Some thoughts on how to design blade flex into a cruising paddle for greater efficiency and less fatigue over the long haul.



http://www.nashwaakpaddles.com/Secrets% ... emaker.pdf

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The web site did not impress me much.

First, I saw no objective data support.

Second, I think his physics are on the mystical side and leave a lot to be desired.

Third, He makes a lot of assumptions about what peple think and feel about paddles.

Of course, that does not mean some people will not like flexible blade paddles. It only means that their reasons for liking them may have nothing to do with efficiency or any physical superiority but may have a lot to do with perceptions of efficiency and superiority. The two differ considerably.

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Cheers,

John Winters

Several years back, when I was just getting into canoe building, I decided i needed a good wooden paddle to go with the canoe. I ordered one off the internet, cost 125.00. The maker had endorsements from Trudeau and Bill Mason too. Had lots of fancy flex, etc. Anyway, lesson learned the hard way....I hated the paddle, it was little more than a glorified toothpick, there was nothing mystical about it, and instead of feeling closer to nature, I was forced into the dark side as I cursed my stupidity for spending my hard earned cash on the useless twig. However, I am sure that there are those out there who like to carry their paddle in fleece liners and have prestigious name brands flashing around who will beg to differ with me. On the upside, that little mistake convinced me I could make better paddles myself, and a couple of hundred paddles later, I now see the wisdom of the old adage of "learning from our mistakes"

JW,



Your statement (and I fear it comes close to blanketing the entire universe of paddlers out there) suggests two things:

(1) All paddlers paddle identically, with no variation in technique or style.

(2) Efficiency and energy put out are measurable for all paddlers

Certainly neither is true most of the time. There's a great deal of variability in technique from paddler to paddler, some will paddle the way they've been taught and others will paddle in a way that causes the least fatigue. Some will paddle while kneeling while others will paddle sitting and switching. Some will burn more energy trying to paddle faster while others will be more relaxed.

Determining what the right paddle is for any individual is subjective. How can the efficiency and the amount of energy burned while using one paddle compared to another be measured across the diverse range of paddlers and across the range of conditions on the water? Isn't individual perception of efficiency all we've got most of the time?

Rick (blistered and sunburned, not wearing the lab coat today)

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frozentripper wrote;



I may not have made myself clear. My comments concern the paddle and its efficiency not the skill level or feelings of the paddler. We have adequate data on the unreliability of human perceptions to know that we must look askance at any opinion beyond "I like that" or I don't like that". Since the web site discussed paddles it seemed appropriate to comment on its accuracy and reliability.

We can measure the efficiency of paddles and stroke mechanics. If a person cares about paddle effiiciency then knowing what characteristics provide greater efficiency will help him/her make a choice when buying a paddle.

Of course, no matter what paddle you use, poor stroke mechanics will not produce optimal power.

My concern with the web site had to do with claims based on opinions and not supported by objective data.

If a person is content with a paddle and dosn't care about finding the optimal paddle then it really doesn't matter what he/she has. On the other hand, if one searches for the best possible paddle then it does make a difference. To that person, misleading or erroneous information can become costly.

Anyway, our perceptions are not all we have. We can, if we want, have quantifiable information on a large range of paddle charcteristics. Such as its weight, flex characteristics, drag coefficient, lift coefficient, moment of inertia, dimensions etc.

A methodical paddle maker might make a large number of paddles with a range of characteristics and then have a range of people use them. From this he would do a regression analysis to see relative effects of those characteristics on perceptions.

This kind of study would tell you if ones opinions have much basis in fact.

Granted, this probably exceeds what most paddle makers want to do.

frozentripper asked how we could measure efficiency and energy burned over a diverse range of paddles and conditions. We have access to a number of techniques from oxygen up-take devices to load cell arrays and speed measurement devices such as the Brookes and Gatehouse Speed Boss. All lend themselves to intergration with video to evalute how the paddle characteristics affect the stroke.

We can, of course, test the paddle in a tank. These results can then be compared to paddling in a test tank from a base attached to a load cell.

Anyway, this is just a long winded way to say that we do have objective ways to measure paddle efficiency and we also have ways to correlate it to paddler perceptions. Unfortunately the web site did not use them.

