Encyclopedia

The mainsail is the primary sail on most sailboats, typically mounted behind the mast. It plays a central role in powering the boat by catching and controlling the wind. The mainsail is usually triangular, with three key edges: the luff (attached to the mast), the foot (along the boom), and the leech (the trailing edge). The sail’s design and dimensions are critical for performance, and its area is traditionally calculated by multiplying the luff and foot lengths and dividing by two, treating it as a basic triangle.

However, most mainsails include an additional feature known as roach—a curved extension beyond the straight triangle at the leech, which adds extra sail area and improves performance, particularly in light winds or upwind sailing. This roach allows for better airflow and increased lift, making the mainsail more effective.

Mainsails can be further customized with reefing points, which allow the sail to be reduced in size during strong winds, and full-length battens, which help maintain the sail’s shape and reduce wear from flogging. The battens also contribute to better sail performance by keeping the sail smooth and stable, even in variable conditions.

In short, the mainsail is the engine of a sailboat, responsible for driving the boat forward and providing control, balance, and power across a range of wind conditions. A well-designed mainsail offers both efficiency and durability, ensuring smooth sailing in any condition.

A headsail refers to any sail set forward of the mast on a sailboat. The most common types of headsails are jibs and genoas, and they play a crucial role in generating forward propulsion along with the mainsail. The size and design of a headsail are often determined by the boat’s dimensions and sailing conditions.

Some headsails, like genoas, are classified by a percentage figure—for example, 150% No. 1 Genoa. This percentage indicates the LP (Luff Perpendicular), which is the shortest distance from the clew (the bottom rear corner of the sail) to the luff (the leading edge attached to the forestay). The percentage is calculated relative to the boat’s J dimension, which is the distance from the base of the mast to the point where the forestay attaches to the deck. For example, if a boat has a J dimension of 10 feet, a 150% genoa would have an LP of 15 feet.

Different headsails are designed for different weather conditions. For example:

A working jib or storm jib is designed for high-wind or stormy conditions and typically has a much smaller surface area for control in rough seas.

A No. 1 Genoa is typically the largest headsail on the boat, used in lighter winds.

A No. 2 Genoa is slightly smaller, used in moderate wind conditions.

A No. 3 Genoa, often around 100% LP, is a versatile sail suitable for heavier winds.

A spinnaker is a large, balloon-like sail used on sailboats, specifically designed for sailing downwind or at broad reaching angles. It is typically made of lightweight material and is larger and more curved than other sails, making it highly effective in catching wind from behind and propelling the boat forward.

There are two main types of spinnakers:

1. Symmetrical Spinnaker: This spinnaker is identical on both sides and is flown using a spinnaker pole attached to the mast. It is ideal for sailing directly downwind.
2. Asymmetrical Spinnaker (or Gennaker): This version has an uneven shape and does not require a spinnaker pole. It is easier to handle and performs better on a broad reach (wind coming from the side to behind) rather than directly downwind.

The spinnaker is often used in racing or when maximizing speed is the goal, as it creates a large sail area and can dramatically increase a boat’s speed in light to moderate wind conditions. It’s typically deployed when the wind is coming from behind the boat, helping to “catch” the wind and fill the sail, pulling the boat forward.

In terms of design, the SLU (Spinnaker Luff Length), SLE (Spinnaker Leech Length), and JSP (Spinnaker Pole Length) are often considered when customizing or purchasing a spinnaker for specific boat types.

A staysail is a smaller sail that is set between the mast and the forestay or another stay on a sailboat. It is often used in combination with the mainsail and sometimes a jib or genoa, depending on the boat’s rigging. Staysails are typically triangular and are secured along a stay, which is a cable or rope that supports the mast.

There are different types of staysails, depending on the boat’s configuration:

1. Inner Staysail: Used on cutter-rigged boats or ketches, this staysail is typically set between the mast and the inner forestay. It is smaller than the headsail and is often used in heavier winds, where it provides additional control and stability without overwhelming the boat.
2. Jib Staysail: This type is often found on sloops or cutter rigs and can be used with a jib or genoa. It adds more sail area and increases power, especially in moderate conditions.
3. Heavy Weather Staysail: This is a small, sturdy sail designed for stormy or heavy weather conditions. It is typically used with a reefed mainsail when high winds require a smaller sail area for better control.

