--- 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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