The profile of the Powerface of the paddle is also a very important consideration and several theories exist to describe the action of paddling.

It is essential to realise however, that all of these theories rely on the assumption that water is a pure medium with laminar flow, which of course, anybody who has ever dipped a paddle in a river will know that it is not!! For the exercise though, pick the water model which best suits the water in which you paddle most of the time.

The most efficient way to paddle is to place the paddle in the water and pull the body past the paddle. This make the assumption that the paddle blade does not move through the water towards the paddler, (it usually does a bit, but not a lot if you are paddling correctly). The little known theory of "Glide" as applied to river racing and slalom utilises minimum paddle slippage through the water. This achieves a state of equilibrium and maximum kayak propulsion for minimum effort by reaching as far forward as possible and smoothly accelerating the kayak past the paddle. Bounce and yaw are also tightly controlled to achieve this "Glide", but the basic precept is not to cause cavitations behind the blade. Flat profiles achieve this ideal to the greatest effect.

 

Dihedral Theory, assume that the water in which you paddle neither moves nor behaves like water usually does. A dihedral shape is inherently self stabilising in a freefall situation in a pure medium acting perpendicular to the axis of descent!!  Unfortunately it does not really describe what happens when you stick your trusty paddle into the water beside your kayak.   In the first instance you usually stick your paddle in, oblique to the axis of the kayak, secondly if the water is turbulent and not Laminar (Laminar: Hydrodynamics term for consistent & uniform flow), then the self stabilising effect of the dihedral never comes into play. 

But what the hell, they look very elegant and cool even if they are not very efficient. Dihedrals shed water pressure and reduce initial grip or bite and rely on the passage of water over their power faces to achieve stabilization.

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Symmetric paddles evolved as a result of Slalom competition paddling, the tall vertical style stroke was necessary to pass between the hanging poles without touching them. Touching a gate would of resulted in a five second time penalty being added to your timed run down the course. 

Also upstream and reverse gates necessitated the applying of the brakes and pivoting around the paddle shaft as an axis. This meant digging deep into the lower water layers where the water was travelling slower. Consequently paddles of the sixties/seventies slalom era were wide blades with square ends that did not snag the bottom and were maximised for an almost vertical paddling style.

The changing of the slalom rules in the nineties eliminated the need to pivot so often and put the emphasis on paddling quickly rather than just cleanly. This resulted in a change of paddling style to a less vertical style and consequently a new slalom shape. The kinetic.

Slalom paddlers typically use this style because it reaches into deeper layers of slower moving water. This lends itself to faster changes of direction in relation to the water surface. It also reduces the tendency of the kayak to Yaw or swing, whilst being paddled. The ideal rectangle for this style is vertical. Symmetric paddle shapes are better for this style.

Asymmetric blades are probably the oldest profile shape around. They evolved from long thin Greenland paddles where the very long length of the blade made the depth of penetration into the water much less effected by the action of waves. Essentially you did not catch a crab when you tried to paddle in a trough. The low horizontal style of paddling was the principal style used by Greenlanders. When paddling started to develop in Europe the long skinny paddle blades were shortened since paddling in waves was not so much of an issue.

In shallower waters the blades became adapted to fit more blade in the water at a 45 degree angle and the ideal rectangle that the blade fits into is a horizontal one. Racing in the fifties and sixties then figured out that max speed of propulsion was gained by paddling in the layer of water in which the craft floated and this maximised to the aspect ratio we see to day.

Touring or racing paddlers favour this style because of increase stability and have better reach. For travelling forwards it is more efficient because its using the same surface water layer that the kayak is in. Its main disadvantage in short kayaks is the increased tendency to yaw. This is not manifested in longer touring kayaks. The Ideal rectangle for this style is horizontal. 

The kinetic was developed by an excellent Scottish slalom paddler in the early nineties, Niel Baxter. The basic theory is to maximise the average area of the blade in the water at lower angle paddling strokes. The resultant blade shape was carefully calculated to achieve balance either side of the blade.

There have been many derivations and deviations of the original shape since by others. The advantage of it for rodeo paddles is significant, firstly the big area blades provide tremendous bite on the water and secondly, the shape is more suited to the trending more vertical strokes of rodeo.

Slalom racers, in the constant quest to make slalom as exciting to watch as it is to play, have been cutting down turns and contra flow moves . This speeds up the flow of the event and reduces the need to dig deeper slower layers in order to turn more quickly. Neil Baxter came up with a shape in the mid nineties that reflected the compromise between the styles. The "Kinetic" as he christened it , was the first genuinely new innovation in platform shape for a very long  time. 

Straight shafts are perfect mechanical devices. They have predictable characteristics and no natural weak spots. They behave according to two principal parameters. Diameter and Material. The larger the tube diameter the stiffer it is and the more carbon is in it the stiffer it is, though a narrow glass shaft is flexible where a larger carbon shaft is stiff. In pure terms , stiff is good, there is no propulsive energy wasted in the flex. Olympic racers like stiff shafts. The opposite end of the scale are rodeo boaters. There life is all about shock impacts hyper extension, involuntary movements, unintendo's. These guys need a shock absorber between them and their blades to prevent injury.

There are 2 types of crank shaft, the Double Torque & Modified Crank.

With regards to structural strength, any bent shaft no matter how it is constructed is inherently weaker than an straight shaft. This is because the fibres are bent rather than straight. Any fibre is at it's strongest when in tension, and not compression as in a crank shaft structure.  

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There are only two valid reasons for bending and already perfectly good straight shaft.. one is to improve reach, for racing, and the other is to relieve the stress angle in your wrist. The double torque shaft improves reach by placing your hand behind the centre line of the shaft and hence the paddle blade further in front of your hand than you would ordinarily be able to reach. This unfortunately de-stabilises all of the strokes you do behind yourself ,i.e. reverse sweeps etc. 

So for general paddling and rodeo this layout is not great. Still, relieves the wrist issue and is great for touring (sea paddling) and racing where reverse strokes are not an issue.

The big down side of bent shafts is that they can never be as strong as a straight shafts because of the bend. the difficulty is that the fibres tend to fold under compression on the back side of the shaft and this is far worse on braided shaft types rather than uni-directional fibre type. All crank shafts are going to be heavier than their straight counterparts for a given strength. 

This type of paddle shaft neither improves your reach nor impairs your pry strokes. It is basically neutral just like a straight shaft. It does however greatly reduce the stress on your wrist. There are two principal stress components at work on your wrist. Firstly there is an up down movement associated with the feathering of your paddle. This is easy to reduce by reducing the feather angle of your paddle. The second component is a horizontal movement from side to side associated with reaching forward and back. This is much harder to reduce and is the far more erosive or damaging movement. Essentially, if you paddle every day you will eventually experience repetitive stress injury due to this movement. More mature individuals taking up paddling for the first time are the most susceptible group to suffer from this. If you are over thirty and you either have taken up paddling or are doing a lot more than you used to and have sore forearms, wrists, thumbs, sharp or dull pains in your shoulder that don't go away when you take a short break or return when you recommence paddling. Then you are probably suffering from tendentious or repetitive strain injury.

There are two way to get rid of it, the first is stop paddling (a non option!!), the second is to get a modified crank paddle shaft and to paddle gently until it goes away.

Setting the feather to 55° has been calculated and proven to be the optimum feather angle to reduce the associated strain on you back and shoulders.

Trainee Level 3 instructor.