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.

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

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)

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

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

--

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