Re: [Paddlewise] speed with versus against the current

On Fri, 29 May 1998, John Winters wrote:

> Jerry wrote;
> 
> >
> >It has always seemed to me harder to paddle against the current as opposed
> >to with.  I mean that even with my eyes closed I think I can feel the
> >difference, i.e., without looking at the fixed shoreline.  I always
> >attributed this to my imagination since I can't think of a physical reason
> >it could be true.
> >
> 
> 
> I believe this has to do with one's normal stroke rate. If you are paddling
> at your normal still water stroke up current  the force on your paddle will
> be less because the paddle speed through the water is lower. To get the
> same velocity to the water you have to increase the paddle velocity
> relative to you.  Even though the paddle force is the same your rate is
> higher and that may give the sensation of greater work.

I'm not sure about this.  When you say "the sensation of greater work" do 
you mean that you feel like you're working harder, or that you feel like 
you're working more efficiently (i.e. more results for same level of 
effort)?  I definitely find that it feels easier to paddle into a 
light-moderate headwind and seas than to paddle with a light-moderate 
tailwind and following seas - same as what Jerry was saying.  

You said that when going upstream:

> the force on your paddle will
> be less because the paddle speed through the water is lower

Now I never took physics past high school, and I'm not mechanical, but 
won't the force on your paddle be the combination of your force against 
the water and the water's force against your paddle?  So the paddle speed 
is lower because there is opposing force from the water, but in fact the 
combined forces should be the same, no?

I've never timed myself going upstream and downstream over the same
distance in the same conditions.  However, I think one of my paddling
buddies said he did, and it wasn't an illusion of speed - he actually went
upstream/upwind faster than downstream downwind.  (Greg, have I got that 
right?)

Earlier this week, before reading this stream, I found just the same 
thing - out on a lake in a borrowed K-light, going downwind with small 
following swells was no fun and the boat didn't handle well and 
definitely moved slowly.  I thought I was just tired, but when I turned 
to go home I positively flew, and it was a blast!  I really wish I had 
timed it.


Joy Hecht
Arlington VA

> 
> Bruce Winterbon once called to my attention to an interesting phenomenon
> involving the force developed when the blade is inserted in the crest of a
> wave as opposed to the trough. The ideal would seem to be to make sure the
> paddle was always inserted in the wave where the flow was opposite the
> action of the paddle blade for greatest thrust. This may even have some nit
> picking effect on rolling since the lift effect would be greater when blade
> is travelling against the flow.
> 
> Donna wrote;
> 
> >Along these same lines, I'm new to kayaking and I've been going out
> recently on
> >a lake.  For some reason, I seem to paddle straighter and easier going
> INTO the
> >wind and against the current, heading into the waves.  When I turn around
> and
> >head to shore the way I came but with the wind at my back, I feel awkward
> and
> >have a hard time keeping on a straight course.  Is this difference because
> it's
> >a lake rather than a river?
> 
> The reasons for this are rather complicated. Maybe this much simplified
> explanation will help.
> 
> The water molecules in a wave travel in circular orbits. At the crest they
> travel with the wave but in the trough they travel in the opposite
> direction. When paddling down wind the bow might be in the trough while the
> stern will be on the crest (also vice versa) . If there is any angle
> (almost always) there is a turning moment on the boat causing it to veer
> off course. This is aggravated as the boat travels more closely to the wave
> speed (period of encounter) when the forces have more time to act on the
> boat. Against the wind the period of encounter is very short and the
> relative flow is always in the same direction so there are no (or minimal)
> turning moments.
> 
> The only time being in a lake or river would make a difference is when the
> waves are due to the river flow rather than wind driven waves. Waves cause
> by velocity variations in a river behave differently from waves caused by
> wind.
> 
> If that isn't clear let me know and I will try again.
> 
> Cheers,
> John Winters
> Redwing Designs
> Specialists in Human Powered Watercraft
> http://home.ican.net/~735769/
> 
> 


(Greg, Mike - in case you're not on Paddlewise, I thought this discussion 
would interest you.  I think you have to be on the list to respond, 
though.   - Joy)

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