Rob I do have more questions, but don't encourage me too much
I'm still confused how the foils can be liftable. When you say "centre of rotation is mid chord" do you mean the actual pivot point is mid foil thickness as well? (ie: The hinges will be recessed into the foil) or are the pivots mid distance along the chord and mounted outside the foil. I realise the foil will have less camber on the lee/hinge side, but unless it is negative the chord will lie inside the foil (won't it - correct me if I'm wrong).
My thought was to cant the rudder (tilt the bottom towards "under" the lee hull) to put the offset pivot point mid way on the longitudinal (Top to Bottom) of the rudder, the cant angle would be quite small to achieve this
I reckon you might be right about the Blind Date crew wrestling with the rudders, if the direction of travel hadn't changed and the rudders turned it would be difficult if not impossible to force them round.
Rob Rassy
--- In harryproa@yahoogroups.com.au, Rob Denney <harryproa@...> wrote:
>
> Glad you are contributing. You are correct that the rudders are
> bidirectional, although it is not yet decided if they will be used on this
> boat. They will be used on the 12m. They will be able to be raked aft
> (centre of rotation is mid chord) to balance them.
>
> Not sure what you mean about raking them to leeward?
>
> Flutter has not been a problem, although on the hull mounted Vis rudders,
> they had to be raked forward (centre of rotation ahead of the leading edge)
> to get the balance right and this has caused them to twist.
>
> There is no sailing reason for the rudders to be hard work during a shunt
> as they are lightly loaded as the boat is moving slowly. Therefore it is
> more likely to be stiffness between the wheel and the rudders. They are
> large areas to move through the water, so it is easier if you don't start
> moving them until the boat is stopped, or even moving slowly in the other
> direction.
>
> Keep the questions coming.
>
> regards,
>
> rob
>
> On Wed, Nov 7, 2012 at 8:55 PM, rob_rassy techsmart@... wrote:
>
> > **
> >
> >
> >
> > Greetings all
> >
> > I've been following the group with interest for a long time now and
> > haven't managed to motivate myself to join in! (probably didn't want to
> > show my lack of boating & sailing knowledge when I think about it). The
> > new website & the new Visionary Schooner are the inspiration for posting
> > a couple queries now
> >
> > The rudders on the Vis Schooner appear to be bi-directional foils on the
> > lee hull. I am wondering how much tourque / load they will generate in
> > the steering as the pivot will need to be off center on a case if they
> > are to be liftable(or am I missing something). Maybe some leeward
> > canting of the rudder bottom would help balance them but I have trouble
> > picturing that working. I can actually see then getting a flutter up at
> > speed!
> >
> > On viewing the video footage of Blind Date sailing the front steering
> > appears to be fairly heavy during some shunts. I'm wondering what the
> > reason for this might be and if it happens on the other Visionarys?
> >
> > cheers
> >
> > RobRassy
> >
> >
> >
>