A casual and unscientific study of canoe boutiques leads me to believe that most paddlers buy their paddles based upon price, appearance, and someone's recommendation. Sometimes these are good reasons. If all you have is twenty-five dollars, the merits of a one-hundred dollar paddle are academic. If paddling is a purely aesthetic experience, who cares how it works so long as it makes your heart soar when you use it. And, if your significant other tells you brand "X" is the best, would it be wise to contradict? A week with a grumpy partner is a high price to pay for a better paddle.
Suppose, however, that you simply want the most efficient paddle for your needs. Your concerns in that case will be much different and function will take priority over all else. It is for you practical people that this article is written. Nevertheless, the romantics might find something of interest since form and function are not always conflicting religions.
There are six considerations in buying a paddle which are (in no particular order of importance:
Weight - In this age of miracle adhesives and even more miraculous materials, there is no reason why anyone should be subjected to a heavy (more than 24 ounces) paddle. You're going to lift that paddle a lot in the course of a long trip so it makes sense to lift as little as possible. The obvious question is, will a light paddle be strong enough? The qualified answer is, yes, if it is made properly. My own 18 ounce paddle has survived a cavalier attitude to paddle care and feeding and a love of shallow whitewater creeks. Yes, it has been cracked and dinged but it always gets me home.
Because the lightest paddles have not had the test of time you must rely on the manufacturer's reputation. There is no way to look at $175.00 worth of carbon fiber and know if it was well made or not. Wood, on the other hand, can be evaluated by eye. The grain should be straight, the shaft should be laminated with the outside layers made from the hardest and strongest woods (usually ash which is hard enough to withstand gunwale rubbing). The blade can be of lighter woods but there should be some form of impact resistant such as cast urethane, glass, or such. My own preference is carbon fiber which is light and terrifically strong. I am currently testing a ceramic material that promises great things. Of course, the paddle should be no larger than necessary since size is weight which leads us up to -
Shaft Size - The diameter of the shaft (not length) is determined by the size of your hands. If the shaft is too small, you must grip the paddle more tightly. A tight grip constricts the blood vessels in your hand which in turn promotes fatigue. So, how big should it be? Let your arm fall naturally to your side and let your hand assume its natrual attitude. Note that it curls naturally. This is called a state of "natural repose" and the shaft should fit your hand in this state. Bigger than you thought? Probably. Most solid hardwood paddles have relatively thin shafts in order to keep the weight down and to achieve some kind of mystical flexibility (see "feel" later). The same applies to aluminum paddles which are usually off-the-shelf extrusions chosen for economies of production. Don't worry too much about the shape of the shaft. U.S. government researchers studied this many years ago and discovered no significant comfort advantage in oval over round although the oval shafts are usually stronger and stiffer.
Length - First let's clear the air. The overall paddle length relative to your nose, shoulder, navel, or any other part of your body is meaningless. What counts is whether the paddle blade is in the water when your arms and body are operating in their most efficient manner. This means that the upper arm is pushing straight away from the shoulder (like a boxer making a jab) And the lower arm is pulling at about belt level and the body is in comfortable position. Obviously this means that a key element is the height of your shoulder above the water which varies with seat height or whether you kneel. In short you need a different paddle for every boat you own or paddle. (Can you hear thousands of paddle makers applauding?). Well, not necessarily. (The applause stops). You will also be doing some control strokes like draws and braces so a little extra length for leverage is helpful and an extra two inches or so should do the job while providing a satisfactory cushion for changes in boat or style. Marathon, freestyle, and white water play boaters can just ignore all this since you have very specialized needs which must be treated in isolation.
Note that this applies only to the shaft. The blade is not a factor. Yes, paddle lengths supplied by manufacturers almost always include the blade and that is unfortunate since your concern is for the shaft length which includes and leads us up to the -
Grip - There is no end to grip shapes and sizes and it's usually Hobson's choice when you buy the paddle. Here is what to look for. The size should be governed by the same considerations as the shaft, i.e. the size of your hand in natural repose. The shape is up to you although something nicely rounded to suit your hand (sort of like a well formed yam) is nice. Some paddles have unidirectional grips that allow the fingers to curl neatly over the top. Not everyone likes them but they are the best bet for getting a proper fit. I have bought and made over fifty paddles for myself and, of them all, the very best grips have been sculpted and sanded to fit my hand. If you don't mind putting your personal mark on a new paddle buy one with a grip that is obviously too large and shape it to fit. My favourite grip material is teak which, because it has natural oils, requires no finishing, is not slippery, and has a silky feel that improves with age. It is also hard and resists scuffing from careless use. Obviously there are plenty of other woods and materials that work well. Just be aware that soft woods turn rough with abuse.
