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

rebyl_kayak_at_energysustained.com wrote:
> G'day,
>
> First I should mention that Niels and I have been discussing our power
> estimates back channel
Did we? I must have forgotten to change the "to" address of the email.
Sorry about that. Feel free to quote any part of those posts; they're 
public.

  and I believe we are agreed that my estimate of
> 17 watts transient power differs from Niels 30 watt estimate only
> because of differences in paddle weight and paddling style.
> Also when comparing the average power to move a kayak with the average
> power to lift a paddle I make the crude assumption that the power to
> lift a paddle is used during half the paddle stroke, so that my average
> power to lift a paddle is about 8 watts.

Eh... No, no, and no. I calculated from those same numbers that you get 
31 watts.
The energy to lift one arm, 31Nm, is spent every second. It doesn't 
matter that it's done in half that time; all that's matter is that 31Nm 
is spent every second. That makes it 31 watts. No need to divide by 2.
>
> Niels wrote:
>> I've studied one of those tables - but it indicated that,
>> at rest, a man consumes 750 watts of energy. All other >sites claim it
>> to be about 100W, so I don't trust the >table I used.
>
> Peter response - I'd agree. Whereever that figure of 750W came from it
> is quite wrong. The value of 100W is consistent with many studies
> including the Bicycling Science review table, which quotes 105W.

Could you find, in those same tables, what a human uses while outputting 
his full 200 watts? It's not important to the discussion; I just wonder 
how efficient a human actually is.

> Peter response - I see your point about the different muscle types and I
> have been thinking in terms of tests to exhaustion.

I just made some attempts to measure my heartrate. Those measurements 
failed, but I've found that keeping a paddle steady, at chestheight and 
2/3 arms length, is _hard_. Holding it for twice that time in a 
vertical-rest is easy.
(More on that, and new measurements, in a new video, that uploading 
right now.)


, whereas Matt's
> example paddler may not have been exhausted only working at maximun
> capacity.

Huh? Sorry, you lost me.

> I'm left with the quandary that the estimates of the power used to lift
> a paddle seem credible. Yet your points about the different muscle
> types, together with Matt's long experience in this area, are compelling
> reasons to accept the lower values of power to paddle a kayak.

Wait for the video...

> The
> problem is that 9 Watts to 18 Watts for a 4knot speed seems to be
> inconsistent with the 8 watts to 15 watts of average power that might be
> used just to lift a paddle.

There will be big losses where the paddle transfers its energy to the 
water. I estimate a loss of about 50%. That means you need to output 18 
to 36 watts to get a netto propulsion of 9 to 18 watts. That seems 
consistent with my measurements.

> But I'll bet a beer at Skiffies that there is an answer to this somewhere!

And I WILL find the bastard!
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