Is there any other reason for the shaft to go through the center except being able to steer both ways? Reason I am asking is that if the rudder is used for steering only to one direction it could be locked when sailing to the other direction. That way we could have the shaft on right place to make it more stable and balanced.
Arto
--- On Tue, 2/23/10, robert <cateran1949@
The Speer ogivemakes sense but there is always the problem of the shaft needing to go through the fore aft centre and the creation of an unstable foil. It is possible to lock the two rudders together and thus cancel the forces outbut this leads to other complications.
I've played around with the concept of either a shaft that moves forward on the foil to bring it into balance, a sleeved foil that moves back from the centre of rotation, a foil that kicks backwards and with swapping between two shafts to get the balance . Not suprisingly, none seem satisfactory but suprisingly, the twin shaft seemed feasible.
The design on rare bird and Aroha seems to work OK except when partially lifted when It becomes out of balance. I feel this could be overcome by either being able to adjust the angle of rake for shallow sailing or by having curved foils. I feel that adjusting the rake for shallow water would be relatively easy. I am starting to come back to this style of rudder but the supports set either a bit higher above the waterline or at the resting waterline as a slight lifting foil, though I will wait and see how well Rob's set up on Sol works.
--- In harryproa@yahoogrou ps.com.au, Mike Crawford <jmichael@.. .> wrote:
>
> Gardner,
>
> Here's what I believe is happening:
>
> a) With the quadrants, if you look at the cable, you'll see that it
> doesn't have to wrap 360 degrees around the quadrant. Just 358 degrees
> -- because the rudder only rotates 270 degrees, the cable doesn't have
> to pass through the sleeve that holds the rudder. That leaves the
> sleeve free to have a "fuse" that will break, allowing the rudder to
> kick up, without interfering with the cable.
>
> b) With tillers, you're probably going to have a somewhat short
> tiller with a very long tiller extension. This extension will then
> allow you to either:
>
> 1) Turn the rudder 180 degrees between shunts, with the tiller
> then on the opposite side, or
>
> 2) Turn the rudder 180 degrees, flip the tiller back to the
> original side, and then steer as before, or
>
> 3) Just kick up the foreward rudder and use the aft for both
> steering and leeway prevention.
>
>
> Anyone: please fee free to correct me if I didn't get it.
> / /
> I'd personally prefer speer sections that don't have to rotate more
> than a few degrees between shunts, allowing steering with a whipstaff or
> vertical tiller, but I'm not willing to bet on that solution without
> first doing some real-world tests.
>
> - Mike
>
>
>
> gardner@... wrote:
> >
> >
> > Hi,
> >
> > I have been looking at all the photos I can locate of the rudders on
> > different harryproas, but particularly sidecarry, aroha and blind
> > date. I can't figure out how the kickup mechanism works.
> >
> > With the boats that have a quadrant at the rudder, it would seem that
> > the cable would either hold the rudder in place, or else rip things
> > out of the rest of the boat.
> >
> > If you use tillers, when the rudders are 20' apart, then doesn't the
> > long (10+') tiller jump all around when the rudder kicks up?
> >
> > Can someone point me to some photos that explain this better?
> >
> > Thanks,
> > - Gardner
> >
> >
>