Also have to consider cavitation
As you pull a standard paddle through the water, it creates an air pocket (or foam) on the non-power face (forward side of the paddle). That cavitation makes it harder to pull on the paddle since you’re pulling against the water with air behind it.
With a wing paddle, there is a smoother flow over both sides, lessening the cavitation.
My Small Endurance Race Wing 18" x 6"
– Last Updated: Jan-08-11 5:50 PM EST –
has about the same resistance (feel) as my Full Tour 19.125" x 7.125" Yet boat speed is easier to keep up and top end potential is higher.
Compared to the Full Tour:
1. Same boat speed for less effort than the Full Tour.
2. Faster boat speed with same effort.
Above using heart rate for measure of 'motor' output.
Full Tour used with the same, more efficient, wing stoke.
Edit to add ... Though I wish I could put one of these in everyones hands, the wing is still not everyones cup of tea.
It’s All HANDS, Right?
– Last Updated: Jan-08-11 6:42 PM EST –
A paddle is just something to push and pull with your hands. Your hand bones are eventually connected to your ass and feet bones which are connected to your boat.
So if a wing paddle is 'faster' than other paddles it is just providing more resistance or resistance for a longer time per stroke than other paddles. Right?
Not so sure about that
– Last Updated: Jan-08-11 6:53 PM EST –
First, you are talking about ventilation, not cavitation. Ventilation is where turbulence behind the blade allows an air pocket to form, but that air pocket is atmospheric air (hence the term "ventilation", not water converted to gas as in cavitation. Humans lake the horsepower to create cavitation. Cavitation is when such extremely low pressure is created that the water turns from liquid to gas. This is a problem with large ship propellers when "power exceeds grip", and the vacuum effect of this action is also extremely destructive to the propeller itself, popping out pieces of metal from the low-pressure side of the blades.
Second, if what you said were true, that it is "harder to pull" on the paddle with an air pocket behind it, that would be a GOOD thing, not a bad thing, as by definition that would mean there is less slippage. In actual fact, air pockets behind a paddle blade reduce the blade's resistance to slippage, rather than increase it. Thus, both cavitation (in the world of motor-driven propellers) and ventilation (for us mortal paddlers) are to be avoided if you want maximum propulsive power.
That’s basically it
– Last Updated: Jan-08-11 6:38 PM EST –
The wing paddle may be a more efficient way to grip the water, but ultimately, you can't apply more forward thrust to your boat than that which is transmitted between your hands (your connection to the paddle) and your butt and feet (your connection to your boat). You could generate just as much, and probably a lot more thrust with a huge paddle blade of conventional design, but in actual practice that would work poorly because you also have to be able to accomplish entry, exit, and recovery in an efficient manner, whereas the huge flat blade would only be good for the power phase of a stroke, though potentially only for the middle part of the power stroke if the blade were big enough to "stay put" in the water that well, since in that case simply changing the angle/orientation of the blade in the water during the course of a power stroke would require energy-wasting slippage (a prying action) in opposite directions at the top and bottom of the blade (on a conventional blade that is slipping a little bit during the power stroke, changing the orientation of the blade in the water only causes differential rates of slippage from top to bottom, so this would not be as much of a waste of energy because at least the direction of applied force is the same across the whole surface of the blade).
So many wrong answers
yet so many you seem to use wings? The strongest power stroke is done by keeping a straight arm and rotating the body. This keeps you from using to much of the bicep muscle which is one smallest muscles in the body and using your back, torso, hips and legs. The arm should only bend when the blade exits the water which should be at the hips and no further. However when you do this you cannot keep the blade close to the boat, it naturally moves away from the boat. A wing paddle should exit the water 18 inches from the boat while a touring paddle should exit no more than 12 inches from the boat. If you move a touring paddle away from the boat it loses efficiency. This is where the “lift” comes in: the lateral movement actually creates forward movement of the kayak. Not much but you also do not lose any efficiency and are able to use the strongest muscles of your body.
There are 2 great forward stroke videos available. One by Greg Barton and Oscar Chalupsky and the other by Brent Reitz. They both address wing paddles as well as wing paddles. If you are willing to dish out $400+ for a wing, you should invest the $30 for the video so you can get the most out of your investment.
Efficiency
A boat is propelled forward just like a rocket is, by throwing mass backward. The more mass you can throw backward, the slower it has to go to get the same forward thrust. A normal paddle accelerates the same volume of water backwards when you pull straight backwards. A wing paddle accelerates a larger volume of water because you are moving the paddle sideways. This results in less slippage. The amount of energy lost in each stroke is equal to the force applied times the distance that the paddle slips compared to sticking it in the sand. The force going through your hands will be the same for either type of paddle. The amount of thrust generated in either case depends entirely on how hard you pull on the paddle. The only difference is a slight increase in efficiency with the wing paddle.
