Kayaking power

In article <j1tUd.66306$8a6.13749@trndny09>, Kieran
<URL:mailto:kc_news@sonic.net> wrote:
 > Bob Arledge wrote:
  > > Why not put a strain gauge on the paddle shaft just below the paddler's
  > > hand. This would give you the moment at that point, so the force would be
  > > the moment divided by the distance between the strain gauge and the
  > > centroid of the paddle blade.
  > >
  > >
 >
 > That's the general idea, but because the paddling motion is 3-d, it's
 > not very easy to determine power just from the strain in the paddle
 > shaft.

The flex in a paddle-shaft will be a reflection of all the forces acting upon
the blade in the water. Using the force profile: t v deflection) and
suitable calibration, it will be possible to determine the power.

 > You need to know instantaneous velocity (direction and magnitude) at every
 > moment. In a fixed-pivot environment like rowing, you can just put a
 > potentiometer on the oar-lock. But the kayak/canoe paddle has no fixed
 > pivot point. So, I imagine that a virtual pivot point would have to be
 > derived via 3-d kinematic video analysis.

It seems there is a virtual point (see Plagenhoef, 1979 and others), just as
there is a virtual point where all the forces that propel the boat seem to
meet - a valuable tool for those athletes with adequate imagination.

 >
 > I haven't yet sat down and done a free-body of the system, but in my
 > head, it seems like it's going to be an indeterminant system... not fun.

...and the ultimate purpose?


Allan Bennett
Not a fan of virtual science


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In article <ssaNZ4BsM1ICFwlc RemoveThis @rowing-cdrs.demon.co.uk>, Carl Douglas
<URL:mailto:Carl@carldouglas.co.uk> wrote:

 >
 > Sounds a nice easy problem, only slightly more difficult than the one
 > about life, the Universe & everything. Have fun, Keiran!


So, there's the answer!

42



Allan Bennett
Not a fan of fish

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In article <38f5gmF5ml4v0U1.DeleteThis@individual.net>, riverman
<URL:mailto:nospam@sorry.com> wrote:

 > blade at all times. If all you are interested in is the resultant force,
 > put a potentiometer on the bow and brace it against a wall.

Unfortunately, like all the suggestions about tethering the boat, this idea
misses the point by a mile: Kieran wants to measure the forces during a
paddling stroke - paddling against a resistance is just not the same.

 > --riverman (I love trying to sound like I know what I'm talking about)

....keep trying...


Allan Bennett
Not a fan of immovable objects

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"Allan Bennett" <albenito DeleteThis @eclipse2k.freeserve.co.uk> wrote in message
news:ant021122916Novh@freeserve.co.uk...
 > In article <38f5gmF5ml4v0U1 DeleteThis @individual.net>, riverman
 > <URL:mailto:nospam@sorry.com> wrote:
 >
  > > blade at all times. If all you are interested in is the resultant
force,
  > > put a potentiometer on the bow and brace it against a wall.
 >
 > Unfortunately, like all the suggestions about tethering the boat,
this idea
 > misses the point by a mile: Kieran wants to measure the forces
during a
 > paddling stroke - paddling against a resistance is just not the
same.

Evidently I've gone and bought myself a bad boat. It resists
movement. However, this is probably not as bad as it sounds. It
turns out that we also have peculiar water in my neighborhood......it
resists the motion of my paddle.

Wolfgang
who, apparently, is no physicist.<!-- ~MESSAGE_AFTER~ -->
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Ah, we have a D. A. fan. Yes of course 42. I should have thought of that.

