Interesting
I guess after three days, the combined force of the two paddlers together (with one being tired) was no longer sufficient to counteract the hull drag at cruising speed, so the top end speed dropped. Once a stronger paddler was substituted, the effect was reversed.
The fact that the weaker paddler was fine once put into a short boat clearly demonstrates that hull length should be tailored to the paddle force one is able to generate on a continuous, consistent basis.
Fine
I’ve already said that I have respect for the opinion of experienced racers - if Iceman is one of those, I’ll take your word for it.
I take exception to his belittling of a technical discussion that he feels is ridiculous. If he doesn’t believe in the merit of the discussion, fine, keep out of it.
Mostly, however, I object to the glaringly incorrect, quasi-technical explanations he is offering. In the vernacular of physics, his descriptions are “not even wrong”, which is to say they are so far from being correct that they don’t merit a point-by-point refutation. They demonstrate a lack of understanding of fluids, physics, etc. The fact that they are riddled with spelling and grammar errors doesn’t help either.
Iceman is not following the discussion closely enough to realize that I don’t disagree with him - I agree that at top racing speed, in-sync paddling is necessary. At lower speeds, this will probably not be the case. He seems to not like my explanations of the physics of paddling. But while he may be a top racer with plenty of experience, I am also an experienced paddler and have a doctorate in experimental fluid mechanics. In fact, I am currently teaching Fluid Mechanics and Dynamics both, so I think I can claim the edge in the technical portion of the discussion.
Lack of understanding is on your part…
– Last Updated: Oct-01-10 4:03 PM EST –
... this time. You say...
"A kayak/canoe is not a "paddle boat" as used to be seemed in Southern US. The paddle of the "paddle boat" works as a propel -moving water. The paddle of a canoe/kayak should not move water, it should allow the paddler and his/her craft to move through a fixed point: the catch."
... and all of that is based on "ideal" theory which is often presented as a means of explaining some things that many people fail to understand at first glance. However, explaining it this way is a huge oversimplification which ignores a host of physical laws and real-world observations. In actual fact, the same things are often said when explaining the method of operation of ship propellers (they don't call them "screws" for nothing), but the idea that there's no slippage and no movement of the water is far from being true in that case too.
The simple fact is that the forces applied to the water and to the boat are balanced, and just as force applied to the boat causes it to move, that same force applied in the oppostie direction ("equal and opposite forces", right?) to a fluid medium causes that medium to move. You know the formula F=MA? It works when applied to water too. When applying a force which causes the boat (having a defined mass, M) to move in one direction, the opposing force causes a certain volume of water (again with a defined mass, M) to move in the opposite direction. The real problem is in "pinning down" exactly what happens to the water when set in motion by a force. The overall expenditure of energy and quantity of force can be explained very simply, but the actual details of the resulting motion of a fluid is much more complex than defining the motion of an object that is independent of the material that supports it. The short explanation of this is that instead of a defined volume and mass of water being set in motion at a speed defined by F=MA, some portions of water are set into motion at one speed, and other portions are set into motion at other speeds, and every definable portion of moving water is likely to be a different size (therefore having a different mass) than every other. The TOTAL movement of water can be approximated, but not the actual details. The movement of water is so complex as to defy accurate mathematical description, and in actual fact, that's exactly the feature of fluid mechanics that makes forecasting the weather such an inexact science.
You don't believe that the water moves? Never mind the fact that you have applied force to a material that can freely take on any shape that it wants - ignore that if you want. Do this instead. Have one of your friends, someone with the most techinically perfect forward stroke of anyone you know, paddle past you while you are stationary. Watch what the water does at the location of each paddle stroke, and watch what that little pocket of water continues to do for about the next 30 seconds (or for the next few minutes if you are halfway observant and care to look carefully enough) after the paddle has left the water at that location. It moves. A lot. Now do the whole demonstration again with a whole bunch of floating markers in the water (like a bunch of twigs) to use as stationary reference points at locations where the water does NOT move, and notice how far the paddle slips relative to the stationary twigs that are not close enough to be immediately affected by the turbulence created by the blade. Jack says you are a K-1 pro, so since your stroke is so brief, I'd suggest making a video of this which you can slow down.
