A force applied to a free-floating boat tends to change the linear (that means straight line) velocity (that means speed and/or direction) of the boat. And such a force also usually tends to change the angular momentum of the boat (that means rotation of the boat around a pivot point). In this article we are focusing on that pivot point. Knowing where a boat’s pivot point is at any given moment helps to dispel much of the mystery and prevent the disconcerting or unpleasant surprises inherent in self-directed boat travel. The tricky thing about the pivot point is that the location of the pivot point changes from moment to moment because the location of the pivot point of a boat that is underway depends on how or even whether the boat is already moving relative to the water that it is in contact with at that moment.
It’s wise to be always aware whether you are drifting with the current, or you are moving ahead or astern or sideways through the water that is immediately surrounding you. Your pivot point is only at the center of gravity (center of mass to be precise) of the (loaded) boat when the boat is motionless with respect to the immediately adjacent water. When the boat moves ahead through the adjacent water the pivot point also moves ahead (as the speed of the boat increases to hull speed) – to a point in the longitudinal center-line of the boat that is approximately one-third of the waterline distance abaft (behind) the cutwater (bow). When the boat has sternway (i.e. is moving backwards through the water) the pivot point moves aft, in essentially the same way. Any force that is applied to the boat, which does not act directly in line with the pivot point, tends to spin or turn the boat around wherever it’s pivot point is located at that moment.
Just a quick note to help you keep your focus where it needs to be: During this entire essay, and whenever we are thinking about your vessel’s pivot point, remember that we are always and only considering your vessel’s motion relative to the water that is immediately surrounding your boat. We are NOT talking about your vessel’s motion relative to the dock, the shoreline, the ground, or the rocks or islands in the water, or relative to other floating objects, or even relative to nearby water that is not in direct contact with your boat. In other words, regardless of whether you are headed (pointed) downriver or upriver (relative to the shore), regardless of whether you are in the main current or a back eddy, regardless of whether you are paddling forward strokes or back strokes (or any other kind of strokes or no strokes), the important thing (as far as your pivot point at that moment is concerned) is which way your boat is moving relative to the water that is right next to your boat. The simple question is, are you moving ahead through that water, or are you moving astern through that water, or are you dead in that water?
For several reasons – not just for determining your pivot point, by any means – it’s a good habit to maintain situational awareness at all times of the movement of your boat relative to the water that is in direct contact with your hull. And that requires only a quick glance and/or using your peripheral vision – or maybe just a feel for your boat and the water. As you learn and acquire more experience, this will become both more automatic and more useful to you – in any kind of water, and in any kind of boat.
The precise location of the pivot point, why it works, and how the boat moves in response to a force, depends on a lot of things with which we don’t have to concern ourselves right now. Just be aware that when a non-planing displacement hull (like a canoe, a kayak, a fishing boat, a tug, a ferry boat, or a supertanker) moves forward relative to the adjacent water, its pivot point moves forward in the boat. And when the boat moves ‘backward’ relative to the adjacent water, its pivot point moves aft.
Would you like a little more precise explanation? Okay. When you’re moving through the water at “normal” hull speed, your pivot point is located about one-third of the length of the boat’s waterline, measured from where the bow meets the water towards the center of the boat. If your waterline length is 15 to 18 feet, and you’re moving forward relative to the nearby water at normal speed, your pivot point is five or six feet abaft the bow. And since the forces of nature don’t care one bit about what you’re thinking, or which way you’re facing, be advised that when your boat gains sternway (relative to the water close to your hull), the pivot point of your boat moves aft towards a point about one-third of the total waterline length forward of the place where your stern meets the waterline. Remember, we’re talking about the relative motion of your boat and the water that is immediately surrounding it.
The basic seat-of-the-pants experience, and operating assumption you need to have is that the pivot point of your canoe or kayak is up towards the bow when your vessel is moving forward through the water, and the pivot point is back towards the stern when you are moving backward through the water, and the pivot point is only at the center of mass of the boat when the boat is “dead in the water” – motionless with respect to the immediately adjacent water. (Disclaimers: [a] This pivot point discussion does not apply to a planing hull, like a speedboat when it is “on step”. [b] “Force” has a precise definition, but it basically refers to anything that acts to change your boat’s speed, direction of motion, or rate of turn. [c] While quick turns and sudden changes in speed and direction are both common and crucial in whitewater boating, the extremely short waterline of modern solo whitewater playboats, combined with the rapidly changing hydraulics impinging on the hull from moment to moment, make conscious awareness of the current precise location of the pivot point both difficult and often irrelevant. The pivot point of a whitewater play boat is always literally well within your reach.)
Knowing how the pivot point moves helps us to understand and anticipate many otherwise mysterious attributes of boats underway. “Weathercocking” is one example. Wind pushes on all exposed parts of the canoe or kayak, including you, but when the boat is moving forward, most of the sail area is usually aft of the pivot point, so no matter what direction you wish to go, or even what direction the wind is blowing, most displacement boats tend to head into the wind, just like a weather vane. Conversely, if you’re backing through the water, once you have established sternway, a typical boat will tend to back into the wind. (Exceptions occur if the below-waterline shape and trim and/or the above waterline wind profile – “sail area” – is very asymmetrical.) If weathercocking causes problems, it can be addressed either by hull design or by improvising. A tendency to head into the wind while making way ahead can be reduced by increasing the sail area at the bow, or by decreasing the sail area aft. An open canoe is less affected by wind when it is wearing a spray cover. When a canoe or kayak drifts in windy conditions it tends to lay broadside to the wind and seas (depending on the geometry of the wetted area and that of the sail area) as the pivot point returns to the center of gravity of a symmetrical boat on an even keel that is making no way through the water.
