Re: [Paddlewise] Hull speed and Olympic Kayaks

From: "Fischbein, Mike" <mike.fischbein_at_gs.com>
To: <michaeldaly_at_home.com>
Sent: Thursday, September 28, 2000 11:13 AM
Subject: [Paddlewise] Hull speed and Olympic Kayaks


> A problem with your analysis lies in your assumptions.
> 

Not my assumptions - they're others' assumptions.  
Folks were stating things about the traditional formula
and I said (paraphrasing) "it isn't a speed limit... watch 
the Olympics in a couple of weeks to see paddlers exceed it."

> The 1.43*sqrt(LWL ft) = hull speed (kts) is a thumbrule,
> not an absolute.  It's an average, based on typical
> displacement hull forms.  

Actually, it's based on the relationship of wavelength to 
velocity of waves:

 wavelength = 2*pi* velocity squared/ g  (g = acc. of gravity)

which is 0.557 * velocity squared,  for velocity in knots.

Swapping the equation around gives:

 velocity = 1.34 * sqrt(wavelength)

(See my memory is bad.  I wrote and figured with 1.43 instead of
1.34... <blush> numbers don't change much, though.)

If the wavelength is equal to the LWL, you can substitute.

My point was to show that the rule has limited applicability
in the case of kayaks, as can be seen in the paddlers speeds.    

> I, also, was unable to find actual specs on a K1; but
> the ICF rules have a max length for K1 of 520cm and
> a minimum beam of 51cm, which is pretty close to
> ten for a L/B ratio for the real boats.
> 

All I could find was that and the minimum weight limit of 12kg.
I figured there must be more restrictions than that.


Mike


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