Although you don't really have to know how your yacht works to enjoy a bareboat sailing charter, finding out how it works can be fascinating. Boat movement is a highly complex problem dealing with fluids of vastly different densities (air and water), and your bareboat operates on the confused interface between those two fluids.

To understand the physical principles involved, take a look at the basic forces that propel a sailing yacht: the motion of air over sails, and water over a centreboard or keel. When a yacht is sailing with the wind behind it, what's going on is pretty obvious: The sails act like a parachute out in front of the boat as the boat moves with the wind. But the dynamics get more interesting when your crew wants the yacht to sail at an angle to the wind.

Here's what happens when your bareboat sails upwind. First, look at the sail. When you pull in the mainsheet and fill the sail with wind, the sail creates a wing shape. That wing has an angle of attack to the wind flow. Just like your hand out a car window, see below ( or any airfoil at an angle of attack to the flow), the air over the back side of the sail goes faster then the air on the front side. The resulting difference in pressure creates lift - a force pushing the boat sideways and forward.

Hands out a car window at different angles to the wind feel different forces.

If the airflow over the sail was the only force involved, a sailing yacht would slip sideways as well as forward. A yacht, however, has wings above and below the water. When a yacht begins to move through the water, the underwater wing (keel) also creates an opposing force that, when combined with the sail force, moves a yacht forward.

Here's how: Like any other wing, the water passing over the back side of the keel goes faster than the water passing over the front side. The resulting difference in water pressure created by this flow of water pulls the boat forward and sideways - but in the opposite sideways direction of the sail force. The opposing sideways forces cancel each other out, as shown in the diagram below and the forward forces remain.

Flow over sail and keel and the resulting forward force.

Together, the forces of the wind on the sails and the water on the keel enables your bareboat to sail a close angle to the wind.

The fact that the physics involved are so complex can make sailing even more fun, because you, the sailor, can be a test pilot, fiddling with the various adjustments of sail shape and the boat's angle to the wind to squeeze even more performance out of your craft...or you can just go sailing.

All bare boat sailing yachts have sails

The main or mainsail sets along the back edge of the mast. See below. Some boats carry just the mainsail, while others have a headsail as well. The headsail sets in front of the mast. The most common headsail is a jib. Large jibs that overlap the mast are also known as genoas.

As you can probably guess, each part of a sail has a name... a number of these terms have been identified on the mainsail below.

• Head: The top corner of a sail
• Tack: The front, bottom corner of a sail
• Clew: The back, bottom corner of a sail
• Foot: The bottom edge of a sail
• Leech: The back edge of a sail
• Luff: The front edge of a sail
  Note:Like a few other words in the sailor's dictionary, this one has multiple meanings.
• Battens: Solid slats inserted into packets along a sails leech to help maintain its shape... Refer to the diagram below.
  

The clean lines of the mainsail reveal the fact that it is not an exact triangle: the outward curve of the leech adds and extra area of fabric, called the roach, which improves the sail's shape when it is filled with wind.

Furthermore, the sail is not perfectly flat; it has a tailored-in bulge, or draft, allowing it to assume the airfoil camber it needs to propel the boat into the wind.

To help preserve this camber and to keep the roach from flapping, the trailing edge is reinforced by battens - thin flexible strips of wood, plastic or fibreglass inserted into the batten pockets (see below). To keep the edges of the sail from raveling, extra layers of cloth, called tabling, are sewn along each edge.

A batten inserted into a straight pocket like the one at left must be tied in place by a line sewn into the leech of the sail - otherwise the batten will slip free while sailing.

The lock sleeve pocket allows the batten to be slipped in at an angle; it is held by a seam. Battens require gentle handling: dented or torn edges can tear the sail.

The shape of the jib (right) is maintained underway by the pull of its halyard, which draws the luff taut along the headstay, and by tension on the jibsheet attached to the clew. On a small jib like this, all the panels of sailcloth are horizontal. Larger jibs are miter-cut; a diagonal seam runs from clew to luff.

The panels above it are horizontal and those below it are vertical, a design that adds strength where the strain is greatest.

A sailing yacht has lots of rope

When a yacht is rigged (prepared and ready to go sailing), all the ropes used to raise and adjust the sails are part of the boat's running rigging, and each has its own name. Just to make things more confusing, the ropes on a sailboat are "properly" called lines, as in "Throw me a line."... Understanding what the lines do is more important than worrying about what they're called.

Just in case you're curious, here are the names of many lines and other equipment used to control the sails.

• Sheet: The primary line that adjusts the sail trim (the angle of the sail to the wind), usually referred to with the sail it adjusts (for example, mainsheet).
  
  
• Halyard: The rope running up the mast used to pull the sails up. Refer to figure
  
  
• Block: A pulley.
  
  
• Cleat: A fitting used to tie off or secure a line so that it doesn't slip.
  
  
• Cunningham: The control line system near the tack of a sail used to adjust luff tension.
  
  
• Outhaul: The control line system (mounted on the boom) used for controlling the tension of the foot of the mainsail.
  
  
• Traveller: A sail control system that can move the mainsheet attachment point on the boat from side to side.
  
  
• Boom vang: The control line system running from the boom to the base of the mast that tensions the leech of the mainsail.

Don't think that you have to memorise all these terms before stepping on a sailboat. Just look them over, put on your sunscreen, and go sailing.

Every sailing yacht has a mast

The mast is the vertical pole that supports the sails, made out of a strong, lightweight material such as wood or aluminium. On the bigger bare boat the mast is supported by an array of wires called the standing rigging. You can see an example of typical rigging component in the diagram in All sailboats have lots of rope

A boost up the mast

A bosun's chair is an essential piece of gear aboard any cruising yacht. Attached to the main halyard, it provides a reasonably safe and convenient means of going up the mast, either for urgent repairs or for periodic inspection and maintenance chores.

When going aloft, however, the safety belt alone should not be depended on for safety. The person to go up the mast should be the lightest member of your bareboat crew, while the two huskiest crewmen do the actual hoisting - one cranking the winch, the other tailing.

While going up, the person on the chair should always keep firm hand contact with some part of the mast or rigging. And remember!...an additional safety line should always be carried to secure aloft.

Except in extreme emergency, work aloft should be performed only on a calm day and preferably by a member of the charter operators staff... otherwise, the roll of the yacht can bang the crew member going up painfully against the shrouds, stays or the mast itself.

Preparing to go aloft, a crew member checks the shackle connecting the bosun's chair to the halyard to be certain the clevis pin is locked. The chair's safety belt has already been tightened around the waist.

Just before starting up, about 8 or 10 feet of line will be fastened to the rings at the top of the chair. Once aloft, this line is secured to nearby rigging to prevent a fall if the halyard parts.

As one crewman cranks the winch and the other keeps a steady strain on the end of the halyard, the climber is slowly hoisted up the mast.

1. When the work area is reached, the life line is tied to the spreader and one leg is hooked over to steady.
   
   
2. On deck, a crewman secures the halyard around its cleat. When the work has been completed, the climber will cast off the safety line and swing back to the mast. On deck, one crewman will then ease off on the halyard slowly, while his partner guides the line to keep its turns aligned on the winch.