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From: Nick Schade <schade_at_guillemot-kayaks.com>
subject: Re: [Paddlewise] 2ndry stability
Date: Mon, 20 Nov 2000 12:24:05 -0500
The advantage of starting with rigid hunk of meat is that all other 
conditions can be extrapolated from the response of the boat with the 
meat. It takes effort but by looking at information such as the slope 
of the curve and the area under the curve you can predict the 
response of the boat if the person does more than sit there like a 
rigid hunk of meat. The hunk of meat is just a useful non-subjective 
starting point.

I will admit that the best way for any individual to determine how a 
boat feels for him/herself is to get in the boat and see how the boat 
feels for him/herself. But there are a lot of boats out there and if 
you are looking for a new boat, you really don't want to have to try 
every one before choosing the best one for you. Knowledgeable 
inspection of stability curves is one way to reduce the field. Or if 
you have a design you want to change by some criteria, knowing what 
aspect of the stability curve represents that criteria will save a 
lot of time testing boats.

Nick

-- 


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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From: Harvey Golden <qayaq_at_pacifier.com>
subject: Re: [Paddlewise] 2ndry stability
Date: Mon, 20 Nov 2000 21:45:28 -0800
Nick wrote:
> The advantage of starting with rigid hunk of meat is that all other
> conditions can be extrapolated from the response of the boat with the
> meat. It takes effort but by looking at information such as the slope
> of the curve and the area under the curve you can predict the
> response of the boat if the person does more than sit there like a
> rigid hunk of meat. The hunk of meat is just a useful non-subjective
> starting point.

I've found through my experience (disclaimer non-pareil) that when I start
out in a new "tippy" kayak, that I am in fact the rigid hunk of meat you
mentioned, i.e., filled with tension, fear, and a sense of cold, miserable
impending doom. (The rigidity being a firmly-fastened set-up for the easiest
roll I know).   The "hunk-of-meat" lack of subjectivity is indeed valuable,
but when I am that hunk of meat, notions are quite objective, if not
blasphemous.   But seriously, the curves are indeed valuable (but do take
effort to read)  for a sense of what one is getting into, but stability can
be "learned", and for most paddlers, an unfavorable curve may simply keep
them from ever giving a fine boat a chance-- In a vessel so connected to
conditions and "captain's skills", stability is the other 1/3 of the factor
(and the key is to honing the captain's skills in harmony with ambient
conditions.)  Much like learning to ride a bike, (a skill I have mastered,
if I may brag), one can get-used-to a 'tippy' kayak with LOTS of patience
and practice.

Snip:
> I will admit that the best way for any individual to determine how a
> boat feels for him/herself is to get in the boat and see how the boat
> feels for him/herself. But there are a lot of boats out there and if
> you are looking for a new boat, you really don't want to have to try
> every one before choosing the best one for you. Knowledgeable
> inspection of stability curves is one way to reduce the field. Or if
> you have a design you want to change by some criteria, knowing what
> aspect of the stability curve represents that criteria will save a
> lot of time testing boats.

Yes, actually trying a kayak is best-- perhaps we'll all agree. With kayaks
whose curves exhibit low initial stability, the "trying" may be quite
trying, and negative opinions can be formed hastily (and/or for good reason
as well!)  Patience, again-- just as when bicycling was learned.  My
experience with very tippy kayaks comes from learning to use various
traditional kayak replicas-- one in particular was calculated as having -.03
meter/kilograms of righting moment with 1 degree of heel (as per Zimmerly's
calculations of the MacKenzie Delta Kayak CMC IV-D-1058, as published in
Eugene Arima's "Inuit Kayaks In Canada", 1987 (Pg. 165).