Get the right grip and shaft size and all you need is a -
Blade - There is not enough room here to discuss the hydrodynamics of blades so we will keep it short and sweet.
The efficiency of the blade is a function of its shape, size, and your body's physical attributes. Blade shape determines the coefficient of drag and lift produced by the paddle. No need to understand what this means except to know that the more efficient blades get the same job done with smaller area. Smaller size means lighter weight which translates into even more paddling efficiency. Hydrodynamicists love this kind of thing but who else cares? What you want to know is whether the blade is right for you and that is determined by how you paddle. If you naturally paddle at a high stroke rate, say 50 to 60 strokes per minute, you will want a smaller blade in the order of 140 square inches. If you paddle slowly or do a lot of braces and such 160 square inches or so will be better. Why the difference? Because the force exerted by the paddle is a function of its area and the paddle's velocity. Velocity? Yes, velocity.
Contrary to popular opinion, the paddle moves through the water with each stroke. Not far, but then it doesn't have to if the velocity is high. In fact, the force exerted increases by the square of velocity and doubling the velocity results in four times as much thrust. Doubling the area only doubles the thrust (if the velocity is constant) so if your stroke is slow you need large area but if it is fast, you are better off with less area.
Why is this so important? Because people are biomechanically better suited for fast motion at lower power than they are for slow powerful movements. (This is one reason why bicycles with all those gears are so efficient). There is one problem. Paddle makers don't tell you how much area a paddle has. They give blade length and width which aren't very useful since two paddles of the same dimensions can vary significantly in area. Since the size of the blade is so intimately tied to how you paddle, your best course is to try a large number of blades until you find the one that is most comfortable which leads to -
Feel - No one can tell you how a paddle should feel because no one paddles in exactly the same way, at the same tempo or has the same physical characteristics. So how can you tell if a paddle "feels" right? by comparing it with other paddles. If it feels good, it will stand out. Mind you, there may be several that feel good and then you will have to turn your thoughts to more practical issues like -
Durability - Gentle paddling about the cottage doesn't put a heavy demand on a paddle unless one is plain careless. Wilderness tripping, on the other hand, can make a perfectly lovely paddle a piece of expensive kindling. While aluminum shafted thermoplastic blades probably offer the ultimate in abuse resistant paddles, wood paddles have come a long way. Reinforced tips and blades, as well as clever laminating have made lightweight almost synonymous with durability. Many paddlers carry one of each, a lightweight delight to use when the going is easy and a heavy spare for the worst conditions. Somehow that seems defeatist to me and I insist on two lightweight paddles. My wiser friends tell me I will regret it some day but I tend towards studied laziness and that leads us up to -
Efficiency - First a word about what we mean by "efficient". Efficiency is the difference between how much power you put into the job versus how much you get out. Some inefficiency is always with us. Because the paddle must push against a fluid there is always some propulsive energy lost in converting potential energy into kinetic energy and, as mentioned earlier, there is energy lost in each return stroke. Since we are all built differently and function best at different speeds, it is important to match the paddle to our natural motion. Some years ago I did a series of tank tests to determine what aspects of blade design made a paddle efficient. It was hardly the last word in such studies but it did provide some general guidelines.
Some of what was learned was that for blades of the same area, wide short blades are more efficient than narrow long blades, spooned and cupped blades are more efficient than straight, increased camber (the curvature of the face of the blade) decreases efficiency, that the profile (beavertail, sugar island, etc.) didn't make any measurable difference, and that the tips and edges should be as sharp as is practical.
Now do not rush out and buy a short, wide, spooned, flat faced, sharp edged paddle. You may have specific needs that mandate something very different. I use regularly eight very different paddles. Each does something exceptionally well or fits a particular boat best (can you hear the paddle makers cheering?) you may not need that many but it has often been said that you cannot be too thin, too rich, or have too many canoes. To that you might add that you can never have too many paddles.