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From: Larry Bliven <foxhill_at_shore.intercom.net>
subject: [Paddlewise] LightFoot
Date: Mon, 1 Feb 1999 21:06:53 -0500
Certainly Gordon Lightfoot is one of kathy's favorite singers
however
since it's winter in the northern hemisphere, i'm thinking about execise
equivalence.

in particular the speed vs resistance number that is given for kayaks so
that we get an idea of how easy/hard it is to propel them throw water. For
example, see a SeaKayaker magazine review that provide resistance numbers in
*pounds.* the values at 5-6 knots are usually in the range of 5 to 14
pounds.

What does that mean?

if all of our effort goes to our feet against the foot pegs, can we expect
to feel 5 to 14 pounds? that seems like a light load... and my legs feel
much too tired after an outing for me to easliy accept that i just been
pushing a load of a few pounds... after all, when i walk, i have 100's of
pounds trying to push my feet through the ground.

so what gives with the LightFoot speed vs resistance numbers?


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From: Dave Kruger <dkruger_at_pacifier.com>
subject: Re: [Paddlewise] LightFoot
Date: Mon, 01 Feb 1999 22:16:09 -0800
Larry Bliven wrote:

> [snip] see a SeaKayaker magazine review that provide resistance numbers in
> *pounds.* the values at 5-6 knots are usually in the range of 5 to 14
> pounds.
> 
> What does that mean?

The 5 - 14 lbs is the minimum force just required to maintain constant
velocity.  In other words, it is the native air/water resistance of the
craft.  If you apply exactly that force **in a direction collinear with the
kayak's path,** the kayak will neither accelerate nor decelerate.

> if all of our effort goes to our feet against the foot pegs, can we expect
> to feel 5 to 14 pounds? that seems like a light load... and my legs feel
> much too tired after an outing for me to easliy accept that i just been
> pushing a load of a few pounds... after all, when i walk, i have 100's of
> pounds trying to push my feet through the ground.

See the phrase I emphasized above.  Your legs are tired because in order to
apply the necessary 5 - 14 lbs to the kayak in a direction collinear with
its direction of travel, you have to use a lot of counterforce to keep
control of the craft.  In other words, you flex your thighs (etc.) to keep
good contact with the thigh braces (etc.).  The effort you use to brace
inside the yak is largely expended locking you in -- and does not go to
propelling the yak.  It is only the force exerted on the yak **in a
direction parallel to its direction of travel** which goes towards that 5 -
14 lbs.

I bet some of the racing folks have this figured out very precisely,
because they want to get the most speed out of their effort.

-- 
Dave Kruger
Astoria, OR

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