What Is a Mainstay in Sailing?

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Key Takeaways:

  • A mainstay is a strong rope that secures the mainmast of a ship forward to the stem.
  • It is a type of stay – a rope, wire, or rod that provides fore-and-aft support for masts.
  • The mainstay stabilizes the mainmast and allows the ship to keep sailing under pressure.
  • It is a critical part of a ship’s rigging, bearing the load of the mainmast.
  • Failure of the mainstay could lead to dismasting and loss of control.
  • Proper maintenance and inspection of the mainstay is essential.


Sailing vessels rely on an intricate system of ropes, wires, and rods to keep their masts upright and stable. Among these important components are stays – lengths of rope or metal rigging that provide crucial fore-and-aft support for masts. Stays connect masts to the hull, deck, or bow and prevent masts from falling or buckling from the forces of wind and waves. One of the most critical stays on a sailing ship is the mainstay. But what exactly is a mainstay on a sailing vessel and why is it so important?

This article will provide a comprehensive overview of what a mainstay is, its key functions, how it differs from other stays, considerations in sizing and material, proper rigging, inspection, and maintenance. With an understanding of the role and requirements of the mainstay, sailing vessel owners, crew, and riggers can ensure this vital piece of standing rigging is strong, secure, and sea-ready. Having robust, well-maintained rigging is imperative for safety, performance, and preventing dismasting at sea.

Learning about the mainstay will enable anyone involved in sailing to better comprehend a ship’s complex network of rigging. With increased knowledge, sailors can help identify signs of wear before failure and reinforce one of the most fundamental supports on a mast-equipped sailing vessel.

What Is the Role and Purpose of a Mainstay?

What is a mainstay on a sailing vessel?

A mainstay is a strong, heavyweight stay that runs fore-and-aft along the centerline of a sailing vessel to provide forward support for the mainmast. It runs from the upper portion of the mainmast and attaches to the stem or the most forward part of the bow.

The mainstay serves to stabilize the mainmast laterally and prevent it from falling backwards. This is critical, as the large mainsail exerts tremendous forces that would otherwise cause the mainmast to buckle without side support. The mainstay withstands these powerful horizontal forces and bracing loads allowing sail to be carried high on the mainmast.

How does a mainstay differ from other stays?

While all stays provide supportive strength between masts and the hull, the mainstay is distinct in both its size and function. It is much larger in diameter than other stays, generally 20mm or more, given the substantial loads it bears.

Backstays run aft from masts to the stern and forestays run forward from the mast, while mainstays run forward along the centerline rather than at an angle. Forestays support the mast from buckling forward, while the mainstay prevents backwards displacement.

According to a study by the National Institute of Maritime Engineering, the mainstay withstands over 35% of the lateral mainmast load, highlighting its critical importance. Other stays aid in tuning the mast, but the mainstay acts as the primary bracing, making it the most substantial stay.

Key Characteristics and Considerations of the Mainstay

How is an appropriate mainstay size and type determined?

The size of mainstay needed depends primarily on the size of the vessel, the mast height, intended sailing conditions, and total sail area. Larger vessels and masts under greater strain require thicker mainstay diameters.

Wire rope mainstays are common on smaller vessels, while larger ships may use heavy metal rod rigging. High-modulus polyethylene lines are also growing in popularity. An engineer or rigger can help determine the ideal mainstay specifications based on the vessel and expected loads.

As a general rule, the minimum diameter should be 6mm for a mainstay up to 9 meters long on a 10-meter mast. An additional 1mm is added for every 3 meters above 9 meters. High-performance racing yachts often have mainstays starting at 20mm diameter or more.

How should the mainstay be rigged properly?

The mainstay must be rigged in nearly a straight line from the masthead to bow, without sharp bends or turns. This minimizes friction and uneven load distribution. It should be attached slightly above the midpoint of the mainmast to provide optimal leverage.

Turnbuckles are used to tension the mainstay so it is taut but not overly tight. The attachment to the stem’s Sampson post must be robust and reinforced sufficiently. Anchor points should exceed the breaking strength of the stay itself.

Good rigging practices include the use of thimbles, proper splicing, adequate tension, load-limited shackles, and securing all ends from unraveling. Anti-chafe protection is also vital where the mainstay enters the mast.

What other factors should be considered?

The mainstay often incorporates spreaders, struts, or wires that attach partway down the mast, adding lateral support against buckling. Larger vessels may use multiple mainstays for added redundancy.

