Re: [Paddlewise] Rudders/ frequency

Dan wrote;
re: tank test accuracy;
>I'm not sure what that "+/- 5%" refers to, but if it is the error
>associated with a single test, and if the error is random, then I would
>think that averaging the results from repeated tests would improve the
>accuracy substantially.

(SNIP)

No one tests a ship with just one run down the tank. It would be poor
science and irresponsible professionally. The +/- 5% is based upon tens of
thousands of tests in tanks around the world.

When reading reports like the fellow in rec.boats.paddle one has to ask a
simple question - Is the test repeatable by some one else. The answer is
simple. NO. No one else can duplicate the test. You can't duplicate the
conditions his mental attitude, his physical status, his prejudices and
bias (show me a person without them) etc.. ad nauseum etc.. More
importantly,
the paddler was testing at maximum output when the resistance curve is
climbing at a steep angle. Thus, any increase in power would have minimal
effect on speed. Where power output varies most is at the cruising rate
where most of us paddle and what most of us are interested in.

A fundamental of science is that every theory and experiment carries with
it test that a will prove the theory or experiment wrong. Demonstrating the
flaws in his method is easy.
>
>. The bottom line is that such tests
>are probably not worth the effort.


They might be useful to you, however. For instance, suppose you found that
you could tolerate considerably more yaw than you normally do (or the
opposite).

Might change the way you paddle in rough water.

Andy Knapp's experience is a good example of a test that establishes a
rational need for a rudder in his case but would be unreliable in
establishing a rational need for a rudder in another person's (or boat's)
case. Andy's methodical method, (even if a bit flawed from a scientific
standpoint) is exactly what most paddles should do to satisfy themselves
that they are getting what they think they are getting in their boats,
paddles, and equipment (if you care that is).


Just to provide some perspective, every boat that I design (and those of
some competitors) is tested using a Brooks and Gatehouse Speed Boss. All
tests are done by me using the same paddle on the same body of water in
calm conditions. Each test series involves over 100 runs. 50% are done at
cruising power (for me) and 50 % done at gradually increasing power output.
Suffice to say and without boring you with reams of data. I don't get
nearly the repeatability that others get in their tests. No doubt this is
because I am not so good a paddler but I suspect that I am closer to the
norm than the experts. I have tried some expert paddlers but have not yet
found one a whole lot better. Perhaps it is just more difficult to get
accurate results when the tests are controlled.


Cheers,
John Winters
Redwing Designs
Specialists in Human Powered Watercraft
http://home.ican.net/~735769/


***************************************************************************
PaddleWise Paddling Mailing List
Submissions:     paddlewise_at_lists.intelenet.net
Subscriptions:   paddlewise-request_at_lists.intelenet.net
Website:         http://www.gasp-seakayak.net/paddlewise/
***************************************************************************