Canoe Shape

Entry Shape

There are a number of factors relating to canoe shape that affect suitability as a tripping boat.

Canoes with sharp, narrow bow lines are fast and efficient, but tend to "knife into" or slice through waves rather than ride up and over them. 

Conversely, a canoe with a blunt, wider bow will handle waves and rapids more efficiently, because it has more area at the front that a wave can lift up.

Is there a right choice? It depends on the type of paddling you are doing. Those of us who mainly do flatwater paddling can tolerate a bit more "fineness" in the bow. 

If we paddle large, wavy lakes or the occasional whitewater, we have to choose a boat that will not gather water by the bucketful - a canoe with a wider, blunter entry shape.

Width

Width is a complicated variable - it depends whether we are talking about width at the gunwales, width at the water line, or width at the widest point of the canoe. These are all common measurements. In general, a tripping canoe will be about 36" wide, but the handling of the canoe is dependent more on shape than this property.

Rocker

Rocker has to do with the "flatness" of the keel line when viewed from the side. A highly rockered canoe has a definite curve along its keel line. Another canoe might be almost dead straight along the keel from bow to stern, in other words it would have no rocker. 

As in all areas of canoe design, selecting the amount of rocker involves tradeoffs. A high degree of rocker means that a canoe will turn on a dime and handle wonderfully in whitewater, where quick maneuvering is required. It will also be very hard to keep in a straight line while paddling. Zero rocker means that we have a canoe that runs like it's on rails - it will be simple to keep it tracking perfectly straight. Don't count on it for fast turns or maneuverability when that rock appears in front of you in the rapid though!

Tumblehome and Bottom Shape

Tumblehome refers to the amount a canoe narrows from the widest dimension as it approaches the gunwales. A boat with tumblehome is narrower at the gunwales than at its widest part below - it "bulges" a bit at the centre. A canoe with no tumblehome is basically a rounded or slightly vee'd shape. The widest part of the canoe is at the gunwale line. What's the difference?  Tumblehome is often added to make it easier to paddle a canoe - a narrower width means the paddler doesn't have to reach out as far.

To understand the disadvantage of tumblehome, we have to understand the concepts of initial and final stability.

Initial stability is how stable a boat feels at rest, when it is sitting flat in calm water.  A flat-bottomed boat has the highest initial stability and a round boat has the least.  A round bottomed boat feels like trying to sit on a log or a steel drum in the water.  It rotates easily, resulting in a less-stable feel to the boat.

Secondary stability refers to the stability experienced (or not) as the boat is leaned or heeled over to the side.  As a canoe is leaned this way, it may become more or less stable, depending on the shape.  A canoe that increases in stability is one with high final stability.  One that doesn't has low secondary or final stability.

So what does this have to do with tumblehome?  Picture a canoe with a rounded or vee shape.  As it is leaned, it displaces more water.  The more it leans, the more water it has to displace, so it becomes increasingly difficult to tip.  It has high final stability.

A canoe with tumblehome has increasing stability as it approaches the widest part (the bulge) but once it leans beyond this point (into the tumblehome) it gets suddenly easier to lean.  This low final stability can result in some sudden and surprising action.

In general, a boat with tumblehome probably has a flatter bottom and feels much more stable in calm water. A boat with a rounded bottom has a sensitive, tippy feel.

Great - what does this mean to us? It means that although a flatter boat will feel more comfortable at first, it can end up surprising us in rough conditions. A round or vee bottomed canoe may take a bit of getting used to, but it will be more forgiving when we hit the waves and rapids. Not that we should eliminate canoes with flat bottoms - if we do primarily flatwater tripping, this shape will do just fine.

Depth

Adequate depth is critical in a wilderness tripping canoe. We have to remember that we'll be carrying large loads, and quite possibly paddling in large waves. Adequate depth is a must-have for whitewater paddling also, to ensure you stay dry.  

A canoe with a twelve inch depth is the bare minimum. A depth of thirteen to fourteen inches is not uncommon in good tripping canoes. If we buy a shallow canoe, we had better be prepared to do two things:

  • some bailing if we hit even moderate whitewater or waves
  • trim down the gear list to lighten our load and leave some freeboard

Keels

Keels are put on canoes for two reasons; to help them track (stay in a straight line) better, and to strengthen the bottom. They certainly do their job, making for a much straighter-running boat, but if we're planning on paddling whitewater or shallow, rocky areas we're going to be catching that keel all the time. Unless we're sure that the canoe is for flatwater tripping exclusively, we should avoid keel construction

In Summary...

So where does that leave us, other than thoroughly confused? 

First, we have to realize that there is no perfect tripping boat. If we're a flatwater paddler, we will probably be looking for a different canoe than somebody that paddles rivers with lots of rapids, fast water and rock gardens.

Some general guidelines always apply, though. The canoe should always have an adequate depth and volume. Small canoes take on water and can't carry the loads necessary for wilderness tripping.