Re: [Paddlewise] chine and stability

On Thu 16 Nov 2000, Matt Broze wrote:

> Imagine we make two ramps in the shape of a stability curve to roll a ball
> bearing up and over. The front side of the curves are identical but one then
> drops straight down to zero at its peak and the other falls away like most
> static stability curves do. Question: Which ball will reach the (ground)
> zero point on the back side the quickest (if you were to roll it over both
> ramps equally hard and with plenty of momentum to easily make it over the
> hump)?
> 
> I don't believe the path (through space) the two balls would take would be
> any different with these two ramps. 


Let's imagine me running down the stairs of a twelve story building and somebody
else simply stepping of the edge from the roof.  Your right.  The path would
not be that different.  But what's your point?
 
 
> That's my point, how many of us can sense the stability of the backside once
> our momentum has put us there and into the virtual freefall we call a
> capsize.


Let's say I take a tippy boat and lean my torso out close to the going over pt and
snap my head and shoulders to create a capsize, and then catch it with a high
brace.  Now I do the same with a very stable boat.  Which is more likely to cause
a shoulder injury?  I'm guessing the more stable boat would be more likely to cause
an injury because of the hull righting force being all used up on the front side 
of the curve.

I would have to add that while the discussion on this thread (at least to my mind)
tends to indicate that tippier boats would have less violent and more frequent
instability events it's impossible to say that shoulder injury would be more 
likely as a result of the force or the frequency of events (ie I am not saying
stable boats cause injuries).  This would depend on the paddler and the waters
paddled.  I probably should have left injury out of the discussion, but thought
it might serve to add meaning to the stability forces.  There are no meaningless
or insignificant stability forces, there are only trade-offs.

I could be wrong about all this as I am not a boat designer.  I do have an 
engineering degree so I feel qualified to discuss design criterion, but I'm not
real certain about my theories right now as I am new to the discussion of boat
design.  Oh, and I didn't mean to be rude about the jumping off a bld thing...
I just thought that was a humorous way of pointing out that every little bit of
supportive resistance is important.

-- 

Mike McNally		mmcnally3_at_prodigy.net

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