Definition of Planing

It is exactly the same. I spent a good number of years of my wasted youth on a surfboard and the board responds exactly the same as the boat. Too far forward a cg is not as fast as properly trimmed, and too far back is slower also. Trimming the board for speed is critical and surfers do it naturally as they learn the sport. The board has an angle of trim relative to the wave, but the weight of the surfer riding "down" the wave is what provides the propulsive force and it all behaves in a similar manner to a boat, the only difference is the fact that the wave is a "moving hill" that you are riding down.

For a given angle to the wave (which defines the speed) there is an optimum trim location. At extreme angles a surfer can go forward, toward the nose, and the rocker in the board will suck down the back and keep the nose from submerging, but that's an extreme case and it doesn't relate directly to proper trim for the speed you are traveling.

 

so a falling weight is is not a source if energy ???

no energy input for forward motion

Yes there is . the surfers is applying energy by using his weight he is able to trim the board by moving his weight to different parts of the board ! with out his weight the movement (Planning ) would not happen as much if it was just the weight of only the board !!the weight of the board along is insufficient to make the board surf or plane continuously and successfully for any great distance ,the speed of the wave will always out run it but with the gravitational weight of the surfer which is applying energy its able to overcome the wave !

 

A long board will move with a tiny wave without planing. It is then in semi-displacement mode, as some call it. Using a surfboard as an example does not provide a definition or an explanation of the exact transition point.

 

I am pretty certain that the pressure wave that a boat generates and has to climb over has a maximum speed of about 25 MPH and a boat will leave behind that wave when greater power and speed is applied to the boat.
Sea surf can get along about that same speed but other waves such as made by earthquakes are much faster. The maximum benefit for an economic boat crusing speed would be about 25 - 30 MPH. Then dynamic left helps extra speed. Naturaly that is just my humble opinion.

 

You must be talking about some specific boat, I presume?

 

Not necessarily I would say what has been said is pretty close to what I experience if I take off slowly !!
In most all smaller runabouts and even ordinary smaller power boats up to 25 feet or so its close give or take a couple of mph !!.
The maximum benefit for an economic boat cruising speed would be about 25 - 30 MPH. Then dynamic left helps extra speed. definitely !!

 

Come on guys, you know very well that it will depend on boat size, weight, shape, CoG position and propulsion type, and cannot be taken as a general rule. Even two boats of same size can have very different minimum-consumption speeds:

An Azimut 40, for example, has it at around 29 kts: http://www.nauticalweb.com/boatshow/azimut/40eng.htm

An Azimut 43s, though having a bigger LOA, has it at around 20 kts: http://www.nauticalweb.com/boatshow/azimut/43seng.htm

A Pershing 54 has it at at 36 kts, and again at 58 kts: http://www.boattest.com/Partners/Partner-Main.aspx?lp_id=464&t=BOAT-TEST&Videoid=145&p=0&s=

So no such fixed optimum speed exists.