Re: [Paddlewise] speed with versus against the current

David wrote;

(SNIP)
>
>The V, of course, is velocity of the paddle relative to the water.  So,
>if you are paddling with
>the same cadence and stroke length, etc. (neglecting for the moment the
>effect of
>wind speed on your velocity relative to the water), you produce the same
>thrust whether you
>are paddling upstream or down.

Keep in mind that you are paddling at the same cadence relative to the boat
and yourself. The paddle velocity relative to the water is the key point.
The thrust developed is a function not of the paddle velocity relative to
the boat but the velocity relative to the water.

>You also move at the same velocity
>relative to the water.

Maybe maybe not. Even if the force developed is the same you may not move
at the same speed due to the way the transverse wave system forms around
the boat. I don't klnow if nayone has studied this but my observation is
that the wave system created by the boat is much modified by the flowing
water. Perhaps Bruce has some thoughts on this. Are you there Bruce?

>Your speed made good (speed over ground) is then the vector sum of your
>velocity
>relative to the water and the velocity of the water relative to the
>ground.

Also not necessarily so since it assumes that the two are perfectly
additive but they aren't because of the time between strokes when the boat
will slow at different rates.
>
>Of course, you do feel your acceleration/deceleration (relative to
>ground) when
>you enter water that is moving.  Maybe that's the basis for the feeling
>that
>you're working harder when you're paddling in a contrary current.  It
>doesn't
>explain the apparent difference in boat performance, however...

A good possibility. We feel the tug on the boat and maybe that gives a
sensation of speed.

(SNIP)

>I have noticed that when paddling with the wind, I "feel" like I'm going
>slower.  But
>I'm pretty sure it's just because my velocity relative to the wind and
>waves is
>slower, so it "appears" like I'm going slower.  In hot weather, I think
>the additional
>cooling one gets when paddling into the wind is significant.  Also,
>sometimes when going
>with the waves (wind), I have to work harder to keep the boat going
>straight.  Especially
>if I'm using poor technique.  This is related to wind and waves, and not
>directly
>to current speed/direction.

That is A really important point that Dan makes. Often our sensations of
speed are not consistent with speed and that is why designers either like
or dislike subjective opinions of speed depending on the result. :-)

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

and



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