Hugh P wrote:
[ ]
Watching a marathon kayak race will show you that it is not accurate to
say that paddling fast is just a matter of not making mistakes that
slow the boat down: everyone sprints off the start until the field is
broken into groups (the wash-hanging or drafting effect is immensely
important); then they settle down and paddle less quickly for a while,
except for occasional tactical bursts, and finally there is a sprint
finish. Clearly, the faster parts of the race are not a result of
racers simply being more careful not to slow their boats down, but of
increased effort - much increased, because the boats will be travelling
at somewhere around 'hull speed'.

Hi Hugh : ) It still sounds like perhaps the *average* speed of the
winner *might* well be hull speed or very close to it and the losers
will be less than that, due to mistakes. The bursts above hullspeed
would be tactical and probably wouldn't affect an average much. Yeah,
drafting is a big factor I didn't mention---it's probably effectively
lengthening the waterlines of boats.

There are typical zones for winning speeds for various sports and
probably most sports have more variability than paddling---I bet that
water is a far worse medium than air (for cycling) or snow or, uh,
pavement (for running).

I wouldn't be surprised if hull speed is quite easily attained compared
to the huge efforts required to go even a tiny amount above it. So
sprints would be brief but still serve to sort out groups. The gaps
between paddle groups probably aren't as big as in other sports. The
leaders in most sports are out of sight ahead of me in less than a
minute but in fla****er paddling even when I'm in a slow boat design I
only lose a few yards a minute to the leaders. It gives a very illusory
hope! : )

So I still think the screw-up/skill factor is what makes for the clear
losers rather than the "can't go as fast." Skill involves taking the
best line thru the unknown topography of a water course.

There's also the HUGE issue we haven't even mentioned of SUCK
WATER---in shallow water a boat's natural hull speed is interfered with
by waves off the bottom (maybe?) so hard effort to make the boat go
starts earlier in the speed-range but doesn't spike up as quickly
either, so effort is rewarded (yet overall speeds probably rarely even
hit hull speed in shallow water) and maybe the hull speed limitation
also really relates to the size of the wave---because a lighter team
tends to be able to go faster in shallow water. Is shallow water the
uphills of paddling? I think maybe so! : )

[ ]
To say that hull speed is at about 5lb: that means that to move the
boat at hull speed requires average thrust of 5lb (eg to tow it at that
speed, the tension in the rope would be a steady 5lb). Of course,
paddling is inconstant, so the peak force will be higher.

Maybe the above relates to my coach-pal's remarks. I'll have to ask
him!

I suppose this would relate to skiing such that you'd have to figure
out how much force is needed to keep a skier going his max down a trail
then divide that in half for each arm when doublepoling and if a skier
can't go faster than that speed then that force is the highest they can
sustain. (Like tow the skier behind a snowmobile on a spring scale and
read the resistance.)

Of course, this is mostly guesswork, and this kayak coach presumably
has access to data. I am trying to remember enough schoolboy physics to
calculate double-poling thrust from some flat and uphill time-trials.

He mentioned that "Sea Kayaker" magazine publishes hull speeds for each
boat design they analyze, so I gather that this is a constant which is
determined based on parameters you and I mentioned: shape, length, even
surface finish. --JP outyourbackdoor.com

Hugh