Re: [Paddlewise] chine and stability

Peter wrote:

,
>
> It might be that Navel Architecture does not consider and define
"secondary
> stability", as John points out, because it is not relevant to the vast
> majority of vessels.  Only in kayaks and perhaps smaller canoes can one
> even perceive such a phenomena since you more or less wear the kayak and
> control it by twists and shifts of your body.  In an ocean liner or
> freighter no one can feel secondary stability, it is a meaningless concept
> to the designer and the crew.  The same is true of sail boats, catamarans,
> fishing boats, etc.

First, I referred to the use of the term "secondary stability" and pointed
out that naval archirtects refer to the phenomenon as "overall stability".
Oveall stabilty applies to all boats.


>
> Why would an industry attempt to define an undetectable, meaningless
> phenomena with no commercial application?  It is only kayakers that
> perceive it, and they are unique.  And since it appears to be largely a
> perceived phenomenon not apparently detectable on the stability curves,
> hence the difficulty in measuring it.

It is neither undectable or meaningless and does have a commecial
application.


>
> It had not even occurred to me until Matt mentioned that it does not show
> up on the stability curves.


It does show up in the stabilty curves if you know what to look for.

>One would think that in a kayak with good
> secondary stability, the curves would get steeper toward the top, and ones
> with low secondary stability would have more rounded, flatter stability
> curves.  But this is not the case so it must largely be based on
perception
> of the kayaker.

Tell me what you perceive if not the forces acting on the boat.

(SNIP)

> It looks like if there is some measurable difference in secondary
stability
> in hull designs it is up to the kayaking community (designers,
> manufactures, etc.) to figure out how to define and measure it.
Apparently
> no one else is interested or even cares.  You may even have to measure the
> kayaker's skill and coordination, and factor that into the physical
> parameters of the hull.

People do care, C.J. Marchaj wrote an entire book on it. The IMO has done
extensive studies on it.

Cheers,

John Winters


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