Wing curve

– Last Updated: Sep-21-08 9:59 AM EST –

I am not sure that the wing curve falls off below the others. I think with proper rotation and angle it can maintain higher power peak over the entire range.

Why would a GP or a Euro have more power at the middle or end of stroke compared to Wing? Have not paddled GP enough to make conclusinos there but to me the wing has plenty of power in the second half of the stroke if one rotates well.

Again, my thoughts are based non-numerical data -;) And I'm an engineer so I can't trust that with my life, but my "engineering gut feeling" tells me so -;)))

One more clarification is needed. The horizontal axis may be representing time in the water, of which the GP may just as well spend more during a stroke cycle compared to a Wing. But the wing spends a shorter amount of time, all of it at higher power IMO, assumint early take out.

So, to me the charts as they are directly superimposed, do not yeld a meaningful comparison, beyond the relative measure within each curve (not compared to other curves) of how fast the power during the catch and release cycle raises and falls for each paddle individually.

More meaningful would be some sort of measure about the energy transfered to forward motion during the stroke and I am willing to bet that the more efficient paddles in the water (wing) will be on top in all segments of the curve.

Lastly, I think the point is well taken that "in-water" efficiency is one thing and "muscle and body efficiency" is another. And a paddle may as well have better "body efficiency" with a low "water efficiency" and thus make it a better choice for some people, while others would be better served with the opposite. I whish there was a way to measrure the two factros (water & body efficiency) and come-up with a compund measure in relation to paddling distance or energy output by the body over time or something like that at different speeds (e.g vs. different boat resistance in the water, to eliminate the type of boat as a factor).

There, now someone in physics or physical education with a decent math background or help can go collect and analyze data and write a thesis on this -;)

Engineers in the crowd?
Sorry I’m not an engineer but I started my career as an engineer and have a background in molecular physics, which I do not use any more.

I think the curves are actually his guess of “Force vs Time” not “Power Application”, so the integrated area would be the total power and the first derivative would be more representative of “Power” application.

It’s all a guess. I think my Onno surf paddle would have a much different profile from, my Mike Johnson surf paddle, or even my Onno full tour which would be hugely different from my Hungarian no name plastic/aluminum europaddle I bought with my first boat. They are all europaddles and have hugely different blade shapes.

No data. It’s fun to speculate but don’t believe any of it.

OK, count me in

– Last Updated: Sep-21-08 12:05 PM EST –

I'm designing the modification of a tow tank into a water channel at the moment. It will be used for teaching ship model studies in a naval architecture program. However, I am designing it for two ulterior motives: 1/4 scale kayak model and full-size paddle studies. I plan to start with flow visualization of paddle vortex dynamics. Depending on what that tells me, I will plan a hard-data experimental program.

Greyak's curves I find very useful - I consider them to be his hypothesis of power distribution during the strokes of different paddles, using an idealized technique with each. To those who bash the graphs, that's fine, but he never said they were hard data. A hypothesis is there to be proved or disproved by those with research funding (I'm planning to be that nerd). But research without a starting point is just noodling around.

One of the better points made above is that as shown, the curves are normalized to be the same width in the horizontal axis, which is clearly not ideal. I think it would be easy to alter them to make an indication of average paddle stroke duration, but that's just quibbling.

By the way, I'm keeping the wave generator that was part of the tow tank and hope to incorporate it into the water channel. I think it will be interesting to make time-dependent drag measurements of kayaks in a wavy sea, a test that has not been done as far as I know.

Not until you logged on here! Ha.

Greyak

– Last Updated: Sep-21-08 1:30 PM EST –

No offense intended. With an off hand guess, your charts are probably right on the money. But if you took two people, and gave them each one of those paddles, your results would vary. I was just agreeing with Charlie as to the method.

Last year at Raystown, I asked David Yost what his method was in designing canoes. IE testing, mathamatical equations, etc... He essentially said to me that his experience has shown him what hull aspects would best fit the type of canoe he was designing. Intuitive would probably the the best description. But that intuition comes from many years of experience and success.

Your original post says simply "Paddle Power curves" as if that were gospel. Perhaps you should have said a bit more.

Andy

horizontal axis
They are very useful visualization curves. I would label the vertical axis as force, not power. The horizontal axis should be labeled time. But then the wing stroke, which is shorter, should end before the GP stroke.

The wing stroke develops max force just after the catch, then exits the water quickly. The GP develops force much more gradually and holds it longer because the stroke is longer.

