What is the significance of camber in canoe paddle design?
Should it be a factor in selecting a paddle or is it just present in any efficient and comfortable paddle?
What is the significance of camber in canoe paddle design?
It’s absent in some comfortable and
effective paddles. Ask us about dihedral.
Something new to worry about in the quest for the perfect paddle!
A quick Google search only told me that some paddle marketers consider it an asset for ease of paddling. However, I don’t remember ever reading Marc or Charlie extolling the virtues of a dihedral shape.
When I hear dihedral, I think of airplane wings; thus leading to the obvious question - what is a dihedral shape as it applies to a canoe paddle?
Isn’t hard to find. Camber and dihedral
are part of the same thing, where the paddle power face angles away from the center to the edges.
“Recent research shows that cupped and flat power faces transmit more propulsive power, holding water on the face longer than cambered blades. The convex, dihedraled face allows water to stream off the paddle throughout the stroke where the flat and cupped faces lose purchase on water abruptly at the stroke’s end. This is apparent in use, as cambered powerfaces ventilate easily. This is observable by watching the air being drawn down the blade and off its edges when a partial vacuum is created by the water flowing off the blade. Cupped and flat powerfaces lose their catch on the water and ventilate suddenly with a glop and a shimmy. Emphasizing control rather than propulsive efficiency, a double-cambered blade is preferable for freestyle paddling.”
I don’t know what sort of research was done, but from a practical point of view, flat and cupped paddle faces do tend to have a stronger “grab,” but may flutter under strong effort. Adding dihedral reduces paddle bite, but may cut the tendency to flutter.
I don’t know of any stock formula for the amount of camber/dihedral, but I prefer little or none.
I thought I'd weighed in on this before?? Probably everyone should read Winter's The Shape of the Canoe on paddles before proceeding.
The original concept with camber was to fair in the blade's reinforcing spines to eliminate hydraulic jump when slicing the paddle. Modern materials and chemistry including carbon fibre has eliminated that function.
I still prefer paddles with dihedral. They lose catch more quickly for obvious reasons, but that can be compensated for be selecting a larger blade.
They also reduce flutter, when properly made, and slice more truly, which is important for in water recoveries on Cross Forwards, Draws Prys and Back Strokes, and yes, if one must, the Indian Stroke.
[Much better to eschew that stroke; too much time and drag lost on the long in-water recovery.]
Cambered blades get more "lift" on bow rudders and SideSlips, so optimal blade placement varies somewhat between cambered and flat blade paddles.
Wouldn't it be nice to edit Subject lines for key mis-strokes and spelling?
CEW has addressed these topics…
in this forum and others, as did I several times on some of the old groups.
Camber and dihedral are best examined by cross-sectional views of the blade at intervals from tip to throat and can vary widely.
Charlie quite correctly explained his preferences with regard to camber and included the reasons and applications. This was the correct approach, because each paddler has different preferences according to a number of variables. Among them are water and wind conditions, hull design, payload, paddling style and the biggie, ability and experience. Winters touches on this when he writes:
“Blade size, then is a function of the paddler’s style, activity, and strength. Striking the proper balance is the objective, but without quantified data, highly subjective.
We are no better off regarding blade shaping. No published research exists. Subjective opinion still predominates and we don’t know whether existing blades are inherently good or whether we adapt to their deficiencies.
This observational ambiguity applies to many aspects of paddle design. Are sharp edges better than rounded edges? Is “V’d” camber better than arched? Is one tip shape better than another? We have plenty of opinions but no real proof and should be careful in evaluating paddles and try not to discuss the “feel” of a paddle. A paddle can “feel” wrong because we lack familiarity with it or don’t know how to properly take advantage of its features. Like the “best” canoe, the best paddle is a product of individual parochialism”.
For PC, say diHERdral and diHedral.
Charlie, I don’t know how many whitewater slalom paddles you’ve tried, but they meet your goals for non-flutter, neutral slicing, and backpaddling. I use them almost all the time, but for just cruising I prefer a flat-faced 5 degree bent shaft I made myself. It doesn’t flutter either.
I’m so glad I was away when this thread
began. Charlie and Pag have so eloquently covered the topic that I’ll say little more. The only point that I’ll add is that some paddles will have two small dihedral cross sections where the throat and shaft meet. One on either side of the spine. With in water recoveries or during a strong power stroke a small amount of turbulence may be observed in those locations. From a practical standpoint, it is of little consequence except perhaps for serious racers.
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Custom Paddles and Wood Strip Canoes
I’d like to add what I know about …
...... dihedral and anhedral , but like wenonah related to , what I understand is about airplane wings (other than the mathmatical angle discript.) .