A staysail is highly versatile and can be adjusted to provide extra power in light winds or better control in heavy winds, depending on the configuration. It adds flexibility to a boat’s sail plan, particularly for cruising or offshore sailing.

A drifter is a light-wind sail used on sailboats, designed specifically for sailing in light air (typically under 10 knots). It is similar to a spinnaker or genoa but is typically made of lighter fabric and cut to perform well at broader wind angles. Drifters are most effective when sailing downwind or on a reach and are often used when the wind is too light for a genoa or jib to provide sufficient power.

Drifters differ from spinnakers in that they are typically easier to handle, and they don’t require a spinnaker pole for setup. They can be tacked similarly to a genoa, making them more manageable for short-handed crews or cruising sailors. Drifters also have a fuller shape compared to regular jibs, allowing them to catch more wind in light air conditions.

Key characteristics of a drifter:

• Lightweight material: Often made from lighter fabric, such as nylon, to be efficient in light winds.
• Full shape: The sail is cut fuller to maximize wind capture, providing power even when the wind is weak.
• Downwind performance: Like a spinnaker, the drifter excels when the wind is coming from behind or at a broad reach.

A drifter is particularly useful for sailors who want to maintain speed and maneuverability when the wind is light, providing a smooth and steady way to harness even the gentlest breezes.

A storm sail is a small, heavily reinforced sail designed specifically for use in severe weather conditions, such as high winds and rough seas. It helps maintain control of the boat by reducing the amount of sail area exposed to the wind, which minimizes the risk of overpowering the boat and provides better handling during a storm.

There are two main types of storm sails:

1. Storm Jib: A small, triangular headsail that is attached to the forestay, replacing a larger headsail like a genoa or jib in heavy weather. The storm jib is typically made from durable, thick sailcloth (such as Dacron) and has reinforced corners to withstand extreme conditions. It helps the boat stay balanced and manageable during strong winds by reducing the amount of sail area forward of the mast.
2. Storm Trysail: A small, strong mainsail replacement, the storm trysail is used in place of the mainsail during severe conditions. It is hoisted on its own track on the mast and is significantly smaller than a regular mainsail. Unlike reefing a mainsail (which reduces its area), the storm trysail is specifically built for high-wind conditions and provides extra control and durability.

Key features of storm sails:

Ease of handling: Designed to be quickly hoisted and lowered, ensuring rapid sail changes during rapidly changing weather conditions.

Smaller size: Designed to minimize the sail area exposed to the wind, allowing better control in strong winds.

Reinforced fabric: Made from heavy-duty materials with reinforced seams and corners to withstand high wind loads.

Mainsail trimming is essential for optimizing performance in various wind conditions and adjusting the sail’s shape to balance power and control. While the process may seem technical, it revolves around managing the tension on key sail components and adjusting the boom position. The three primary areas of focus when trimming the mainsail are:

1. Tension on the sail edges (luff, foot, and leech)
2. Mast bend (to adjust sail shape)
3. Boom angle (to control the sail’s relationship to the wind)

Key Concepts:

• Draft: This refers to the depth or curvature of the sail. The draft location (where the curve is deepest) can be moved forward or aft by adjusting tension on the luff or foot.
• Luff Tension: Adjusting the halyard, Cunningham, or downhaul alters the tension in the sail’s leading edge (luff). Increasing luff tension pulls the draft forward, while easing it moves the draft back.
• Foot Tension: Controlled by the outhaul, tightening it flattens the lower part of the sail, while easing it increases the sail’s curvature. This is especially useful for tuning the sail to light or heavy wind conditions.
• Leech Tension: The tension on the trailing edge of the sail (leech) is primarily managed by the mainsheet, traveler, and vang. A tighter leech provides a straighter, more efficient shape for upwind sailing, while easing it allows more twist, which helps in lighter winds or downwind conditions.

Key Adjustments:

Mast Bend: By adjusting the backstay, you can bend the mast, which flattens the sail by reducing draft. A straighter mast increases the sail’s curvature, which can be useful in light winds or rough seas.

Luff Tension: To pull the draft forward, increase the tension on the halyard or Cunningham. Easing them will shift the draft aft.

Foot Tension: Tighten the outhaul to flatten the sail and reduce the draft. Loosen it when a fuller sail is required, especially in lighter winds or when sailing downwind.

