Re: [Paddlewise] RE:Secondary stability

From: Nick Schade <schade_at_guillemot-kayaks.com>
Date: Wed, 22 Nov 2000 12:15:45 -0500
I think there is value in a quantifiable parameter. I will say that 
it is only valuable if you understand the parameter and how it 
relates to boats you have paddled. But more important is finding a 
way to let people look at the data available and come to conclusions 
that will be consistent.

I agree that it might not be possible to boil this down to one or 
even several numbers. However, finding some points on the curve which 
are significant is possible. For example, I think the presence of a 
inflection point is probably significant. Where that inflection point 
is located ( angle, relation to maximum of the curve), what the curve 
does on either side of it and the relative slope at that point are 
all likely to be noticeable to greater and lesser degrees.

I don't disagree with Peter that some on-the-water testing would help 
out understanding. But before you test, it helps to have a hypothesis 
you are attempting to verify. Otherwise you are just out in the 
middle of a lake rocking back and forth - fun in its own right but 
not necessarily very enlightening.

It would probably be interesting to strap an inclinometer to the deck 
and start wiggling your hips. I expect you could learn something you 
don't know now.

Nick



At 4:12 PM -0500 11/21/00, 735769 wrote:
>Peter wrote;
><snip>
>>  I do not claim to be anykind of an expert on hull design but I have spent
>>  many years analyzing aircraft stability and control curves know well how
>to
>>  read a chart and its derivatives, you have to look at how the changes
>>  affect the "human factors", hard to predict from purely a mathematical
>>  stand point.
>>  I would suggest someone get together a group of paddlers of various skill
>>  levels and compare perceived secondary stability with all kinds of curve
>>  properties in various hull designs.  If you can find any kind of
>>  correlation (which you may well not find) then we might have a working
>>  definition, and something to look for in a cure (maybe an article idea for
>>  SK mag?).  As one of my engineering professors used to say, one simple
>>  experiment is worth a thousand expert opinions.
>
>Unless I read Nick incorrectly, he (and I) would rather see quantifiable
>physical parameters that would allow a paddler to get an idea of how a boat
>might feel. I get the feeling that some people want a definition in human
>terms rather than physical terms. I do not believe this would ever have  a
>lot of value since such information only tells us what some people think.
>
>With a quantifiable (and reproducible) method of presenting stability
>characteristics germane to the paddling experience a paddler could paddle
>several boats, compare their curves and from that discover how the curve
>applies to his perceptions.

-- 


Nick Schade
Guillemot Kayaks
824 Thompson St, Suite I
Glastonbury, CT 06033
(860) 659-8847

Schade_at_guillemot-kayaks.com
http://www.guillemot-kayaks.com/

>>>>"It's not just Art, It's a Craft!"<<<<

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Received on Wed Nov 22 2000 - 10:10:10 PST

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