Multihull sail work

Brush up on multihull sailing skills before heading off on charter with Gavin Le Sueur's guide to spinnaker handling, tacking and gybing

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Light multihulls achieve high speeds downwind by running an asymmetrical spinnaker and flying it shy. By building up a high apparent wind (keeping the breeze that is felt either on or just forward of the beam) it is possible to carry the apparent wind direction forward. Very often the multihull will be heading well downwind (from the true wind) yet the apparent wind remains beam on.

The wide beam of multihulls enables traditional spinnakers to be set without a pole. By bracing the spinnaker with a line from each outboard bow and one from the middle hull (or beam) the spinnaker tack is variable in position.

A short spinnaker pole (termed a 'prodder') can be permanently mounted on the middle hull (or middle of a catamaran forward beam) to provide a rigid position for the tack. The advantage of this system is that there's only one line to tighten when setting the tack in most reaching positions.

It is an advantage to have the ability to pull the tack windward.

This is because in very light winds asymmetrical kites set from the mid-line will collapse or force you to sail way off course with a resultant poor velocity made good (VMG) downwind.

On high-performance multihulls, it's also possible to keep the headsail up when running under spinnaker. On racing yachts, there is a definite advantage to trimming and maintaining as much sail area as possible - the mainsail, the headsail and the spinnaker. To achieve this the sails should have efficiently mounted telltales and the crew should be aware of the need to work the sheets to maintain your multihull 'in the groove'.

The aim is to keep the apparent wind moving across the boat at about 90°.