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

--