[Paddlewise] Stability

Nick an I have been working off list to sort out why we get different 
numbers and this is my report. If Nick sees any errors I hope he will jump 
in.

First, I used a fixed CG relative to the waterline because I felt I wanted 
as many parameters constant as possible and wanted the effect to be that of 
the shape only. Nick set the CG relative to the bottom of the boat which is 
what one normally does when calculating stability.  Who is right? We both 
are. Depends upon your objective.

Second, Nick's "V" bottom had the chine below the waterline. I placed my 
chine close to the waterline. Nick's version is more typical of kayaks. For 
Nick's the in and out wedges of area do not change much with heel because 
the section shape near the waterline is almost identical to the box shape 
near the waterline. For mine the change is more noticeable because the in 
and out wedges on the "V" bottom differ more at small angles of heel. Mine 
was extreme because I wanted to discover if shape had an effect and not the 
relative effects of specific shapes. Since the box boat was extreme and not 
typical of kayaks I wanted to use another extreme and untypical shape for 
comparison. Who is right? We both are. Depends upon what you are trying to 
discover.

Nick was gracious enough to send me his raw data which is below for the two 
shapes in question at angles of heel of 0.2,and 4 degrees. You can see where 
he is coming from.

      Box
      0
      0.011
      0.022


      V Bottom
      0
      0.011
      0.022


This all reminds me of the story about the two priests arguing over whether 
it is appropriate to smoke while praying. One says it is and the other says 
it isn't. So they appeal to the Pope for an answer and are surprised when 
the Pope agrees with both of them. So one priest asks the other, "What did 
you ask his holiness? To which the other priest replies "I asked if it was 
acceptable to smoke while praying and the pope responded that it wasn't 
because you should devote your full concentration on the act of prayer."

"What did you ask him.?"

"I asked if it was acceptable to pray while smoking and his holiness replied 
that it was always acceptable to pray"

Sometimes the answers we get depend upon how we ask the question.

Is that a fair assessment, Nick?

Cheers

John Winters
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