Different types of propulsion
This is certainly not true - your statement comparing paddling to rocket (reaction) propulsion does apply to drag-based propulsion, i.e. Euro paddles. In this case, momentum-impulse concepts can be used to analyze the situation (with caution, the system must be defined properly).
Lift-based propulsion, as in a wing paddle, is entirely different. A wing paddle could drive a kayak with NO motion in the direction of travel, just lateral paddle movement through the water. That is the nature of lift. It’s got nothing to do with ‘grip’ or ‘slip’ or any of the other bizarre notions that have cropped up on this thread.
A wing paddle used correctly creates a big lift force - this force points mostly in the direction of travel, so the boat is pushed forward. And in order to generate lift, an airfoil must be moving relative to the water it is touching.
Now We’re Talkin’
So if I put 30 pounds of pressure on a wing paddle for a stroke am I going any faster or farther than if I put 30 pounds of pressure on an equally long stroke with a euro paddle?
this thread kills me!
Yeah - winter is definitely here!
Pounds
Pounds are force, not pressure.
Onno answered your question above.
I’m not a kayaker and have never …
– Last Updated: Jan-08-11 10:00 PM EST –
...... touched a wing paddle so given that , here is why I believe a wing paddle delivers more forward efficiency than a standard paddle .
In the first place it is not only dynamic force (which you may call thrust, push or whatever) that is delivered from the power face side of blade ... it is also "lift" which is the negetive pressure on the non-power face side of blade that is "PULLING" you forward .
That pulling force is basically free to you ... when compared to conventional blades which have no such pulling force .
Also two other commenters gave additional reasons of benefit ... the paddle "is" constantly moving into undisturbed water (both on non-power face and power face sides) ... also the water ahead of the paddle is less disturbed because of that "clean" water ... and the convex and concave cambers of the faces . The convex (non-power face) adds "some" lift but additionally it allows for less turbulance ahead of the blade ... the concave (power face) retains the water it grabs longer than a flat blade (less slipage of water) , remember you can't compress water but you can force it to stay in one place longer as a surface is passed through/against it .
Does a wing paddle work like an aircraft wing ?? ... NO ... Well , yes it does but only a little bit ... but that little bit is enough to have the paddle's exit point farther forward than it's entry point (not having used one myself I can not verify that , but I believe it will be true if proper stroke is applied (and also because Eric said so which I believe) ... where as just the opposite happens with a conventional blade .
The wing paddle will move foward during the stroke and that forward motion is transfered to the kayak ... my belief is "FREE" forward motion .
In a general aviation aircraft wing (say a prop job) , dynamic lift is about 17% (dynamic is that air striking the underside of the wing pushing it upwards) ... lift that is created from above the wing is a result of lower pressure across top camber of wing , think of it as a suction pulling the weight of aircraft upward . When angle of attack is increased , lift is increased (that's why an airplane climbs) ... but only until "critical angle of attack" is reached !! Then "ALL" lift is lost completely and almost immediately . Also the faster the wing moves through the air the greater the lift developed .
The air being split by the wing at it's leading edge goes over , and under the wing . The air that goes over the wing "INCREASES" in speed because the upper camber of wing (surface distance) from leading to trailing edge of wing is "longer" than that of the underside wing camber . Think of it as the top of a wing is a bump and the bottom is flat (close enough for a mind picture) . Another way to see it is think of 2 molocules of air (on top each other) both getting to the leading edge of wing at the same time ... one goes under , one goes over . Both molocules will reach the trailing edge of the wing at the same time (the one on top had to go faster to get there at same time as the one on bottom) . For visual purposes you can say they both are stuck to each other again at exit of trailing edge , but not really .
This faster air above wing causes a lower pressure on top surface and "the lift" developes on upper wing surface (only within the linear boundry layer which is very , very close to the wings actual surface) . This smooth linear boundry layer is easily upset and turbulance begins (low pressure boundry layer peels away from surface) from the trailing edge forward towards leading edge as "near" critical angle of attack is reached . The pilot feels what is called a buffeting in the controls at this stage (eminent stall-about to happen) , that is the lamiar air flow becoming turbulant (peeling away) . At "critical angle of attack" the wing has lost (looses) all lift (beginning from rear) and "stalls" .
Since a wing paddle is drawing through the water with it power face pushing against the water (as in a conventional paddle) ... the only other benefit that can be gained is the water that ends up going around the paddle that remains stuck (moving linearly) to the non-power face , and it is this water that creates the lower pressure on the front side of paddle and consequently pulls the paddle forward during the stroke .
Just felt like typing but this is how/why I believe a wing paddle could deliver better efficiency (in terms of forward motion of kayak) .
