Subject: [harryproa] Re: Current rudder design?
From: "Robert" <>
Date: 5/26/2008, 1:29 AM

-There are various iterations, depending on boat. The earlier ones are
attached to the side of the hulls and work well but add to the
complexity of the hulls and possibly drag (I am not so sure that they
add significant drag and would be quite happy with them). These
rudders had 270 degrees maneuverability. They can be seen quite
clearly on the harryproa website on 'rare bird' and 'aroha'. Rob has
been working on beam hung rudders, playing around with them on the
little Elementarry, and you can see how they have developed in some of
the files and photos. They are designed for 360 degrees. He has done
some finite analysis engineering to work out the stresses to make sure
the mounts are strong enough. From what I can gather, the beam hung
rudders can be lifted for skinny water or swung out of the way. They
also have means of kicking up either direction if necessary. If the
motors are placed on the rudders it becomes more difficult to retract
them for skinny water. The rear rudder is a large part of the leeway
resistance and therefore need they need to be fairly substantial and
strong. Some find it useful to lock the rear rudder and steer with a
partially lifted front rudder. For tight maneuvering the two rudders
together allow you to crab or spin in circles. The early rudders had
the toe leaning forward to allow balance. This may have helped in
avoiding ventilation.
Robert - In, "gardnerpomper"
<gardner@...> wrote:
> Hi,
> Is there any information (sketch or drawing, preferably) of the
> current rudder design? This is one of my areas of concern, and I would
> like to see what the current thinking is. Specific questions are:
> what are the dimensions of the rudders?
> are they designed to lift in the rudder assembly for shoal draft
> sailing, or do they tilt?
> Do they need 360 degrees maneuverability, or just +/- 45 degrees from
> the direction of motion? (i.e 335-45 degrees, and 135-225 degrees,
> relative to the hulls)
> I am specifically speaking of the charter proa, but I am curious if
> the basic rudder design applies to pretty much any size harryproa.
> Thanks,
> - Gardner

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