Leech Tension: Control the leech with the mainsheet upwind and the boom vang downwind. Tightening the mainsheet flattens the leech, while loosening it opens the sail, allowing more twist.

Headsail trimming focuses on adjusting the sail’s shape to optimize its performance based on wind conditions. Several factors, such as luff tension, lead position, sheet tension, and headstay tension, determine the headsail’s efficiency.

Luff Tension:

This affects the sail’s leading edge and is controlled by the halyard or Cunningham. By tightening the luff, you shift the sail’s draft (the deepest curve) forward, while easing it pushes the draft aft. In strong winds, increased tension flattens the sail, while lighter winds benefit from less tension and a fuller sail for better power.

Lead Position:

Adjusting the jib lead block fore and aft helps distribute tension between the leech and foot. Moving the lead forward tightens the leech and loosens the foot, creating a fuller, rounder sail shape—ideal for light wind conditions. Moving it aft flattens the sail, reduces heeling, and is more effective in heavier winds. A balanced lead position creates equal tension between the leech and foot.

Sheet Tension:

Tightening the jib sheet flattens the sail by pulling the draft out, while easing it introduces more draft and allows the sail to twist. Tight sheets are generally useful upwind for minimizing drag, while easing the sheet allows more twist and power when sailing off the wind.

Headstay Tension:

The headstay’s tension determines the sail’s overall shape. A loose headstay causes sag, increasing the sail’s curvature (draft) and making the sail more powerful in light winds. Tightening the headstay flattens the sail and sharpens the entry angle, which is useful in strong winds when you need better control.

Adjustments for Different Conditions:

Downwind Sailing: Ease the sheet and lead forward, allowing the sail to twist and capture more wind.

Light Wind: In gentle breezes, ease the halyard and move the lead forward to create a fuller, more powerful sail.

Strong Wind: Tighten the halyard and move the lead aft to flatten the sail and reduce heeling, spilling excess wind from the leech.

Upwind Sailing: Trim the sheet for a flatter sail and tighter leech, optimizing for pointing ability.

A telltale is a simple yet highly effective indicator used in sailing to monitor wind flow over a sail, helping sailors optimize sail trim and steering. Telltales are small yarns or ribbons attached to both sides of the sail, typically along the luff (the leading edge). Their purpose is to provide real-time feedback about how well the wind is flowing over the sail and whether the sail is operating efficiently.

How Telltales Work:

Telltales are placed in pairs, with one on each side of the sail. Their position along the luff is key to understanding how the wind flows at different heights of the sail. Ideally, there should be three sets of telltales evenly spaced from top to bottom, giving a complete view of airflow across the entire sail.

When the wind is flowing smoothly over the sail, the telltales stream straight back on both sides, indicating that the sail is in its optimal trim for that wind angle. If one of the telltales stops streaming and hangs limp or flickers:

• If the windward telltale (upwind side) stops streaming, it means the boat is sailing too close to the wind, and the sail is starting to stall. In this case, the boat should “fall off” (turn slightly away from the wind) to restore proper airflow.
• If the leeward telltale (downwind side) hangs limp, the boat is sailing too low, and you should “head up” (turn slightly toward the wind) to improve sail efficiency.

Uses of Telltales:

• Steering and Course Adjustment: By reading the telltales, sailors can adjust their course to ensure the sail is functioning as an efficient airfoil, maximizing speed and reducing drag. For example, sailing too high (pinching) or too low to the wind can stall the sail and reduce performance.
• Fine-tuning Sail Trim: Telltales also help fine-tune genoa sheet trim. Adjusting the position of the jib lead block can change the tension between the leech and foot of the sail, ensuring proper airflow and sail shape.
• Wind Conditions: In light wind, it’s important to avoid pinching, as this reduces speed significantly. In contrast, in heavy winds, a slight “pointing mode” (sailing closer to the wind) can help reduce heeling and improve control.

Telltale Behavior:

Limp or hanging telltales: Indicates stalled airflow, meaning the sail isn’t working efficiently.

Straight streaming: Indicates optimal airflow and proper sail trim.

Dancing or fluttering: Shows turbulent airflow or improper trim.