My use of “grip” and “slip”
– Last Updated: Jan-08-11 8:55 PM EST –
I can see what you mean about the inappropriateness of those terms. For my use of the word, "slip" is NOT the sideways motion of a wing slicing through the water. I was only referring to "slip" as paddle motion that would not occur in reaction to thrust when within a completely solid medium. To clarify my intended meaning, I'll ask what you think about the fact that a wing of any sort, when generating lift against an opposing force, pushes the fluid medium into motion in a direction roughly opposite that of the lift? That's the kind of "grip" and "slip" I was talking about, even if it's not "proper" terminology. In this case, "grip" is the ability of the blade to develop thrust and would be pretty much interchangeable with that term, and "slip" would result in the motion of the fluid medium in the opposite direction of the force applied to the boat.
I don’t see an “answer”
– Last Updated: Jan-08-11 9:11 PM EST –
All I see is a user's perception of how it feels to use a wing paddle, along with evidence that it is really more efficient. I am sure that it is a true statement, but that does not constitute an explanation of what is happening, so it does not answer Kudzu's question.
Let's say Kudzu intended to use "pounds" as a measure of the force transmitted to the boat. I think that's a fair assumption since we know he is using lay terms and the strict definition of "pressure" would have no application in this context (force applied toward propulsion, as measured at the paddle-hand connection). I think he understands what's going on, in that 30 pounds of force (thrust) applied using one paddle has the same effect as 30 pounds applied by another, but IF that force/thrust has a longer duration per stroke with a wing paddle, you'd get more return for your effort, since in that case applying slightly LESS force per stroke would actually provide the same overall result (this is reminiscent of another discussion we had about paddling physics some time ago).
How's that sound to you?
I think you nailed it
– Last Updated: Jan-08-11 9:18 PM EST –
in your first few paragraphs.
An airplane wing
that develops “lift” does so because it deflects air downward. The more lift a wing develops, the more air is pushed downward. It is easier to visualize with a helicopter. It has to push a certain mass of air times it’s velocity to generate lift. Harrier jump jets that push a smaller mass of air down at a higher velocity are much less efficient then a helicopter. When a wing paddle is developing lift, it does so by pushing water backwards.
How much pressure difference?
carldelo, thank you for correcting my lay man bad physics terminology of ‘compression’ vs bernoulli derived pressure differentials due to speeds in the laminar flows whatever stuff.
How fast do you think that a typical wing stroke has the paddle moving sideways, likely a tenth or two of a mph? Sure water is denser than air, but how much ‘lift’ is really being created as a percentage of power input? Propellers and hydrofoils are moving at significantly higher velocities.
The shape of the wing helps keep its fore/aft position neutral to slightly moving forward (but only for the very best paddlers) as it moves out to the side.
I still think the most important part of a wing’s efficiency is the clean water column it is continually entering. pilotwinz put is like this below… “the paddle “is” constantly moving into undisturbed water (both on non-power face and power face sides)”
The two parts of this clean flow and new water may be what adds up to the single digit increase in efficiency attributable to the paddle itself. The torso rotation and larger muscle groups likely account for the bulk of the speed gain and reduced perceived effort for an average paddler using a wing.
PAX
you don’t really believe I gave that …
… explanation about an airplane wing’s “lift” because I didn’t know what I was talking about , do you Flet ??
Just in case you might be wondering now … I did know exactly what I am talking about in reference to a wing’s lift .
Your comment is completely inaccurate , but nice try .
A propeler or rotor developes lift in the same exact way … it generates a low pressure on the leading (forward) side of the blade that “PULLS” the craft … it does not “push” it as a jet engine does .
Push versus Pull
Actually, when you are talking about a difference of pressure on one side of the blade than the other, the net force is simply the difference between the two. Both sides of the blade are being “pushed”, but one side is pushed a lot harder. It makes no real difference I suppose, but it’s best not forget that the pressure exerted on the low-pressure side is not zero, so there IS a force applied in the “wrong” direction. It’s just a smaller force.
It’s the answer to what he asked
– Last Updated: Jan-08-11 11:39 PM EST –
He asked for a given stroke force, which paddle will make him go faster, which is what Pat answered. He didn't ask for an explanation. As far as proof, I think Pat has a lot of credibility. I didn't see anything about stroke duration in his question.
The whole force discussion is a little sloppy. When using a Euro, the paddler force is applied sternward against the water, and the paddle moves in that direction - therefore it represents useful work.
When using a wing, the primary motion of the paddle is lateral. The force exerted by the paddler is that which balances the drag in the lateral direction, and that force is exerted in the lateral direction. So the majority of the work is put into the system laterally. The lateral motion of the wing generates the lift force (or thrust). The force to balance this thrust obviously comes from the paddler, but it's less about pulling the paddle backwards, than it is restraining the paddle from accelerating forward, away from you.