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Discover the magic behind the number

This article originally appeared in Canoeroots and Family Camping magazine.

If there’s one thing that most people think they know about canoe design, it’s this: A longer canoe is always faster than a shorter one.

Well over a century ago, British engineer and hydrodynamicist William Froude came up with a simple formula that, to a certain extent, proves this theory. Froude determined that the top sustain- able speed in knots of a watercraft is equal to the square root of its waterline length multiplied by a constant value of 1.34.

This means that a 16-foot canoe would have a hull speed of 5.36 knots, or roughly 10 kilometers per hour. Of course, it’s possible to propel a 16-foot canoe faster than 10 kilometers per hour, but according to Froude, beyond this speed frictional resistance increases rapidly.

However, it’s clear that Froude wasn’t thinking about paddlers. There is a threshold where a canoe becomes excessively long and in- efficient. Naval architect John Winters, whose designs are built by Swift and Hand Crafted Canoes, recalls a man who entered a “very long canoe” in a marathon race. “Despite a superhuman effort, he lost,” writes Winters in The Shape of the Canoe, a comprehensive book on canoe design. “Excessive wetted surface...did him in.”

A pair of paddlers can move a 16-foot prospector faster than two paddlers in a 26-foot voyageur canoe because of the greater surface area (and corresponding resistance) of the larger hull.

So where does this fit into canoe design? According to Winters, length is only one element juggled in the conception of a canoe.

First off, Winters outlines the canoe’s desired usage—flatwater, whitewater, sporting or tripping, solo or tandem. Then he sets an ideal cruising speed for the hull and works backwards to determine a possible length range.

Beam, draft, displacement and dozens of other measurements are compared as a ratio to length to yield values to estimate how easily the canoe will move through the water and how well it will suit a given application. This is why “boats of widely different lengths can have similar performance characteristics,” says Winters.

The reason tandem recreational canoes typically measure 15–17 feet while solos are traditionally a foot or so shorter is simply a matter of stability and space. These lengths essentially yield the most user-friendly ratios when compared to the appropriate widths to make a canoe sufficiently comfortable and voluminous.

Did the generations of Aboriginal builders who designed canoes have their own mathematical formulas? Not very likely, says Winters. “Thousands of years of trial and error are bound to get close, even if it doesn’t explain why it works.” —Conor Mihell

This article appeared in Canoeroots & Family Camping, Spring 2012. Download our free iPad/iPhone/iPod Touch App or Android App or read it here.

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About Canoeroots

Published in the heart of canoe country, Canoeroots celebrates the rich tradition and heritage of canoeing with the gear, adventure and soul of today's canoeists. Every issue is loaded with canoes, news, techniques, gear and tips from the very best outdoor writers and photographers. In 2008, we merged Family Camping magazine with articles, stories and product reviews for North America's largest outdoor audience—camping families. Canoeroots & Family Camping is the best combination to come along since the S'more.