Had I read of this stability "fact" prior to 'wasting' so much time building
a replica of this kayak, I perhaps would've dismissed it as "impossible."
I've found the kayak very possible indeed,(though with practise,) and I
attribute my ability and love of this kayak to perserverence, patience, and
a large chunk of naivete regarding stability curves and their meanings
(e.g., The coyote never falls until he realizes he has over-stepped the
cliff)

A stability curve does say a lot-- certainly more than the holy but
insignificant measurement of "beam" does. (I have a 19" wide kayak that's
tippier than my 15-1/4" wide kayak. [Heresy!])   As Nick said, there is no
substitution to trying the kayak yourself.  He also says that it takes
effort and knowledge to use the curves.  I personally think that for the
average paddler-non-naval-architect, that the kayak could be paddled
extensively before the curves for the particular design can begin to make
practical sense.  (Lest we presume to understand the "curve" before we
really understand the kayak.)
    Harvey Golden
            www.pacifier.com/~qayaq



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From: Nick Schade <schade_at_guillemot-kayaks.com>
subject: Re: [Paddlewise] 2ndry stability
Date: Tue, 21 Nov 2000 10:08:42 -0500
As a guy who likes to design kayaks and tends to have an engineering 
bent, I place some value on the stability curve. But I don't feel I 
really know how a kayak handles until I've paddled it for a while. I 
don't think anyone should let a stability curve convince them to buy 
a boat they otherwise don't feel comfortable in or scare them away 
from a boat that they really like. If a lumberjack can stand up and 
run around on a half submerged log, most people should be able learn 
to stay upright in just about any kayak built.

  One value of knowing how to read a stability curve for the layman is 
to protect themselves from salesmen who hide behind simple, logical 
sounding phrases like: "This boat is wider than that one so is more 
stable." or "Because this boat is hard chined it has very good 
secondary stability."

Just knowing that stability is more complicated than width or chine 
shape will go a long way to making a more informed buyer. And maybe 
having the idea in the back of their mind that there may be a point 
in the stability where it changes from getting stiffer to getting 
looser, will make the buyer try to look for that point when they try 
a boat. They may or may not like the feeling, but at least they might 
think to look for it and form an opinion.

This knowledge can also help organize their thoughts about what it is 
they like about the boat. Instead of just "I like this boat and it is 
hard chined, therefore I like hard chined boats." it can be "I like 
the way this boat gets harder to tip before it goes all the way 
over." and look for boats which respond the same instead of just 
looking the same.

This could all be learned without ever looking at a stability curve, 
but learning about the curve can help understanding the factors 
involved.

Nick

At 9:45 PM -0800 11/20/00, Harvey Golden wrote:
>  <snip>
>
>A stability curve does say a lot-- certainly more than the holy but
>insignificant measurement of "beam" does. (I have a 19" wide kayak that's
>tippier than my 15-1/4" wide kayak. [Heresy!])   As Nick said, there is no
>substitution to trying the kayak yourself.  He also says that it takes
>effort and knowledge to use the curves.  I personally think that for the
>average paddler-non-naval-architect, that the kayak could be paddled
>extensively before the curves for the particular design can begin to make
>practical sense.  (Lest we presume to understand the "curve" before we
>really understand the kayak.)
>     Harvey Golden
>             www.pacifier.com/~qayaq
-- 


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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From: <JSpinner_at_aol.com>
subject: Re: [Paddlewise] 2ndry stability
Date: Tue, 21 Nov 2000 08:02:29 EST
In a message dated 11/21/00 12:26:47 AM, qayaq_at_pacifier.com writes:

<< In a vessel so connected to

conditions and "captain's skills", stability is the other 1/3 of the factor

(and the key is to honing the captain's skills in harmony with ambient

conditions.)  Much like learning to ride a bike, (a skill I have mastered,

if I may brag), one can get-used-to a 'tippy' kayak with LOTS of patience

and practice. >>

This is reassuring in that it says that if I hang in there with my boat I can 
get to the level of comfort I want. This is the fundamental reason for me 
reading as much of this as I have. The issues I've had with comfort in my 
boat have lead to extreme frustration on my part. Perhaps understanding how a 
23+" boat can be tippy will give me some tools to dealing with my own sense 
of being "filled with tension, fear, and a sense of cold, miserable impending 
doom."
    Thanks to all of you who have contributed. I don't always understand what 
you are saying but I get the drift.

Joan Spinner
Still working on her
CD Gulfstream

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