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There are a number of factors relating to canoe shape that
affect suitability as a tripping boat.
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Entry
Shape |
 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.
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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.
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Rocker |
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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!
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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.
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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
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Keels |
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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
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In Summary...
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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.
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