Reference Frame
It all depends on the frame of reference.
In the stop-action photos, the tripod is on land, so the frame of reference is fixed with the water, hence the pivot point appears to be the blade and the couple applied to the shaft.
If the frame of reference was fixed with the boat (i.e. camera mounted on gunwale) it would look like the lower hand is the pivot point, hence a Class I lever (type I, whatever).
Additional Thoughts
It looks like this discussion has well ended. Imre gave me a heads up about this forum as I do enjoy brainstorming on such topics.
First lets looks at a real world example. The gondola is pushed/pulled through the water with a long lever. The water bed is the fulcrum, the pole the lever, the boat the load, and the body the effort.
If you think about it, the canoe and kayak have similar principles. Ah, but the paddle/lever of these boats do not touch the water bed. But, if water is smacked smartly, water acts like a solid. Thus the water bed is still the theoretical fulcrum.
Can these forces change with technique? Ah, basically no. What changes is the characteristics of water on a marathon course. Thus the load will change, and the amount of support the fulcrum might give. Sprint, very little change.
Effort like the gondolier is the whole body.
A paddler will change technique on a marathon course to optimize speed due to varying conditions. Example, the load increased in more shallow water. With certain corrections, boat speed can be maximized for these conditions.
What changes by a variance of position is the amount of torque on the effort or the body.
Yes the paddle stays basically fixed as noted by the photos. Does the paddle slip? It depends on the amount of pressure the blade has on the water. More pressure less slip.
To test theories, build a machine or mechanism to mimic the actions of a paddler. You will find by doing so at least in your mind that these thoughts are pretty much on track. -E.
Fulcrum for 3rd in wrong location
The moving illustration shows the fulcrum in the wrong location. It should be placed above the lever and not below it, for it will not work as shown, unless fasten or attached in some manner. To see what I mean, try using a broom in the manner it is used in the illustration. This is why a canoe paddle is usually mistaken for a 3rd class lever. If a canoe paddle is used as a 3rd class lever, you would be moving backwards, for the load moves in the direction of the force (that is the rule).
Fulcrum Should Be Over End of Line
– Last Updated: Nov-13-10 7:23 AM EST –
And not "under" the end of the line. See the following for correct placement of fulcrum for 3rd class lever:
http://www.sciencebyjones.com/third_class_levers.htm
With a 3rd class lever, the load travels in the same direction as the force. So basically, all we are doing is shoveling water, if we use our paddle as a 3rd class lever. Only when the paddle is used as a 2nd class lever does the canoe move in the direction of the force. (Note: When the paddle is used as a 1st class lever, the load travels in the opposite direction. Such as moving water backwards.)