[Paddlewise] More Rudders redux

Rob G wrote;

.
>
> First off, if you used the same rudder on a couple of different hulls  is 
> it
> possible the drag percentage could change to a higher or lower  figure?

Absolutely. Ditto if you tested at different speeds. Wave making increases 
more rapidly than friction and rudder resistance would not lilely increase 
as rapidly as the boat resistance. Of course, the rudder design would play a 
role.


> Second, if you were to tank test a few kayaks and you had a series of 
> things
> to test for, what will you test for?

I would test for resistance and, if I had access to an appropriate tank 
(circular tank with a rotating arm) I would test for directional stability. 
Resistance in waves would be interesting if only to see how it compared with 
the data from the Gerritsma/Delft tank tests of sailboats. If it were 
comparable it would make calculating resistance in waves possible.

Another test I would like to see done is for leeway using small keels. A 
small keel might reduce leeway significantly as well as reduce weatherhelm 
at the same time. Rudders do not reduce leeway very well, they just 
compensate for weatherhelm so a keel might be a neat addition particularly 
if located close to the CG where it might not affect rotation.

Cheers

John Winters 
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