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SJ23 Hull Speed






As Eric Johnson has told us, the theoretical maximum Hull Speed for a 
displacement hull is:

		1.34 x sqrt(LWL)

where:     The speed is in knots and the LWL is in feet.  

For those that might not understand what this is all about let me quote from 
the U.S. Coast Guard Auxiliary's book "Sailing and Seamanship":

	"Displacement boats generally cannot go faster than a certain speed which is 
closely related to the boat's waterline length.  You can figure your boat's 
maximum displacement speed - called its hull speed - quite easily:  take the 
square root of the boat's length at the waterline (often known as its LWL) in 
feet, and multiply it by 1.34, to find the boat's approximate maximum speed in 
nautical miles per hour" (knots).

The LWL for a SJ23 is 20' 4".  So for a SJ23 the theoretical Hull Speed = 1.34 
x 4.51 = 6.04 knots (or 6.96 mph).

One of the interesting things about this is that with a 5hp outboard motor on 
my SJ23, my GPS tells me that I am getting about 5 knots speed in still water. 
 Given the above limit of about 6 knots, I would not be able to get more than 
about 1 additional knot of speed even if I were to put a 50hp motor on my 
boat.  On the other hand, if I were fighting a head wind then more power would 
probably help.

Of course if you are racing my SJ23 it is at least several time faster than 
this so you might as well give up before you even start!

Art Brown

San Juan 23 Internet Fleet:   http://www.geocities.com/Yosemite/Trails/5492/
This list sponsored by PEAK,Inc., ISP and Education Center, Corvallis, Oregon


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