I've been researching which kayak I'd like to buy, and I keep coming across the notion that longer kayaks are faster than shorter ones. I can understand that shorter kayaks have a greater tendency to alter course with each stroke, thus affecting your overall forward velocity, but if you correct for this in your calculations, it seems to me that a longer kayak would have more overall surface area than a shorter one, and would thus be slowed.
It is perhaps the case that this slowing of the longer kayak is not as pronounced as the loss of forward velocity experienced by the shorter kayak. Is there something else physically going on that affects the kayak's performance in the water that I'm not thinking of?
tl;dr: is there any truth to the fact that, all things being equal, a longer kayak will have a higher top speed for a given kayaker, and if so, why?
Note that I ask about length specifically. In other words, two boats of identical design and type, with identical beam widths, identical hull materials, and the same pilot.