On Thu, 01 Sep 2005 10:31:25 GMT, Brian Nystrom wrote:
Worrying about the most efficient cadence is
rather pointless when you're throwing away massive amounts of energy due
to an inefficient boat.

That is true, but I applaud Paul's effort in trying to better his
forward stroke. Buying a better, faster boat is easy, perfecting the
forward stroke is not. And no matter what boat he gets, the issue of
forward stroke and cadence will still be there.

BTW, I really appreciate your input Brian, as well as Paul's
statements regarding muscle fatigue. You guys are great and Brian I
have enjoyed your posts in pnet as well. I mostly just read these
posts, but though I would comment this time.

Regarding maximum hull speed I have been thinking of an experiment. It
would be nice to tow a kayak at different speeds and measure the tow
line force. I would love to see the speed vs. force curve for a
variety of kayaks. The towing would have to be done is such a way
that the kayak in tow is not in the wake of the towing boat. It would
show how closely the maximum hull speed formula in Brians link applies
to kayaks. Does anybody know if this has ever been done?

Lou

Mr. C wrote:
On Thu, 01 Sep 2005 10:31:25 GMT, Brian Nystrom wrote:

Worrying about the most efficient cadence is
rather pointless when you're throwing away massive amounts of energy due
to an inefficient boat.


That is true, but I applaud Paul's effort in trying to better his
forward stroke. Buying a better, faster boat is easy, perfecting the
forward stroke is not. And no matter what boat he gets, the issue of
forward stroke and cadence will still be there.

True. My point was that it's a matter of degrees. For a performance
oriented paddler, a more efficient boat will yield a much larger
improvement than fine-tuning one's cadence, but both are beneficial.

BTW, I really appreciate your input Brian, as well as Paul's
statements regarding muscle fatigue. You guys are great and Brian I
have enjoyed your posts in pnet as well. I mostly just read these
posts, but though I would comment this time.

Thank you for the kind words. I'm glad to be of help.

Regarding maximum hull speed I have been thinking of an experiment. It
would be nice to tow a kayak at different speeds and measure the tow
line force. I would love to see the speed vs. force curve for a
variety of kayaks. The towing would have to be done is such a way
that the kayak in tow is not in the wake of the towing boat. It would
show how closely the maximum hull speed formula in Brians link applies
to kayaks. Does anybody know if this has ever been done?

Sea Kayaker did some tow-tank testing several years ago. I have the back
issue somewhere, but I'm not sure what issue it's in. Perhaps you can
order a reprint of the article, as they do offer that service. The boats
used no longer exist, but it may make for interesting reading.

On 1-Sep-2005, Mr. C wrote:

It would
show how closely the maximum hull speed formula in Brians link applies
to kayaks. Does anybody know if this has ever been done?

We know it doesn't apply strongly and it is not worth worrying about. First
of all, there's no such "maximum" speed. The hull speed given by Froude's
speed-length ratio of 1.34 is an somewhat arbitrary value that links the
waterline length to the wavelength of the bow wave. Unfortunately, a lot of
folks have interpreted it as a speed limit of some sort.

The page Brian linked to discusses the speed-length ratio in terms of sailboats.
In the case of a displacement sailboat, most designers know that you can't
realistically increase the speed over the so-called hull speed, so the design
of the sail rig is based on that. If you could carry a _lot_ more sail, you
could start pushing past the hull speed. However, that sail rig would cost a
lot (if a significant speed increase is wanted) and it would be a bitch to
handle in most conditions. Since the average sailor never sees his craft
exceed the hull speed with a typical sail rig, the speed-length rule of
thumb starts to look like an absolute law and it enters into the sailors'
legends.

Multihulls and other displacement craft show that the speed-length ratio is
not so much of a limit. Olympic class kayaks do it routinely:
http://www.kayakforum.com/cgi-sys/cgiwrap/guille/wiki.pl?Hull_Speed

The way to interpret the speed-length ratio or the hull speed is to
recognize that it represents a speed that takes a lot of work to achieve.
If you want to paddle fast all the time, then a longer waterline length
is one thing to look for. However, it isn't an absolute guide to the
behavior of a kayak. For example, based on the analyses of a bunch
of kayaks reviewed in Sea Kayak magazine, you can see the following

http://www.greatlakeskayaker.ca/loaVSlwl.htm

You can see that the resistance generally goes down with waterline length,
but there are some exceptions.

Mike