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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