Do you sail faster with the wind or across?

Question

Im going a science assignment on this question but i dont really understand all the technical stuff on it. could someone please explain the reason in a simpler way..

Answer 1

ok say your in an 80s model truck

if the wind is blowing at the truck from the front its like bushind a sheet of 4ft by 8ft piece of plywood at what ever speed your going.

if the wind is blowing from behind you more than 15 miles per hour its like having a 4ft by 8ft sail trying to help you move faster but there is always going to be some wind in front of you pushing back

Answer 2

Lots of possible variables here, but, generally speaking, in a modern sloop rigged sailboat you will sail faster across the wind. Sailing across the wind, known as "reaching" in sailing terms,  allows one to be able to align your sails so they act much as a plane's wing does. But instead of lifting up, your vertical sail/wing is developing forward thrust from the same Bernoulli(sp?) principle. Your literally flying sideways. The wind forces generated in this manner far exceed the plain pushing power of the wind against a sail going downwind. Going downwind you can only sail nearly as fast as the wind.

Then there is also the matter of apparent wind. As you begin to move forward, you begin to feel the effect of your forward motion as apparent wind, just as you would feel on bicycle when taking off from a stop. When going 10 mph downwind in a 10 mph breeze on the bike, you aren't going to feel any apparent wind. Going 10 mph upwind in the same 10mph breeze would feel like a 20mph breeze to you. Biking 10mph across the breeze will feel like  15 mph apparent wind coming from a point halfway between forward and the windward side. Sailing across the breeze, your sail feels the same thing you do, 15 mph of apparent wind in a 10mph breeze.

More apparent wind = more boat speed, to a point. The closer you point toward the wind, the more apparent wind, but the practical limits of sailing into the wind limit you to approx 45 degrees off the wind direction. You can't sail directly at the wind, but into it about 45 degrees. Once you start pointing closer to the wind than (sailing directly across it), the apparent wind increases but actual speed over ground starts to diminish. Likewise, pointing downwind will automatically decrease apparent wind, (remember the bicycle)

It's not easy to understand, and harder to explain it, but long story short, the sailboat's fastest point of sail is usually directly across true wind, although it will feel like you are headed somewhat into the apparent wind.

Answer 3

The fastest point of sail is a broad reach.

Answer 4

Your science teacher has given you a trick question...

If you are sailing directly with the wind... you will make greater "time"... As you have already learned, the shortest distance between two points is a straight line... and therefore, you will get to your destination sooner, and thus... you will have made the trip faster...

However, when a sailing vessel is "tacking" (or sailing cross wind) the vessel itself is traveling much faster across the water then when it is sailing down wind... but it will take longer to reach its destination - because it is not traveling in a straight line... in fact it has to "zig zag" back and forth across that straight line - many times.  

The dynamics are the same as in throwing a ball straight at its target... unless your a professional base ball pitcher, you might get the ball to reach 70 mph... now, put the ball on the end of a string... twirl it around your head, and you can get the ball to travel twice the speed... In a sail boat, the cross wind rudder against the water acts as your string... as the water holds the rudder (and thus your vessel) in a constant angle against the opposing force of the wind.

Wha La! You feel like your flying man... and you are indeed going much faster...  but, you are simply not going in a straight line...