Kayaking power
 

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

Kieran wrote:
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.

For swimming, one method I know of consists of a line with floats
attached to it in a pool. The swimmer then pushes his hands against the
floats with each stroke and the power for each stroke is then measured
in the floats IIRC. There ought to be a better description of this on
the web. Another method might be to just drag a kayak with a line
accross the water at paddling speed and measure the force needed to do
this, but I suspect you want some more detailed measurements. Maybe you
can combine this with a videocamera.

greetings,
Michiel

Kieran 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.

google back on RSR just a couple months, someone posted
a link to a E. Euro site that did some technique vids for
kayaking - maybe there are links from there, I didn't save the link.

M.C.D. Roos wrote:

For swimming, one method I know of consists of a line with floats
attached to it in a pool. The swimmer then pushes his hands against the
floats with each stroke and the power for each stroke is then measured
in the floats IIRC. There ought to be a better description of this on
the web. Another method might be to just drag a kayak with a line
accross the water at paddling speed and measure the force needed to do
this, but I suspect you want some more detailed measurements. Maybe you
can combine this with a videocamera.

greetings,
Michiel

Thanks for the reply...

Yes, we've used the towing technique for determining work done by
swimmers, and have applied it to kayaks, we're also familiar with the
pushing bouys (and submerged paddles) for swimmers... but I want a more
direct measurement of the forces at the blade and the hands. Hoping to
possibly also apply this to an inverse dynamics solution of joint
reaction forces at the shoulder.

-Kieran

Kieran wrote:

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.

If you just want average power generated then you could use some of the
test and model data from Sea Kayaker magazine in their kayak test
reports that shows the drag force of each boat model at various speeds.
Combine this with measured speeds of paddlers in races and it should
give an idea of the effective paddling power.

On Sat, 26 Feb 2005 17:55:31 GMT, Kieran 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.

Kayaking is an Olympic sport, and every such sport has a wide range of
technical work done. You might get in touch with a college with a
kayaking program, or the US Olympic or Junior Olympic teams.

Seems like an opportunity for some synergy.

Happy trails,
Gary (net.yogi.bear)
--
At the 51st percentile of ursine intelligence

Gary D. Schwartz, Needham, MA, USA
Please reply to: garyDOTschwartzATpoboxDOTcom

"Gary S." Idontwantspam@net wrote in message
...
On Sat, 26 Feb 2005 17:55:31 GMT, Kieran 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.

Kayaking is an Olympic sport, and every such sport has a wide range of
technical work done. You might get in touch with a college with a
kayaking program, or the US Olympic or Junior Olympic teams.

Seems like an opportunity for some synergy.



Wasn't there an extensive conversation here a few years back (maybe 3 or 4)
from someone who was doing his PhD thesis on this? IIRC, he had lots of data
and graphs showing where in the stroke the power was applied, and was
looking at bentshaft vs straight shaft paddles, depth of the blade, angle of
the shaft, etc. He was doing work in a pool, with sensors, flow meters, and
the like. The conversation might have branched out into different hull
materials, different types of boats, etc.

--riverman

AFAIK http://www.marinerkayaks.com
has information about this.

The most recent and comprehensive work of this kind that I am aware of
is a phd thesis from the Technical University of Denmark:
Determination of Transient Loads on Anisotrophic Paddleshafts,
issn 0903-1685, 1994.
It is in Danish, with a summary in English.

Kieran 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! :-)

Thanks,
Kieran Coghlan

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.

Why not measure the HR of the engine? I've read that the well trained
athelete can output something in the neighborhood of 1/4 HP. All the
variables of measuring the work accomplished would not change the power
rating of the motor, if it is power you are after! TnT

On 27 Feb 2005 06:35:50 -0800, "Tinkerntom" wrote:

Why not measure the HR of the engine? I've read that the well trained
athelete can output something in the neighborhood of 1/4 HP. All the
variables of measuring the work accomplished would not change the power
rating of the motor, if it is power you are after! TnT

Different muscle groups may output different amounts of energy/power,
whatever the potential of the CV system.

