Fast paddler in slow boat won’t be fast.
That’s not a true comparison.
Apalachicola about three years ago. 18 boats started. I beat 13 boats with my Chesapeake 17 and a GP paddle. Two Epics, a paddle board racer and a Old Town Egret were in front of me. The Egret 13.5ft, 24" beam. The C-17, 17ft, 24" beam. I have both boats.
Of course here’s is the thing…
The Egret was paddled by a youngster. The C-17 a Master Class paddlerr. … 50 year plus.
The SUP…a race board, average 5mph.
I like reading all the theory’s and opinions but you’ll have to pry my cold dead hands from my 18"-10" x 21" Extremes / Nomads. Can’t be beat when all conditions and hauling capacity are factored in. Take off fast, cruise good, fast top speed, carrying gear, dry ride, smooth ride. My CD Expedition with same dimensions is faster with rounder bottom but bit more tippy. It will take more seat time.
I can paddle my 18’ kayak all day at 4.5 mph.
Same. Not so with my 14 footer; always climbing my bow wave. Refer to Fn = 0.5. https://en.wikipedia.org/wiki/Froude_number#/media/File:Froude_numbers_and_waves.png
Both boats are similar width but cross section is flatter on the 14.
What is it? That’s fast for 8 hr.
My normal paddling routine IS fast and distance. I have been paddling and in that manner for 25 years. And I’m a lousy group paddler.
Length equals speed. Simple physics.
To a point.
I think what is being missed here is that we’re not taking the paddler into account. Sure, we have lots of data for fit athletes who absolutely, 100%, will benefit from a longer boat. If that’s you, congrats!
But for the average, not completely in shape person, both Shultz and Schade are making the case that a shorter boat may be faster than a longer boat since drag is a large component of the forces that must be overcome.
It is an interesting question, but I think there are too many uncontrolledly variables to settle on an answer. I can give one data point, in case that helps. I am a somewhat fit paddler, who is a bit overweight, and does not try to race or hold a fast speed while paddling. My wife and I tour, averaging around 3 mph.
My first kayak was a Wilderness System’s Zephyr 160, 16 feet long, 23 inches wide, rotomolded plastic. To me it felt fast in comparison to my wife’s Eddyline Denali, 15.25 feet, 24.5 inches wide, Carbonlight Plastic Laminate. It was a marked difference, noticed by both me and my wife. I was always having to slow down for her.
We both moved to P&H Cetus MV kayaks, 17.75 feet, 21.5 inches wide, composite. The difference in acceleration and glide was surprising to me and again quite marked. Much better acceleration and glide than my Zephyr. My wife has a much easier time keeping up now, though I still slow my pace a little. She also finds the Cetus a lot faster, acceleration and glide, than her Denali.
My son went with us a number of times last year, using an Oru Coast XT kayak, 16.17 feet, 25 inches wide, plastic folding. When I let him try my kayak this year, he was delighted at how much faster it was. I tried the Oru and found it to be sluggish.
Going strictly on length, same engine, longer kayaks seem faster to me. At least for acceleration and glide. But my samples are flawed due to other variables.
It would be very interesting, in my mind, to compare two models from the same manufacturer, with the same hull design, but different lengths, to reduce variables as much as possible. For example, comparing the P&H Cetus with the Volan, might be close enough?
Cetus MV: 17.75 feet, 21.5 inches wide, composite
Volan MV: 16 feet, 23 inches, composite
Both seem to follow a similar hull design, from what I can tell. Get an average paddler, non-racing type in each and see what they say…
Physics is rarely this simplistic…
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I think the width might play a part. But this is a good test, just need a perfect pair of boats.
I currently own 3 boats:
Old Town Nantucket - 14’9"
Impex Assateague - 17’10"
Seda Glider - 19"0"
From my experience, they go in that order of speed. Hull design is important.
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Here are some additional anecdotal data points. My wife and I paddle together. We started with a pair of Oru Bay 12 foot folding kayaks and generally paddled at the same speed.
After a year, we got more serious and got a pair of Eddyline Sitka kayaks. Mine was an LT (14’6" by 23.5"), hers was an ST (13’9" by 22.5"). With these boats, my wife was consistently faster. While I liked the Sitka LT, it never felt quite right, rather the volume always felt just a bit too big.
I recently traded the Sitka LT for a Fathom LV (15’5" by 21"). The Fathom LV is definitely a better fit for me. Now my wife and I paddle at the same speed again.
Not sure what this proves but it is more data.
Designers routinely make two or more versions of the same boat ; one longer and wider and the other shorter and narrower. This allows paddlers of less horsepower to keep up with their larger more powerful partners . Skin surface wetted friction matters.
There are a LOT of equations in the “simple physics” Of course longer is faster in the abstract world with the assumption that there is ample horsepower to drive to hull speed.
A lot of you are missing the point.
Two boats with the same hull shape, the longer one is always faster. 100% of the time.
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There are so many factors, that affect speed, other than just length, that it’s hard to predict how fast a canoe/kayak will be in the hands of a paddler based solely on length.
A round bottom has less wetted surface area, but is less stable, so you might paddle more timidly.
Fuller ends give a higher top speed, but are less easily driven at lower speeds.
Rocker factors into the equation…
Length to width ratio.
Designed waterline vs. actual waterline as loaded.
Speaking in general terms, a long boat will have a higher “top speed” but might take more effort to maintain an easy cruising speed.
That’s my two cents.