Re: [Paddlewise] Paddle flutter

From: "Alder Creek Kayak & Canoe" <aldercreek_at_qwest.net>

>> If you choose to define flutter your own way, it can mean anything you want.
>> You're taking any form of instability to be flutter.  If you can't agree on a standard
>> terminology, there's no point is discussing anything.
>
> The Webster's II dictionary I have actually defines flutter: "to flap or
> wave rapidly *and* irregularly."

> I would say that any form of paddle instability that causes rapid and
> irregular waving or flapping could be called flutter.

Except that Webster's isn't a standard reference in the realm of hydrodynamics.
My Webster's New World Dictionary (1976) defines oxygen as the most plentiful
substance in the universe - which it clearly isn't.  The English language often fails 
science and law - that's why scientists, engineers and lawyers can't be understood
by anyone else and why life scientists stick with Latin in many cases.  For science,
etc, the language can't be general, it must be specific.  That's my point wrt flutter.  
There are lots of forms of instability, but when most paddlers talk about flutter, they 
seem to mean the same thing.  We can dig up names for the other kinds of 
instability, if we need to discuss them.

> Seems what we're discussing here is more of a regular wave with a defined
> wave shape and length.  Maybe even a pulsed wave, caused by Karmen vortex
> shedding.

Calling it a wave is iffy, except in the context of having a regular frequency.  If you call
it a wave, that would influence the thinking of paddlers that are looking for it.  It's only
a wave in the sense that the sweep second hand of a watch can be described as a 
wave.  And yes, it would be pulsed as in +on, off, -on, off, +on, off -on, off..., though
the exact shape of "on" I could only guess.

Vortices peel off the edges of the paddle on alternating sides, first one side, then the 
other.  This tugs the paddle around, first one way then the other (as I said in another 
post, I can't see these; they seem to be swamped by the vortices that are caused by 
broken flow around the edge of the paddle, where vortices are visible at all).  In a 
steady state environment, this frequency can be predicted -hence, wave like.

Paddling isn't steady state, but there's a point in a draw-type stroke that will allow 
several oscillations, seemingly regular, to occur.  Most of us have felt this at some 
time.  Loosely holding almost any paddle and drawing it straight back will usually do it.

BTW, several folks have suggested that angling the paddle reduces flutter by 
generating lift.  I believe that they can angle the paddle enough to break the 
symmetry that can give way Karman vortex shedding without actually generating
much lift.  This intermediate point's existence would depend on the angle of 
attack at which stall would occur (I think).   (Intermediate, of course, meaning 
between high drag and high lift states - sort of "relatively high drag without much 
lift but we got rid of vortex shedding")  This set of complications is one thing that 
affects my lack of acceptance of "conventional" thinking on lift, wing paddles, 
Greenland paddles etc.  But that's another story...

> I also agree that all aspects of anyone's technique should be considered
> when an irregularity like this comes up.  We sell a tons of paddles and have
> yet to see one that was so far out of line that *flutter* was a problem.

Well, when one paddle works for John and another doesn't, I won't jump to
the conclusion that technique is to blame.  There are so many good paddles
on the market, I don't see the point in sticking with one that doesn't work for
him - whether or not it's his or the paddle's "fault".  The paddles I've tried that
flutter badly have been off the market for a while.  As I stated in another post,
I can see a case where the paddle is inappropriate for _him_ even though
it's fine for others.  If we can isolate the paddle as not part of the problem,
then certainly, let's critique technique.

I guess that I react when I see people go into "solution mode" when "analysis
mode" hasn't finished.  None of us has seen John or the paddle - I would
prefer to give him the benefit of the doubt and have him try other paddles.
If the problem is frequent with other paddles, we've narrowed it down.  As 
you and I have said, in different ways, the majority of paddles sold today 
are good.

Mike

PS - I can't help but notice that the vendors on this list tend to recommend 
changing the paddler rather than the gear - or is that my imagination :-)

PPS - I do get my back up when misquoted.  A couple of times in this thread
folks have suggested I said that paddles shouldn't flutter.  In fact I have repeated
that all paddles flutter, but some are better than others.  I apologize if I have
offended anyone with the apparent sharpness of my responses.

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