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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