Tuning your rig is essential to ensure your boat’s mast is centered, straight, and ready for optimal performance. The process helps you balance your helm and control sail shape, allowing you to sail efficiently in different conditions. Tuning occurs in two stages: first at the dock and then while sailing.

Step 1: At the Dock

Begin by loosening all rigging if it’s already set up. This allows you to start fresh and make precise adjustments. You should also lubricate the turnbuckles to ensure smooth operation.

• Set the mast rake: The mast rake (the backward lean of the mast) affects your boat’s helm. More rake increases weather helm, where the boat naturally turns into the wind. If you’ve been sailing the boat and the helm feels balanced, keep the same rake. Adjust the rake by moving the mast step (where the mast is seated on the deck) or partners (where the mast passes through the deck).
• Center the mast: Using a halyard or tape measure from the masthead, measure to equal points on both sides of the boat to ensure the mast is perfectly centered.
• Tighten the shrouds: Start by tightening the upper shrouds, ensuring they are as tight as possible using wrenches (but not over-tightened). Work your way down to the intermediate and lower shrouds, sighting up the mast to ensure it remains straight.

Step 2: On the Water

Once dock tuning is complete, head out sailing in at least 10 knots of wind for fine-tuning. Your goal is to ensure the mast stays straight while under load and that the leeward shrouds (those on the downwind side) remain tight, not flapping loosely.

• Mast bend: Tighten the backstay to induce the maximum bend in the mast, flattening the mainsail to reduce draft in stronger winds. If more mast bend is needed, you can ease the headstay or adjust the mast partners.
• Shroud tension: While sailing upwind, adjust the shrouds so that the leeward ones are not too loose. Tighten the shrouds by removing half the slack, tacking back and forth to make equal adjustments on both sides.

Fine-tuning for Performance

Once your rig is properly set, fine-tuning will improve boat performance by optimizing sail shape and helm balance.

• Adjust mast rake: If you want more weather helm, increase mast rake by moving it aft. For less helm, decrease the rake. Ideal tuning typically has the rudder turned slightly (3 to 5 degrees) to keep the boat sailing straight, indicating balanced helm.
• Control sail draft:
  • Jib draft: This is managed through headstay tension. More sag in the headstay increases draft, providing more power in light winds, while tightening it flattens the sail for heavy wind.
  • Mainsail draft: Controlled by mast bend. More bend flattens the sail, reducing power in strong winds, while less bend increases draft, adding power in lighter air.

Important Notes

Always tape over cotter pins to prevent sail damage, and check rigging regularly, as rigging can stretch over time and throw off your settings.

If the leeward rigging is too loose while sailing, it may indicate the shroud tension was too low at the dock.

A firm headstay in strong winds improves upwind speed by reducing sag.

In rough seas, check if the mast is “pumping” (moving fore-and-aft). If so, tighten the babystay or running backstay.

Taking care of your sails is essential to extending their life and ensuring optimal performance on the water. Regular maintenance and proper handling can help protect your investment and avoid premature damage. Here’s a guide on how to take care of your sails, organized into key areas:

Preparation of Your Boat and Rig:

• Tape sharp edges: Make sure to tape over any sharp corners, cotter pins, or exposed metal on your rigging that could chafe or tear your sails. Pay particular attention to spreader tips, stanchions, and turnbuckles.
• Protect your rigging: Use protective covers like boots or tubes on turnbuckles and spreader tips to prevent wear and tear on the sailcloth.
• Inspect halyards and lifelines: Check for “meat hooks” (frayed wires) in halyards or lifelines that can snag your sails. Clean your lifelines to avoid contamination of the sail material.
• Clean the deck regularly: A clean deck prevents dirt, grease, and grime from transferring onto your sails, especially when hoisting or lowering them.

Handling Your Sails:

• Avoid flogging: Minimize how much time your sails are allowed to luff (flap in the wind) as this accelerates wear, particularly on the leech. Hoist and trim them quickly, and avoid letting them flog while motoring.
• Reef early: When conditions demand it, reef your sails early to reduce the strain on them in strong winds. Overpowered sails are prone to damage.
• Tension control: Be careful not to over-tighten the halyard, outhaul, or leech line. Use just enough tension to remove wrinkles but avoid putting too much strain on the fabric.
• UV Protection: When not in use, protect your sails from UV damage by covering them with sail covers. Roller furling headsails should be furled with the UV cover facing out.

