I follow your question here as I am interested in measureing the shear forces of grass sward in several soil depths.

I am not in this field but your question is interesting . As I understand you are interested in measuring pressure and shear stresses, A possibility (open to correction) is to

incorporate strain guages in the body of the paddle which can be monitored for

bending moments . If the paddle is modeled as first order lever , by simulation

using distributed load on one end it seems we could evaluate the stresses.

Also  we may keep the paddle stationary and use water jet to simulate

the actual paddle action in a lab set up( like a wind tunnel ). The results

could then be analyzed.

 Cheers

Unfortunately we do not want to investigate the bending moments (these are to "general" data) but the hydrodynamicaly awaken forces on the paddle wing. We need to know these forces at different wing angles and speed circumstances. We would like to know when, and how to free the wings from the water at different distances. What is the most biomechenically correct way, in case of different individuals (racers).

I understand that a direct measurement of the surface pressure is what you are seeking.

I find that the surface pressure in aircraft wings are measured by relating pressure

to vortices on the surface, so perhaps some ideas can be obtained by referring to

experimental set ups on aircraft wings . This means we need to measure water velocities on the surface only. Please see if this reference is useful:

"In-Flight pressure measurements on a subsonic transport high-lift wing section

Long P. Yip; Paul M. H. V. Vijgen; Jay D. Hardin; C. P. van Dam"

Read More: http://arc.aiaa.org/doi/abs/10.2514/3.46752?journalCode=ja

Cheers

This area of the paddle is the fulcrum paddle with water points, therefore the force exerted here working at the hands of the paddle and the resistance Power is the body contact point paddle with the boat and therefore can measure the force exerted by accelerating the boat movement account with a mass boat consideration or through water resistant account as an indicator or by measuring the EMG of the muscles working during performance

Dear Mohamed,

Thank you for the answer. We can say that this is a massive matrix with many factors in it. The aim is winning the race. But how? The racers have to react as fast as they can, they have to do the first movements as fast as they can, they have to build up speed (accelerate as long as they can), and also maintain speed during the race. They have to paddle economical and also fast. This is paddling technique. The problematic phase is the first phase from the water touching till the mid phase  (perpendicular paddle position to the water surface). This is the "effective working" phase, but how to free your paddle after it. With rotation? With leaning the stick? When? Why? What is the best solution? What is the best solution at 200m, 1000m or at longer distances? What forces awaken on the wing? And moreover what is the best solution for "A" or "B" or "XY" with different anatomic background? We have to measure it! We have to measure with an instrument on the paddle wing shows us the real time force data correlated to the speed, pulse, and other energetic and biomechanical data we can get. Fundamental question to correct the technical mistakes. The racers feel something and the coach see something but the technique have to be the best mechanically optimal for the given racers.

I think that measuring EMG on a boat is far more problematic. Because we can only get correct EMG data with invasive measuring (with needles). This is not solvable during racing or high speed training.

If you would allow a special paddle construction please consider the following:

1. Make the surface of the paddle wing a separate part.

2. Attach this to a piezoelectric film (e.g. Piezo Film Sensors Technical Manual - SparkFun Electronics https://www.sparkfun.com/datasheets/Sensors/Flex/MSI-techman.pdf ) .

3 Mount 2 on a plate which is then fixed to the pole.

4. Choose suitable electronics wired/wireless to monitor.

Hope it is useful

 Cheers

now we Can be measuring EMG  by wireless  electrodes placed on the roofs of the working muscles و Its results can rationing training loads of required speed and distance by Specials calculations ways 

Thank you for the very useful answers!

Dear Mohamed,

Please let me know the name and availability of the mentioned EMG. Thank you.

