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Effect of large keel on Disney NAUTILUS

Nautilus, Seaview, and more

Postby modelnut » Sat Jul 10, 2004 2:54 pm

Just a thought...

Does that rather large keel on the Disney NAUTILUS have any effect on the boat's handling? Does it detur steering? Or does it fight the torque of the propeller and keep the boat on an even upright in turns?

-Leelan
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Postby Captain Nemo » Sun Jul 11, 2004 6:40 am

Leelan,

I can only speak about the NAUTILUS MINISUB here.

My keel is solid steel and pretty thick; has extra plates for additional weight, also. The intent was to ensure positive dynamic stability in the upright position. One advantage of a whoppin' big keel is the boat tends to stay dirty side down.

Does the keel deter turning capabilities? Probably somewhat. I mean, she doesn't want to wag her tail from side-to-side much at all. Turns like a train: nice, smooth, rounded curves. The rudder aint much, but it's aft of the prop so it does vector the thrust. The keel (and other straight surfaces) makes the boat want to keep going straight. Between the two, I'm getting nice wide turns.

But I think that's characteristic of an ocean-going design that doesn't have side thrusters. Made mostly for travelling on a straight course, but it will turn a circle in a fairly reasonable distance, all things considered.

One thing about that: when it comes to getting from point A to point B, she's a real honest boat. We did our first dive runs in zero visibility water across a Marina. Aimed at a buoy on the other side, started rolling, and kept the rudder amidships while we dived, levelled off, and surfaced. Couldn't see squat. But by estimating time and distance, and counting seconds at a particular speed, we came up right by the target buoy (or at least in the general area) most all the time. That's what I mean by "honest": You set her on a course, and she wants to stick to it. I think the keel probably has a lot to do with that.

In a real NAUTILUS, of course, the split keel allows the boat to be bottomed and still gives the divers room to exit and enter the diving hatch. For me, though, it's just a matter of balance, aesthetics, and making the sub look like the namesake.

Somebody mentioned the possibility of drag on the leading surface of the aft keel: might have some effect on performance, but I really don't think it's much.

That's about all that comes to mind right now...

Pat :)
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Postby modelnut » Sun Jul 11, 2004 4:59 pm

Thanks Pat!

That is what I was thinking. But thought experiments don't stand up to real word experience. So I thought I would ask.

Hmmm...

I guess the keel would negate the effectiveness of a small outboard propeller*. I've heard that modern subs have them for manuevering in tight places without a tug.

-Leelan

* ( Like a trolling motor to you Bass-pros out there ! :D )
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Postby Captain Nemo » Sun Jul 11, 2004 5:38 pm

If you mean would the side keels negate the effectiveness of a side thruster: I think they'd provide some additional drag resistance beyond that engendered by the hull itself; but with the right amount of thrust I think the drag could be overcome.

I've always throught a side thruster in the right place would be a nice addition from the standpoint of maneuvering and functionality. The trick would be hiding it so it's not so visible: maybe inside the tailcone, in a Kort nozzel or the like?

Didn't I read that someone has already done this? Tom's jet NAUTILUS, maybe?

Mounted in the right place, side thrusters could provide the tight maneuvering capabilities I've always wished my boat had when we're getting it back on the trailer. Could enhance turning when underway, too.

Pat
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