Maintenance and Storage:

• Wash and dry your sails: At the end of each season, or after heavy use, wash your sails in warm soapy water to remove dirt and salt. Rinse them thoroughly and let them dry completely before folding or rolling them to prevent mildew.
• Avoid sharp creases: When folding or rolling your sails, avoid creating sharp creases, which can weaken the sailcloth over time. Laminate sails, in particular, should be rolled to prevent damage to the film layers.
• Store in a dry place: Always store sails in a well-ventilated, dry location. Damp conditions can lead to mildew, which, while not structurally damaging, can cause stains that are difficult to remove.

Sail Repair:

• Act quickly: If you notice a tear or damage while sailing, lower the sail as soon as possible to prevent the damage from worsening. For small tears, use sticky-back tape as a temporary repair until you can get it professionally fixed.
• Seek professional help: While small repairs can be patched with tape, it’s best to have larger or more critical tears repaired by a professional sailmaker to avoid further damage.

Seasonal Checkups:

Annual loft visit: Taking your sails to the loft once a year for a thorough inspection and cleaning is one of the best ways to extend their lifespan. Professional sailmakers can identify weak points, refurbish the sails, and return them in top condition for the next season.

A spreader patch is a protective layer of sticky-back Dacron material applied to the sail, specifically designed to prevent wear and tear caused by the sail rubbing against the spreaders during tacks and other maneuvers. This patch acts as a buffer between the spreaders and the sail to prolong the sail’s life, especially for laminate sails like Mylar-based genoas. Here’s how to apply it properly:

Steps to Apply a Spreader Patch:

1. Determine the Patch Location:
   • Hoist the sail in calm conditions and sheet it in tightly as you would while sailing.
   • Go up the mast using a bosun’s chair and mark where the spreaders come into contact with the sail’s leech.
   • The patch should extend about 8 inches in front of this point and back toward the leech. Make sure three-quarters of the patch is positioned below where the spreader hits the sail, as the leech rises when the sail is eased.
2. Prepare the Sail:
   • Ensure the sail is clean, dry, and free of salt or debris.
   • Lay the sail out on a large, flat surface to work on. The smoother and flatter the sail, the better the patch will adhere.
3. Position the Patch:
   • Peel off the backing paper from the first few inches of the spreader patch. Crease the leech edge of the patch to make handling easier.
   • Align the patch parallel to the waterline, ensuring that 2 to 3 inches extend beyond the leech of the sail. This overhang is important for protecting the leech edge during maneuvers.
   • Press the exposed portion of the patch onto the sail, ensuring it is in the right position.
4. Apply the Patch Smoothly:
   • As one person smooths the patch onto the sail, another should slowly peel away the backing paper from the rest of the patch.
   • Use your hands or a tool like a plastic squeegee, wallpaper roller, or the blunt side of scissors to smooth the patch and eliminate air bubbles or wrinkles.
5. Finish the Leech Edge:
   • Once the main part of the patch is applied, go back to the leech and fold over the excess material, sticking it firmly to the other side of the sail.
6. Repeat on the Opposite Side:
   • Apply another patch in the same way to the opposite side of the sail. This ensures full protection on both sides when the sail rubs against the spreader.
7. Mark Other Contact Points:
   • While the sail is hoisted, mark any additional areas where the sail may come into contact with other rigging components, such as stanchions or the shrouds, and apply protective patches to those areas as well.

Tips for Application:

Apply pressure evenly with a squeegee or roller to make sure the patch sticks firmly.

Keep tension on the sail as you apply the patch to prevent wrinkles or bubbles from forming. You can use your knees or ask a partner to help hold the sail taut.

Afterguy: The line attached to the spinnaker pole that controls the position of the spinnaker. It takes more load than the spinnaker sheet and is typically a stronger line. Often just called the “guy.”

Aspect Ratio: The ratio of a sail’s height to its width. A high aspect ratio sail is tall and narrow, while a low aspect ratio sail is shorter and wider.

Bias Stretch: The stretch of fabric at an angle to the weave’s primary threads (warp and fill). It’s the most vulnerable direction for sailcloth.

Bi-Radial: A sail construction method where radial panels radiate from the sail’s head and clew, improving strength and shape.

Boom Vang: A mechanical device used to control the vertical angle of the boom, tightening or loosening the mainsail leech for better sail shape.

