Backstay, what it is used for and why it is important for it to be adjustable

The shape of the sails changes with the tension of the halyards, the point of sheet, the trolleys, and then there is the good old backstay, a maneuver that even today, despite the fact that on some cruisers it is fixed or disappears altogether, is still essential for proper sail fat control.

Paterazzo, how it evolved

It used to be just a fixed backstay, then “evolved” into maneuvering with the first tension adjustment systems that were later well developed during the 1970s-80′ of the last century. Today the backstay sometimes reverts to fixed, not adjustable, on some pure cruising sailboat models, such as those for charter, but it has not stopped evolving into its “maneuvering” version, with the introduction of a material such as textile that has greatly improved its performance.

Until about 20 years ago the most popular backstay material in fact was steel, today textile materials have almost totally replaced the old solution offering the same or better performance in cable tenacity, along with significant weight savings.

Backstay, what it’s for

The main function of backstay adjustment is to change the shape of the sails, both jib/genoa and mainsail, by slimming or increasing their depth. When we cock the backstay, the masthead goes backward, thus stretching the forestay, especially in masthead rigs, while the middle area flexes going forward. The curvature of the mast causes the fat of the mainsail and jib to move toward the bow reducing, “eaten up” by the mast’s pre-flexion and the reduction of the catenary. The sails are thinner, and the two effects combined cause the boat to swerve less and be less eared.

Conversely, when we leave it we give power to the sails: the forestay increases su catenary and the jib has a deeper shape, the mast straightens and the mainsail fat increases moving aft. In very light wind conditions upwind, 4-5 knots, the backstay should only be pinned (in the case of masts with in-line spreaders) or even, in masts with quartered spreaders, practically banned.

In the stern, if the mast has in-line spreaders, the backstay will have to be held at all times with a minimum of tension, and totally capped in high winds. In guns with angled spreaders, the shrouds already support a good part of the mast load, and a different adjustment can be dared, leaving it totally in little wind and holding it at moderate tension in a stiff wind.

Mauro Giuffrè