Subject: [harryproa] Re: harryproa rudder fastening stiffness issue?
From: "Robert" <>
Date: 1/9/2006, 9:20 PM

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

--- In, "Mark Stephens" <stephens@o...>
> 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
> 0431 486814
>   ----- Original Message -----
>   From: Robert
>   To:
>   Sent: Saturday, December 24, 2005 10:03 AM
>   Subject: [harryproa] Re: harryproa rudder fastening stiffness
>   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
>   stiffness as an especial issues. The boat was travelling pretty
>   for the wind strength. Make it too stiff and the shock loads on
>   bearings would be greater. Running stays would need a reddesign
>   the rig in terms of loading and sail shape. Possibly the flex
>   the boat a little movement without effecting the velocity of the
>   section of the mastas much?
>     Certainly impressive the motion and the speed and lots of nooks
>   crannies for the kids to explore.
>   Loved it
>   Robert
>   --- In, "dominiquebovey"
>   <dominiquebovey@y...> wrote:
>   >
>   > Hi all,
>   > after seeing the video I have the feeling of two potential
>   > issues on the visionarry and HP in general, the second is
>   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-
>   (I
>   > am translating from metric for you anglo-saxon people ;-) where
>   > 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
>   > 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,
>   > 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,
>   > the cable-based system breaks.
>   >
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