Sándor

Dear Béres Sándor

You can benefit from the following locations

- http://www.biometricsltd.com/semg.htm?gclid=CLeo3NKGwcICFcPJtAod6iMA_Q

- http://www.cometasystems.com/cometasystems/en/

- http://www.delsys.com/products/wireless-emg/

- http://glneurotech.com/bioradio/physiological-signal-monitoring/wireless-emg-measurement-analysis-teaching/

I guess my response is a bit late and you may have resolved your problems by now. Using piezo electric film is a good idea, but I expect you need more accuracy than this material can provide. As an earlier respondent suggested, using strain gauge in the location of interest could be useful, especially if you combine this data with information about total force on the paddle shaft.

There are many free apps that log GPS locations. try a few to find one that suits your needs.

Thank you Jacob!

Beres, I just read your question and some of the comments you made on the responses again. I am very interested in your project as I coach dragon boat racing which requires a similar physical action as canoeing.

Firstly re EMG http://www.instructables.com/id/Muscle-EMG-Sensor-for-a-Microcontroller/ gives information on how to set this up and sensors are available from https://www.aliexpress.com/wholesale?catId=0&initiative_id=AS_20170605173156&SearchText=emg+sensor+arduino. All arduino boards can also be found on this site.

Regarding measurements on the paddle, I think the forces on the different parts of the blade are not so critical. What you are looking at is the efficient application of human power to propel the boat. So maximum force on the blade while it is in the water (and at right angles to the direction of travel). Strain gauges on the shaft at the top of the blade will give you data of how much side ways force as well as force in the direction of travel is applied.  Add a position sensor (really cheap https://www.aliexpress.com/item/Free-Shipping-GY-521-MPU-6050-Module-mpu6050-module-3-Axis-analog-gyro-sensors-3-Axis/1872261387.html) and you'll have all the data relating to the paddle that I think you need. [just in case you are wondering, I haven't built any of this yet, only a force measurement "clip-on" for the paddle).

The other part is of course video analysis. From the video you posted on Youtube, I think you already use Kinovea. So with that you can determine air time. Minimising air time and maximising the efficiency of water time will make optimal use of available human power. 

.... and then use emg to see what muscles are used and need to be trained ...

That's a lot of data to be analysed!

As one of the other responders suggested, using a flow tank you can get data on blade forces at different angles, including lift.

One problem you have is that human subjects are difficult to control and there will be significant variability in a series of paddle strokes.

A better approach would be to build a scale model of the canoe and use a electro-mechanial setup (i.e. a "paddling robot") to create the paddling action. (also quite cheap https://www.aliexpress.com/item/1set-DIY-6-DOF-3D-Rotating-Metal-Mechanical-Manipulator-Robot-Arm-Kit-For-Smart-Car-Arduino/32754286497.html)

You can then precisely control angles, forces, and speed in all phases of the stroke. Once this action has been optimised (i.e. minimum power input for maximum speed) you can use this information to instruct human paddlers. The only problem I foresee with using a robot is that the weight transfer characteristics during the action are likely to be different from a human. So a custombuilt electro-mechanical system may be better. As the action is quite limited, this will not be very difficult to make.

I like the model canoe as you can play around with variables and get a mathematical model which will enable you to advice athletes which things will create the biggest gain in their performance.

email me on [email protected] if you like to discuss further

Dear Jacob,

My college (Attila Szabó, many time world champion, and Olympic athlete) and me started to study the theme. I will send your very useful answer to him too. We will discuss it and looking forward the next steps we would like to do. Thank you very much for your kind help and for your reachability!!

Something that Attila Szabo may be interested in. I have used Kinovea to track boat speed as detailed in the attached image. I can see how the speed changes during the stroke and make it easy to observe changes in boat speed due to changes in technique. I have built a prototype that can be clipped on to the boat to measure boat speed real time at 0.1s intervals. I think the raw data from such a system this could be useful for research.

Beres, I just came across Article Hybrid Foam Pressure Sensor Utilizing Piezoresistive and Cap...

...and one more Article Piezoresistive Foam Sensor Arrays for Marine Applications

Thank you very much Jacob!