The Physics of Sailing

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Sailing is a skill and an art which requires much time, practice and understanding to master. One may not understand the physics behind driving a car, however one can understand the basic principals behind using a car: press on the accelerator and the car will go faster; press on the breaks and the car will stop; turn the steering wheel left and the car will turn left. The same mentality applies in sailing, although in order to understand the physics behind sailing one must have a general knowledge of sailing terminology and how a sailboat is made.

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        Let us start by learning the different parts of the boat. The shell of the boat is called the hull; the large, vertical pole is known as the mast. The mast is held in place with two shrouds and a forestay (jib stay). Most boats, with a few exceptions, have one, two or three sails. Every sailboat has a main sail; this is the larger sail which is always directly attached behind the mast - it is controlled by the main sheet. The jib sail is the small sail in front of the mast; it can be adjusted with the jib Sheets. The third sail is called a spin sail (not shown on the picture below) and is used by advanced sailors to increase the boat’s speed in specific instances.

Sailboats don’t have a steering wheel; instead they have a rudder which is controlled by a tiller. When the tiller is pushed to the right, the rudder will move to the left causing the boat to turn left. Large boats have a keel, while small boats have either a centerboard (cannot be physically removed from the boat) or a daggerboard (can be easily removed from the boat). Regardless of the type of boat, these sharp blades project from the bottom of the boat into the water and stop slide slipping – a phenomenon that will be explained later on.  The front of the boat is called the bow while the back, or aft, is the called stern. The right side of the boat is referred to as the starboard side; the left is called the port side.

                                                                                                   

Points of Sail  

        

After covering the essential terms of sailing, it’s time to learn how a sailboat works. As mentioned earlier, a sailboat is powered by the wind. Before getting too technical, let us get an idea of how a boat functions. On a sailboat there is no motor or steering wheel. Therefore, the sails must be adjusted or trimmed according to the boats angle or position to the wind. There are of course many other adjustments that should be made, (centerboard, mast rake, weight...etc) but for now we will only discuss the appropriate sail shape relevant to the boats position to the wind.

        The first thing every sailor must always know before heading out onto the water is where the wind is coming from. Without this crucial piece of knowledge, it would be impossible to start sailing. On the picture below, the wind is blowing straight down the lake. This concept may be difficult to grasp, but a clear way to think about it would be to imagine the wind as a gigantic fan blowing in a straight line.

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        There are five different points of sail. In other words, there are five different positions the sailboat can be in. The first is when the bow of the sailboat is facing directly into the wind. This is known as being stuck in Irons or the No Go Zone. Both sails, the main and jib sail, would simply luff (a term used in sailing to describe sails that are flapping). Since the boat does not get propelled forward in this case, it would most often drift down wind. Therefore, since a boat cannot travel upwind it has to “zig-zag” its ...

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