Re: [Paddlewise] A new way to teach the forward stroke?

Hi Peter. Up for another night of rock hard reality? I myself could use 
a night of solid fantasy - but that can wait.

rebyl_kayak_at_energysustained.com wrote:
> Regarding using one or two arms in the calculation of potential energy
> created by lifting a paddle and the associated power (PE). To the extent
> that a paddler is lowering both arms simultaneously during the power
> phase of a stroke then I can see that its justified. However, when
> carrying through the power stroke my upper hand is held level in the
> horizontal plane, and passes across my eyes, so I should only use one
> arm in the calculation of PE for my stroke.

You certainly need to calculate from the movement of both arms.
To make things easy, I used the _average_ movement of my arms in all 
calculations. I don't have to calculate that average: The middle of my 
paddle _is_ that average.

If one hand drops 60 centimeters and the other 0, the average is 30 
centimeters - which is what the center of the paddle does. Now, assuming 
one hand + half a paddle weights 3kg/30N, you can calculate the 
potential energy in two ways:
- left weight * distance + right weight * distance = 30*0.6 + 30*0 = 18
- total weight * average distance = 60*0.3 = 18

(I consider these numbers unrealistic: All paddlers I've seen drop both 
hands. It's just for the ease of calculation that I drop only one hand 
in my example)

That's how I calculate my own potential energy:
- Total weight = 7kg/70N;
- Average drop (middle of paddle) = 0.4 meters;
Energy output = 7*0.4 = 28W

If I may paraphrase your other argument: You drop the paddle for perhaps 
0.2 (or 0.5, or 0.1) seconds out of a total stroke, and you think that 
changes the calculation.

I'll do the math for 0.2 seconds out of each second, to show that it 
doesn't matter.

During the 0.2 seconds of the drop, you release 18Nm of energy (which is 
the result from my earlier, unrealistic example). You do that in 0.2 
seconds, so the energy output during that time is 18/0.2 (wattage = 
energy/time) = 90W.

During the remaining 0.8 seconds, you release no energy to all - so the 
average energy release over time is 90/5 = 18Nm/s, or 18 Watts.

I tend to skip all those calculations, and simply ask "How much energy 
is released every second?" since that gives the same answer immediately.

That's 28 Watts for me - but I've lost track of the estimates of your 
own numbers. Were you talking the weight of one arm, both arms? Using 
distance travelled by lower hand or by the center of the paddle? What's 
your stroke-rate? I'll be happy to repeat the calculations with new data.
***************************************************************************
PaddleWise Paddling Mailing List - Any opinions or suggestions expressed
here are solely those of the writer(s). You must assume the entire
responsibility for reliance upon them. All postings copyright the author.
Submissions:     PaddleWise_at_PaddleWise.net
Subscriptions:   PaddleWise-request_at_PaddleWise.net
Website:         http://www.paddlewise.net/
***************************************************************************