Happy trails,
Gary (net.yogi.bear)
--
At the 51st percentile of ursine intelligence

Gary D. Schwartz, Needham, MA, USA
Please reply to: garyDOTschwartzATpoboxDOTcom

"Kieran" schrieb im Newsbeitrag
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

Look for

http://www.fes-sport.de/kanu.htm

But I am not sure how much of their work is published

Eberhard

Excuse me for my stupidity . . . How about a spring scale on a boat
and the paddler paddling with comparable strain to what would be a
normal paddle effore for an hour watch the weight and average it. For
the strain at the hand use the same scale or replace it with a preasure
scale ( bathroom scale ) and again replicate the average paddle strokes
preasure.
Just a thought.
Or if you are good at math you can nick someone elses work.
Sorry, Kieran; I am that simple .
Alex McGruer

Peter wrote:


If you just want average power generated then you could use some of the
test and model data from Sea Kayaker magazine in their kayak test
reports that shows the drag force of each boat model at various speeds.
Combine this with measured speeds of paddlers in races and it should
give an idea of the effective paddling power.


Actually, we want direct measurement of force through the paddle,
applied by the paddler. This way, we can not only determine the overall
power, but also do an inverse dynamics analysis of the joint forces in
the paddler's arm and shoulder.

-Kieran

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. 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.

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.

Thanks,
-Kieran

"Kieran" wrote in message
news:j1tUd.66306$8a6.13749@trndny09...
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.
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.

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.


Actually, it should be quite managable, seeing as how the paddle is a line.
You only need two points to track all the motions of the paddle shaft, and
two more on the sides of the blade to track the feather. Everything else
follows.

Seems like someone out there must have some sort of pressure plate: two
sheets of material with a lor of sensor points between. Put one on the blade
and get a readout of the water pressure against all points of the 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.

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

Might be worth looking at the reaction forces on the boat - ie/
footrests/seat, as these would be relatively easy to measure, and with
a bit of meathematical modelling could probably give you a fair amount
of information about paddle force & direction.

riverman writes
"Kieran" 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.
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.

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.


Actually, it should be quite managable, seeing as how the paddle is a line.
You only need two points to track all the motions of the paddle shaft, and
two more on the sides of the blade to track the feather. Everything else
follows.

Seems like someone out there must have some sort of pressure plate: two
sheets of material with a lor of sensor points between. Put one on the blade
and get a readout of the water pressure against all points of the 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.


Since it is more the reduction in pressure on the convex back of the
paddle which moves the boat than the increase on concave face, you'll
need a sensing surface on both faces. Even then you'll measure pressure
but not shear (frictional) forces.

Might be better to measure the forces at the paddle neck directly by
means of strain-gauge rosettes. Then there's angle of shaft, direction
& velocity of blade motion & (variable) location of centre of pressure
to consider.

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

Cheers -
Carl

--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing low-drag Riggers/Advanced Accessories
Write: The Boathouse, Timsway, Chertsey Lane, Staines TW18 3JY, UK
Email: Tel: +44(0)1784-456344 Fax: -466550
URLs: www.carldouglas.co.uk (boats) & www.aerowing.co.uk (riggers)

"Carl Douglas" wrote in message
...
Since it is more the reduction in pressure on the convex back of the
paddle which moves the boat than the increase on concave face...

Huh?

Isn't it the force of the paddler's butt, feet, or whatever other
parts are in contact with the boat that propel it?

Wolfgang

On 27-Feb-2005, "riverman" wrote:

Actually, it should be quite managable, seeing as how the paddle is a line.
You only need two points to track all the motions of the paddle shaft, and
two more on the sides of the blade to track the feather. Everything else
follows.