I've tried to discover a relation between how dihedral/anhedral designed into an airplane's wings (which aids in the overall stability of the airplane about the longitudenal (roll) axis , but only during a sideslip) ... could be associated to how a paddle moves through the water .
I could envision the centerline of the paddle shaft being like the longitudenal axis of the airplane .
But I can't see it (dihedral/anhedral) aiding in the paddle's stability during movement through the water , as I can in the airplane sidesliping through the air .
Yes , I know this was a useless post , but I put hard pressed thought into the matter and finally gave up (at least in the sense of relation between wing and paddle and dihedral effect) ... so I deserve to say that , useless or not .
Off-topic, but it brings up a question
Why would dihedral wing alignment only provide stability against roll during a side-slip? It should be continuous. With dihedral alignment, any tipping of the plane in level flight will provide off-center loading and a self-righting tendency. Do the same with with a plane having wings aligned 180 degrees from each other and no such differential loading occurs, so there's no self-righting action. Maybe you are pointing out that a plane that tips (other than to provide on-center G forces during a turn, of course) will also side-slip? THAT would make sense to me but is a backward way of making the point.
Oh, and by the way, I envision dihedral paddle surfaces acting by the same mechanism as dihedral airplane wings - twist the shaft so that the paddling force is applied at some angle other than 90 degrees to the overall blade surface and a force will result to self-align the blade back to a proper orientation. This mechanism also is in agreement with what g2d posted above, and it seems really straightforward to me, but then, I'm not imagining that side-slip is necessary (only an applied paddling force is necessary). In fact, with both airplane wings and paddle blades, you could demonstrate this principle with static forces, varying the angle of the normal force and noting the resulting magnitude and direction of the forces on each wing, or on each side of the paddle centerline. It's also a pretty simple mind puzzle to which you can apply the principle to all sorts of objects of that shape (not just wings or paddle blades) for which forces on each supporting surface counteract a normal force at center.
...... when an airplane is in a coordinated bank turn (no slip) , both wings are experiencing equal lift . Both wings are at the same angle of attack . The relationship of the wings banking to the horizon of the earth does not make one wing generate more lift than the other . It is not as you believe that the lower wing will try to raise and level itself with the earth's horizon just because the the earth's horizon is level .
The airplane must become uncoordinated in a bank turn to effect a sideslip . This uncoordinated attitude is also what will cause an airplane to enter a spin if a wing stalls (pass critical angle of attack) .
When an airplane enters a sideslip , one wing is forward of the other (in relation to relative wind) . This forward wing is also lower (off level) than the rearward wing which is higher (off level) .
The forward/lower slipping wing will be at a greater angle of attack than the rearward higher wing . It is this greater angle of attack that gives the forward/lower wing greater lift than the rearward/higher wing (which has less angle of attack , thus less lift) .
When the attitude of the airplane is in a sideslip ... the longitudenal axis of the airplane is not opposite reletive wind (as it would be in straight and level flight or a coordinated bank turn) , but instead at an angle to it .
The forward/lower wing will have more lift ... the rearward higher wing will have less lift . This is the dihedral effect . This dihedral effect will cause the lower wing to rise because it has more lift than the higher wing , thus aiding in the overall stability about the longitudenal (roll) axis .
The airplane must be in a sideslip for this un-equal angle of attack , unequal wing lift to occur .
Depending on a number of other factors in the design of the airplane , most noticably the postion of it's CG , an airplane may need anhedral to achieve the dihedral effect .
I’d like to add what I know about the topic… oh yeah I have no idea what you guys are arguing about. Of if you are even arguing.
You didn’t understand what I said.
There was no need to explain all that. I went to the trouble of explaining that a coordinated turn - centering of G forces - is NOT the same as a sideslip just so you wouldn't "go there" and yet you did it anyway. I agree with everything you said but none of it has anything to do with what I actually said.
So forget about how wings generate lift and think only about the primary and resultant forces, not HOW those forces are generated. This is a geometry/vector problem, not an aerodynamic problem (well not involving any of the aerodynamic factors that you are mentioning). For a paddle blade, it's the resisting force on each half of the blade that is resisting an applied force at the center of the blade, but geometrically it's identical to the situation where you support a mass against a normal gravitational force at two points on opposing "arms" extending upward at an angle away from that mass.
Pictures would make this abundantly clear to anyone who understands force vectors and geometry. Here's another try with words. If a mass supported between two dihedral arms tips to one side, the the mass effectively moves closer to the side with the higher "arm", resulting in unequal support forces on the two sides, and self-leveling is the result. Impart the same amount of tilt to an object suspended between two opposing arms in the same geometric plane, and the mass remains centered between the two supports, because both supports become "effectively" shortened by the same amount, and therefore the supporting forces on each side remain equal. If those forces remain equal, there is no force pushing the system back to its original orientation.
