Swivel Keel?

[alex folen]

Hello all, we were thinking about making the whole keel swivel. It already wobbles which needs tending to. I'm sure this was thought of before, and would there be an advantage. Just a thought for now as the list of things is mounting before we pull it. In a small nut shell my friend and I were talking about servos and a lap top to control the keel and the rudder in unison, optimized as we man the trim and other. Transducers would indicate various forces with loads in real time 60 times a second. He's computer data acquisition a nut! Corrections 60 times a second times an hour, in three, in ten? It is an existing Coronado 30 footer with a fin keel 5 feet and already has a keel trim tab inoperable at the moment. Has this been accomplished before?

[Eric Sponberg]

Been there, done that. Go to this website for CBTF--Canting Ballast Twin Foil technology. This was born out of the America's Cup in the early 1990s.

http://www.cbtfco.com/Technology/technology.php

Eric

[limeyus]

Are you talking about rotating about a vertical axis or 'swinging' about a fore/aft axis?

Both have been done before...

[alex folen]

[quote=Eric Sponberg;248569]Been there, done that. Go to this website for CBTF--Canting Ballast Twin Foil technology. This was born out of the America's Cup in the early 1990s.

Nice to know the idea was thought about espically with the America's Cup, and not to far in the past! On with some more. Thanks for the site neighbor!

[messabout]

If you are thinking in terms of pivoting the entire keel, you are getting into serious structural complications. The advantage gained, if at all, will not be worth the problems that it will ultimately cause. That kind of sophistication is appropriate for full on, no holds barred, no budget constraints, race boats but much less so for a cruising boat. Fix the trim tab and call it good enough.

[chabrenas]

Messabout is quite right. Your buddy's control system is the trivial part - you'd have to rebuild the hull, to try something that's a complete waste of time on that kind of boat. Anyway, even doing it yourself would cost you more than you probably paid for the boat, and you'd end up with something with a zero resale value.

When you say the keel wobbles, what do you mean? Fixing that and the trim tab will cost you quite enough time and dollars (:=>

[alex folen]

Originally Posted by chabrenas

When you say the keel wobbles, what do you mean? Fixing that and the trim tab will cost you quite enough time and dollars (:=>

Yeah, the keel wobbles… It does not sway, as if hanging on a thread, yikes. The frequency of wobble is about 3-4 times a second when the boat bumps against the dock (a better description?). The keel trunk fiberglass is flexing, with rigidity. Maybe flexing is the wrong word. It wobbles. The keel bolts are tight and the wobble appear to be coming from the trunk area and extending maybe 1.5 feet up then dissipates. You have to stare at the area to see the motion. It is hull #6 and I was wishing it was just the design! Maybe I can just add extra glass in the area if need be. Oh, I lost the idea of making keel rotate (pretty quickly), thanks to you all, and the been theres and done thats. The money I may save will go towards the retractable masts and accordion airplane wing sails! Thanks for the feed back for sure!

[ancient kayaker]

Originally Posted by limeyus

Are you talking about rotating about a vertical axis or 'swinging' about a fore/aft axis?

Both have been done before...

Rotating about a fore/aft axis would move the keel ballast laterally, rotating it about a vertical axis would create lift to compensate for leeway. Both have been done as noted above.

Another approach is to increase the rotation about the vertical axis to the point where it can be used for steering. I am looking at a design to do that. The advantage would be virtually instant tacking, as the sail thrust could take effect on the new tack without waiting for the hull to complete rotation. It should be useful in very narrow waters and for long boats with poor agility. A stern rudder would be unnecessary except for close quarters manouvering, a fixed skeg would normally be sufficient.

[limeyus]

good luck.......

just might have a problem with such a short lever arm

[chabrenas]

sail thrust could take effect on the new tack without waiting for the hull to complete rotation

Not if the sails are attached to the hull. That's what re-orients them on the new tack.

[quote=alex folen;248600]

Originally Posted by Eric Sponberg

Been there, done that. Go to this website for CBTF--Canting Ballast Twin Foil technology. This was born out of the America's Cup in the early 1990s.

Nice to know the idea was thought about espically with the America's Cup, and not to far in the past! On with some more. Thanks for the site neighbor!

------------------
The 100' Wild Oats XI just won the Sydney-Hobart Ocean Race for the 4th time in a row using CBTF technology!

[ancient kayaker]

Originally Posted by chabrenas

Not if the sails are attached to the hull. That's what re-orients them on the new tack.

Sheet is slackened, sail is pushed out to accept wind from other side using a pole. Thrust is generated by combination of sail and keel, the hull just provides a platform and trails along behind.