Sail Control

Sails are sophisticated aerofoils assembled from precisely shaped panels of closely woven synthetic sailcloth. The mast and boom along with their fittings allow adjustment to the cut of the sails enabling a wide range of sail shapes to suit changing wind conditions. Ropes that control the sails are termed running rigging to differentiate them from standing rigging those that support the mast.

Understanding the different shapes required of a single sail, a comparison can be made to the shapes and sections of birds' wings. Birds possessing high speed flight, such as swifts and hawks, have narrow, curved wings which are very thin or flat in cross-section.

Likewise, a flat sail is required in strong winds and is achieved by tightening the boom vang (kicking strap) to tension the sail bending the top of the mast toward the stern, and the middle of the mast is bowed forward.

The front edge of the sail, the luff, is tensioned by the halyard and Cunningham tackle, producing in cross section a flat sail. This takes the power out of the sail allowing the boat to be more efficiently handled and reducing heeling and sideways movement.

In light winds, the sail controls are eased producing a straight mast and a full-section sail similar to the thick wing of a soaring

bird such as an eagle or a buzzard. The result is a powerful sail, enhancing what little power there is in the wind.

Jib Sail Rigging

Jib sail rigging, being a one-man job, is carried out by the crew, whose responsibility is to handle the sail. Check the sail for damage as it is unfolded and attached to the boat, in particular the corners and seams for worn or frayed stitching.

Jib Fittings

Some jibs have a wire sewn into the luff that takes the high loads that are imposed on the edge of the sail while others have rope or high strength tape sewn into the luff. Be aware that if a luff wire is kinked and weakened, broken strands can tear the sail.

Rig the jib by attaching the tack to the bow-fitting using a shackle or lashing. Attach the luff to the forestay with a series of clips, known as hanks. Hank on the luff from the tack towards the head, making sure that the luff is not twisted between the hanks. Attach the halyard to the head now or before launching the boat.

The jib is trimmed using two jib sheets on each side of the boat passing through fairleads on the side decks and then to cleats and attached to the jib clew. Cleats

Jib Temporary Stow

If not sailing immediately, the rigged jib is gathered into a bundle on the foredeck and secured with a jib sheet preventing it blowing around. Alternatively, hoist the jib, and furl it on the forestay by wrapping it around the stay.

The mainsheet adjusts the position of the boom to help control the shape of the mainsail. When the mainsail is full of wind, there is a heavy load on the mainsheet. To make it easier for the helmsman to hold and adjust it runs through a system of blocks, called a mainsheet tackle.

Mainsheet Systems

The main types of mainsheet system are centre and aft. The former system has the end of the sheet leading to the helmsman's hand from a block, forward of the helmsman. In the aft mainsheet system the sheet is led from aft of the helmsman. Either may have a traveller on a track, which positions the mainsheet athwartships. Centre mainsheets offer more control of the sail whereas boats with an aft-mainsheet system provide more room in the cockpit.

Rigging Mainsheets

When the boat is not being sailed, mainsheet systems are left in place. At the time of sail rigging, check the fittings and the sheet runs smoothly through the tackle and the mainsheet has a figure-of-eight knot in the end preventing it from running out through the blocks.

Centre Mainsheet Systems

Centre-mainsheet systems mostly have the top block of the mainsheet tackle attached to the middle of the boom meaning less leverage and more load than an aft mainsheet requiring more blocks in the tackle.

The lower block is attached to an athwartships-track, running across the middle of the boat, or fitted on the floor, on a raised hoop, or on the centreboard case, with a cleat attached allowing the sheet can be jammed securely.

With an athwartships track, the mainsheet tackle's lower block is attached to a traveller running on the track. The traveller’s position is controlled by lines leading to the side deck.

Aft-Mainsheet Systems

An aft-mainsheet system, has the top block of the tackle attached to a swivel plate at the end of the boom with the bottom block attached to a traveller running on a track across the transom.

Sometimes the lower mainsheet block is attached to a rope bridle attached to the transom corners. When a traveller is used, it has control lines adjusting its position on the track. Aft-mainsheet systems may not have a jamming block for the sheet, but a ratchet block reducing the load. As the mainsheet leads from aft of the helmsman, he must face aft when tacking.

