Subject: Re: [harryproa] Re: harryproa rudder fastening stiffness issue?
From: "Rob Denney" <proa@iinet.net.au>
Date: 1/14/2006, 12:30 AM
To:
Reply-to:
harryproa@yahoogroups.com.au

G'day,
 
You have overcome my objections (apart from drag), give it a go.
 
regards,
 
rob----- Original Message -----
From: Robert
To: harryproa@yahoogroups.com.au
Sent: Wednesday, January 11, 2006 11:29 PM
Subject: [harryproa] Re: harryproa rudder fastening stiffness issue?

G'day,
You're right I do mean the rudder supports, but I can't agree with
your arguments in dismissing the idea
(a) They could be left where they are and keep that extra lever arm
(b)Not necessarily a bad thing but it would probably remain out of
the water according to my  reading your pics. It wouldnt necessarily
make a rooster tail
(c) don't see that necessarily follows. The supports would have a
thicker cross section and allow the top surface where the pintle
emerges to be near horizontal
regards,
robert
--- In harryproa@yahoogroups.com.au, "Rob Denney" <proa@i...> wrote:
>
> G'day,
>
> I assume by braces, you mean the horizontal rudder supports?  If
so, I would keep them horizontal.  a) they have now been moved clear
of the water, b) the aft one would act as a scoop and c) they put the
rudder pintles in bending rather than shear, which is much easier to
resist.
>
> regards,
>
> rob ----- Original Message -----
>   From: Robert
>   To: harryproa@yahoogroups.com.au
>   Sent: Tuesday, January 10, 2006 10:20 AM
>   Subject: [harryproa] Re: harryproa rudder fastening stiffness
issue?
>
>
>   Thanks Mark and Rob for detailed replies.
>   I was considering making the braces in a foil cross section set
about
>   15-20 degrees attack for the forward facing rudder. This would
>   provide stiffenning as well as a bit of lift. Possibly vetilate
them
>   in case of severeely depressing the bows. makes sense to put the
big
>   quadrant under the floor. When I look at just about any other
foil
>   arrangement in other boats they are all vulnerable. Breking waves
>   from behind can put enormous strains on the rudders of most
boats.
>   overall your present design looks pretty good and they obvoiously
>   work.
>   Robert
>
>
>
>   --- In harryproa@yahoogroups.com.au, "Mark Stephens"
<stephens@o...>
>   wrote:
>   >
>   > I really wouldn't be concerned about the rudder brackets and
>   quadrants from a vulnerability to waves point of view. However
the
>   loads they see from leeway prevention are huge. For the last few
>   months, prior to the first sail, I had been concerned about their
>   ability to withstand these loads and was tempted to take them off
and
>   beef them up. I decided to leave them for a number of reasons:
Better
>   to test them gently and see where the cracks develop, we may need
to
>   adjust the rake angle which would also requires a rebuild, there
was
>   plenty of other things to get on with. As it happened a shear pin
>   broke which put enormous twisting loads into the case causing
>   breakage. I fixed this quickly to get us sailing again. You can
see
>   the repairs in the photos and video.
>   >
>   > On return from the second sail we noticed some hairline cracks
on
>   the unrepaired rudder case which I have since repaired, again
just
>   strengthening it enough to go sailing again. Rather than
completely
>   rebuilding the rudder cases I am interested in keeping the
variables
>   to a minimum.
>   >
>   > The triangular brackets that attach the rudders to the hulls
are
>   remarkably strong. They may look a bit flimsy but there are 4 per
>   rudder with plenty of carbon and glass and are well triangulated.
>   There are more upwards loads than expected so a 45 deg brace will
be
>   put in from the bottom pivot bearing to the hull. When the first
>   rudder broke from the shear pin shearing it caused the top
bracket to
>   bend up about 120 degs. When I detached the broken case and
quadrant
>   it sprang back into position without damage. I just had to
replace
>   the composite pivot bearings.
>   >
>   > The rudders were always going to be the major challenge for us.
>   Consider that they have to rotate 240 degs., raise up and down 2
>   metres, break away if hit (but not under enormous sailing loads)
and
>   be balanced under all points of sail. Also keep in mind they are
>   dagger boards, resisting all the sail loads, as well as rudders
