Subject: RE: [harryproa] forces on the rudder
Date: 5/5/2007, 6:51 AM

It is balanced when it is around one third back but you don't want it balanced otherwise it will oversteer. About 15% back is where you are nearly balanced but have control and feel. It's a bit like a Balestron rig, if it were balanced it would swing around uncontrollably so you underbalance it so the sheet can keep it in control.
It is the front part of the rudder in front of the shaft that is acting as a servo and lightening the helm.
Mark Stephens
-----Original Message-----
From: [] On Behalf Of Doug Haines
Sent: Saturday, 5 May 2007 5:08 PM
Subject: [harryproa] forces on the rudder


       I would like to hear some explaination on the rudder balance.
       How is it, that a shaft that exits the top of a rudder a third the length back - should this then be tending to turn the shaft around because of the large surface area back from the shaft?
       I understand the shaft is at the thickest , which is a third from the forward edge.


sigurd grung <> wrote:

rob said to me, regarding my tornado conversion:
< Make it as long as you can within handling
< constraints.

I am not sure why.

1: I am expecting a bow-up attitude, since there is no
mast to push it down. This will be draggy, and I think
that extra length will not be enough to prevent it to
my satisfaction.
Thus I will need a T rudder or something anyway, so
hobbyhorsing will be much less of a nuisance.

2: speed, I was looking at this michlet calculation of
the tornado drag, and it appears that wave drag is
only a tiny part of the total drag, even as fast as
20kt. Thus I guess a longer hull will be draggier,
except maybe at *very* high speed, since WSA must be

Let me know if I'm wrong, please!

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