Ivar Dedekam is the author of Illustrated Sail & Rig Tuning brings us this guide on how to tune the rig of a yacht and make your sailing better

It is important to have a correctly tuned rig. Boats that have poorly tuned rigs are slower, point lower, heel more, make more leeway and may be more difficult to steer. Making changes can be dramatic on any class of boat. They will reduce crew fatigue, widen the skipper’s options and improve their reputation. Boat value is enhanced and things will be safer in extreme situations.

Rig types

The Bermudan rig is the most widely used rig in the world. It may be split into two main groups: the masthead rig and the fractional rig. The masthead rig is relatively easy to tune but less ‘tuneable’ than a fractional rig. The fractional rig, meanwhile, is more ‘tuneable’ than a masthead rig but more demanding to tune and then keep well tuned.

(Left) Use the halyard to gauge the distances from the top of the mast to either side of the deck. (Right) Measure the distance between the mast and the vertical halyard

Sideways tuning

Ensure the boat is upright and the wind is light. Set up the mast on the boat and lightly tension the cap (upper) shrouds, backstay and forestay until the mast is standing fairly upright. It’s worth noting that if it is a keel stepped mast, the chocks should not be inserted in the mast ring yet. If the boom is mounted, let it rest on deck to release the topping lift. The lower shrouds and inner forestay (babystay) should be loose.

Find two fixed points, e.g. on the toe rails or gunwales symmetrically located across the boat. Check that these points are equally distant from the mast at deck level. Then start measuring with the halyard. If the distances are unequal, tighten the rigging screw on the side with the longest distance. When the lengths on both sides are equal, the mast is upright.

Many yachtsmen do this check by eyesight. It may be good enough, but requires an upright boat. The halyard check is better if the boat is symmetrical. Finally hand tighten the cap shrouds with equal numbers of turns on each rigging screw and do the halyard measurement again.

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Adjusting the mast rake

The mast is usually set with a slight aft tilt – the so-called mast rake – which will help improve the boat’s upwind performance. Mast rake is usually between 1-3 degrees. You can adjust mast rake as follows:

  • Trim the boat upright
  • Measure the b-value using the halyard as a plumb bob. It helps to attach a heavy object (e.g. a shackle or a wrench) to the end of the main halyard to measure b (the distance from the mast to the vertical halyard). Placing the halyard’s weighted end in a bucket of water will dampen the oscillations.
  • Adjust the forestay and backstay rigging screws to set the desired rake. With a fractional rig, use a running backstay instead of the backstay when adjusting rake.

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