Rob,
I would like rudders that can lift up to allow a 1' draft, and still be able to lower to 4-5'. When using a "traditional" rudder with a shaft, that would mean 3-4' of shaft above the blade, which means that the beams would have to be 3-4' above the water line, which seems impractical, as well as requiring a huge amount of strength because of the moment arm.
This is something I can see doing easily with Todd's design, because I can just have a long blade, instead of counting on a shaft that has to rotate. Plus, I can support the blade closer to the water, only limited by how often I am willing to have water hit the support strut.
Do you have a sketch or photo of a "traditional" rudder that can raise at least 1m, and controlled by a wheel, along with the usual kick up on impact, etc? I really want to be able to sail (not race) in shallow water, and have good lift in deep water.
- Gardner
On Mon, Oct 24, 2011 at 4:17 AM, Rob Denney <harryproa@gmail.com> wrote:
I don't believe a single unattended foil with the rotation axis at 50% of the chord will point straight ahead at 15 knots. Until I see one, and the physics that explains why, I cannot agree that it is a good thing to have on a boat.
Linked rudders solve a lot of problems, but unless they work when one is raised, are no use. Rotating them aft is a solution, but is an extra layer of complexity. As the rudders have to turn for steering, turning them through 180 on a shunt is no big deal, unless they are mounted on the hull or utilise wheel steering, but even here, there are simpler methods.
regards,Rob
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