Backstay Tensioner

Easy Upgrades: #1 of a series

Every fractionally rigged boat will have (or should have) a means of adjusting backstay tension. Its main purpose is to flatten and depower the mainsail in stronger winds, putting off the time at which a reef will be required. Because very few masthead-rigged boats are provided with backstay adjusters, cruising sailors regard them with the deepest suspicion–“just another thing to go wrong.” But on a masthead rig, backstay tension determines how much tension there is in the forestay, and therefore, how well the genoa sets.

In light winds, ease the backstay for a fuller, more powerful genoa; in stronger winds, tension the backstay to get the draft out of the genoa and improve the boat’s pointing ability and balance.

Few production boats have backstay adjusters fitted as standard, because of the cost, and because builders are worried that owners who do not know what they are doing would misuse the device and damage the boat or rig.

Installing a backstay adjuster need not be an expensive process, depending on the backstay arrangement. Masthead-rigged boats over 35 feet or so, with single backstays taken to a chainplate installed centrally on the transom, will require a hydraulic or mechanical adjuster. Mechanical adjusters are operated either by winch handle, wheels or flip-up handles; they’re simple and sturdy but they’re also slow to operate.

A typical self-contained hydraulic backstay adjuster like those made by Navtec is quick and easy to adjust, and usually has the advantage of a relief valve that will prevent the adjuster from overloading the rig. Both types of adjusters should have a scale or gauge installed so that the optimum settings can be noted and repeated. Backstay adjusters should be installed by professional riggers, as the penalties for poor installation can be severe.

On fractionally rigged (and some masthead-rigged) boats you will often see split backstays, with chainplates on the quarters. Usually, the twin backstays are joined to a single wire two or three meters up from the deck like an inverted Y. Replacing the tang with a sheave and one arm of the Y with a tackle is an easy and cost-effective process.

The sheave must be large in diameter and the tackle purchase should be 6:1, with good quality low-friction blocks. Measure it carefully, because it will probably need to be longer than you think—up to 3ft at full extension. A wire or Spectra strop should be installed between the backstay and the chainplate to ensure the mast won’t fall down if the tackle breaks or is accidentally released.

Another common method on boats under 30 feet is to rig a pincher tackle—a block on each arm of the Y attached to a 6:1 downhaul that draws the two together, thereby tensioning the backstay. These offer great purchase at light loads, but it decreases as the wires are drawn closer together; the longer the legs of the Y, and the closer together they are to begin with, the more efficient the tackle.

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