Re: [Paddlewise] paddlefloat photo

From: Mike McNally <mmcnally3_at_prodigy.net>
Date: Sun, 23 Dec 2001 16:39:17 -0600
What water knows...  I think you all are missing something which can be
clearly seen from a proper free body diagram (let's hope I can draw one).  

                                Wt-W&Y (wt of water & you & yer stuff)
  
                                  |
                                  |
                                  |
                                  |
                                  |
                                  |
                                  |
                                  |
                                  V  
          -------------------------------------------------         
                 ^                ^                ^
                 |                |                |
                 |<- - - - - - - >|                |
                 |       dx       |                |
                                  |                 
                S_L               |               S_R (sponson, right)
                                  |                  
                                  |                  
                                  |                 
                                  |                 
 
                                 B_E (bouancy from ends)

These forces are all algebraic functions varing in both magnitude and 
direction realitive to the angle of tip (ex tip gives slosh & shifts
center of mass).  But, the basic geometry tells us a few things.  The
difference between interior and exterior sponsons is the distance dx,
where the turning moment from force S_L=(in the simplest case) F*dx.

The hull stability forces from the hull design are largely made
null by the evacution of air from the hull, hence the lack of stability,
but now that we are adding more air and particulary adding it in a
manner in which the dist dx is set (superior to what a seasock does), we 
are increasing these previously insignificant forces of stability
provided by the hull.  

Catch 22 is: we know the significant quantity of air in the ends isn't
doing much for us, stability wise, so we are going to have to very
significantly replace water with air.  The design as initially described
did not seem to be doing this, so I don't disagree with other posters in
the sense that the forces I'm discussing here wouldn't provide much
change in stability, in that particular design.  But, with a more
significant interior sponson it would provide the flooded state
stability we are looking for.  I think in the future we will see this
design incorporated in many boats.  

With the completion of this post I do hereby declare myself the
sovereign pope of the church of the interior sponson.  You may not here
from me for a while because I'm feeling an almost unquenchable desire to
post on rec.boats.paddle.  gotta go

-- 
Mike McNally		mmcnally3_at_prodigy.net

You are capable of planning your future.

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Received on Sun Dec 23 2001 - 17:43:30 PST

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