G'day,
Form my armchair my two cents worth:
I wonder about making the top support to stiff and posibly leading to
breaking of pintles. Also excessivee stiffness can impart point
loadings. Just bracing the bottom support should theoretically be
enough to resist upward forces. These upward forces are obvious in
retrospect but nobody made any comments about it.
If the rudders hit something at speed something has to give and if it
can be done in flex rather than breakage all the better. Though I
suppose you could have sacrificial pintles to avoid breakage
elsewhere. Not sure why the premature release of the fuse caused the
rudders to jam and put strain on the top bracket but once that is
sorted then those loads shouldn't happen again.
Overall the present system seems far less likely to cause damage to
the hull than daggerboards and through hull rudders and slightly less
likely than kickup rudders and cenreboards.
I agree that a new concept boat like a Harry has to be more reliable
than other boats as it is more noticable. There are lots of boats
with rudder and foil problems that garnish no publicity. having the
whole build process, includingthe teething problems, out there in the
public eye rather than a more secretive R&D gives me more confidence
in the rest of the boat as there is very little room for bullshitting.
The problems with the rudders seem relatively minor teething
problems: How strong to make the fuse to take the working loads but
give out under the shock loads, stiffening and bracing of the lower
support and making sure that the rudders don't jam upwards when fuse
is released
Looking at the construction pictures the internal support is ample
and from what I remember there is a bulkhead separating the rudder
section from the centre section with a bulkhead forward that the foam
bows attach to. Don't think another bulkhead would improve things
that much and the time money weight and effort could be better used
elsewhere for safety considerations.
If I sail a Harry in my home waters (Twofold Bay on the south coast
of NSW) I will want it at least bluewater "A" or I will be holed up
half the time looking for gaps between black noreasters and southerly
busters. These are the waters that the Sydney Hobart fleet gets
mashed up in. I have more confidence in the Harry than the fishing
boats I worked on over many years. (Two of them have sunk and another
split its deck seams) and they are supposed to be built to survey.
I wonder how they can allow those canted keels in the Sydney Hobart
but claim that multihulls don't belong. Possibly we need to declare
the ww hull a permanently canted keel at 90 degrees.
The trip up the coast to Gladstone would be a nice venue for
comparisons but that is really up to the owners.
Robert
--- In harryproa@yahoogroups.com.au, "dominiquebovey"
<dominiquebovey@y...> wrote:
>
> Hi all,
> About horizontal brackets, couldn't they be stiffened by diagonal
> ones: one from the top rudder pintle to bottom bracket base, the
> other diagonal from bottom pintle to top base?
>
> To which part of the LW hull structure are the brackets attached? A
> bulkhead? And if for some reason they get teared off, is there some
> provision that the hull remains structurally relatively sound,
> allowing to reach a harbour half an ocean away? Even if there is a
> hole in the hull, this could be catered for with two watertight
> bulkheads in the LW hull for each rudder.
>
> The rudders are definitely the most difficult problem on a
harryproa,
> and it would be unfortunate that the HP had repeated reliability
> problems when the boat comes out of the "aficionado" circle.
> Racing proas had repeated problems 10-20 years ago, which led to
> discrediting them in he general sailing public (well I do not speak
> about the current 60' tris ;-). The HPs have to avoid that fate!
>
> So all issues must be solved and the big single issue is rudder
> reliability, in the corresponding nav conditions as defined by
> european design categories: Bluewater "A" for Visionarry (more than
8
> beaufort, more than 4m waves), and probably Coastal "C" for
> Elementarry (up to Bf6, 2m waves). And "B" for harry and harrigami
> probably.
> So I am looking forward for a real test: Rob, what about Visionarry
> doing Sydney-Hobart ;-)
>
> regards,
> Dominique
>
>
> --- 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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