You SHOULD be able to see this for yourself, but clearly you haven't, so next time you go paddling, pay attention to the shape of the water's surface around your paddle blade. Notice the low spot that is formed on the forward side. That low spot is there because the paddle is slipping at a fast enough rate that the water from the surroundings can't flow into that location fast enough to completely fill the void that is left behind. See those little whirlpools at the paddle edges? That's caused by motion of the water around the paddle edges, from the rear edge of the blade to the front edge as the paddle slips due to the force you are applying. If the paddle did not slip relative to the water, there'd be no little whirlpools at the paddle edges, no depression alongside the blade's forward edge, and no big whirling pockets of water (pockets which gradually progress in a direction opposite the direction of boat travel) left behind long after the boat has left the area.
Knowlegable athletes…
– Last Updated: Oct-01-10 2:25 PM EST –
... may know what works, but that's not the same as understanding why. As another example, all of us instinctively know the very best way to regain our balance if we are falling over, not matter what complications are involved with each particular instance, but I bet that not one person out of many millions can explain why that motion accomplishes the task. Carldelo has provided ample evidence that he's willing to accept that there may be aspects of this that are difficult to quantify simply by the thought process, allowing for the possibility that a technique which is "effective" at providing a maximum speed when racing need not be the same technique as one which is "efficient" in terms of using the least amount of energy to move a boat from Point A to Point B at a more normal speed. In that regard, arguing this particular aspect of the issue with him clearly misses the point.
only at very low speed if at all
""""“while for general paddling, the more uniform power application of out-of-sync paddling will require less energy overall.”""""
I’ll wager that to be true only at very low speeds if at all.
I don’t care if I’m in a 70lb plastic tandem canoe dipping down the New River or in an OC-6 out on the Gulf or in a k2 going 18kph, synchonized paddling gets more speed for any given effort level. The instantaneous force application is so much higher when the power is together that it doesn’t matter that there is a “recovery” period during which the boat decelerates. The boat doesn’t decelerate to the speed it would be going with paddlers out of sync unless the recovery period is absolutely ridiculously long.
Shoot, in a OC-6 if you’re stroking and someone isn’t keeping time behind you, you’re in for a long hard day. Just one paddler being a split second out of phase will kill the boat speed.
Yep
The definition of a ‘fluid’, is a substance that deforms continuously under an applied shear. So a paddle must move when in the water. And in fact, there must be relative motion between the paddle and the water in order for any thrust to be generated.
Because of the properties of the fluid medium, as you describe above, it is usually necessary to analyze the situation using the Momentum-Integral Equation, rather than Newton’s 2nd Law (F = ma). This is more difficult to deal with, in large part because the situation is unbounded, and care must be taken to fully define the system.
I don’t think that’s how he meant it
– Last Updated: Oct-01-10 4:06 PM EST –
""""You don't believe that the water moves?""""
That isn't what he literally meant. Of course some water moves but that isn't what you are trying to do. From a physical standpoint you should be able to treat the catch as a fixed point. Doesn't really affect the discussion of why synchonized paddling works better anyway.
Catch
The catch may be a fixed point in space, but the paddle blade itself has to move relative to the water. That’s just a necessary consequence of the fact that water is a fluid and you’re exerting a force on the paddle.
yeah
The less fore/aft movement the better. Ideally the paddle would stick right where you put it with no loss to drag and imparting momentum to the water. Just like ideally the screw would screw itself forward and shove the boat along without shoving any water backwards. The ideal isn’t achieve in either case but that doesn’t affect the opening post or subsequent discusison.
my take
The key is in the instantaneous force application of one at a time compared to two in perfect sync and how that applies to the continuous function of drag vs. speed on a long hull with the weight of the crew. The synchronized boat will not decelerate from its peak speed reached at exit to the slower speed that would be maintained by a boat with the crew applying force individually out of time, as long as recovery is not ridiculously long.
With out-of-sync paddling there is never at any point enough force applied to the boat to overcome drag to the same degree that the summed forces of well timed strokes will accomplish. I think this is true at what I consider touring speed up to race speed, but especially at race speed.
Here’s an experiment. Put a force meter on each paddle in an OC-6. Tell people to paddle at easy pace, long distance race pace, and 500m race pace. Do this in sync and out of sync. Look at the force on each paddle relative to speed. I can’t give you quantitative numbers but I can tell you that when stroking, if timing behind me is off then my force per stroke goes up while the boat speed drops.
