RE: [Paddlewise] paddle sizing and Technology guides design

 Nick Schade  wrote:
> More apparent slippage is inefficient...."Slippage" is an indication that 
you are
> accelerating water and thus wasting energy.

Your first statement is meaningless, how can you say more slippage is 
inefficient?  Did you ever measure it?  How?  You are making unwarranted 
assumptions.   What is slippage anyway?  (not the 'feel' but something 
measurable).  So it depends on how you measure "slippage"...either it is 
all slippage, or none of it is.

The word "slippage" is meaningless unless you define it, and depending how 
you define it it could mean almost anything.  It is best to avoid such 
vague words.


>
> As long as you move the paddle parallel to the direction of motion
> desired all the force applied will go directly to propelling the
> boat.

This is totally false and again based on uninformed intuitive ideas.  A 
propeller on a boat or aircraft moves exactly perpendicular to the 
direction of travel yet fairly efficiently provides all the forward motion. 
 you can do the same thing with a paddle in a sculling type stroke, 
providing forward motion without any movement of the paddle in the 
direction of travel. You could also have a shape on the blade the provides 
very little forward motion even though you are pulling parallel to the 
hull.  [and do not argue that propellers are different, both paddles and 
propellers are fluid machinery and operate on the same principle, one is 
just optimized for a different type of movement].  Paddle wheel boats move 
parallel to the line of travel, but why do you think they are not used 
commercially?  They are very wasteful and inefficient.

 It does not matter how the force is created: drag, friction,
> turbulence, lift, whatever. The only time there is wasted force is
> when there is a component of motion perpendicular to the direction of
> propulsion, then all the same things - drag, friction, turbulence,
> lift, whatever - are bad things. The only useful force is one
> propelling you in the direction you want to go and it doesn't matter
> how you create it.

this is true, but remember the vortex?  you get lots of fluid movement but 
most of it cancel itself, that is why they are so wasteful of your efforts. 
 The theoretically most efficient thrust you can generate will have no 
vortexes (which is impossible in the real world), and convert all your 
effort into forward thrust (also impossible), how you move the paddle is 
not even important since it will vary with the type of paddle you are 
using.

Take the extremes:  An ice cream scoop type paddle would probably be best 
pulling strait back, linearly accelerating the fluid.  But the other 
extreme, a paddle that looked like an airplane propeller, would be best 
used by sweeping it through the water in an arc, and WAY more efficient 
than the ice-cream scoop paddle--hence the native style paddle.

Do not forget that there are a lot of other demands we put on a paddle 
besides forward motion.  And the propeller blade vs. the ice-cream scoop 
will have to be used very differently to meet these different demands, some 
better than others, and some requiring more skill and practice.  But 
overall it is my observation that the native paddles and techniques are 
superior.  JUST GO TRY IT!  (but learn to use it properly first!).

Perhaps the ice-cream scoop is more easily learned, and proper technique is 
more obvious to the beginning paddler or in rental fleets.  But that is no 
reason for all who hope to become experienced and skilled paddlers to use 
it.  It would be like never graduating from a tricycle or training wheels 
to a two wheeler.  You never experience the full advantage and benefit of 
the sport with such a severe handicap because you are forced to use 
inefficient techniques and poorly designed equipment.

>
> <snip>
> efficient. It will require fewer strokes to maintain the same speed.

There is your inaccurate assumptions showing themselves again; this is 
false.  I have measured this before on a human dynamometer.  The number of 
strokes it takes to maintain the same speed is not related to how much 
energy out put you are producing.  The 10-speed bike analogy makes this 
clear, peddling slow and hard in high gear, or fast and easy in low gear, 
could mean you are expending exactly the same amount of energy.  However, 
with the human "machine" there is an optimum speed for the same output of 
energy to minimize input (this is actually true with most machinery). 
 Generally the low gear (higher speed, less force) IS MORE EFFICENT with 
the human body.

So by your analogy, you should ride a bike in high gear all the time 
regardless of the road conditions, speed or slope, to be most efficient and 
expend less energy.  This is clearly not true, you end up wasting a lot of 
effort and energy doing this.  Fortunately water is level, but you still 
have to deal with wind and surface conditions (as you do with a bicycle).

>
> It does not take any knowledge of fluid dynamics to understand this,
> and no amount of fluid analysis will change it.
>

This may be true, but it is clear from your arguments you still have a lot 
to learn. Why don't you just go out and learn the native paddle technique 
and try it,?  You do not need to know anything about fluid mechanics to 
know which works best, but you are at a clear disadvantage if you put forth 
technical arguments about things you do not understand, and without the 
knowledge of actually trying it out.  I contend IF you use PROPER 
technique, you will know how much better native paddles are.

If you think of the forces on the paddle surfaces as high and low pressure 
areas (rather than moving fluid, which is actually what causes the high and 
low pressures, but in very complex ways) to create the forward movement you 
want, it become easier to understand.  with a propeller shaped blade (i.e. 
native paddle blade) you make your stroke a downward slicing arc movement, 
kind of like a quarter turn of a propeller (but also pulling back at the 
same time with your body), you get a very efficient stoke that is also easy 
on your body.  You can not do this with a "Euro" paddle.

You also learn real quickly that you get little resistance against the 
paddle for rolls or braces unless you have some lateral movement of the 
blade through the water.  And it is much less effort to create, and the 
amount of power you can generate is much larger on the high aspect ratio 
blades than with the "ice-cream" scoop Euro blades.  This is why you must 
learn proper technique to get it to work, and it has to become automatic.

So if you want to scoop ice-cream, or shovel manure (as it appears many on 
this list are in the habit of doing), use your Euro blades, for efficient 
paddling you need a high aspect ratio paddle.  There is no way around it. 
 Do not argue, it is a FACT of any fluid machinery.  You can go look this 
up for your self in any fluid mechanics textbook if you are so enchained 
(check out aspect ratio, propeller design, etc.), but do not put forth such 
statements until you have done so.  Short of that you will either have to 
take the word of people who do know, or just go out and try it!

Peter Chopelas
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