Here's one more try since you want to compare this to an airplane. To make the airplane example exactly like a paddle in the water, you should imagine the plane falling straight down, but with a horizontal orientation just as if it were sitting on the ground or flying straight and level. In THIS case the wings are acting just like the right and left halves of a paddle blade, and the force of gravity is analogous to the force applied to the paddle by the paddler, and the air resistance of the wings pushing at a right angle to the direction of travel is analogous to what each half of the paddle blade experiences when pushed against water. Now, if that plane that's falling like a rock has a dihedral wing alignment, any time it tips to the right or left, the mass will be off-center relative to the resisting forces on the right and left and it will re-level itself. If the wings are in the same plane, and tipping to the right or left will cause the plane to careen off in that direction, possibly not permanently - it could occillating back and forth like a falling sheet of paper (and this is analogous to paddle flutter) - but totally out of control.
Try it with pieces of cardboard. Drop one piece that's flat, and drop another piece that's slightly bent across the center and see which one has better stability in what is the same dimension as "roll" on an airplane. You'll have to come up with some other way of stabilizing the cardboard in the pitch dimension of course, and to do that, you can duplicate a canoe-paddle situation, by mounting the cardboard on a long lightweight stick. Hold the opposite end of the stick and let the end with the cardboard drop several feet. The stick with the dihedral cardboard "blade" at the end will drop in a more-controlled fashion than the stick with the perfectly flat cardboard "blade". The diheral blade will maintain its orientation as it falls, while the flat blade will want to flutter or tip completely away from its original level position. Make sure you hold the stick in a way that does not prevent it from rotating, as that will screw up this demonstration (try this: stick a pin into the end of the stick opposite from the cardboard and hold that pin between your fingers. There will be almost no resistance to rotation of the stick therefore almost no resistance to "roll" of the cardboard if you do that, but you'll still be able to support that end of the stick as you must).
It's that simple. It took me a while to work my way into thinking of that illustrative model that you can build and operate yourself, but the principle behind how it works is ALL I was trying to explain earlier. Remember if you start thinking about lift, you are missing the point.
Now, camber across the whole surface of the blade, well, refer to what Charlie said. That's different from what I'm talking about.
...... you ask "why would dihedral wing alignment only provide stabilty against roll in a sideslip ??" .
I did understand what you said .
I answered your question , my answer was sufficient and accurate to explain .
You questioned me , my words ("but only during a sideslip") in the prior post ...
Your explanation that delves into airplane wings and associated flight is sooo far from accuracy and compitent explanation that you should not speak about it with an instructional attitude .
I answered your question with an instructional response , because I am qualified to do so and understand what I am saying .
Somehow we are talking past each other
First, you seem to think I disagreed with you about the side-slip vs stability thing. I wondered about your reasoning, and though what you said did not address my actual question the way I tried to frame it (and to explain why would take too much time), I agreed that everything you said was correct. We are not talking about the same things here, and therein lies the problem, so what you call "understanding" looks more like "cherry-picking with a preconceived motive" to me since it is missing my whole point in the process. I tried to relate this to paddles, and I tried to relate the geometric principle of self-righting and how it works with some shapes and not others, but you don't seem to perceive any of that or the forces involved as relevant, and have addressed none of it, even though it's truly the only point I tried to make. For my part, I may be missing something about what you are saying too, because though I can see that you understand flight and lift and I can't and don't disagree with a single bit of your explanations, none of it relates to the topic of paddles in the strict context of force-resistance situations (note how that eliminates any pertinence of lift) or to what I've said regarding basic stability principles as applied either to paddles or to illustrative geometric shapes and forces, so I just don't know what else to say.
I assume you guys are talking about the spine or ridge that is more or less pronounced on the middle of some paddle faces.
I don’t think it matters much to the average paddler.
Paddles can flutter with or without spines. Some of the highest-end paddles I have tried flutter when held loosely. Fluttering usually stops with proper top gripping – and, by that, I mean the both the shape of the top grip and how it is held.
Dedicated face bent shaft paddles are usually spineless and flat. Some dedicated faces are curved or cupped without spines. These paddles bite hard and pull strong.
Then Harold Deal and Bob Foote designed the double scoop paddle for the Sawyer Stingray, which necessarily involved a mid-face ridge. This concept moved into the Sawyer Manta series, and is now also present in the ZRE Powersurge racing paddles. I think double scooping provides a very nice balance of bite and smoothness on dedicated face paddles.
The splendid Gillespie Free paddle, which has a straight shaft and symmetrical faces, has no pronounced spine or mid-ridge, though there is a very modestly greater thickness in the middle of the blade than at the edges.
There is always some greater mid-face thickness near the top of the blade where it merges into the throat of the shaft. To save weight, some of this thickness is sometimes shaved off on some paddles by some designers, such as Brad Gillespie and Jim Snyder.