You need three points in total to measure all the motions of the paddle.
If you have two on the shaft and one off the shaft (say, normal to the
mid-point) you can determine what's going on.

I thought about this and figure that measuring the motion of these
points is more trouble than it's worth. I'd be inclined to try the
following:

A six-degree-of-freedom accelerometer system (all in a box costs a
few hundred US$) attached to the paddle shaft. This will measure
all accelerations of the paddle in every direction. A six-channel
A-D converter actually costs more than the accelerometer.

A computer that integrates the above data from a starting point
(say, a paddle "saddle" as a zero-reference point on the deck
in front of the paddler). This can be used to determine the
position and orientation of the paddle at every point in the
experiment. Can be done in real time or after the fact.

A seat mounted on a three-support frame. This would be statically
determinate and will allow all paddler forces to be measured
directly from strain guages in the seat supports. The "seat"
would in fact be a frame that includes foot support, since
foot forces can be a considerable component of the paddler's
actions. The problem with this may be reinforcing the kayak
to allow all forces to be transmitted thru only three points
to the hull. You'd have to also design the seat frame to
have very little friction for certain degrees of freedom
at each support in order to have it determinate.

The geometry of the seat relative to the paddle starting point
can be measured accurately and then all paddle positions are
known in time. Forces at the three seat supports can then be
resolved into the forces exerted by the paddle.

Mike

"Michael Daly" wrote in message
...
On 27-Feb-2005, "riverman" wrote:

Actually, it should be quite managable, seeing as how the paddle
is a line.
You only need two points to track all the motions of the paddle
shaft, and
two more on the sides of the blade to track the feather.
Everything else
follows.

You need three points in total to measure all the motions of the
paddle.
If you have two on the shaft and one off the shaft (say, normal to
the
mid-point) you can determine what's going on.

I thought about this and figure that measuring the motion of these
points is more trouble than it's worth. I'd be inclined to try the
following:

A six-degree-of-freedom accelerometer system (all in a box costs a
few hundred US$) attached to the paddle shaft. This will measure
all accelerations of the paddle in every direction. A six-channel
A-D converter actually costs more than the accelerometer.

A computer that integrates the above data from a starting point
(say, a paddle "saddle" as a zero-reference point on the deck
in front of the paddler). This can be used to determine the
position and orientation of the paddle at every point in the
experiment. Can be done in real time or after the fact.

A seat mounted on a three-support frame. This would be statically
determinate and will allow all paddler forces to be measured
directly from strain guages in the seat supports. The "seat"
would in fact be a frame that includes foot support, since
foot forces can be a considerable component of the paddler's
actions. The problem with this may be reinforcing the kayak
to allow all forces to be transmitted thru only three points
to the hull. You'd have to also design the seat frame to
have very little friction for certain degrees of freedom
at each support in order to have it determinate.

The geometry of the seat relative to the paddle starting point
can be measured accurately and then all paddle positions are
known in time. Forces at the three seat supports can then be
resolved into the forces exerted by the paddle.

All of this sounds terribly complicated to me. Why not just tether
the stern of the boat to the measuring device of choice anchored to a
dock?

Wolfgang

Ook hier aanwezig, Michiel? :-)

M.C.D. Roos wrote:

Kieran wrote:

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.


For swimming, one method I know of consists of a line with floats
attached to it in a pool. The swimmer then pushes his hands against the
floats with each stroke and the power for each stroke is then measured
in the floats IIRC. There ought to be a better description of this on
the web. Another method might be to just drag a kayak with a line
accross the water at paddling speed and measure the force needed to do
this, but I suspect you want some more detailed measurements. Maybe you
can combine this with a videocamera.

greetings,
Michiel


--
Wilko van den Bergh wilko(a t)dse(d o t)nl
Eindhoven The Netherlands Europe
---Look at the possibilities, don't worry about the limitations.---
http://wilko.webzone.ru/

On 28-Feb-2005, "Wolfgang" wrote:

All of this sounds terribly complicated to me. Why not just tether
the stern of the boat to the measuring device of choice anchored to a
dock?