Momentum
I think I get your drift, but imparting momentum to the water is the actual mechanism by which thrust is created. So you don’t really want to minimize productive momentum transfer - but minimize effort that goes into non-productive motion like turbulence in the paddle wake (e.g. overpowering the paddle).
Sorry, I guess I wasn’t clear
– Last Updated: Oct-01-10 5:04 PM EST –
The issue was timing only.
The tandem paddlers were not physically tired. The stronger paddler (state cyclocross champion, and seasoned expedition paddler) was the one that couldn't focus to stay in sync. The only fatigue was mental, not a small issue when paddling a tandem.
Once out of the tandem, and paddling my heavily laden boat, she did quite well, although in that situation she was the weakest member of the group. We placed her in the prime drafting position behind the double to keep the group speed up.
Well
OK< now I get it - I think that’s even more interesting…
Maybe it has nothing to do with the…
… topic, but I’m not the one who insisted that it does. The simple fact is that you can’t generate a propulsive force that puts one object in motion without having the same affect on some other object or material, and it was the WAY in which he said this isn’t true that I was addressing.
Both right?
– Last Updated: Oct-01-10 6:47 PM EST –
Interesting discussion. I thought about it as I worked out on the rowing machine today, and mused on how there is a sweet spot in which "strokes per minute" and "power per stroke" are optimized.
When looking at kayaking, it is easy to see that if power remains the same and either of the two variables of blade surface area or rate become ridiculously large that overall speed will suffer. Otherwise, some would be using paddles the size of snow shovels and paddling at 20 strokes per minute and others would be using paddles the size of soup spoons and padding at 200 strokes per minute. So maybe we can agree that when it comes to a single kayak, there is a "sweet spot" which holds paddle surface area and strokes per minute within a certain optimum range.
If you were racing in a single kayak and you were given the ability to to double your blade surface area (and keep your rate the same) or keep your original blade and double your rate, which would you choose? And why?
To my knowledge, top paddlers generally gain extra speed not by using larger blades than their competitors but by having a faster cadence. Is this a clue?
In a tandem kayak, with the greater weight and hull resistance (and also greater length and hull speed), the equation changes. (My logic tells me the size of the optimum blade surface area shifts upward. Would you try to paddle a battleship with a kayak paddle? What would happen if you did?) Paddling out of synch would be equivalent to doubling your rate but halving the blade surface area applied to each stroke.
My guess is that the added weight and resistance of the tandem* shifts the sweet spot such that the increased rate does not bring as much benefit as the increased surface area of the synchronized stroke.
*The tandem, being heavier than a single, has more momemtum also. Probably need to factor that in too.
Quantitive Numbers
– Last Updated: Oct-01-10 7:05 PM EST –
I agree with your reasoning, about how the boat does not lose enough speed between strokes for the benefit of in-synch paddling to be noticable. That must be true for the in-synch method to be better (whether it's better only at high speeds or at all speeds), and I'm not the only one "on this side" of the discussion (suggesting it may not be better for "all" speeds) who's already said so.
At slower speeds, you may be correct about increased effort being needed on your part if one or more of the other five paddlers in the boat are a little out of synch with the group, but it's quite possible that you may not be correct, and here's why. Unfortunately, it's a longshot that this will make sense to very many people here.
Once you are accustomed to applying a certain amount of force and a certain speed of paddle movement (relative to boat position, which is the frame of reference of the paddler in this case), applying that same stroke at a time when the boat does not accelerate as abruptly (because not everyone is helping out at that moment) WILL feel like it takes more effort, even if in fact it doesn't. If the boat doesn't accelerate at the same rate you are expecting it to, because somebody else isn't applying their effort at the proper time, the only way for you to achieve the same paddle speed that you'd otherwise achieve (relative to your own frame of reference, not the water itself) is to drastically increase the force that is applied. You probably won't be able to achieve the same paddle speed (relative to your frame of reference - I must stress that part) since the boat isn't responding as quickly at that moment, and that will really make you think your stroke lacks proper effect. Only quantitative measurement, like that which would be provided by the method you proposed, can provide clear data regarding what is actually happening, since the paddler himself cannot accurately judge the effect of his stroke at different times if the boat does not respond the same way AT THAT MOMENT for the two situations (and that's not the same as saying the boat does not achieve the same overall speed).