which
>   have to operate in two directions. The bottom bracket probably is
too
>   close to the water. I have raised this by 100mm for Blind Date
and
>   subsequent boats.
>   >
>   > Considering the above I think we have a pretty good rudder
design
>   once it has been strengthened. We are considering other
approaches,
>   such as beam hung rudders, but so far this is the most workable.
I am
>   considering replacing the large quadrant wheel with a small one
and
>   getting the 'gearing' from a large quadrant under the cockpit
floor.
>   >
>   > The slow progress must be frustrating for all of you who are
>   watching this from afar. Now the boat is sailing, repairs or
>   improvements and indeed sailing have to be done in 'play time' of
>   which there is little at this time of year. Harryproa has just
landed
>   a very nice contract for 100 carbon fibre masts for GPS aerials
on
>   container terminal forklifts. These have to be completed by the
end
>   of January so we will be very busy next month.
>   >
>   > A big thank you to Luke for the pictures, video and report.
>   >
>   > Merry Christmas to everyone,
>   > Mark
>   >
>   >
>   > Mark Stephens
>   > www.harryproa.com
>   > 0431 486814
>   >   ----- Original Message -----
>   >   From: Robert
>   >   To: harryproa@yahoogroups.com.au
>   >   Sent: Saturday, December 24, 2005 10:03 AM
>   >   Subject: [harryproa] Re: harryproa rudder fastening stiffness
>   issue?
>   >
>   >
>   >   Must admit those forward rudders seemed vulnerable. Don't
know
>   >   exactly how vulnerable as strong composites can be deceiving.
>   >   Probably the loads on the rudder blades under sailing are
greater
>   >   than the loads exerted by waves hitting the supports. Don't
see
>   mast
>   >   stiffness as an especial issues. The boat was travelling
pretty
>   well
>   >   for the wind strength. Make it too stiff and the shock loads
on
>   the
>   >   bearings would be greater. Running stays would need a
reddesign
>   of
>   >   the rig in terms of loading and sail shape. Possibly the flex
>   allows
>   >   the boat a little movement without effecting the velocity of
the
>   top
>   >   section of the mastas much?
>   >
>   >     Certainly impressive the motion and the speed and lots of
nooks
>   and
>   >   crannies for the kids to explore.
>   >
>   >   Loved it
>   >   Robert
>   >
>   >   --- In harryproa@yahoogroups.com.au, "dominiquebovey"
>   >   <dominiquebovey@y...> wrote:
>   >   >
>   >   > Hi all,
>   >   > after seeing the video I have the feeling of two potential
>   stiffness
>   >   > issues on the visionarry and HP in general, the second is
>   rudder
>   >   fixture:
>   >   > I sailed in the irish sea lay May on a 28' monohull, we got
got
>   >   pretty
>   >   > rough sees and wether, like Bf 8, wind against current, 15-
>   20'waves
>   >   (I
>   >   > am translating from metric for you anglo-saxon people ;-)
where
>   the
>   >   > boat  fell hardly because the front of the waves was almost
>   >   vertical.
>   >   > I wonder how the rudders would bear such shocks, especially
the
>   >   front
>   >   > one which takes the brint of the hit.
>   >   > I am especially worried about the horizontal wheel which
could
>   be
>   >   > bent/broken by waves? Visionarry is a light boat which will
be
>   >   > probably very fast with bare mast in 40-50kn of wind and
>   >   correspnding
>   >   > sea (european category A), so it'd better be TOUGH!
>   >   > And sorry, also the fastening to the hull looks fragile to
me,
>   maybe
>   >   > it isn't but it looks so.
>   >   > I would think of an arrangement similar to the catamarans:
two
>   >   tillers
>   >   > with a rod joining them, and sticks. But I agree that with
this
>   >   you'd
>   >   > have problems fitting an autopilot... HAAA compromise, the
>   basis of
>   >   > engineering!
>   >   > But maybe this is a solution for an emergency steering
system,
>   when
>   >   > the cable-based system breaks.
>   >   >
>   >
>   >
>   >
>   >
>   >
>   >
>   >   
>   >   Yahoo! Groups Links
>   >
>   >
>   >
>   >   
>   >
>   >
>   >
>   >
>   >
>   >   --
>   >   Internal Virus Database is out-of-date.
>   >   Checked by AVG Anti-Virus.
>   >   Version: 7.0.344 / Virus Database: 267.14.1/206 - Release
Date:
>   16/12/2005
>   >
>
>
>
>
>
>
>
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