into a forward hatch to avoid tangles with the jib sheets. This technique, known as the stretch-and-blow douse, allows the boat to maintain speed nearly to the leeward mark while keeping the clews out of the water to prevent scooping and instability. Snuffer bags provide a controlled top-down collapse for cruising spinnakers, using a downhaul line to retract a protective sleeve over the sail, minimizing air spill and water drag during retrieval. To douse, the boat bears off to a broad reach, the sheet is eased to collapse the sail partially, the downhaul is pulled to draw the snuffer down from the head, the guy is released, and the halyard is lowered, containing the sail within the bag for easy stowing. This method is particularly valued for shorthanded operations, as it reduces the need for multiple crew to handle the large sail manually. Sock takedowns, similar to snuffers but using a tubular sleeve, involve releasing the downhaul to the by collapsing it from the top, followed by lowering the while the sheet is eased just enough to allow the sock to descend without refilling. In , this facilitates quick transitions such as gybe douses, where the is retrieved during a gybe to maintain momentum, often by blanketing the behind the before pulling the downhaul. The sock then contains the deflated for rapid lowering and repacking. Safety in dousing emphasizes clear crew communication, such as verbal cues for halyard release and sheet easing, to synchronize actions and prevent overloads or falls. Avoiding wraps requires checking lines for knots and ensuring free runs before starting, while in heavy air, wet dousing techniques—where the sail is allowed to touch the water briefly after foot tightening—depower it rapidly but demand quick gathering to avoid dragging or capsizing risks. Crew should never stand in bights of lines and must secure the afterguy until the sail is fully stowed.

Racing and Regulations

Role in Yacht Racing

In competitive yacht racing, spinnakers play a pivotal strategic during downwind legs of fleet races, enabling boats to maximize speed and positional advantages over rivals. Symmetric spinnakers are favored in endurance offshore events such as the , where their design allows sailing at deeper true wind angles close to dead downwind, optimizing performance over long distances in variable conditions. In contrast, asymmetric spinnakers dominate inshore fleet racing classes like the , permitting boats to sail higher and faster on broad reaches, which suits shorter courses with frequent maneuvers around marks. Key tactics involving spinnakers revolve around disrupting opponents and precise execution. Blanketing occurs when a leading boat positions itself to shadow the wind of a trailing competitor, collapsing their spinnaker and slowing their progress, particularly effective in tight fleet situations. Optimal gybe angles for spinnakers typically involve turning through 20-30 degrees from a broad reach to maintain momentum, avoiding excessive heel or , while set timing at leeward marks demands coordinated crew work to hoist the sail immediately after rounding for an immediate speed burst. In Olympic and match racing, spinnaker usage varies by class to balance speed and handling. The 49er skiff employs an asymmetric spinnaker for explosive downwind acceleration, with crews trapezing to manage its 38 square meter area, often emblazoned with national flags for visual impact. Conversely, classes like the Star keelboat ban spinnakers entirely to emphasize simplicity and upwind tactics in one-design competition. The has seen spinnaker evolution from integral tools to obsolescence in modern formats. During the era (22nd to 26th editions, 1958-1987), symmetric spinnakers were crucial for reaching and running legs, providing decisive speed edges in match racing. In the shift to foiling craft, with the 35th Cup (2017) using foiling catamarans and the 36th Cup () using foiling monohulls, spinnakers were eliminated; high foiling speeds downwind render them unnecessary, with stacked asymmetric variants occasionally tested for burst maneuvers in transitional designs but not adopted in final protocols.