Some say a ridge is more important on the back face of a paddle than on the power face – launching into theories about water replacement vs. displacement – but I’m too spineless and thick to discuss that.
I have and like paddles with all, some or none of these ridge features. They all work, in slightly different ways. For bent shafts, I prefer some power face curvature and particularly like the Sawyer-ZRE double scooping. For symmetrical straight paddles, I don’t like a pronounced spine on either face but do believe there should be a very modest taper from mid-blade out to the edges.
Jim Snyder’s paddle shape and stroke theories are interesting:
Pictures of your Gillespie “Free”?
I’d love to see them. Guess Brad doesn’t have any up.
The secret is that the second Gillespie Free paddle has a slightly better design than the first one, but (to my knowledge) the second one is only in my head and is yet to be built.
Brad specializes in bent shafts and is a big name in the outrigger community. He sees no market for himself with straight canoe paddles.
I was was dissatisfied with the straight shaft blade shapes and especially grip shapes on the market. I wanted a straight blade based on sort of a downsized Lutra-Quimby hybrid, which could be used in all waters from freestyle puddles to wilderness tripping to whitewater. I also wanted a grip that had a T-like top, a smooth throat for palm rolling, and thumb indentations at each corner. So, I designed my own paddle and tried to find a paddle maker who would build it, which wasn’t easy. Brad graciously agreed to mock up a prototype for free.
He probably doesn’t expect to build another, and certainly not for the price I paid for his outstanding woodwork of cedars, basswood, butternut, black walnut striping, triple layer maple edging, and a bombproof phenolic resin tip.
I’d make some dimensional changes in the second paddle, except I can’t afford to buy it. (Did you know new shotguns are less expensive than some new canoe and kayak paddles?) I’ll eventually post pictures of my Gillespie Free somewhere, but paddles are really a matter of personal subjective preference and feel.
I was an aerospace engineer for 20 years. I wouldn’t ask either one of you to explain airplane dihedral to anyone. I think that one of you kind of knew what he was talking about…but it was pretty hard to plow through the babble. go canoe.
oh that’s just perfect …
...... you were an areospace engineer for 20 yrs. and you felt my explanation was babble .
Have you ever operated an airplane as PIC , ever passed an FAA Written or Flight exam , ever held a Airmen Certificate , ever attended any flight schools , ever held any meaningful flight discussions with trained pilots , CFI's or FAA Flight Examiners about airplanes and flight , ever read and/or memorized an Airplane Operational Manual or 4 , ever read an FAA Pilot Handbook or an AIM (Areonautical Information Manual), ever studied and been tested on FAR's (FAA Regs.) , ever built an airplane , ever had conversation with a Certified A&P , ever became a member of AOPA or read flying mags. for pilots .
You're an areospace engineer and can probably run rings around most trained pilots with coefficients and mathmatical equations .
If my guess is basically correct , it would make sense to me why you considered my explanation babble you had to plow through . I would be interested though in just what terms (words) , sentence context or lack thereof , and/or parts of my brief explanation that babbled you so much you had to plow through it .
I would be more than interested to hear how your explanation compares to mine , the FAA's Pilot Handbook and many other such explanations on the matter of sideslip and dihedral effect ... consider though , you won't be talking to an engineer but a person who has passed 3 major flight exams , has the hours in the logbook that verified what he learned in the books and schools of flight ., and can answer "yes" to all the questions ask of you in the 1st paragraph .
In all fairness I had considered not presenting you with this post ... but , your broadstroke statement without any accompanying explanation , correctional or instructive merit to verify your claimed knowledge on the matter , leaves me strongly skeptical about your claimed knowledge and understanding of the matter .
mrmannerz , you may take that as a request (or challenge) to offer and verify your knowledge ... about "WHY" my statement ("dihedral designed into an airplane's wings aids in the overall stability of the airplane about the longitudinal (roll) axis , but only in a sideslip") , plus my accompanying explanation to gbg (because he ask it of me) ... and "WHY" it was babble that you felt needed to be plowed though .
mrmannerz , you sir have attempted to harrass me , my knowledge of airplanes and flight , my ability to clearly express that knowledge in an understandable manner ... this is your opportunity to show "just cause" for doing so , if indeed you are able !!
I offer the following to support what I have said prior about the matter , is not babble you have to plow through , but accurate and concise speak .
In the FAA Pilot Handbook , ref: Ch.8-10 "Intentional Slips" (it's a pdf so you'll need to give it time to come up and you'll need to scroll down to find 8-10) ...
believe it or not Wiki ... http://en.wikipedia.org/wiki/Dihedral_(aircraft) ... see (aircraft)
for anyone who is may be interested (save to favs.) ... an intire FAA Airplane Flying Handbook ,