Whether racing or cruising, a well tuned boat will sail faster and tend to heel less than a boat with badly adjusted sails.

On a racing yacht, constant effort and considerable skill is required by the crew to keep the sails trimmed to gain maximum performance, added to which they will choose from a selection of sails on board suited to different conditions, wind strength and direction.

On a cruising yacht, life is generally more relaxed and there will normally be two sails hoisted – a headsail and mainsail, both which can be reefed in stronger winds. However, sail trimming is still important in order to maintain a balanced helm and to prevent excessive heeling.

A balanced helm

A balanced helm is where the boat is not being pulled either towards the wind, known as weather helm, or pushed away from the wind, known as lee helm. Once hoisted, the headsail and mainsail need to be adjusted so that their shapes harmonise and work together, resulting in the most efficient performance.

Sail balance

Keeping the sails balanced involves making adjustments to the sails as the wind gusts or changes direction. This is the job of the sail trimmer (or trimmers).

Having the sails balanced and trimmed correctly for the course that is required will result in the most smooth and efficient ride possible. With the sails being correctly set and trimmed, then the person on the helm can focus on steering to the desired course.

Adjusting the sails – the basics

The sails are adjusted by “easing” or “sheeting in” the jib sheet and main sheet, in other words by either letting out or pulling in the sheets. This action causes the sails to change their shape to take advantage of the direction of the airflow over them.

As the boat sails closer towards the wind’s direction the sheets are pulled in, which flattens the sails and enables the boat to head closer to the wind.

As the boat sails away from the wind the sheets are eased, allowing the sails to be more curved in shape.

Telltales

Telltales indicate how the airflow is moving over the sails and whether they are working at maximum efficiency. If the telltales are streaming horizontally, then the sails are correctly trimmed. Most sails have telltales to help the sail trimmer see how the air is flowing across both sides of the sail.

Once the boat is heading on the correct course, then the trimmer adjusts the sails until the telltales are flowing horizontally. If the telltales stop streaming correctly, this indicates the boat has either gone off course, in which case the helm person needs to steer back on course, or the wind has changed direction, in which case the sails need to be re-trimmed.

Mainsail trimming

• Telltales flying horizontally, luff slack – correctly adjusted.
• Sail flapping – sheet in.
• Sail tight up to the mast – ease the sheet.

Genoa / jib trimming

• Telltales flying horizontally on both sides – correctly adjusted.
• Telltale on the inside of the sail is lifting – sheet in.
• Telltale on the outside of the sail is lifting – ease the sheet.

Other sail controls

Sails can be adjusted, or trimmed, using other control lines that increase or ease the tension of the lines that affect the shape of the sails. These include the main and genoa halyards, the outhaul, cunningham, kicker, genoa car position, mainsheet traveller and adjustable backstay. Here are some brief descriptions:

Halyard – the rope that hoists a sail.

Outhaul – the line that adjusts the tension of the foot of the mainsail, by pulling the clew along the boom.

Cunningham – a control line that is used to adjust the tension of the luff in the lower part of the mainsail.

Kicker (or boom vang) – a strut or block and tackle system used to pull the boom downwards and control the shape of the mainsail. The kicker is usually tensioned downwind and eased upwind.

Genoa car position – a system using a track with a moveable “car” that allows you to change the sheeting angle of a sail so that it has optimal shape.

Mainsheet traveller – a system that allows you to change the angle of the boom across the deck, which can help to quickly de-power the rig in a gust, returning the boom easily to the centre line when the wind drops.

Adjustable backstay – used to either increase or decrease the bend of a mast. It is usual to ease backstay tension when sailing downwind and increase it when sailing upwind.

Tips:

• Novice sailors will find that some yacht crews and skippers are continuously adjusting their sails while others hardly seem to touch them. If you are aboard a racing yacht, the adjustments will tend to be continuous, as the wind shifts and varies in strength. In these circumstances the whole crew concentrates on getting the absolute maximum performance from the boat. If on the other hand you are sailing aboard a laid-back cruising yacht, you will probably find that once the sails are hoisted and a course is set that sail adjustments are kept to a minimum.

• An excellent way for a novice to improve their trimming skills is to go sailing with some experienced racing sailors and watch them at work. There is nothing like hands on experience to build skills.