---

From: Rob Denney <harryproa@gmail.com>
To: harryproa@yahoogroups.com.au
Sent: Wednesday, 14 September 2011 7:32 AM
Subject: Re: [harryproa] Rare Bird rudders

On Wed, Sep 14, 2011 at 2:18 AM, Gardner Pomper <gardner@networknow.org> wrote:
>
>
>
> I have watched all the available videos from Rare Bird and Blind Date and I have a few questions on the rudders (Rob's version, not the replacements that didn't work out).

The current ones are not specifically "my version".  My version did
not work on Rare Bird when first launched.  Mark (builder) then
redesigned them and after a couple of alterations, they work well on
RB.  The beam mounted ones on BD were scaled up versions of the ones
that work on El.  The current BD ones are beefed up (mostly the X
bracing on the cassettes) versions of BD's.  If this is faired, the
spray will reduce considerably.
>
> Can the rudder blades be lifted for shallow water sailing?

Yes, but too far and shunting/sailing gets tricky.  As shunting
experience increases, the sailable draft will drop.  The blades are
raked forward to keep the coe in line with the rotation axis.  As they
are lifted, this gets out of line, so loads increase.  High speeds in
shallow water will not be possible.
>
> I believe they kick up. Am I correct?

No.  They were designed to fall out the back of the case in an impact,
which they do very well on BD.  I don't like this system as the loads
on the case as the board exits get large.  The back of the case was
closed off when the X went on BD and a sacrificial tip put on the
boards, which is a partial remedy.  Now that they are working, we are
looking at various fuses.  Any suggestions, much appreciated.
>
> Other than the excessive amount of spray, these seem to be a very solid and reasonable way to install the rudders on a HarryProa. However, since Rob has been trying alternatives, and Blind Date replaced them completely for a while, there must be some problems with them. Can I get an explanation of why these rudders aren't a good idea? Most of the alternatives seem to lose the support down near the waterline, which would reduce the spray issue, but require stronger, heavier and more expensive rudders.

I don't like the drag, even when faired.  It is also connected to the
hull, albeit above the waterline.  Hence the beam rudders, which are
far less drag, not attached to the hull  but need more support.  This
is a small price to pay for the other benefits, if they work.  I still
prefer the side mounted rudders to in hull rudders for safety.
>
> My leading alternative right now is the asymettrical rudders that Todd has been using, but they also have a support near the waterline, so if the Rare Bird style of rudder works, it seems like less risk.
>
> Related to this, there was a comment about it being possible to reduce the spray from the rudders by sharpening something... I wasn't clear on what. Might it be possible to reduce spray significantly? I am not seeing how to do that. Related to that, have either boat ever run in heavy seas? Doesn't the rudder mount get submerged? Is that a problem?

Fairing the boxes will reduce the spray.  Presumably Aroha was run in
large seas at some stage, but no issues reported.  The rudder mount
will be submerged, but is not a problem per se unless it hits
something.
>
> My criteria are the ability to lift for shallow water and drop for deep water. Ideally, it would be easy enough to lift that I could just pull the forward rudder up and reduce the spray when on a steady course. I also want kick up protection and wheel steering.

Impossibilities on the spot, miracles take a little longer!  I have
high hopes for telescoping beam mounted rudders, but have not built
one yet.  Your requirements are met fairly easily, except for the
wheel steering, which is very difficult.

Nol,
Sorry for the overlap, wrote this before I read yours.  Looking
forward to the next edition.  When does the boat come out of the
water?

rob

rob
>
> Thanks,
>
> - Gardner
>
>
>


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