Rating and Measurement Rules

In the Offshore Racing Congress () and International Measurement System (IMS), spinnaker measurements are governed by specific dimensional rules to ensure fair based on predicted performance via the Velocity Prediction Program (VPP). For symmetric spinnakers, the mid-girth (SMG) must be at least 75% of the foot length (SF), with the maximum width (SMW) limited to 1.8 times the spinnaker pole length (SPL) or J (foretriangle base), whichever is greater. Asymmetric spinnakers follow similar girth requirements, with SMG ≥ 0.75 × SF, but their luff (SLU) is typically 5% longer than the leech (SLE), and the effective luff is calculated as 0.6 × SLU + 0.4 × SLE to account for shape differences. Sails with mid-girth to foot ratios between 0.75 and 0.85 are classified as spinnakers, while those below 0.75 may be rated as headsails or code sails, influencing aerodynamic coefficients in the VPP. Spinnaker area is calculated using formulas such as 0.72 × (0.5 × SL × SF + 0.66 × SL × (SMG - 0.5 × SF)) for asymmetric types, with maximum dimensions often capped relative to rig measurements like ISP (spinnaker height) and J to prevent excessive size; typical limits allow areas up to approximately 175% of the foretriangle base (I × J / 2) in standard configurations, though exact caps vary by certificate. These measurements, taken by certified measurers, feed into ORC certificates for handicap calculations. Under (PHRF) systems, handicaps adjust for spinnaker type to reflect handling differences, with ratings expressed in seconds per mile (sec/mi). Symmetric spinnakers typically incur a penalty of 3-6 sec/mi relative to non-spinnaker configurations in many fleets, while asymmetric spinnakers receive 0-3 sec/mi, depending on setup. For example, boats rated with symmetric spinnakers may sail with an asymmetric without additional penalty if the area does not exceed the symmetric's rated size, but oversized asymmetric girths (beyond 180% of J) trigger progressive penalties of 3 sec/mi per 10% excess. These adjustments are fleet-specific and based on observed performance data to maintain competitive equity. In one-design classes, spinnaker rules emphasize uniformity to control costs and performance parity, often specifying exact dimensions and material restrictions. For the Melges 24, the maximum spinnaker luff length is 11.585 m, with leech limited to 10.000-11.078 m and foot to 6.300 m maximum. Super-light fabrics (below 0.75 oz ) are prohibited to prevent unfair speed gains and excessive wear, with measurements verified at events via girth stations at mid and three-quarter points along the luff. Similar limits apply in classes like the J/24, where spinnaker area is approximately 42 m² based on dimensional rules. These rules prioritize measurable compliance over VPP modeling, with violations leading to disqualification. Post-2000 rule evolutions in /IMS and PHRF have increasingly favored asymmetric spinnakers to accommodate racing trends and reduce physical crew demands. Effective January 1, 2001, IMS updated measurements to use SMG for asymmetric area calculations, replacing prior symmetric-focused metrics and enabling dedicated handicaps for tacked-on-centerline sails. This shift, driven by growing adoption in offshore events, lowered penalties for asymmetric setups in PHRF (e.g., credits up to 6 sec/mi for bowsprits) compared to symmetric poles, reflecting empirical data on faster handling in shorthanded crews. By 2010, VPP refinements further integrated asymmetric coefficients for wind angles 60-150 degrees, promoting their use without disproportionate rating inflation. As of 2025, VPP includes updated asymmetric spinnaker force coefficients for wind angles 60-150 degrees, reflecting trends.

Other Applications

Non-Sailing Uses

Spinnaker-derived designs, leveraging lightweight fabric, have been adapted for traction in wind sports like kite and parakiting since the , where chute-like kites provide propulsion across water or land. These traction kites are frequently constructed from spinnaker cloth for its high strength-to-weight ratio and ability to capture wind efficiently without excessive weight. The durable construction of spinnakers also lends itself to decorative and commercial applications outside . Retired spinnaker sails are commonly repurposed into reusable products such as handbags, canopies, and spinners to minimize waste, with initiatives in regions like transforming end-of-life sails into sustainable accessories. For instance, hot air balloon-themed wind spinners are fabricated from spinnaker for its fade-resistant and weatherproof qualities, serving as ornamental features. In emergency contexts, spinnaker fabric's parachute-like properties have historical parallels in aviation, where , the primary material in spinnaker fabric, substituted for parachutes during shortages.

Modern Innovations

In the 2010s and 2020s, spinnaker design has incorporated smart fabrics featuring embedded s to provide real-time data on sail performance and trim. These innovations allow sailors to monitor load distribution, environmental exposure, and shape retention directly via mobile apps, optimizing adjustments during races. For instance, ' SmartLuff system integrates a Bluetooth-enabled wireless load into composite sails, including spinnakers, enabling instant feedback on luff tension to prevent overload and enhance . Similarly, Spinlock's Sail-Sense , sewn into the sail fabric near stress points, tracks UV exposure, hours of use, , flogging, and tacks to predict wear and inform maintenance schedules, extending sail life in high-performance applications. Automated systems have streamlined spinnaker deployment and retrieval in modern racing yachts, particularly in classes like the TP52, where electric winches and hydraulic controls minimize crew involvement. These setups use powered winches to hoist and drop large asymmetric s rapidly, often via string-drop mechanisms that store sails in seconds, reducing physical demands on the 11-person crew during sets and gybes. Harken's hydraulic pedestal systems, standard across the TP52 fleet, integrate with electric actuators for precise control, allowing smoother transitions in competitive environments like the 52 Super Series. While full AI optimization remains emerging, these automated furlers and winches represent a shift toward semi-autonomous handling, enabling smaller effective crews for downwind maneuvers. Sustainability drives recent material advancements, with bio-based nylons and 3D-printed components reducing environmental impact without compromising performance. North Sails' SOLOTEX fabric, comprising 37% bio-based polymers derived from plant sources, offers a lighter, more eco-friendly alternative to traditional synthetics for spinnaker construction, lowering carbon emissions during production. OneSails has pioneered fully recyclable composite sails using bio-derived resins, adopted in events like the 2023 Rolex Middle Sea Race under the Clean Regattas program, which certifies eco-friendly practices and has grown to over 150 events by 2025. For reinforcements, 3D-printed nylon or carbon-filled parts, such as batten receptacles and corner patches, provide targeted strength with minimal added weight; these custom-printed elements have been integrated into square-top mainsails and spinnaker heads for superyachts and racers, enhancing durability in the 2020s. Foiling integrations have led to ultra-light asymmetric spinnakers tailored for high-speed yachts in the , emphasizing low weight to maximize lift from hydrofoils. These sails, often constructed from advanced laminates like ' 3Di, achieve areas up to 400 m² to generate in light winds while minimizing drag during foiling runs exceeding 30 knots. In the 2024 , IMOCA boats featured these optimized asymmetrical spinnakers fixed to bowsprits, contributing to record-breaking downwind speeds as foils reduce hull contact with water.

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