How the yacht sails
Sailing Course Thailand
Points of sail – sailing course Thailand
Boats can sail in almost any direction except straight towards the wind. Sails harness the force of the wind so that the speed of the airflow against the sail provides lift. As with an aero plane wing, the combination of increased air pressure on the inner side of the sail and suction on the outer surface pulls the boat in the direction of the ‘lift’. Altering the angle of the sails, referred to as sail trim, will adjust the direction of the boat, allowing a course to be steered.
Close Hauled- sailing course Thailand
Sailing close-hauled during the sailing course Thailand, or beating, requires dexterity as steering is influenced by wind direction; slight wind shifts will affect the flow of air against the sails so the course to steer needs to be precise. Too close to the wind and the sails will stall, too far off will slow the boat down.
When reaching the wind blows across the beam to fill the sails. The angle of the wind no longer determines the course so sailing on a reach requires less precision than when sailing close-hauled. This point of sailing is a good start for beginners as it can also be fast and exciting, but the sails are eased out and heel is decreased so the boat becomes easier to handle. Sailing on a reach with the wind forward of the beam is known as close reaching. When the wind is aft of the beam it is termed broad reaching.
It is possible to run before the wind with the head sail and mainsail eased out to opposite sides. A whisker pole attached to the mast to hold the head sail out to one side and the main sail boom eased out to the other.This is known as goose winged. Running goose winged can present problems to auto pilots and can increase the potential of an accidental gybe which may damage your rigg. A spinnaker is commonly used in light to moderate winds only and is hard to handle without experience, especially with short handed. For short handed crews is a asymmetrical spinnaker recommended were you will not need the whisker pole. Some cruising sailors prefer two head sails winged out to sail long distances with the trade winds.
Tacking / Beating
Beating to windward describes the zig-zag route that must be taken if a boat’s course lies in the direction of the wind. Changing course in this way is known as a tack. On a starboard tack, the wind is blowing on the starboard side while the main boom lies on the port side. On a port tack, the reverse applies. To tack, the boat must be turned into the wind while the head sail sheets are let go. As the bow moves through the wind, the sails flap across to the other side and the head sail is then sheeted in. When sailing close-hauled the main sheet, which controls the mainsail can usually remain cleated, and will move across easily, needing only slight trimming. Some yachts have a self tacking head sail which changes sides during a tack the same way as the main sail. The self tacking head sail needs to be therefore on a boom. The advantages are that head and main sail changing fast there sides and readjusting is not necessary. You will sail on the exact same angle towards the wind as on your previous tack. When doing the – sailing course Thailand we will practice the tacking while being at sea.
When the boat is running before the wind, a change of course requires the crew to gybe. This action is opposite to the tack as the stern (not the bow) is now turning through the wind. Gybes can happen suddenly if the boom slams uncontrolled to the other side (known as an ‘accidental gybe’) therefore the main sheet should be fully hauled in and gently let out as the boom moves across and the wind hits the sail. The head sail is then eased out and pulled in from the other side. This is done during the sailing course Thailand.
Spars, such as the whisker pole, can be supported by lines that stop upward movement (up haul), lines that stop downward movement (down haul), or lines that set a fore-and-aft position (guy line). In heavy weather a preventer can be rigged from the end of the boom to the bow to prevent accidental gybing. Telltales (short lengths of ribbon that are often attached to both sides of a sail) indicate airflow across the sails; when the telltales are flying straight aft on both sides of the sail, it is correctly trimmed. Reefing is required to reduce mainsail area in the case of an anticipated change in weather.
The relationship between the course, the angle of the sails and the wind direction require the sails to be adjusted, or trimmed. The possible angles and degree of sail trim in relation to the wind direction are known as the points of sailing, termed as head-to-wind, close-hauled, reaching, broad-reaching and running.
Head-to-wind there is no forward drive; the bows usually need to be turned at least 45 degrees away from the wind to catch it and achieve propulsion. The further the boat’s bows are turned away from the wind, the more the sails need to be eased out. Physics can explain these principles fully, however once on the water, the way airflow acts against the sails and the effects of sail trim will be seen.
When the wind and waves start to pick up it is a good idea to reduce sail area. The decision to reef should be made early, as strong winds can suddenly hit the sails, threatening the safety of crew and boat. The easiest position for reefing is with the boat turned into the wind. The mainsail should be positioned away from the wind (leeward) and the headsail sheeted into the wind (windward). This position is termed as hove-to and prevents forward motion. Though the boat is steady, it will roll sideways. The method of reefing varies from boat to boat, however slab reefing or roller reefing are most commonly used.
The kicking strap is eased and the topping lift is tensioned to take the strain off the boom once the sail luff (the leading edge of the sail) is freed. The main halyard is loosened and the sail slightly dropped so the slackened sail can then be flaked down on top of the boom. The luff cringle (metal rope loop) is hooked over the reefing horn, while the leech cringle is pulled down to the end of the boom. The sail can then be hoisted, the kicking strap adjusted and the topping lift eased, while a line is threaded through the loose sail and secured around the boom.
In this method of reefing the sail is rolled around a rotating boom (a mainsail with conventional stiffening battens cannot be reefed in this way). When roller reefing the sail will not set as well as when slab reefing but it is a more controllable system and more sail area can be reduced. The kicking strap must be taken off and the topping lift tensioned to free the sail luff, while the sail is eased down and the reefing handle turned to rotate the boom. The sail leech should be pulled tight as the sail must be rolled evenly to prevent the sail luff creasing. The topping lift is then eased out, however the kicking strap cannot be secured as the sail is wound around the boom.
Lively seas make for exciting sailing however preparation above and below deck will keep it safe. Objects need to be strapped down so they don’t fly around causing hazards, and hatches need to be secured. It is a good idea to prepare food early to maintain the crew’s stamina and endurance and anyone on deck should wear a life jacket and safety harness. If sailing close to shore and a strong onshore wind is blowing the boat towards it (lee shore), it is safer to alter course to a different destination or stay put at sea until the blow passes.
During the sailing course Thailand most of the mentioned points will be demonstrated to give you the practical side.