(no subject)

Nick wrote about planing:
>>>>>I like the definition where the boat lifts up and drag is reduced. If
a long boat can do this a low speed or a short boat can do this with
an external power source, so be it. Of course since I am not the
arbiter of the English language I guess it is not my call.<<<<<<

I like the lifts up part (which is Savitsky's definition) but drag is not
reduced when planning. Only its rate of increase with increasing speed is
reduced. Or am I misusing the term drag to mean all the energy required to
over come all the "drag" forces including gravity and you are referring to
only frictional drag?

I think someone said earlier that a boat gets more efficient when it is
planing. That is not true (unless we are defining "efficient" differently
too). A displacement boat of the same weight will go from point A to point B
a whole lot more efficiently than one that is planing. The planing boat is
using a whole lot more energy to constantly hold itself up against gravity
than it ever can get back by reducing its wetted surface when it is
planing). In other words, the planing boat will get there quicker but its
gas tank will be emptier when it arrives.

It seems to me that surfing meets Savitsky's (raising the CG) definition of
planing. The CG is higher than it would have been were it not for the motion
of the object. Why quibble about the power source driving the object?

Matt Broze
http://www.marinerkayaks.com


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