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Cheers,

John Winters

Mitchell and Galasport might have the budgets to have acess to such research facitities ( heck 30 minutes of basic physio costs 50 bucks I can only imgine what a sports faclity with output monitoring like John described costs)

Our local artisans are making sometimes one 0f paddles for their clients, and don't have the budget to give you the cerebrial data, sometimes all we have to go on is "feel"......now it would be nice to have data to back it up but in absence of it well, it isn't a crime......I hear what you are saying John but I don't know if it's misleading as much as a small company excited about their evolution of a product.....artistic licence rather than a misrepresentation of data....
MHO
yup, I have one of the paddles but bought it a few years back when I knew even less than I do now....it was pretty and the grip felt good

even beter.....if I was to concider effcieincy as my primary objective....what data should one be looking for? What in your capacity as a marine designer and in your vast expereince are the data that should be concidered?
I've never concidered it really...I just wnet on hearsay, looks feel and trial runs. But I would be interested in an experts outline of what is points to concider and what is garbilygook.

If you only had an interest in efficiency of the blade you only need to study thrust per unit area. However, if you are interested in the efficiency of the paddle/paddler system you will want to find out:

What factors influence thrust and their magnitude.
What factors influence stroke mechanics and their magnitude.

A paddle maker, however, might want to also know how non objective factors affect choice like aesthetics and cultural influences.


The thrust part is easy. You can use existing fluid dynamic data or, if it doesn't give the results you like, you an try your own tank tests. A tank is pretty cheap and easy to build.

The a stroke mechanics part only needs a few paddlers of different sizes, a range of paddles and a video camera.

Keep in mind that you only need to do this if you care about optimizing paddle efficiency. If you don't care and are happy with what you are making (Speaking for builders here) then don't bother. If you decide not to bother you need only say that you think people will like your paddles and that they should try them. Many people will find that satisfactory.

This type of program differs considerably from the wholly subjective type of thing that some paddle makers use. Keep in mind that subjective testing does not tell you which paddle will propel a canoe more efficiently. It tells you which paddle you think propels a canoe most eficiently.

Is it beyond the abilities and pocket books of some paddle makers? Maybe.

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Cheers,

John Winters

God help us when Erhard starts participating in boat design issues... ...but:

if you only focus on the paddle and its interaction with the water, you are leaving a good portion of critical factors out of the considerations.

To illustrate: long ago I used to have two paddles made from beechwood. They were strong and meant to survive being stepped on by dumb kids and clumsy parents and live through years of other abuse. But those paddles were so darn hard on the arms, and I noticed that only after trying out some other types. I'll make the assumption that it was their extreme rigidness that tired the arms - that's a factor for certain even though other ones come into play.

But to assess these paddles as garbage because of that drawback, you have to include the effect on muscles, bones and sinews of the user.

JW: how does the professional designer factor that in?

JW,



The points you raise on quantifying paddle efficiency in test facilities and the numbers and findings such studies produce will, I'm sure, add to the overall efficiency of any paddler. Some of these might be most suited to racing, where very efficient, highly-evolved and ultra-tech designs are used to squeeze out every ounce of speed.

The problem with this approach is that it might create an uncomfortable situation for the average paddler, who paddles mainly for pleasure, and the technical requirements in high-tech designs just might not be a good fit. My guess would be that most paddlers don't want to use an advanced piece of racing technology brought out from the test lab when out on the water. There are other considerations, such as comfort, freedom from pain and fatigue, and just generally feeling good about the way the paddle fits in with the approach and style.

When reading articles on paddle selection, it's often said that the paddle must "feel" right. How is it possible to quantify or predict that on the basis of lab tests? Or any pain or discomfort that the paddler might experience after a long day spent paddling with a paddle that doesn't "feel" quite right?

Part of the subjective evaluation of paddles relates to flex vs rigidity, and flex is said to lessen the stresses placed on joints and muscles, increasing comfort over a long day. If flex reduces efficiency, then it's a trade-off against comfort, and again, a subjective decision has to be made towards one or the other. A long-distance racer might choose for all-out efficiency, hoping that the muscles and joints won't be stressed too much, while a tripper might lean towards greater comfort, and choose a more flexible paddle.

A good paddle might not always the most awesomely efficient one, subjective feelings probably count for a lot in choice and preference.

(I'm tempted to start singing "Feelings" here at this point, but I won't.)

Rick

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frozentripper wrote;



I guess I am not making myself very clear and for that I apologise. Maybe this will help.

Consider for a moment if we knew what characteristics of the paddle produced the "feelings" we are talking about. Would that not help a person in choosing a paddle? If so, then would it not be worthwhile to find out what those characteristics are? Apparently so because at least the web site mentioned talks about the power produced by a paddle.

So how would we learn that information? Can we do it by just going for a paddle? If we could then everyone would agree on the best paddle. Obvioulsy there are many factors of varied importance so we need something more objective than opinion.

Let give you an example. (For the moment forget racing because racing is not the only place one might want efficiency)

Supppose we wanted to find how flex affects the paddler's perceptions of paddle performance.

