Re: [Paddlewise] Planing

  

Peter Rathmann wrote:

  Nick Schade wrote:
  >
  > At 9:36 AM -0500 1/17/02, John Winters wrote:

  > >However, Dr. Savitsky pointed out that
  > >the rise in CG during surfing could occur but you could not call
  it planing

  I ve never seen a definition of planing that specified where the
  propulsion came from.  Whether it's from a following wind in a
  sailboat,
  a following wave in a surfing kayak, a towline pulling a skiff, or a
  propellor pushing a motorboat, I'd consider them all to be planing if
  their hulls rose in the water due to their movement.
   

I'm forgetting who has written what here in this thread, but I am finding
the level of discussion, and all the twists and turns it's taken
(including the square footed slugs) to be extremely well thought out and
presented.  There was a fundamental disconnect in the use of the term
planing initially and it's getting sorted out.  If I may, could I throw
out two questions/2 cents/observations ?

1.    I seem to remember that "planing" occurred when a displacement hull
made a transition to a planing hull and that transition corresponded to a
discontinuity in the speed power curve ( y=f(x) cubed) sorry I can't put
exponents in here.  Is this wrong?  The VCG would also rise during the
transition.  Can't argue with that.

This past summer I was paddling the channels in the bay behind Avalon,
New Jersey.  I noticed that the boats that went past my wife and I were
mostly thoughtful and throttled back, came down off plane until they were
past us and then fired it up again.  The wakes from the planers and non
planers were very different with planers being easier to handle.  What!
you say, well, it suprised me also!  Some of the larger displacement
boats (sport fishers) threw out big wakes when off plane, with similar
sized boats up on plane putting out much smaller waves.  Does this mean
there is noticeably less energy going into wave formation?  I think the
answer is yes because when the hull is up on a plane, the hull shape is
much different with unique wave patterns itself.  Therefore, if there is
a big transition in wave formation from displacement to planing it seems
there should be a discontinuity or transition in the speed power curve. 
And that is where planing starts.  I sure wish I still had my old texts
here so I wouldn't have to do this by memory.

2.    Way back when the discussion started, the question of "planing" as
it was used to describe "climbing the bow wave"  has had me thinking. 
The energy you impart while paddling overcomes both frictional
resistance, and form related resistance.  Form resistance  manifests
itself in all the waves moving away from the hull.  As I remember, there
are 4 points along the hull where the waves crests are generated, bow,
fore and aft transitions to max beam and the stern.  There's standing
wave crests at the bow and probably near the cockpit, the faster you
paddle, the bigger the distance from crest to trough of this standing
wave will be, and from the cockpit it would look like the bow is climbing
the standing wave.  By the time you are up to max hull speed (either your
or the boats physical limits) I'll bet that wave is pretty steep.  Does
this seem a likely explanation for what people were talking about?  Fine
hulls would have a noticably smaller wave height, causing the observation
that that hull isn't "planing" .  Another thought, your own bow to
cockpit standing wave will always look bigger 'cause of your perspective!

John Blackburn
 
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