In general, knowledge of the peripatetic pivot point helps you control your position and trajectory as well as your momentum, and helps avoid nasty surprises. The pivot point helps enable you to punch upstream out of an eddy, into a strong current, and to paddle strongly against that current, without getting swept away. Knowledge of the pivot point helps take the difficulty and guesswork out of forward and back ferry maneuvers in strong currents. Awareness of the pivot point helps you anticipate that initiating a turn, while you’re moving forward through the water, may cause your bow to move one foot to one side, while your stern simultaneously moves two feet to the other side. When a paddler moves the bow aside or turns at the last second to avoid a hazard, that action may place the stern in jeopardy. When you make a sweeping turn while paddling ahead, your pivot point will trace your trajectory, but the part of the boat that is ahead of the pivot point will be inside that arc, while the part of the boat that is behind the pivot point will sweep outside of that arc.
The location of the pivot point on a boat underway will likely change during a hard rate of turn, since the speed of the boat relative to the water will be quickly reduced as a result of the hard turn. If the boat drastically slows as it falls off of its original heading, the pivot point will return towards the center of mass, and the rate of turn will consequently accelerate – like a spinning figure skater. By the way, the quickest way to stop a displacement boat that is going full speed ahead is NOT by vigorous back paddling or by full power reversing the propellers. Instead, if room is available for the maneuver, simply put the boat into a hard 180 degree turn for a quick stop in the shortest distance. In tandem paddle boats, for example, the bow paddler could vigorously draw on one side, while the stern paddler sweeps forward on the other side, in order to get dead in the water right now. Alternatively, the bow paddler could continue paddling forward on one side while the stern paddler rudders hard on the other side. Or the bow paddler could draw hard on one side while the stern paddler rudders hard on the same side. But if you need to suddenly stop moving over the ground while you are paddling ahead in the same direction as, but faster than the current, you will need to first quickly complete a 180 degree sudden turn, and then immediately paddle forward hard (upstream) to stem the current. That’s a good maneuver to practice in a safe place.
In a tandem canoe or kayak that is moving forward through the water, the pivot point coincides approximately with the bow paddler’s position. So the bow paddler has little or no leverage, for turning, and that’s why the stern paddler usually seems to “overpower” the bow. It has nothing to do with who is the stronger or more effective paddler. It’s due to laws of physics.
In river descents or ascents, verbal co-ordination can be initiated from either end of the boat, but typically the bow paddler is best positioned to read the river and initiate the positioning or defensive moves. An alert and aware stern paddler can often, without even any verbal cues, react appropriately based on the bow’s lead. In open water the bow paddler primarily provides the grunt for forward propulsion and the stern paddler establishes and holds the desired course without slowing the forward motion unnecessarily, while efficiently paddling ahead. In open water it’s better for the person with greater endurance and the more powerful stroke to paddle bow, provided that person doesn’t mind breasting the wind and waves and provided that the stern paddler enjoys paying attention to selecting trajectories, and to holding an efficient course.
However, the great majority of tandem mixed-sex couples habitually paddle with the male in the stern and the female in the bow. On technical rivers, is this because these couples acknowledge the woman’s superior river reading skills and capability for decisive action? On open water is this due to their concurrence that the woman has the stronger stroke and because she has selflessly volunteered to take the brunt of the blast of wind and wave that is the special privilege of the bow station? Or is it because of a tradition with no useful or rational basis that men always paddle stern? Is it because the guy would rather not be on the “short end of the stick” when it comes to having the leveraged power of the pivot point? Tell me what you think.
You might prefer learning and enjoying paddlesport in a solo boat. Paddling solo, you won’t have to coordinate and communicate effectively with another person in order to develop an understanding of the subtle and complex interaction of the boat, the water, the environment, and yourself. You will almost certainly enjoy paddling more than you imagine. If, after you’ve achieved this understanding and joy, you wish to challenge the additional complexities and pleasures of communication and coordination with another person in the same boat as you, you may want to do so with someone who has also achieved an enjoyment and comprehension of the basics through solo boating. Be proud and pleased to paddle with a partner who you acknowledge is as good as you are – or even a little better. And switch positions. Paddle on a different side of the pivot point or on the other end of the boat. You just might like it for a change. And you’ll definitely improve as a team.
Learn how to use the pivot point and turning maneuvers to achieve much better control, trajectories, and paddling performance and enjoyment, in “Energy and Momentum – Use It or Lose It“. Go HERE to see the table of contents and other articles in this series. I appreciate any comments you care to make. This article and series is published and copyright by Clyde Winter, canoeist, kayaker, and U.S. licensed master and chief engineer of motor vessels to 1600 gross tons on any waters.
I first read about the peripatetic pivot point in “The Behavior and Handling of Ships”, an excellent text by Hooyer, about 20 years ago.
During the summer of 2009, an article and a video came to my attention that more closely examines and seeks to explain the complex, ever-changing forces that affect the lateral movement and the rotation of a displacement vessel. Although this article and video are directed towards large ship handling, they can significantly improve your thinking and increase your understanding of how and why your boat is affected by various forces, and provide important insights into canoe and kayak control.