Ken

"Allan Bennett" <albenito.DeleteThis@eclipse2k.freeserve.co.uk> wrote in message
news:ant0210211e6Novh@freeserve.co.uk...
 > In article <ssaNZ4BsM1ICFwlc.DeleteThis@rowing-cdrs.demon.co.uk>, Carl Douglas
 > <URL:mailto:Carl@carldouglas.co.uk> wrote:
 >
  > >
  > > Sounds a nice easy problem, only slightly more difficult than the one
  > > about life, the Universe & everything. Have fun, Keiran!
 >
 >
 > So, there's the answer!
 >
 > 42
 >
 >
 >
 > Allan Bennett
 > Not a fan of fish
 >
 > --
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"Allan Bennett" <albenito.DeleteThis@eclipse2k.freeserve.co.uk> wrote in message
news:ant021122916Novh@freeserve.co.uk...
 > In article <38f5gmF5ml4v0U1.DeleteThis@individual.net>, riverman
 > <URL:mailto:nospam@sorry.com> wrote:
 >
  >> blade at all times. If all you are interested in is the resultant force,
  >> put a potentiometer on the bow and brace it against a wall.
 >
 > Unfortunately, like all the suggestions about tethering the boat, this
 > idea
 > misses the point by a mile: Kieran wants to measure the forces during a
 > paddling stroke - paddling against a resistance is just not the same.
 >
  >> --riverman (I love trying to sound like I know what I'm talking about)
 >
 > ...keep trying...
 >
 >
 > Allan Bennett
 > Not a fan of immovable objects
 >
 > --
 >
Well, okay but I was hoping that you'd come to this last point on your own.

You've got too damn many variables, Allan! You cannot run an experiment when
the variables include feather, fetch, grab, speed of stroke, blade depth,
variations of applied power, assault angle, retrieve distance and time,
stroke time, etc etc etc. Add to that a <human> doing the motions, and even
an isolated variable will have abberations. There is absolutely no way to
determine cause and effect if you cannot identify the role of a single
variable.

You need to isolate variables. Build a jig that will hold a blade and rotate
it in a circular motion. Place a paddle in the jig, and adjust the feather
angle, then let it wind out a few dozen times while you measure the pulling
effect on a rope tethering the boat. Change the feather angle, and go at it
again, until you have a 'feather angle vs forward force' graph. Change the
length of the paddle shaft until you have a 'blade depth vs. forward force'
graph. Change the rotational velocity until you have a 'stroke speed vs.
forward force' graph. Etc.

Then build a jig that will hold a paddle and move it horizontally with the
shaft vertical, lift it out and replace it a few feet forward. Maybe
something on a caterpillar tread. Place a paddle in this jig with no
feather, and run this several times and vary the feather variable until you
have results. Then change the speed, the length of the stroke, the angle of
the paddle, etc.

The build another jig that will do something else, and run a host of tests
on that.

When you are done, you need to solve <each> of these equations for the
representative curve, the K factor, and then meld them together into a
joint/inverse relationship equation that takes all the variables into
account with a single K.

And good luck!! IIWY, I'd identify 3 or 4 variables and call it a day. Just
think of all the minor adjustments a paddler makes within a single
stroke...and you want to quantify THAT?

--riverman<!-- ~MESSAGE_AFTER~ -->
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In article <38lvrjF5prjqeU1 DeleteThis @individual.net>, Wolfgang
<URL:mailto:wolfgang@mcw.edu> wrote:
 >
 > "Allan Bennett" <albenito DeleteThis @eclipse2k.freeserve.co.uk> wrote in message
 > news:ant021122916Novh@freeserve.co.uk...
  > > In article <38f5gmF5ml4v0U1 DeleteThis @individual.net>, riverman
  > > <URL:mailto:nospam@sorry.com> wrote:
  > >
   > > > blade at all times. If all you are interested in is the resultant
 > force,
   > > > put a potentiometer on the bow and brace it against a wall.
  > >
  > > Unfortunately, like all the suggestions about tethering the boat,
 > this idea
  > > misses the point by a mile: Kieran wants to measure the forces
 > during a
  > > paddling stroke - paddling against a resistance is just not the
 > same.
 >
 > Evidently I've gone and bought myself a bad boat. It resists
 > movement. However, this is probably not as bad as it sounds. It
 > turns out that we also have peculiar water in my neighborhood......it
 > resists the motion of my paddle.

Good stuff, Wolfie - you're half way there to understanding the point that
was made.

But you forgot to mention this wall and the bungee...

 > Wolfgang
 > who, apparently, is no physicist.

....nor a rocket scientist, don't forget...

Allan Bennett
Not a fan of memory lapses

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"Allan Bennett" <albenito RemoveThis @eclipse2k.freeserve.co.uk> wrote in message
news:ant021541b49Novh@freeserve.co.uk...

 > Good stuff, Wolfie - you're half way there to understanding the
point that
 > was made.

I like to think I'd get there faster if someone would identify it for
me.

 > But you forgot to mention this wall and the bungee...

