Boat speed is traditionally defined as how fast your boat is moving with respect to the water. This is an important definition as I've seen boats running at top speed but unfo…rtunately for them they were caught in a strong current so the boat was not moving at all, or moving backward, with respect to the ground.
http://www.answers.com/Q/Where_is_the_beam_on_a_boat_measured
The SL Ratio is a simple formula for calculating displacement hull speed which is typically 1.34. 1  Velocity = (g * Length / 2 pi) ^ ½. 2  g = acceleration of gravity (32.15 ft/sec ^2)  Convert ft./sec. to Knots and the result is 1.34 * L^½.
http://www.psychosnail.com/boatingarticles/boathull/hullblockmeasures
For example if you have a boat that is 10 long (feet, meters, I don't care), and you throw something in the water at the front of the boat and notice it takes 1 second to get to the back of the boat, then your speed is 10/second. A paddle wheel you would see how fast it turns and compare it to other known speeds.
http://www.answers.com/Q/Where_is_the_beam_on_a_boat_measured
So a displacement boats theoretical hull speed is when the wave length is equal to the waterline length. The important thing here is the length of the wave is relative to the length of the boat. The SL Ratio is a simple formula for calculating displacement hull speed which is typically 1.34. 1  Velocity = (g * Length / 2 pi) ^ ½.  g = acceleration of gravity (32.15 ft/sec ^2)
http://www.psychosnail.com/boatingarticles/boathull/hullblockmeasures
At the widest point. Think of it this way; what is the smallest door this boat could fit through?. At the widest point. Think of it this way; what is the smallest door this boat could fit through?.
http://www.answers.com/Q/Where_is_the_beam_on_a_boat_measured
This means you need to pay attention to the beam, which is the measured width of the boat at its widest point. Wider ski boats and wakeboarding boats can mean more interior space available, which means more friends can hop aboard.
http://www.waterskimag.com/features/2010/01/20/how-to-buy-a-boat-what-you-need-to-know/
The beam is the width of the boat at its widest point.   If something is 'on the beam' it is to the side of the boat. Making the world better, one answer at a time.
http://www.answers.com/Q/Where_is_the_beam_on_a_boat_measured
The affect on performance is much more difficult to measure as the beam changes. The prime length for boats designed primarily for water skiing is about 20 feet or so, and a wider boat will often ride higher, thus displacing less water and providing a smaller wake.
http://www.waterskimag.com/features/2010/01/20/how-to-buy-a-boat-what-you-need-to-know/
The important thing here is the length of the wave is relative to the length of the boat. The SL Ratio is a simple formula for calculating displacement hull speed which is typically 1.34. Velocity = (g * Length / 2 pi) ^ ½.
http://www.psychosnail.com/boatingarticles/boathull/hullblockmeasures
The important thing here is the length of the wave is relative to the length of the boat. But of course, not all hulls are the same; depending on other factors like displacement and beam the boat may create a larger or smaller bow wave in proportion to its length.
http://www.psychosnail.com/boatingarticles/boathull/hullblockmeasures
what is a boat beam measurement
A boat beam measurement is a width of the boat at its widest point. A boat beam measurement is the measured width of the boat at its widest point.