Subject: Re: [harryproa] Current rudder design?
From: "Rob Denney" <>
Date: 5/26/2008, 11:58 PM


See Rough beam rudders & fea of rudder supports in the files section.
The first one is an fea model for Blind Date's new rudders. Shows
what happens with 7 tonnes of load. This has been built, should be
sailing pretty soon. The others are pictures of the set up on my
Elementarry (7.5m/25' test bed. These worked really well with both
rudders, or just the aft one, although there were some bearing binding
issues at speed. A function of pvc drain pipes for bearings, I think.
Blind Date is having roller bearings to get round this. I am
building much bigger diameter (still pvc drainpipe) to try and get a
handle on the forces involved. Not sure why the pictures are so small.
Does anyone know how to make them bigger?

The rudders are roughly 1% of the sail area, with aspect ratio between
3:1 and 4:1, depending on the boat use. They lift to the depth of the
hull and can still be steered. They kick up in either direction in a
grounding or impact. Blind Date is using a rack and pinion to turn
them, JT a spur gear, Solitarry a tiller and I am working on a
quadrant. 360 degrees is great if you accidentally tack or luff too
high. Simply reverse the rudders and steer in the other direction.
Same applies for 270 degrees of course, but you have to be careful
which way you turn the wheel, which could be an issue on the cgharter
boat. 270 also needs two wheels as shunting and normal steering
require them to go in opposite directions. With 360, one wheel will



On Mon, May 26, 2008 at 9:30 AM, gardnerpomper <> 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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