My apologies. Consider them hereby mentioned.

  > > Wolfgang
  > > who, apparently, is no physicist.
 >
 > ...nor a rocket scientist, don't forget...

I won't......well, I'll try not to.

 > Allan Bennett
 > Not a fan of memory lapses

Nor am I.......um.......if memory serves.

Wolfgang<!-- ~MESSAGE_AFTER~ -->
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In article <38lv18F5n9ms3U1 DeleteThis @individual.net>, riverman
<URL:mailto:nospam@sorry.com> wrote:
 >
 > "Allan Bennett" <albenito DeleteThis @eclipse2k.freeserve.co.uk> wrote in message
 > news:ant021122916Novh@freeserve.co.uk...
  > > In article <38f5gmF5ml4v0U1 DeleteThis @individual.net>, riverman
  > > <URL:mailto:nospam@sorry.com> wrote:
  > >
   > >> blade at all times. If all you are interested in is the resultant force,
   > >> put a potentiometer on the bow and brace it against a wall.
  > >
  > > Unfortunately, like all the suggestions about tethering the boat, this
  > > idea
  > > misses the point by a mile: Kieran wants to measure the forces during a
  > > paddling stroke - paddling against a resistance is just not the same.
  > >
   > >> --riverman (I love trying to sound like I know what I'm talking about)
  > >
  > > ...keep trying...
  > >
  > >
  > > Allan Bennett
  > > Not a fan of immovable objects
  > >
  > > --
  > >
 > Well, okay but I was hoping that you'd come to this last point on your own.
 >
 > You've got too damn many variables, Allan! You cannot run an experiment
 > when the variables include feather, fetch, grab, speed of stroke, blade
 > depth, variations of applied power, assault angle, retrieve distance and
 > time, stroke time, etc etc etc. Add to that a <human> doing the motions,
 > and even an isolated variable will have abberations. There is absolutely
 > no way to determine cause and effect if you cannot identify the role of a
 > single variable.
 >
 > You need to isolate variables. Build a jig that will hold a blade and
 > rotate it in a circular motion. Place a paddle in the jig, and adjust the
 > feather angle, then let it wind out a few dozen times while you measure
 > the pulling effect on a rope tethering the boat. Change the feather angle,
 > and go at it again, until you have a 'feather angle vs forward force'
 > graph. Change the length of the paddle shaft until you have a 'blade depth
 > vs. forward force' graph. Change the rotational velocity until you have a
 > 'stroke speed vs. forward force' graph. Etc.
 >
 > Then build a jig that will hold a paddle and move it horizontally with the
 > shaft vertical, lift it out and replace it a few feet forward. Maybe
 > something on a caterpillar tread. Place a paddle in this jig with no
 > feather, and run this several times and vary the feather variable until you
 > have results. Then change the speed, the length of the stroke, the angle of
 > the paddle, etc.
 >
 > The build another jig that will do something else, and run a host of tests
 > on that.
 >
 > When you are done, you need to solve <each> of these equations for the
 > representative curve, the K factor, and then meld them together into a
 > joint/inverse relationship equation that takes all the variables into
 > account with a single K.
 >
 > And good luck!! IIWY, I'd identify 3 or 4 variables and call it a day. Just
 > think of all the minor adjustments a paddler makes within a single
 > stroke...and you want to quantify THAT?

Nope. I don't want to quantify anything - Kieran does. But, he wants to
measure force on the shaft *during* a paddle stroke, which will be different
to the forces during a tethered stroke or when braced against a wall or on an
erg or whatever. Just try it.

Ultimately, all the variables you mention - plus a load more - will finish up
as force on the immersed blade, which can be recorded using simple (these
days) tensiomentric devices.


Allan Bennett
Not a fan of superprotractedmegaovercomplication

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"riverman" <nospam.TakeThisOut@sorry.com> wrote in message
news:38lv18F5n9ms3U1@individual.net...

 > Well, okay but I was hoping that you'd come to this last point on your
 > own.
 >
 > You've got too damn many variables, Allan!