Efficiency is only slightly related to the force time history. Most losses occur in the human body not the paddle/water interaction. Whichever paddle enables you body to work most efficiently is the most efficient paddle. For instance, “slippage” or “grabbing the water” just are different ways of saying there are different drag coefficients. And a higher blade drag coefficient is not necessarily more efficient. Each paddler will have a paddle drag coefficient and paddle length that are most efficient for him, at the speed he intends to paddle. At a different speed, another paddle might be more efficient.

Curious how you envision…
… setting up and doing these paddle tests.

Anything I’ve seen has the paddle being drawn back through still water, and and looking at flow across/around the blades. That’s just not how they work when paddling (despite what people think they feel) unless you’ve tied your stern to something solid.

Since you’ll have a tow tank, I’m assuming you’re planning something more interesting - with paddle stroke simulation at speed (seems very difficult to rig - unless you just use real paddlers for the mechanics (you did say full size). I also assume that you’ve seen stop motion photos of this, and you look at the paddle primarily as a couple (lever), and not as something slipping back through the watter like a paddle wheel as most do (very secondary and in arcs vs. linear to what extent it does exist).

I totally agree technically
Just not looking at it that technically.

Depending on the axes, same paddle at different cadence, or slight technique variation, would have a somewhat different curve too. Interesting, but gets into more than I’m looking to share. Same for comparing 5 different euros (though there are better things to look at on that level than this).

Even these curves should probably not be same lengths, but that gets into really subjecting things about long vs short strokes (which can be changed with any paddled).

These only compare general type/technique combos - for same paddler - with both force and time as relative things. So force is the force the paddler applies (however much that is), through the duration of the stroke (however long that is).

– Last Updated: Sep-22-08 12:19 AM EST –

How to study paddle dynamics - a good question without a clear answer. My facility is being modified from a tow tank (still water, moving model) to a recirculating water channel (moving water, still model). It's about 4 ft wide by 2ft deep, although we may make it deeper.

For initial flow viz studies, I envision a kayak cockpit set up next to the channel, with the water moving by at cruising speed. A paddler will sit in the cockpit and do his best imitation of someone paddling at cruising speed. This may require another body of water on the other side of the 'kayak', the cockpit may need to be on gimbals, etc. If done properly, it should be possible to reproduce the relative (vector) velocities between the paddle and the moving water. High speed video from multiple directions (side, top, end) and release of dye trails from ports in the paddle should allow visualization of the vortex flow around the paddles.

All of that would be qualitative, but it is usually better to do visualization first to see what's going on. Quantitative data could be got by connecting the cockpit mounts to force transducers, but quantifying the flow downstream of the paddle would be hideously difficult. I'm a flow viz guy, so I tend to concentrate on that, which I think gets you 90% of the way to understanding the dynamics.

No study will ever account for the huge range in paddles and paddling styles - there's just too much variation. But hey, that's no reason not to try - we can start with the basics and see what there is to learn. If nothing else, I should be able to say whether there is a fundamental difference in the vortex dynamics of different style paddles, e.g. GP and Euro - that would be an interesting result in itself.

PS for the record, if the graphs show force vs. time, then the area under the graph is called the Impulse. Impulse measures the change in momentum from before the stroke to after; momentum is mass times velocity:

(mV)state 1 + Impulse = (mV)state 2

My favourite quote
42.5% of statistics are invented on spot.

Things that are not right with the graphs:

1. I heard that wing paddles are tunable - that is can tuned for a particular cadence, power delivery, arm span. You graph sort of forgets that. Which paddle was used?
2. Euro paddle - the recreational special is shown, right?
3. Which hybrid?
7. Is it really a figment of your imagination?

My favorite stat

NM

NM

Feel free to start a “good” one NM

This is a Rorschach test

interesting graphs

– Last Updated: Sep-23-08 10:45 AM EST –

however without a real biometric powermeter flat water test tank and a stop watch it is speculation.

Cycling sort of has paddling beat by being able to measure scientifically how many watts you generate with the drivetrain. But it is an expensive piece of equipment.

I tend to agree with the curves to an extent. But they don't mean anything. This is actually more speculative than the pull-test shawna and Leon had us do at Symposium.

Greyak never posts stuff without
good reason.

paul

Well as a fellow hornet nest
kicker I applaud him.

boat curves?
Greyak - fun stuff. As an engineer I was also curious around how the curves were generated but knowing that they represent your (subjective) experience and are to be used to generate dialogue…they are great thought-starters.

Sometimes I ponder similar characteristics in boats (canoes) themselves…Hemlock Peregrine requires some muscle at beginning of stroke but then delivers big speed/glide at low effort for remainder of stroke, Bell Fire boats take virtually no muscle at beginning but start to take muscle at end of stroke if you go fast enough…Merlin II is easier at beginning of stroke than Peregrine but does not deliver same speed…

fun stuff!