[Paddlewise] speed and resistance

I was just reading Matt Broze's article in August's Sea Kayaker magazine
about the amount of resistance generated at different speeds.  Its clear
that the drag resistance builds up pretty quickly going from
3.0->3.5->4.0 knots:
 
3.0 knots -> 2 pounds of resistance
3.5 knots -> 3 pounds of resistance
4.0 knots -> 4 pounds of resistance.
 
So, going from 3.0->3.5 knots there is a 50% increase in resistance for
only a 17% increase in speed, and from 3.5->4.0 knots a 33% increase in
speed for only a 14% increase in speed.
 
Given the significantly increased resistance going from 3.0 to 3.5
knots, and that this is in the common cruising speed range, I wonder why
Sea Kayaker doesn't give resistance figures for 3.5 knots in their kayak
reviews.  Are kayak's resistance just too similar at this speed to make
this info worthwhile?
 
I've also noticed that when short sprint speeds are given (determined
with a knotometer),they often peak out at about 6.25 knots, even though
the resistance fiqures at the 5 & 6 knot range may be quite different.
Any thoughts?
 
Norman Strutin
(SF Bay Area)

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