Here's another example of that "feel" thing which I'm talking about, and it's one that every river paddler has experienced, but one that is likely to be misinterpreted by nearly everyone. By the same token, it's very likely that a lot of people won't make the connection between these examples and your six-paddler example, but I'll present it anyway. When paddling downstream in turbulent sections of rivers, the boat may have a constant speed relative to the water (or more accurately, relative to the major portion of the water, which is flowing at average speed) but if your paddle encounters a pocket of water that is moving faster than the main current to which you have become accustomed, that particular stroke will feel much less effective, as if the response of the boat to your effort during that stroke is sluggish. Your natural response will be to push much harder on the paddle to achieve the same speed of backward blade motion relative to the boat as you've been applying up until that moment, and you may fail to achieve that rate of paddle motion from your point of view (however, the paddle's speed relative to the water that it is surrounded by WILL be faster, and the resulting thrust WILL be stronger). This makes it feel like you didn't do as much to accelerate the boat during that stroke (which translates to your perception of your degree of effectiveness at maintaining cruising speed), but in actual fact you accelerated the boat during that moment to a greater degree than you would have with a normal stroke, and that is completely contrary to what your muscles are telling you. On the other hand, if a particular stroke encounters a pocket of water having reverse flow relative to the average main current (meaning it is probably still flowing in the proper direction but at a slower speed, though in extreme cases it could actually be flowing the "wrong" direction), you will feel like "paddling is a breeze" and the boat seems to be flying relative to the effort which you expend, but in fact you are contributing less to maintaining boat speed than you are during a normal stroke. Experience shows that very few "non-science" people understand ANYTHING in a consistent way when it comes to frame-of-reference problems such as these (and I'm just saying that right now rather than waiting to be blasted with non-logic for the umpteenth time regarding frame-of-reference boating issues since I joined this site) but I'm putting this out there because it is true, and there's a very good chance that it explains the phenomenom you have experienced in the six-person canoe. If it doesn't explain it, that's fine too, but there's really no way to know right now. The bottom line is that there's no substitute for actual measurements, no matter how convincing the information supplied by your muscles may be.
Physics, engineering and sport
There are plenty of examples in sport where the application of physics and engineering principles have improved performance.
Cycling is maybe one of the best examples. For years cyclists spent time drilling out parts of their bikes trying to make them light. Then at some point someone thought about using aerodynamic shaped tubing - neglecting the fact that there is many more square feet of body than of tubing causing drag. Finally someone had the great idea of putting a bike and rider together into a wind tunnel. Now we have aero helmets, aero riding positions, disk wheels and faster riders.
Same thing happened with downhill skiing and swimming.
Kayaking got the wing paddle.
Applied physics and engineering gave an edge over “what everybody knew”.
Seems foolish to dismiss a possible competitive advantage just because “everyone knows that’s not the way to do it”.
Maybe the physics really does favor in-sync. If so, great. If not, why pass up the advantage because it’s “not traditional”.
Carl seems to have the pedigree and facilities to do the investigation. Even though I don’t compete I’m interested in the outcome.
thrust vs drag
Bing! Light bulb moment.
If the instantaneous thrust is less than the instantaneous drag the boat is decelerating.
Is the drag of a racing boat at racing speed higher than the thrust that a single paddler can exert?
quantative measure in the six
I’m in seat one stroking the boat with a heart rate monitor and a GPS. And I can feel how much pressure I’m putting on the blade and how quickly the blade is moving relative to the boat. I’ve got an objective measure of my output and the boat speed. I can also tell when the boat is slow because it is out of time and when the boat is in time but someone has hit the wall. I’ve been in fresh boats with strong paddler and we’re all working our butts off and not going anywhere.
I’d like to see some real numbers but I think this can be tested (and likely has been tested) through trial and error.
force of effort
The added wetted area and weight of two paddlers in a tandem is a factor. The kayaks in races are ussually being propelled at greater than hull speed, thus friction is multiplied. Try pushing a refrigerator across a tile floor, then pushing same refrigerator with a helper. The necessary force is the same but the felt effort is greatly reduced by sharing the effort. So, if you push, then your helper pushes, while that is the same force over time, the felt effort is greater and the speed is slower. Just cause your in water does not change physics. Synchonized technique wins. Cause it is more efficient. If the two paddlers are willing to try sprints and have a friend time them, as they get better at synchronozing, I am willing to bet they achieve greater speeds. Moving friction may be less to overcome than static friction, it still must be overcome. John