Re: [Paddlewise] aspect ratio?

>Uh oh - I've missed something basic again. What is "aspect ratio" as it
>applies to paddles? I need a really basic, practical description. This is
a
>new concept to me - ove which has probably been explained in group
postings
>and which I either overlooked or never understood in the beginning.

We call the ratio of blade length to blade width the aspect ratio.
Aeronautical engineers use the term in describing the characteristics of
wings, propellers etc. Paddles with narrow long blades have high aspects
ratios and paddles with short wide blades have low aspect ratios. The use
of the terms "high" and "low" lack precision but work well enough when
people have some familiarity with the object under discussion.

Most paddlers would call a paddle with an aspect ratio of approximately 4:1
or less a low aspect ratio paddle anything above a high aspect ratio
paddle. Nit pickers might prefer a moderate aspect ratio range as well.

The aspect ratio primarily affects lift and drag. In general, higher aspect
ratios generate greater lift with lower drag and low aspect ratios generate
greater drag with less lift. So, the ideal aspect ratio for a paddle
depends upon how it will get used (stroke mechanics). Ideally one would try
to achieve the greatest thrust per unit area to minimize the paddle size.
Sail boat designers have a similar challenge in designing sailing rigs. For
windward work they seek to reduce drag but increase lift. For off wind work
they increase drag (spinnakers etc.) and try to optimize both drag and
lift.

Cheers,
John Winters
Redwing Designs
Specialists in Human Powered Watercraft
http://home.ican.net/~735769/



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