Clew: The aft lower corner of a sail where the sheets attach. On the mainsail, the outhaul is attached here.

Crosscut: A sail construction where panels run horizontally across the sail, perpendicular to the leech. This is the most common sailmaking method.

Cunningham: A line used to increase tension on the luff of the mainsail to move the draft forward and fine-tune sail shape.

Draft: The depth of the sail’s curve, affecting the power and shape of the sail. It can be adjusted by tensioning the halyard or Cunningham.

E: The measurement from the mast to the outermost point of the boom along the foot of the mainsail.

Fill Threads: Threads running across the width of a fabric, perpendicular to the warp threads.

Flattening Reef: A control used to flatten the lower part of the mainsail, reducing power in strong winds. It operates similarly to a regular reef but only reduces draft without significantly reducing sail area.

Foot: The bottom edge of a sail, running from the tack to the clew.

Foreguy: A line used to pull the spinnaker pole downward, keeping it from lifting off the deck when flying the spinnaker.

Foretriangle: The triangular area formed between the mast, the deck, and the forestay.

Gooseneck: The joint that connects the boom to the mast, allowing the boom to pivot while keeping it attached.

Halyard: The line used to hoist and lower sails.

Head: The top corner of the sail, opposite the tack and clew.

Headstay Sag: The amount the forestay bends to leeward when under load. More sag adds draft and power to the headsail, while less sag flattens the sail.

I: A measurement representing the height of the foretriangle, from the deck to the highest point on the mast where the headstay is attached.

J: The horizontal distance between the base of the mast and the point where the forestay attaches to the deck.

Jib Lead: The block through which the jib sheet passes, affecting the trim of the headsail by controlling tension on the leech and foot.

Laminated Sailcloth: A multi-layer fabric composed of fiber and film bonded together. The film controls bias stretch, while the fibers provide directional strength.

Lazy Sheet: The sheet that is not under load when tacking or jibing the headsail or spinnaker.

Lee Helm: The tendency of a boat to turn away from the wind when the helm is released. It is the opposite of weather helm.

Leech: The aft edge of a sail running from the head to the clew.

LP: Luff Perpendicular, the shortest distance from the clew to the luff of a headsail. Genoa sizes are often expressed as a percentage of the LP relative to the boat’s J measurement.

Luff: The forward edge of a sail, from the tack to the head. Luffing occurs when the sail flaps due to insufficient wind or poor trim.

Outhaul: A line used to tension the foot of the mainsail by pulling the clew outward along the boom.

Overpowered/Underpowered: A boat is overpowered when the sails are too large for the wind, causing excessive heeling. Underpowered refers to having too little sail area, slowing the boat down.

P: The distance between the top of the boom and the highest point the mainsail can be hoisted on the mast.

Rake: The tilt of the mast, either forward or aft. Adjusting rake can affect the boat’s helm balance.

Roach: The curved section of the mainsail’s leech that extends beyond a straight line between the head and the clew. Roach is supported by battens to add sail area without increasing mast height.

Scrim Cloth: A loosely woven fabric laminated to film, commonly used in high-performance sails for strength without added weight.

Shelf Foot: A sail construction option where the bottom of the sail has extra fabric that forms a shelf when eased, allowing for more depth and power in the lower part of the sail.

Shroud: The standing rigging wires that support the mast from the sides.

Spreader: A horizontal strut on the mast that increases the shrouds’ angle, providing greater mast support.

Stay: Rigging wires that support the mast fore-and-aft, such as the forestay and backstay.

Tack: The forward lower corner of the sail where it attaches to the deck or boom. Tacking also refers to changing direction by turning the bow through the wind.

Tape-Drive: A sail construction method where high-strength tapes are laid along specific load paths to distribute stress and maintain the sail’s shape.

Telltales: Small pieces of yarn or fabric attached to sails to indicate airflow over the surface, helping sailors trim the sail for optimal performance.

Tri-Radial: A sailmaking technique where radial panels radiate from all three corners of the sail, improving strength and shape control.

Warp: Threads running lengthwise in sailcloth, providing strength in that direction. The fill threads run perpendicular to the warp.

Weather Helm: The tendency of a boat to turn into the wind when the helm is released. It is generally desirable in small amounts for better control.