Whether you’re cruising or racing, an adjustable backstay is a helpful device for changing sail shape and controlling forestay tension for improved upwind and downwind performance. By dialing in the right backstay tension you can increase boatspeed. Regardless of whether you have a masthead or fractional rig, using an adjustable backstay is essential to good sail shape. While an adjustable backstay isn’t as popular on a cruising boat, it is an important tool for easy and comfortable sailing.
Backstay adjusters for cruisers
Most manufacturers of roller-furling gear recommend that you sail with a tight headstay, as this allows the luff foil to rotate more easily and improves the furler’s overall performance; this is particularly important in a gathering breeze when you need to roll a reef into the jib. Whether you have roller-furling or hanked-on headsails, it is useful to be able to control forestay tension easily and quickly. A forestay that sags off to leeward increases the fullness of the headsail as the wind builds; this leads to excessive heeling, which in turn contributes to weather helm. By keeping the forestay taut, you are flattening and depowering the headsail, and the boat sails more upright. While it’s possible to increase headstay tension by simply tightening the headstay or backstay turnbuckle, this is not something you’d want to do under sail.
And when turnbuckles have been tensioned in this fashion, all too often crews forget to loosen them again, leaving the rig overtensioned for extended times. This puts the hull and deck, the mast, and the standing rigging under constant—and unnecessary—stress. On a masthead rig, a backstay adjuster allows you to increase headstay tension when sailing, and to release tension when it’s not needed. It will improve furling-system performance, and allows you to bend the mast aft if you have a fractional rig. This helps flatten the mainsail, often allowing you to postpone reefing, and reduces heeling. Tensioning the backstay, however, won’t increase headstay tension on a typical modern fractional rig with aft-swept spreaders; this is controlled via tension in the cap shrouds, which often induces some pre-bend in the mast.
Choosing an adjuster
Backstay adjusters are either hydraulic or mechanical. Hydraulic adjusters consist of a hydraulic cylinder fitted between the backstay and its chainplate. Integral adjusters have a pump incorporated into the bottom of this cylinder, while other types (typically found only on high-end raceboats) have a remote hydraulic-pump panel connected to the cylinder with a high-pressure hose. When you pump the handle, oil is forced into the hydraulic cylinder, causing the cylinder’s piston to retract, thus increasing backstay tension. A pressure gauge indicates the amount of load on the backstay. The load-multiplying capabilities of a hydraulic system allow you to exert several thousand pounds of pressure on the backstay.
Some mechanical backstay adjusters are essentially precision-machined turnbuckles that employ either a winch handle, built-in handles, or an integral wheel to adjust backstay tension. They have high-strength stainless steel and/or silicon-bronze threads or worm gears designed to be adjusted under load without compromising strength. Some have enclosed gears, which can be fully lubricated without the risk of grease coming off on sails, clothing, or the deck. You might think that simply adding handles to a standard rigging turnbuckle would have the same effect, but the threads on a turnbuckle aren’t designed for repetitive tightening and loosening under load, and so they shouldn’t be used in this manner.
Another form of mechanical backstay adjuster is simple tackle arrangements that use purchase, not hydraulic fluid or precision-machined threads, to tighten the backstay. These systems, which are common on both cruisers and racers, attach to the backstay with a single point of attachment; this single point (usually comprised of high-strength cordage) then multiplies as it travels around and through a series of blocks before terminating at a cam cleat. Tackle systems can either look like a tackle-style boomvang, or they can form a triangle (from the single point of attachment at the masthead down to a block. High-strength cordage attaches at one stern quarter via a padeye, travels up and through the block before turning into a tackle system on the block’s other side, which attaches to a second padeye on the appropriate stern quarter).
Other times, a boat might have twin wire backstays with a car in between the two stays; by pulling down on the car via a tackle system, you can create more load on the backstay. Most of these systems are designed so that the helmsman or mainsheet trimmer can easily adjust the backstay on a racer; most cruising boats have the line termination near the backstay itself, ideally in easy reach of the helmsman. While these systems are fairly simple compared to hydraulic units, they can generate a lot of force if they are properly spec’d for the boat and the rig.
The choice between a hydraulic or a mechanical adjuster is largely one of convenience versus dollars. The hydraulic adjuster is faster and physically easier to use—both for applying backstay pressure and for rapidly bleeding it off—but it is the costlier option. Depending on the model, a mechanical adjuster takes a bit more time and muscle power to tension and release, but it costs less and is mechanically simpler. Whether you choose a hydraulic or mechanical system, installation is usually as simple as comparing the length of the current backstay turnbuckle to the new adjuster and trimming the backstay to fit the new adjuster’s length, using a mechanical-compression terminal such as a StaLok, Norseman, or Hayn.
If the new adjuster is shorter than the existing turnbuckle, add a toggle below the adjuster to make up the additional length. Installing a hydraulic backstay with a remote pump and panel is a complicated job that likely involves multiple hydraulic runs (especially if the pump/panel also controls the boomvang and the outhaul). You are best off to have this installed professionally as your backstay is your rig’s backbone and failure isn’t an option.