Wednesday, April 8, 2015

How shopping is like canoeing: a primer on steering a canoe

I have never lost my joy of hopping on the back of a shopping cart and riding it through the parking lot on the way to the car.  I personally think I would medal, should shopping cart riding ever become an Olympic sport.  I find there is a certain finesse to it, as the further away from the centerline I push off from the more the cart veers off course, and so it’s about slight adjustments in my pushing foot to the left and right to stay the course.  Now my favorite are the downward sloping parking lots, where pushing is not required.  In these circumstances I find applying slight downward pressure with my foot on top of one wheel or the other is a very effective way to steer, once I have momentum.  If fact, with a good tailwind and a solid stomp, I can get the cart to spin all the way around!  The judges would love me.

Here’s the thing, riding a shopping cart is excellent practice for steering a canoe.  For starters both are steered from the back.  Both utilize slight adjustments in momentum to help steer.  Both require a bit of finesse, and for sure both a shopping cart and a canoe unflinchingly abide by Newton’s 3rd law of motion, which states “for every action there is an equal and opposite reaction”.   The harder I push off, the faster I go in the opposite direction.  The harder I step down on one wheel, the more pronounced the cart will swing around in that direction. Even just the act of pushing a cart works the same way, push hard with your left hand and the front of the cart goes right, pull back and the front swings to the left.  Hard science, right there in the grocery store parking lot!

In a canoe, the person in the front (AKA bow) is primarily the motor, paddling to provide forward momentum, as well as being the navigator / lookout.  The person in the back of the boat (AKA stern) also provides power but with the additional responsibility of steering the canoe.  The stern paddler is the one we will be focusing on here. 

Unlike the shopping cart where we push from behind to propel ourselves forward, momentum in a canoe is achieved by reaching forward into the water with our paddle, and in effect, pulling ourselves along, known as the forward stroke.  The harder we pull, the more forward momentum we generate.  The problem is, we are sitting on the centerline and therefore have no real option other than reaching off to one side. 

Imagine riding a shopping cart and only pushing off with your left foot, not right
behind the cart but way out to the side.  Repeat.  Repeat.  Repeat.   That pesky Newton and his laws pretty much makes it impossible to go straight!  The cart will inevitably veer in the opposite direction, towards the right.  One solution would be to switch feet every couple of pushes, so that after pushing a few times way out to the left, you switched feet and pushed a few times way out to the right.  The cart would zig zag a bit, but the end result would get you to your car straight ahead way out there.  The other solution would be to periodically step down on the left wheel slightly.  The left wheel has now slowed down, while the right wheel continues at full speed pushing the cart in the opposite direction, or in this case, back towards the left. By slowing one side, you’ve in effect, pushed from the other.  

The forward stroke is the one used most often to get the canoe to move in a generally forward direction.   As we discovered however, repeating the exact same stroke is certainly not going to propel your boat in a straight line!  By switching sides of the canoe every so often and using just the forward stroke, we can zig zag along, with the end result over time of ending up pretty much straight ahead.  The harder you pull with the paddle the more pronounced the zigging and zagging.  The other way is to “step on the wheel”.

Once the canoe has forward momentum, by simply sticking the paddle straight down into the water and holding it still, you create drag which in turns slows that side of the boat.  In effect you have just “stepped on the wheel” and the other side is now traveling faster causing the boat to turn towards the side youhave the paddle on.  This technique is known as ruddering.  By angling the blade of the paddle and its position one can achieve a myriad of varying momentum adjustments.  Its effect can be increased substantially by actually pushing the paddle towards the front of the boat (a reverse stroke) which attempts to reverse the forward momentum resulting in sharp aggressive turns in the boat, but really dampers forward momentum. Pulling or pushing the boat sideways are also useful techniques know as draws and prys.   

A combination stroke, part forward stroke and part rudder, (with a bit of prying) known as a J-stroke is a great way to use momentum to your advantage and keep the canoe on a fairly straight path without switching sides of the boat. The Art of Manliness has a great explanation of the J-stroke.

Now if you’ve ever shopped at Ikea, you’ll notice their carts are different than most other American retailers.  Most grocery carts have fixed rear wheels with
the front wheels on casters.  At Ikea, each of the four wheels is on a caster allowing it to fully rotate.  One can literally move the cart sideways or spin it 360 degrees in place.  Because of that flexibility in movement they can be trickier to steer than your average grocery cart! A canoe is more akin to an Ikea cart.  The scientific principles still apply.  In fact, there is a more science that goes into paddling a canoe than one might think.  There is a dizzying array of Einsteinesque mathematical formulas to explain it all, which frankly, tend to confound me, so I think of it as more of an art form. However, for you brainiacs, here are links to a Science of paddling series that is very enlightening, complete with some of those intense mathematical equations.  

The fact is, virtually anyone can get in a canoe 5 miles upriver, and eventually make it back to our livery.  (That’s due to the science of rivers, a topic for another day!)    The question is “how much time and effort do you want to spend at it, and do you want to look good doing it?”


The forward stroke, the reverse stroke, the rudder, draw and pry will collectively get the job done.  The better approach is to combine them, chain them together, blend them, dance with them, and use them to massage your craft where you want it go.  It becomes less about science and more about finesse, and in the right hands is a beautiful thing!  
 Don’t believe me?  Watch Rolf Kraiker teach some paddling techniques.  The last two  minutes demonstrate a beautiful dance of canoe and water, things only possible with "an Ikea cart"!

Here's a great article written by a Ph.D about canoe stroke efficiency. 

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