I'd probably stick with the standard hull or beam-mounted rudders.  Yes, they have a lot of force on them, but one can design for such force.  It's just some more carbon and epoxy.  Probably less stress than a normal rudder shaft on an ORMA trimaran.

  But I have reasons for liking the existing rudders -- I'm focused on a boat that can easily collapse down to a 12' beam with a minimum of protrusions and attachments, and also be easily disassembled.

  Your design sounds interesting, though.  You'd certainly have plenty of rudder area even when lifted, which is something that vertically-lifting rudders would not have.

  How would you get the rudder to kick up in both directions, or kick up if it grounds while at a 45 degree angle?

       - Mike


Gardner Pomper wrote:

I once owned a one-tonne IOR racing boat from the 1970s, from a designer named Carter. He was known for his swing keels. We had 7000 lbs of lead that gave us a 7' draft when it was down, and a 4.5' draft when it was up. The really neat thing about it was that it was a hydrofoil in both positions.

The reason I bring this up, is that it seems like the same could be done with a rudder. If we took the Blind Date rudder, which is about 5' by 1.5' and hinged it where the rudder post attaches inside the rudder, about 17-20% back from the top and leading edge, it could be used as a deep draft rudder normally, then flipped up (manually or by a grounding) to a 1.5' draft with the same square footage steering surface.

By having the hinge below the water line, we could support the rudder post in 2 places.. the beam and a strut out from the hull.

If we are worried about surface level impacts, the hull strut could decouple and the shaft could be hinged again up higher, near the beam.

It seems that this could be simple to construct, would not have to be as strong (since it has support below the beam) and provides alot of rudder surface at low speed in shallow water for shunting.

Anyone think this idea might be practical?

- Gardner