Subject: RE: [harryproa] Re: rudder frame desgn
From: "Jim Baltaxe" <>
Date: 4/10/2008, 6:54 PM

Hi Rob &al
Very interesting and straight forward design but I have just one question, which may be answered by John's question about where the swing up pivot pin is located: What happen if the rudder is not centred when it strikes an object is tries to swing up? Would it not be better to flare out the bottom of the support box so it will centre the rudder as it comes up? This is so obvious that I'm sure you're planning to do something like it anyway, but I still thought I'd ask.

Jim Baltaxe

They said, get a life. I looked on TradeMe but I couldn't find one.


From: [] On Behalf Of jhargrovewright2
Sent: Friday, 11 April 2008 3:19 a.m.
Subject: [harryproa] Re: rudder frame desgn

Mr. Denney,
I am fascinated.....with the finite element analysis image.
Impressive and colorful.
Can you elaborate a little for us laymen. This is the bracket that
attaches to the beam that holds the rudder shaft which will fit in
the channel, vertically? This assembly replaces the fabrication
shown in the other pictures in that folder? Is there a picture of
the pivot pin (point) that allow the rudder to swing up. And last,
what holds the rudder down?
--- In, "Rob Denney" <harryproa@...>
> G'day,
> I have just uploaded a finite element analysis (fea) of the beam
> mounted rudder supports for Blind Date to the "Rough beam rudders &
> fea of rudder supports" file in the Files section. The picture
> the loads and exaggerated deflection of the rudder box with 7 tonnes
> load on the rudder, which is what we ended up designing it for.
> is more than double the weight of the boat, so we are pretty
> that this part won't break. The test rudder shaft took 15 tons so we
> are pretty confident about that as well. Now just have to sort
> all the details.
> The other pictures in the file are the test version on my
> Rough, but so far nothing has broken.
> All engineering from now on will be done with fea. Costs more, but
> gives a much better result, plus I like looking at the pretty
> pictures. ;-)
> There will be some more pictures of Blind Dates rudders on the web
> update, which unfortunately can't happen until I get a password from
> the web host, which comes by surface mail, for some reason.
> regards,
> Rob

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