Comparisons
The late D P Moynihan often mentioned that while everyone is welcome to their own opinion, they were not welcome to their own facts. He also loved to paraphrase Lazerfeld, that assigning numbers to things immediately increases our understanding and comparative knowledge. Lets apply those thoughts to Zephyr and Vagabond/Kestrel.
The speed differential noticed between Hemlock’s Kestrel and Curtis’s Vagabond is interesting because they are the same hull, the Kestrel plug being a FG Vagabond with a little bow layout added for cosmetics. Both hulls are 14’2” waterline length, by 24” at the 3” waterline with ~3” off at each end’s length to adjust for Yost’s radiused stems. They both have Length/Width ratios of 7.08 and have the same prismatic co-efficient. Why might one seem faster than the other? Probably skin condition. It’s easy to acquire a new Kestrel by arriving in Hemlock NY with $2500. You’ll have a hull with new, out of the mold, surface roughness of ~ 1mill. Any Vagabond used in comparison was made before 1992. Chances are its surface is scratched. The older boat, will accelerate more slowly due to increased drag caused by surface roughness. Interestingly, they’ll have the same top velocity, but the older boat will get there more slowly. Why?
Top end speed of a displacement hull is a function of length and wave making resistance. There is a formula; 1.55 X the Square root of the length in feet, describing a hulls theoretical maximum velocity in mph, which is 5.84 mph for Vagabond/Kestrel. This is the point where transverse waves spread apart with increased speed until the first and second waves support the hull at its the stems. Any increase in speed beyond that level arrives at “Hump Speed”. Variations from the formula occur with excessive cheek and variation in prismatic co-efficient among other causes, but not when hulls are identical. Naturally, the hull with rougher surface will require more effort to maintain at hull speed due to its increased skin friction.
Zephyr measures 14.2 in overall length. While it has the usual 3” bow layout it’s retrocee’ stern sits almost over the stern waterline, so overall waterline length is 13’10”. The 3” waterline is 24”, so the functional Length to Width ratio is 6.96. Computed top speed is 5.76mph, close to Vagabond’s 5.84. This is not a great surprise as both hulls have about the same waterline length and width and neither designer made mistakes. Their similar L/W ratios, 7 +/- small change indicate good tracking potential.
To develop meaningful speed test results would require several paddlers, a measured course and stopwatches and lots and lots of speed runs in both directions with all hulls at the same skin condition, either all new or all sanded to, say, 1000 grit.
Turning is the main difference between the two hulls. With rails flat both hulls have moderate rocker, Zephyr more on a slightly shorter hull. I’d like to measure that, but Zep should flat turn better than Vag. Heeled is a different story. Both have similar max beam widths, 27.5” for Vag, 27.25” for Zephyr, but at molded rails Vag measures 25.5” and Zephyr 26.75”. Vagabond has 2” of tumblehome total, 1” per side, while Zephyr totals .5” for .25” per side. That difference results in a ~10 dg heel angle differential. Vag heels farther; lifts her stems higher and consequently, will turn through a greater angle of rotation when heeled.
Phil Sigglekow was a stunning boat designer and a fine man with passion for building canoes. He developed dual track side pods for stability and trim adjustability, external molded, bonded-in float tanks and decks, and tried several design concepts including differential and stepped rocker and reduced windage stern shear. All his boats were creative and functional and fun to paddle, and Zephyr the best of the lot, but not magical. Anecdotal evidence can shape opinion toward belief based rather than fact based comparisons.