Good idea - unless of course you want to measure something useful.

Mike

"Michael Daly" wrote in message
...
On 28-Feb-2005, "Wolfgang" wrote:

All of this sounds terribly complicated to me. Why not just tether
the stern of the boat to the measuring device of choice anchored to a
dock?

Good idea - unless of course you want to measure something useful.

Refresh my memory. What is it you wish to measure?

Wolfgang

Wolfgang wrote:
"Michael Daly" wrote in message
...

On 28-Feb-2005, "Wolfgang" wrote:


All of this sounds terribly complicated to me. Why not just tether
the stern of the boat to the measuring device of choice anchored to a
dock?

Good idea - unless of course you want to measure something useful.


Refresh my memory. What is it you wish to measure?

Wolfgang


Force on the paddle shaft, at the handgrip.

"Kieran" wrote in message
news:_R9Vd.73792$g16.11180@trndny08...
Wolfgang wrote:
"Michael Daly" wrote in message
...

On 28-Feb-2005, "Wolfgang" wrote:


All of this sounds terribly complicated to me. Why not just tether
the stern of the boat to the measuring device of choice anchored to a
dock?

Good idea - unless of course you want to measure something useful.


Refresh my memory. What is it you wish to measure?

Wolfgang
Force on the paddle shaft, at the handgrip.

Extrapolate. Look at the tables. Call the company. Do the math.

Wolfgang
who is no rocket scientist.

Kieran wrote:
Wolfgang wrote:
"Michael Daly" wrote in message
...

On 28-Feb-2005, "Wolfgang" wrote:


All of this sounds terribly complicated to me. Why not just
tether
the stern of the boat to the measuring device of choice anchored
to a
dock?

Good idea - unless of course you want to measure something useful.


Refresh my memory. What is it you wish to measure?

Wolfgang


Force on the paddle shaft, at the handgrip.

Makes me think of a big torque wrench. Do you get any deflection of the
paddle shaft while paddling? Use a smaller shaft until you do, Take
video, or measure the deflection of the needle! Then in the lab,
measure the force needed to duplicate the deflection. You should then
have an idea of what the possible force exerted on the shaft would be
for a particular paddler.

The potential force would be based on as wolfgang points out the
effectiveness of the engine mount, the paddlers seat and feet, the
grip, and other loss of efficiency factors that could be isolated for
significance. TnT

In article nK2Ud.65307$8a6.4571@trndny09, Kieran
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



--

In article .com, Tinkerntom
wrote:
Why not measure the HR of the engine? I've read that the well trained
athelete can output something in the neighborhood of 1/4 HP. All the
variables of measuring the work accomplished would not change the power
rating of the motor, if it is power you are after! TnT

HR is a measure of sympathetic stimulation and oxygen demand by the working
muscles. It will not give an accurate assessment of power, esp when
anaerobic fibres become significantly invloved... Those who have used a HRM
will also have noticed that HR can remain high even when the workload is
reduced to plodding pace or slower, plus weekly or daily variations.

Allan Bennett
Not a fan of horse-sense

--

In article j1tUd.66306$8a6.13749@trndny09, Kieran
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


--

In article , Carl Douglas
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

--

In article , riverman
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

--

Ah, we have a D. A. fan. Yes of course 42. I should have thought of that.

Ken

"Allan Bennett" wrote in message
...
In article , Carl Douglas
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

--

"Allan Bennett" wrote in message
...
In article , riverman
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

"Allan Bennett" wrote in message
...
In article , riverman
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.

"riverman" wrote in message
...

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!!

In article , Wolfgang
wrote:

"Allan Bennett" wrote in message
...
In article , riverman
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

--

In article , riverman
wrote:

"Allan Bennett" wrote in message
...
In article , riverman
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

--

"Allan Bennett" wrote in message
...

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