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Goff Nautilus prop

Nautilus, Seaview, and more

Postby TK-7642 » Thu Aug 21, 2003 2:03 pm

I was wondering where Goff got the idea for the hammer-head prop. I saw a picture of a steamship called the Great Britain. It was the first iron steamship as well as the first large ship to use a screw propeller. It was based on a small boat called the Archimedes. The 1840 Great Britain originally used a very large 6 bladed hammer-head prop. It seems as though Harper Goff really did his research for the Nautilus, and thought it out very well. I think I may make a 7 bladed hammer-head prop that fills the whole prop space in the fin, and I will also move the propeller gaurd aft to ust cover the rim like McClintock's Hunley. I think Goff was inspired by this sub's design also, as it has the rods supporting the propeller shroud/guard just like his design. McClintock almost made a pump-jet, very advanced. I want my Nautilus to be able to reach "collision speed" like in the movie, and I think this will help. The hammer-head prop design should work very well with the rim covered by a shroud or guard that is only as long as the props pitch to keep it looking similar. Going to look up the Archimedes now.
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Postby Carcharadon » Thu Aug 21, 2003 4:34 pm

I should send you some video of the 4ft JetNautilus when considering "collision speed" . Its fast "for a sub"
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Postby Scott T » Thu Aug 21, 2003 5:33 pm

Can you post some closeup pictures of your jet nautilus that show where your jets are located and how they perform?
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Postby TK-7642 » Fri Aug 22, 2003 2:12 am

Thanks, it would be great to see some more details of your jet system.
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Postby Carcharadon » Fri Aug 22, 2003 10:09 am

I'll see if I can get some video captures of the bottom of the sub showing the Jets. And e-mail them to you. No guarantees on this because I'm working off a spare parts PC. I had a motherboard blow on me, bought a new one, that didn't work so now I'm waiting for another one. But I'll see what I can do. Also I'm still making adjustments and changes on the sub. It's a prototype and its had lots of abuse but it still works great just a few adjustments.

Well here is my rudimentary web site
http://home.comcast.net/~tyourk/test.html




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Postby Sub culture » Sat Aug 23, 2003 6:33 am

The shovel bladed prop on the S.S Great Britain was later replaced with a more conventional looking four bladed propeller. This proved to be considerably more efficient.

I believe that Brunel, and his design team, benefited from the work of an engineer called John Ericsson, the designer of the Monitor, a ship that needs no introduction and also the original inventor of the ship propeller.

I've seen the Great Britain prop up close, it's a pretty impressive piece of work (a replica though).

The design is good enough for model use, but it isn't as efficient as modern designs.

A footnote, most folk acknowledge that anymore than three blades on a model prop leads to greater inefficiency.

Andy




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Postby Bigdave » Fri Aug 29, 2003 9:09 am

I just wanted to say I have been using a Goff style prop on my 54 in Ray Mason hull for 4 years now. I can say from experience that that prop is very efficient. I was running a 540 motor on 3/1 but I had to change to 6/1. It was to fast and drew to much current. Even at 6/1 the Nautilus is quite fast. I also get alot more run time. You will also find the faster you get that hull going the harder it is to keep it on the surface. I wants to dive! I have both front and rear planes hooked together in my Multiplex computer radio. I can change the ratio of front to rear mix and try to compensate for the speed changing dive effect. The hull usually wins. I would go with a scale Goff prop. Dave. :)
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Postby Thomcmdchief » Wed Sep 17, 2003 12:28 pm

Well if anyone knows where I can put my hands on a metal hammer prop for my Custom Replicas 66" model, please let me know. Somewhere around 3.75" would be perfect.


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Postby Sub culture » Thu Sep 18, 2003 8:42 am

Well, I will need to fashion a prop for my 1/32nd scale Nautilus.

I was going to fabricate one from brass, but if I could interest a few folk, it may be worthwhile producing a green wax master and have them invetment cast in aluminium.

I need drawings and decent photo's for an accurate replica.

Cheers

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'Why are you staring at an empty pond?'

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Postby TK-7642 » Thu Sep 18, 2003 10:31 am

Bob Martin has a pic of the prop on his Nautilus Drydocks page. I have a SB 31 inch Nautilus. The model is good but the propeller it comes with is too small , very unhydrodynamic and not very authentic. The blueprints show the full size prop as 11 feet in diameter. I would make a prop that totally fills the propeller space in the fin in diameter for efficiency and speed. This would fill up the prop space nicely, help to provide collision speed like in the movie and be slightly closer in size to the book's prop. It may help to add some slight camber or curvature to the blades if possible (this would increase the lift on each blade - at a set speed).
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Postby Sub culture » Thu Sep 18, 2003 12:23 pm

A few thoughts on propeller efficiency and Disney Nautilus collision speed.

1. The size of prop on the Disney Nautilus is huge, so if it's a little smaller than original, it doesn't really mater that much- just so long as it 'looks' right. I don't think it'll make that much difference to the performance if the prop doesn't fill the void it's located in. Full shrouding of the prop (as in a kort nozzle) would be a different matter, however this wouldn't look scale. Also the bigger the prop the higher the drag.

2. There is an all too brief shot of the blade of the Disney Nautilus prop in the documentary that accompanies the DVD of the film. This shows the end (hammerhead) of the blade as a symetrical blade section- the worse possible shape for an efficient design.

3. The shape of the Nautilus dictates that at high speed the boat has a marked tendency to 'nose-under'. This has been born out in practice by those who have managed to get a boat in the water and working.
One chap I know got round this problem by literally planing the baot out of the water. This doesn't look very much like the movie however.

4. You are going to need a very high torque motor to generate enough poke to drive a 66" Nautilus through the water at any decent speed.

As far as I'm aware, there isn't a model motor on the market man enough for the job.

I recommend a fan motor off of a motor car, running at a minimum of 12 volts.

I have one with four brushes and a 3.5" 22 pole armature. On 6 volts it's unstoppable, at 12 it'll chew through anything! lol
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