To do this we might make paddles that cover a wide range of flexibility.

Then we would test them under varied conditions to see how people respond. Suppose they prefer the flexible paddle.

Now, suppose after we "learn" that a scientist looks at our work and asks," Did you make sure the weights and moments of inertia were constant?"

OOOPS. We goofed. We can't say for certain that it was flexibility or weight or moment of inertia or some combination that the paddlers preferred.

So we need another series of tests to find out how the weight of a paddle affects the paddler's perceptions of the paddle.

We could make a bunch of paddles identical in every way except weight. Then we could have a wide range of paddlers test them and tell us what they thought.

When finished we would have a good idea of how weight affects paddler perceptions.

Then we need another series to see how the moment of inertia affects paddler perceptions. From this question we could formulate another test where only the moment of inertia varied. The results of such a study would add even more to our knowledge of what people perceive in a paddle.

From that, a scientist might ask, '"What effect does the paddle grip and shaft thickness have on perceptions?"

OOOPS. Missed another possible variable.

Each time we ask a question we have a test that will shed more light on paddler perceptions (and there are many tests we can do).

Supppose we found out that it was not flex that made the paddle feel good but the drag coefficient and that a paddle with a low drag coefficient but a much different shape produced the same feel? Would we not have to revisit our statement that it was flex that makes the paddle feel good?

The point I am trying to make is that there are physical reasons why a paddle "feels" good (unless, of course, one believes in magic). To simply accept a gut feel without doing objective testing is coinvenient but not very reliable.

Often people will say, "Only racers need efficiency". This assumes that efficiency only has to do with speed. Consider the fuel efficient car. My wife's Corolla won't win Le Mans it is considerably more "fuel efficient" than a Formula I racer. This also applies to paddles. You might not want to race but you might want the most "fuel effcient" paddle" .

Then again you might not. You might want a gas guzzler that looks sexy.

Once again I would like people to return to the web site. It makes a number of claims but offers no objective proof. If you believe the function of a paddle has nothing to do with physics then you will be quite comfortable with what it says there. If not, you might want something else.
.

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Cheers,

John Winters

Erhard wrote:


I haven't suggested ignoring the human factor. I have suggested that examining the physical reasons of why people "feel" as they do about paddles tells you a lot about how to design and make paddles. Opinions are just opinions.

The interaction of the paddle with the water is how one develops the feel of the paddle. Try paddling without putting the paddle in the water and see how good it feels, and, more importantly, how far you get. No water, no interaction. No interaction, no feel.

If you don't understand how the paddle interacts with the water you only know how you feel not why. If you feel bad you want the doctor to to find out why. The same applies to paddles.

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Cheers,

John Winters

Naw, JW, I understand the validity of tests that leave the paddler out. You get good information that allows you to choose between different design options. What I am suggesting is that in addition to such tests, there should be some that modelling that includes the participation of the human physique, with such things factored in like muscle, tendon and skeletal considerations. That's beyond the naval engineer, but if you guys would get together with the folks that specialize in sports medicin, there might be some valuable feedback that could affect your paddle design. I am sur ethat has been done by the rowing community - these guys are a lot more competitive than the paddle folks and there's probably more money to make it happen also. Am I way off?

I agree with John that there are a number of variables that may effect how a paddle feels, but that paddle efficiency, and even which paddle a particular paddler can paddle the most efficiently, are issues that can be determined given sufficient time and money.

For me it really doesn't matter why it feels good, only that it does. I have any of a variety of paddles that feel good for a certain purpose. Often I give up some feel for strength in my whitewater paddle. Is that loss of feel the result of a stiff fiberglass sheathed shaft and blade, or is it the result of the added weight? Who knows and very few people have the time to figure that out... so we go by feel.

By the way, I've paddled the Nashwaak paddle. It has a nice feel for me for a nice quiet cruise around the lake in the evening. I wouldn't use it for whitewater, or even probably for a big water crossing. But I'm not sure that is what it's intended either.

PK

Gee, Erhard, Read my posts more carefully and you will see that that is exactly what I suggested. Ain't it nice to agree.

I should point out that I have actually participated in the kind of biomechanical research you are talking about and, in fact, was one of the first to suggest that we adapt the techniques of Physcophysical scaling to paddle development and evaluation.

My concern about the web page that frozentripper mentioned was that it made claims without any support and that the manufacturer could have easily run tests to prove or disprove his theories. My last post gave some methodology for doing that.

Often people will say that such-and-such is subjective when what they mean is that they don't understand it and really don't want to take the time to understand it.

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Cheers,

John Winters