Running backstays are primarily fitted on racing and performance sailing yachts. They are essential on fractional rigs, where they are used to increase forestay tension and ensure optimal mast support.
Adjusting running backstays requires a careful balance between performance (speed) and structural safety, and therefore demands a solid understanding of sail trim and rig tuning. To ensure consistent settings, visual markers such as reference bands and calibrated indicators are commonly used.
Definition of a running backstay
A running backstay is an adjustable stay fitted on sailing yachts, particularly on those with a fractional rig, where the headsail is not attached at the masthead. It is typically tensioned באמצעות a tackle system.
Running backstays operate in pairs—one on each side of the vessel. They are attached near the forestay connection point on the mast and led aft to the deck, preventing the mast from moving forward.
- Upper running backstays are attached at the forestay attachment point
- Lower running backstays are fixed midway between the forestay attachment and the gooseneck
The lower backstays stabilise the mid-section of the mast, preventing uncontrolled flexing and the so-called “pumping” effect.
Function and use
To maintain mast stability under sail:
- The windward running backstay is tensioned
- The leeward running backstay is eased to allow the mainsail to pass freely
This operation must be repeated at every tack and gybe, requiring coordinated handling.
Their role varies depending on rig configuration:
- Neutral spreaders (perpendicular to the yacht’s centreline):
Running backstays provide essential longitudinal support to the mast - Aft-swept spreaders:
Running backstays are also used to control mast bend, allowing fine-tuning of sail power and aerodynamic efficiency
On a fractional rig, tensioning a running backstay pulls the mast aft, increasing forestay tension. This affects overall rig balance, including lateral stays, and may increase the risk of mast compression or reverse bend if improperly adjusted.
⚠️ Excessive tension may result in inverted mast bend, which can compromise structural integrity.
How to adjust running backstays according to wind conditions
Upwind in light airs
To increase power:
- Tension the lower running backstay to deepen the mainsail
- Minimise mast bend
- Lightly tension the upper windward backstay to prevent reverse bend
Calm conditions (flat calm)
The opposite approach may be used:
- Flatten the mainsail as much as possible
- Maintain airflow efficiency to capture light wind
Upwind in strong breeze
- Ease the lower running backstay to induce mast bend
- Flatten the lower mainsail, reducing power and improving pointing ability
- Tension the upper running backstay to:
- Increase forestay tension
- Improve headsail shape and entry
Downwind in light airs
- Fully ease both running backstays
Downwind in strong breeze
- Maintain moderate tension, similar to upwind settings, without overloading
⚠️ Avoid inducing forward mast rake (negative rake)
- Always tension the upper backstays first to prevent reverse bend
⚠️ Caution: this is a high-risk configuration. In the event of an uncontrolled gybe, the boom may strike the windward running backstay, potentially leading to mast failure if it is not released in time.
In choppy conditions
When faced with irregular wave patterns:
- Tension the lower running backstay
- Reinforce with the upper backstay
This stabilises the mast and reduces structural stress.
The role of the backstay trimmer in racing yachts
On competitive racing yachts, the running backstay trimmer is a dedicated crew position combining technical expertise and tactical awareness.
Technical role
- Upwind: optimises headsail shape and enables tighter angles to the wind
- Downwind: monitors mast support under increased sail loads
Tactical role
- Maintains constant communication with the helmsman
- Provides performance data (heading, speed differentials)
- Works closely with the tactician, relaying compass and positioning information
On racing yachts, the running backstay trimmer plays a critical role in manoeuvres, particularly during tacks and gybes, ensuring precise and safe adjustment of the rig.
Close coordination with the helmsman and tactician is essential to optimise performance and maintain competitive positioning.
Improper handling—especially during a gybe—can result in severe structural damage, including mast failure, underscoring the importance of expertise in managing running backstays.