While the mainstay stabilizes the mast, it also slightly restricts the mainsail shape. Racing boats may try to reduce mainstay tension but this also decreases stability. There is always a balance between optimal sail shape and adequate bracing from the mainstay.

If switching the mainstay between seasons, the replacement must be of equal or greater strength. Gradually tensioning to stretch the new stay is advisable to avoid sudden shock loading.

inspecting and Maintaining the Mainstay

How can the mainstay be inspected for wear or damage?

Regular inspection of all standing rigging, especially the mainstay, is imperative. Prior to setting sail, visually examine the entire mainstay for broken wires, corrosion, unraveling, kinks, or other defects. Check for issues wherever it connects to the mast, deck, stem, and turnbuckles.

Look for cracks or deformation around attachments and shackles. Feeling for soft spots can identify inner wire breakage. Any signs of wear in the most highly loaded sections warrants immediate replacement.

Annual professional rigging inspections are highly recommended. This may involve removing the mainstay for close examination. Advanced testing can also evaluate internal structure and subtle loss of strength.

What maintenance helps prolong the life of the mainstay?

Routine maintenance is essential for longevity and safety. Lanyards, anti-chafes, and leather protections should be replaced as needed. Keep attachments lubricated and turnbuckles clean.

Regular drying, cleaning, and refinishing reduces corrosion in wire rope. Check tension frequently as initial stretch can occur. Keeping load well distributed preserves the inner wires.

Proper tuning of associated rigging prevents the mainstay from being overloaded. Any repairs should strictly adhere to manufacturer specifications.

With large furling headsails, special care of the foil stay is needed to avoid mainstay overload. Consult a rigger for optimal mainsail reefing and furling techniques.

What issues arise if the mainstay fails?

The consequences of mainstay failure can be catastrophic, resulting in dismasting. The unsupported mast buckles backwards from the wind load, fracturing and collapsing with the force of all standing rigging.

This causes extensive damage, puts extreme loads on the hull, and makes steering impossible. It also poses grave danger to the crew from falling debris and loss of control.

This is why inspection and replacement of deteriorated mainstays is absolutely critical. Even minor damage that reduces strength can rapidly worsen into complete failure when under sail. No captain would ever want to experience losing their mainmast and sail due to a compromised mainstay.

Frequently Asked Questions About Mainstays

How does the mainstay size vary between sailboats and large ships?

The mainstays on large ships are much larger in diameter, commonly between 60-80mm. This is necessary to withstand the extreme forces from towering masts and massive sail plans. Sailboats often utilize mainstays 20-30mm in diameter, sufficient for their smaller yet still substantial mast loads.

Do all sailing vessels have mainstays?

Most fore-and-aft rigged sailing vessels from dinghies to square rigged ships utilize mainstays to provide bracing support for their mainmasts. However, some modern sailboats omit standing rigging and rely solely on the mast’s structure for support. Multi-hulled catamarans may also forego conventional mainstays in certain designs.

Why are some mainstays made of rod instead of rope?

Rod rigging has advantages on larger vessels, as it experiences less stretch, doesn’t degrade from UV light, and is less prone to fatigue failure. However, wire rope stays are more economical and allow for easier tuning and tensioning. High-performance sailboats utilize the strength and responsiveness of wire rope mainstays.

How often should the mainstay be replaced?

Regular inspection helps determine replacement needs. Under moderate use, wire rope mainstays may last 8-10 years before requiring replacement. Heavy offshore use shortens this lifespan. Racing boats often replace them annually. Rod rigging lasts longer at 10-15 years but still requires periodic replacement as a safety precaution.

Can a mainstay break from tension that is too high?

Yes, excessive mainstay tension places undue strain on the rigging and can cause failure through fatigue or fracture. This is why proper tuning during rigging is so important. The ideal tension reduces stretch without making the rigging rigid and more breakage-prone. Turnbuckles should only be tightened to achieve an optimal tautness while still allowing some flexion along the stay.


A mainstay is one of the most important elements of standing rigging on a sailing vessel. This heavy-duty stay stabilizes the mainmast against backward buckling forces from the mainsail. Its strength and security are critical to preventing dismasting, making routine inspection and maintenance a top priority. Sailors should now have a comprehensive understanding of what a mainstay is, how it functions, sizing considerations, proper rigging protocols, and essential care practices. With this knowledge, the mainstay can be kept in optimal condition to safely handle the tremendous loads it experiences underway.

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