If sailing a boat with an unstayed mast and a sleeved sail, fit the mainsail onto the mast prior to it being stepped. In other boats, the sails are attached after the mast has been stepped and the standing rigging adjusted.

A mainsail is attached to the mast along the luff and to the boom at the foot. Two methods that attach the mainsail to the boom are by sliding its foot into a groove in the boom or loose-footed, which means that it is attached to the boom only at the tack and clew. Rope and Rigging

Mainsail Fittings

Battens

Most dinghy mainsails have battens, which are fitted either before or after the sail is attached to the boom. Battens act as stiffeners for the sail, holding out the curved shape of the leech termed the

roach and without them, the sail leech would curl over and be ineffective.

Battens are made of wood, fibreglass, or plastic and slot into pockets sewn into the sail and tied into the pocket and are made for specific. The battens have different flexibility, depending on where they are placed on the sail, along with the difference of flexibility at either end which allows for the curve in the sail.

Boom Fittings

The boom is attached to the mast by a gooseneck and a boom vang. The gooseneck is a hinged fitting that attaches the boom to the mast, below the mast groove opening. It pivots to left and right and up and down allowing the boom to move freely in these directions.

The gooseneck prevents the boom from rotating when fully inserted in the boom. The boom vang, or kicking strap, is a tackle of rope and blocks preventing the boom rising under the pressure of wind in the mainsail and is attached to the boom back from the gooseneck, and the mast just above the heel.

Attaching the Sail to the Boom

Remove the mainsail from its bag and unroll it inside the boat, with the luff nearest to the mast and insert battens Once the mainsail is fitted to the boom, put it inside the boat until ready to hoist the sail. Do not couple the boom onto the gooseneck until the sail is hoisted.

• Hold the clew and slide the boltrope into the groove at the mast end of the boom making sure that the sail cloth does not get caught in the groove with the boltrope.
• Pull the clew until the foot of the sail is in the groove and fix the tack to the forward end of the boom.
• Pull the foot of the sail taut keeping the sail tensioned by fastening the clew outhaul.

Attaching the Sail to the Mast

The mainsail is not hoisted until ready to launch or afloat but can be prepared by inserting the headboard into the mast groove. Check that the luff is not twisted, and the halyard is not caught aloft then attach the halyard to the head of the sail with a shackle knot. Cleat the mainsail halyard and flake the sail on the boom and secure it with the end of the mainsheet. Sailing Equipment and Parts

Sail Reefing

Beyond a wind speed of Force 3, many sailing dinghies become harder to handle so reducing the sail area, known as sail reefing, makes the dinghy easier to control in stronger winds. Three methods of sail reefing a mainsail are: traditional slab reefing; rolling the sail around the boom; and rolling the sail around the mast and the method used depends on the dinghy design. Jibs can be replaced for a smaller one or rolled around the forestay.

Methods of Sail Reefing

Slab reefing lashes down a portion out of the mainsail to the boom via one or two rows of reef points which are thin ropes stitched to the sail or cringles being reinforced eyes in the sail by reefing line. Unstayed mast boats reef by rolling the sail around the mast and dinghies with aftmainsheet systems reef by rolling the sail around the boom.

Slab Reefing

The method of sail reefing is to take a portion out of the mainsail by partially lowering the sail and then tying down a luff cringle and a leech cringle, leaving a fold of sail parallel to the foot, along the boom. Lower the mainsail until the required luff and leech cringles are level with the boom.

Re-cleat the halyard tying the luff cringle to the boom at the gooseneck and the leech cringle to the boom’s aft end. The fold is left hanging or tied up using reef points or lacing a reefing line through a row of cringles and secured to the boom at either end.

Roll Reefing

Aft sheeting enables you to reef the sail by rolling it around the boom with the gooseneck fitting having a square shank to prevent the boom rotating when reefed. To reef a dinghy sail when afloat, heave-to, lower the mainsail and have one crew at the tack and one at the clew. Tuck 6 inches of the leech around the boom then roll it, pulling the sail tight with each roll removing battens.

If you require the use the boom vang, make up a webbing reefing strop, or use the sail bag. Roll it in with the last two rolls and attach the vang to the strop then secure the boom to the gooseneck and hoist the sail ensuring the boom is not lower than parallel to the water.