How does a large ship sail against the wind?

Question

I hope this question isn't dumb, but I can't figure it out. I've never seen a real sailboat or a ship so I have no clue how they are able to sail into the wind.

Answer 1

Sailors use a process called tacking where they point the bow of the boat at a 45 degree angle to the wind and sail off to one direction, then eventually make a 90 degree turn to the direction.  The on coming wind pushes the boat away from the intended straight line, but forward progress is made.  http://www.recsports.ufl.edu/ContentMana...

Answer 2

The Captain's answer was excellent.  The only thing I would add is how the sail pulls the boat somewhat towards the wind.

The grand old sailing ships were "square riggers"  they mostly ran before the wind.  In other words, the wind was behind the ship and "blew" the ship in the same general directions the wind was going.

The modern "sloop" rig sail can be pushed too, but to sail towards the wind, the sail becomes an airfoil just like an airplane wing standing vertically instead of horrizontally.  The physics of the airfoil create lift.  With the sail being vertical, the lift is directed forward, horrizontal to the surface of the water.  The sail is allowed to swing in such a way as to direct the lift more towards the the source of the wind.  The boat can sail efficiently about 45 degrees off the wind.  This is why one must tack or zig zag 45 degrees off the source to either side and eventually move a net gain exactly at the wind.  The boat will have travelled twice as far when the destination is exactly where the wind is coming from.

Answer 3

To really understand the dynamics of what happens when a sailboat sails against the wind... you need to think back on those boring 5th grade math and science lessons that involved "motion... gravity, force and inertia".  

Remember the phrase "for every force there is an opposing force" ?  Well, that is what is happening when a sailboat is sailing against the wind... Sailboats not only have "sails", they also have a "keel" and a "rudder".  The "keel" (though size, length, depth varies) is a solid straight board that runs down the center and underneath the boat from bow to stern (or front to back).  Most keels on deep water, ocean passage vessels are very large... On a typical recreational sailboat, these keels often extend down from the bottom of the boat 4, 5, 6 or more feet.  The "keel's" purpose is to 1. by design - to keep the boat from moving sideways and 2. by weight - to keep the boat from blowing over on its side.

As a result, the keel keeps your vessel upright and moving in a straight forward motion. For example: if you try to cut water with a huge butcher knife, you can't even feel the knife go through the water... but turn the knife sideways and make a sweeping motion through the water, and you feel heavy resistance.  The keel works in the same manner.  

In a sail boat a "rudder" is used to actually steer the boat in the direction you want it to go... The "keel" againt the water is that opposing force...  So... in "tacking" the sail (or sails) are angled to catch the wind in such a way they re-direct the winds' flow (you have certainly experienced this when you stick your hand out your car window).  So, now if the wind can not blow your boat over... it trys to blow it down wind - Since you have angled your sails, the sails are now pulling your boat "off wind" at an angle.  Using your steering wheel - you turn the rudder and thus the boat to a point "off wind" until you begin to feel your boat moving forward... this is because the keel is using the resistance in the water to keep the vessel moving (this is now the opposing force to the wind).

With a bit of steering (changing the rudder, and thus direction of the boat, you will actual "feel" the point where a perfect balance (and thus speed) has been obtained... at this point, you steer "off" the wind at about a 45 degree angle to a point where, you reverse your sale angle and rudder, and steer "off the wind in the other direction... you are now "Zig - Zagging"

across the lake to get to the other side.

Sailing is fun... exciting... I hope you give it a try... Take a lesson... see what you think!

Answer 4

I'll draw you a picture in phy.

Answer 5

Put the Capt. and Joe together and you have a very good answer. My boat(sloop) and in fact, many can sail much closer than 45 degrees to the wind though. Having said that...you can get a greater understanding of lift and sails(a verticle airfoil or wing) and Airplane wings by looking up Bernouli's Principle. It's a negative air pressure/positive air pressure thing....on opposite sides of a foil whether verticle(boat) or horizontal(plane). You see...technically, wings are pulled up, not pushed up. Sails are pulled ahead by the negative pressure, not pushed by the positive.  Also brush up on Newton's three laws of motion.

I think the three of us have now given you what you need.

Cheers.