I mean, Kieran!!<!-- ~MESSAGE_AFTER~ -->
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Allan Bennett wrote:
> In article <nK2Ud.65307$8a6.4571@trndny09>, Kieran
> <URL:mailto:kc_news@sonic.net> wrote:
> > Hey there, sorry for the cross-post!
> >
> > I might be taking on a project where we try to determine the power
> > (force and velocity) developed by a kayaker while paddling. I'm
> > wondering if anyone out there knows of any research that's been
done
> > like this. I know that it is a fairly common thing for rowing
crews to
> > be "instrumented" with strain guages on the oars, and
potentiometers on
> > the oarlocks, to get force/time curves for on-water rowing. So,
I'm
> > wondering if anyone is aware of this sort of study having been done
on
> > kayaking or canoeing.
> >
> > The obvious problem with kayaking and canoeing, is that the paddle
has
> > no fixed pivot point, like a rowing shell does. So most likely
some
> > sort of video kinematic analysis will be necessary. We have the
> > capability to set this up, although I think the physics will be
> > complicated (i.e. statically indeterminant problem). I've done a
search
> > of the scientific journal literature (Medline) and haven't found
any
> > published papers on this topic, but that doesn't mean the work
hasn't
> > been done at some National training center, or product development
> > center somewhere... or that it's in a very obscure journal that
Medline
> > doesn't cover.
> >
> > I'd appreciate any thoughts or hints on who might have done this
sort of
> > work in the past. I'd rather not re-invent the wheel, if I can
maybe
> > work on just improving it!
>
>
> There has been some tensiometric analysis carried out with strain
gauges on
> the shaft (see The Canadian Canoe Association Coaching Manual; The
Science of
> Canoeing, Richard Cox, ISBN 0 95118931 14). The work has
> been repeated from time to time (I've just dismantled my own kit,
sorry).
> All the results are similar, but the usefulness is negligible, IMO.
>
> However, I suggest you set up a paddling ergometer which can give you
the
> data you require w/o the vagaries of water and weather conditions.
>
>
> Allan Bennett
> Not a fan of square wheels
>
>
>
> --

On 3/2, I posted describing the paddle as a large torque wrench. I have
a background in mechanics and have used torgure wrenches. Is this what
you are mentioning for strain gauges?

You say the usefulness of of the measurements are negligible, can you
expound? TnT
 >> Stay informed about: Kayaking power 

I have another simplistic thought on this subject. How about towing the boat
with a load equivalent to the weight of a the paddler measuring the towing
force versus speed. Then all you have to do is measure the speed to know
what force is being applied.
 >> Stay informed about: Kayaking power 

If you want motive power or P = {F}*{V} then you would wish to measure
either the reaction forces of the Kayaker against the boat and/or the
tractive force of the boat (use a line with constant tension and measure the
velocity.)

If you want the forces on the paddle to generate force vs position and/or
time it will get much more complicated but not impossible. Try using strain
gages on the paddle shaft with the data synchronized with video. You can
(with much labor) get position, force and velocity.

There is software already in use that can provide many of the tools you
need. You may need to spend $$ for it though and the learning curve is
probably steep.

"Kieran" <kc_news.DeleteThis@sonic.net> wrote in message
news:nK2Ud.65307$8a6.4571@trndny09...
 > Hey there, sorry for the cross-post!
 >
 > I might be taking on a project where we try to determine the power
 > (force and velocity) developed by a kayaker while paddling. I'm
 > wondering if anyone out there knows of any research that's been done
 > like this. I know that it is a fairly common thing for rowing crews to
 > be "instrumented" with strain guages on the oars, and potentiometers on
 > the oarlocks, to get force/time curves for on-water rowing. So, I'm
 > wondering if anyone is aware of this sort of study having been done on
 > kayaking or canoeing.
 >
 > The obvious problem with kayaking and canoeing, is that the paddle has
 > no fixed pivot point, like a rowing shell does. So most likely some
 > sort of video kinematic analysis will be necessary. We have the
 > capability to set this up, although I think the physics will be
 > complicated (i.e. statically indeterminant problem). I've done a search
 > of the scientific journal literature (Medline) and haven't found any
 > published papers on this topic, but that doesn't mean the work hasn't
 > been done at some National training center, or product development
 > center somewhere... or that it's in a very obscure journal that Medline
 > doesn't cover.
 >
 > I'd appreciate any thoughts or hints on who might have done this sort of
 > work in the past. I'd rather not re-invent the wheel, if I can maybe
 > work on just improving it!
 >
 > Thanks,
 > Kieran Coghlan
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