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Tuning a Sailboat Rig

If your sailboat seems slower, follow our how-to on tuning your rig for optimal performance.

Sailing the deep blue sea

Photo: Bigstock

Spring is a time of prepping your boat for the coming season. While powerboaters fine-tune their engines, sailors should consider fine-tuning their rigs. Doing it yourself may seem intimidating, but it shouldn't be. Anyone reasonably handy can do it in a few hours. The reward is easier and faster sailing throughout the coming season.

Let's start with the basics for new sailors. With a few exceptions, a sailboat mast is held up by a series of stainless-steel wires. But those wires also perform several other equally important functions. When a sailboat is at rest and there is no wind blowing, the stress on these wires is very light with almost all the load downward toward the keel. However, when the boat is sailing and heeled over in a fresh breeze, more stress is placed on the wires and they have to work harder to hold the mast upright and stop it from bending.

The wires that prevent the mast from moving from side to side are called shrouds, and the ones that prevent fore and aft movement are called stays. The larger and taller the mast, the greater the load, and the number of shrouds and stays required. On a typical cruiser, say up to about 35 feet, there will generally be one forestay, one backstay, and two shrouds on each side.

To get the best performance from your boat and sails, the rigging needs to be set up correctly — often called "tuning the rig." The rig should be tuned with the boat in the water on a day with little to no wind. You'll also want to be away from wakes and other boats that can rock your boat. To start, the turnbuckles for the stays and shrouds should be hand-tight only. This is sufficient to hold up the rig but places no strain on anything — yet. Lay on your back on the boat's foredeck and sight up the front of the mast. It should be perfectly straight with no bends or kinks. Next, tighten the lower shrouds — these are the ones that do not go all the way to the top of the mast and often attach to the mast at the base of the crosstrees (the two horizontal spars at the upper ends of the topmasts).

You'll need a large screwdriver to rotate the turnbuckle, and a wrench to hold the shroud fitting and prevent it turning as you tighten. Give a couple of complete turns on either side. Have a helper release the main halyard and keep a little tension while you pull down the end that normally attaches to the mainsail until it just touches the top of the toerail adjacent to the chain plate. Have your helper cleat off the halyard, then swing the halyard over the boom and check the measurement on the other side. They should be the same. If not, adjust the turnbuckles until they the measurement is equal on port and starboard.

Tuning a sailboat rig

Adjusting and tuning a sailboat rig will often bring benefits such as easier handling and better performance.

Next do the same for the cap shrouds, these are the ones that go to the top of the mast, but note that due to the length of the shrouds, it is easy to bend the mast to either port or starboard. With the shrouds adjusted, sight up the mast one more time to ensure that it is still straight.

Next comes the fore and aft adjustment, which is made with the backstay and forestay. Masts should be plumb or lie back slightly. It should never rake forward. A good starting point is to tighten up the forestay and backstay a little over hand-tight. Use the main halyard as a plumb bob. Cleat off the halyard so the free end is just clear of the top of the boom and let it hang. If the shackle on the end of the halyard hits the mast, the mast is likely too far forward, so slacken off the forestay and tighten the backstay. Adjust a little at a time until the end of the halyard hangs free — 4 or 5 inches is a good starting point.

You'll need to install cotter pins into the turnbuckles to prevent them loosening over time, but before doing that, take the boat for a sail when the wind is blowing about 10 knots and see how everything works. With the boat on a beam reach, note the tightness of the windward shrouds. If they appear slack, they will need to be adjusted up. If the boat is hard on the tiller or wheel and tries to turn into wind, the mast has too much aft rake, so you'll want to slacken the backstay and tighten up on the forestay a little. If the bow wants to turn away from the wind, the mast is too far forward, so you'll need to move the mast back a little.

If you are at all unsure about tackling this task, play it safe and smart — seek out the services of a qualified rigger who has access to rig tension gauges and other specialized tools.

Mark Corke

A marine surveyor, and holder of RYA Yachtmaster Ocean certification, Mark has built five boats himself — power and sail. He was senior editor of Sail magazine's hands-on "Boatworks" publication, worked for the BBC, written four DIY books, skippered two round-the-world yachts, and holds the Guinness World Record for the fastest there-and-back crossing of the English Channel, in a kayak! He and his wife have a Grand Banks 32.