----- Original Message -----

From: Mike Crawford

To: harryproa@yahoogroups.com.au

Sent: Thursday, October 15, 2009 7:31 PM

Subject: [harryproa] Re: sailing BD with leeboard

 

  I wouldn't argue against a leeboard, but if the rudders work, I'm not sure there's a good reason for the extra drag and complexity.  The rudders will need to be built almost to the same strength and kick-up ability in either case.

  Was the change to beam-mounted rudders done to get a better kick-up mechanism, a stronger rudder system, or because steering was unbalanced when the boards were partially up?  All three?  If so, is it possible to get the same advantages by refining the design of hull-mounted rudders? 

  Other than the Rare Bird failure, which was metallurgical and can be solved with beefier stainless or carbon, the reports on the hull-mounted rudders seem to be generally good.  If that system can be improved upon with what has been learned with the different rudder designs up to this point, so much the better.

  As a result, Rob's and Robert's plans for hull-mounted rudders are growing on me.   If they are far enough from the topsides to spin, kick up, and avoid squeezing water, that seems like a good approach.

---

  I'd definitely test deeper rudders, with good fairing and smooth paint, without a leeboard, just to see what happens.

  Just for kicks, I'd also try steering the front rudder the "wrong" way, i.e., the same direction as the rear rudder, when the rig is fully-powered.  If that helps turn the boat, then we know that the CLR has moved forward of the front rudder.  Which will reveal much about what needs to be done in terms of rudder placement.

       - Mike
  

 

Rob Denney wrote:

 

G'day,

Will be great to see how a leeboard works.  Do you think the results will be different from increasing the immersed portion of the rudders?  

regards,

rob

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