Definition of the backstay
On a Bermuda-rigged sailing yacht, the backstay is a cable running between the masthead and the stern (via a chainplate secured to the deck structure). In its single configuration, it effectively bisects the yacht along its centreline; in a split configuration, it is attached to the masthead and led to both quarters of the transom.
It should be noted that yachts fitted with swept spreaders are generally not equipped with a backstay. This spreader geometry allows the shrouds to be led aft, thereby providing sufficient support to the mast without the need for a backstay.
Function and adjustment of the backstay
A yacht’s performance also depends on the precise tuning of its standing rigging. Backstay adjustments are carried out meticulously prior to putting to sea (notably after winter lay-up) and/or following any dismasting. They are subsequently fine-tuned under way, ideally in flat water and light airs (below Force 3), and readjusted as required during navigation.
A correctly tuned backstay reduces wear on associated deck hardware and contributes significantly to maintaining a high level of onboard safety.
The backstay is tensioned to induce mast bend while simultaneously affecting the forestay tension of the genoa. The tighter the backstay, the greater the load applied to the forestay. When sailing close-hauled, and when the genoa forestay begins to sag under sail pressure, the backstay must be tensioned accordingly.
This action bends the mast, shortens the distance between the clew and the halyard head, reduces leech tension, and opens (twists) the upper part of the mainsail—thereby improving overall performance.
Adjustment is typically facilitated by a purchase system of varying complexity. A six-part tackle (rope or wire) is commonly found on smaller cruising yachts with a single backstay, whereas larger, performance-oriented yachts equipped with a split (“Y” or bridle) backstay may employ a more complex system incorporating an additional purchase led through a third block.
These adjustments have a cascading effect: increasing backstay tension pulls the masthead aft while pushing the միջsection forward. The forestay stiffens, altering the sail profile—flattening its միջsection and opening the leech in the upper հատված. Backstay tension thus enables precise control of airflow over the mainsail, particularly at its head.
These settings are critical when aiming for a depowered sail plan that deflects rather than retains wind, with backstay tension ensuring optimal airflow management.
Note: the backstay should always be eased when at anchor or in harbour to avoid unnecessary loads on the rig.
What are running backstays used for?
On rigs with straight spreaders, running backstays operate in pairs. When attached close to the yacht’s longitudinal axis, they contribute to the mast’s fore-and-aft stability. On masthead rigs, their function is often associated with the staysail (inner forestay).
They are essential on fractional rigs and must be adjusted so that the windward running backstay remains under constant tension, while the leeward one is eased (with due attention to boom position and sail handling).
Running backstays are divided into two categories:
- Upper running backstays, attached near the forestay termination at the masthead
- Lower running backstays, attached between the gooseneck and the forestay attachment point
The latter stabilise the mast and prevent uncontrolled flexing, which could otherwise induce a “pumping” effect in the sail.
Backstay or running backstays: why choose?
In practice, tuning a yacht’s rigging frequently involves both the backstay and the running backstays simultaneously. Rather than choosing between them, it is generally more effective to use both where the rig design allows.
Typically, running backstays and the backstay are adjusted after the forestays and other rigging elements. To avoid excessive tension on the genoa halyard, it is essential that the forestay is correctly tensioned when hoisting the sail—meaning that both the backstay and running backstays should already be properly set.
When sailing, longitudinal mast trim must be carefully controlled. Provided that the mast step is correctly positioned on deck, this balance results from the combined action of the forestay/backstay, the inner forestay/running backstays, and the tension in the shrouds.
Once again, backstay and running backstays operate in complementarity. Their respective roles are interdependent, and their combined use renders any notion of prioritising or eliminating one in favour of the other both impractical and technically unfounded.
