# My very brief lesson on canoe/kayak stability

I have numerous books on boat design. I know just enough to be dangerous .
A round bottom boat has low initial or primary stability and high final or secondary stability.
A flat bottom boat has high initial stability and low final stability.
The shallow arch and shallow V are generally considered the best all around bottom shapes.
All else being equal, if you have two boats of the same width but different lengths, the longer boat will be more stable.
All else being equal, if you have two boats the same length and width, the boat with more fullness in the ends will be more stable.
And, of course, all else being equal, if you have two boats of the same length, the wider boat will be more stable.

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What are your top three books? I may look for some.

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I have a simple rule for assessing stability of a canoe hull.

A canoe is “stable” until I have fallen out of it. Then it becomes “unstable”.

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What have you learned about width/length/stability and other factors relating to maneuverability and speed? You may or may not be interested in the fastest canoe, but everyone can relate to how well a canoe performs when various straight and turning or control strokes are applied to make it track in a straight line or to move and turn in efficient and pleasing ways. There is a lot to this sport.

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Fun stuff. I can agree that given the same width of a boat, a flat bottom has higher primary stability, and a round bottom lower.
Secondary stability is based upon what submerges when the hull leans to one side or the other. If the volume keeping you afloat goes out of balance between your two sides fairly quickly and significantly, you will feel a force wanting it to return back to level - secondary stability. Higher or lower secondary stability can be achieved with either a flat or round bottom.

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As above. Actually, a perfectly round hull has both very poor primary and very poor secondary stability. Once the hull heels to one side it is perfectly happy to keep going until the paddler stops it or it is completely upside down.

In canoes a hull with a lot of flare in the sides enhances secondary stability. As the hull is heeled, more of the side comes in contact with the water. Tumblehome can have a considerable effect on secondary stability. In hulls with rounded tumblehome as a lot of Wenonah models have, secondary stability is initially good as the hull is heeled. But once the hull is heeled beyond the point of maximum beam on the rounded side, secondary stability drops off dramatically and quickly. The perceived secondary stability of this type of hull can vary a great deal with paddler weight and load which determines just how much of the tumblehome side is submerged.

On the other hand, canoe designs featuring “shouldered” or recurved tumblehome like a lot of David Yost designs have, remain quite stable all the way to where the recurve becomes submerged.

Just look for “hull design” and you should come up with a good selection.

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And in my thinking, a ‘chine’ can be considered a flare as it’s w/in the profile of the hull.

I did a formal year-long program in Yacht Design at the Landing School in Maine 20 (!!!) years ago. I have a decent library of books on yacht design, several favorites although some of these may not be in print anymore.

Understanding Boat Design - 4th Ed - Ted Brewer

Preliminary Design of Boats and Ships - Cy Hamlin

And the classic - Skene’s Elements of Yacht Design - Norman Skene.

None of these talk about canoes or kayaks specifically but the principles are the same as long as it floats.

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