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Author Topic: Pondering propellors for a Jules Verne Nautilus  (Read 1513 times)

ScottW

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Pondering propellors for a Jules Verne Nautilus
« on: July 29, 2022, 12:28:28 am »

Hello again;
Retrieved the years old plans and sketches from the deep dark depths of the back closet.
Yes, another rubberband powered submarine, this one inspired by Jules Verne's Nautilus.
There is a long and widespread tradition of people designing subs to varying degrees of faithfulness to what Verne describes in his 20,000 Leagues Under the Sea text.For instance, https://www.vernianera.com/Nautilus/Catalog/
The model I have drawn up can be considered more-or-less 1/72 scale. Roughly 38 inches long with a 4.5 inch beam.
Construction will be frames, stringers, skin; with interior free-flooding. After all, rubber band motors get along with water somewhat better than electric motors do.  :-))
Working lights are desired.
The big question of the moment is the propeller/propellor(I prefer the less common -or spelling)
Way back in early 2000s when idea originated I had acquired a 3-blade pusher prop meant for .049 airplane motors. At this point on the calendar I am not sure where it is or even if I still have it. Or what condition it would be in. At a previous residence it served to differentiate the ceiling fan chain from the light bulbs chain. I know it was taken down when I moved but that was 3 residences ago. Am also not yet sure whether such a prop is currently available, haven't searched yet.
But ...
I am pondering, well, just barely beginning to, what other propellor might be serviceable.
Decades ago, the 1970s, I built some simple wooden boat and sub models which used regular rubber band airplane props. Being underwater with rubber band power they turned fairly slowly.  The RC deep-vee prop, which is nylon with metal hub insert, on PRS-1 does turn fast enough at beginning to cavitate a bit, but it also pierces the surface at start of run.
Unless the prop on this Nautilus model is something like 4 inch diameter it likely will not pierce the surface.
If a regular boat prop is to be used it will need to be fairly lightweight so as to make pitch trimming of the sub simple, and especially important, have a shaft hole all the way through so as to allow rigging a loop for the motor winder to use.
And that is as far as my brain has got for now.


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JimG

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Re: Pondering propellors for a Jules Verne Nautilus
« Reply #1 on: July 29, 2022, 12:10:51 pm »

As glow .049 engines are still used by some flyers there should still be suitable props available, look for some of the specialist model airplane suppliers. As an alternative small 3 blade propellors are available for the micro drones that are available now, 3 or 4 inch props will be common and are available as right or left handed rotation as drones need both.
Jim
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ScottW

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Re: Pondering propellors for a Jules Verne Nautilus
« Reply #2 on: July 29, 2022, 12:20:07 pm »

available for the micro drones that are available now,
Well that reveals how much of a tech geek I am - no thoughts, zero thoughts, about drones happened!  :}
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Akira

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Re: Pondering propellors for a Jules Verne Nautilus
« Reply #3 on: July 30, 2022, 12:54:20 pm »

Short answer: I doubt it. Aircraft propellors are designed to work in air, not water. They have a narrow cord compared to marine props, as well, their designed speed is much fast than marine props are designed to turn.Your prop needs to be matched to the motor that you choose to use for your sub. Remembering that a sub is a large mass that needs propulsion, and that water has much more resistance than air, the motor to be able to transmit it's power efficiently to the prop and the prop needs to be able to move the sub.
If you look at real submarine propellors, they are long cord and relatively high pitch, much more so than an aircraft prop.
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RST

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Re: Pondering propellers for a Jules Verne Nautilus
« Reply #4 on: July 30, 2022, 01:14:38 pm »

Quote
The RC deep-vee prop, which is nylon with metal hub insert, on PRS-1 does turn fast enough at beginning to cavitate a bit, but it also pierces the surface at start of run.


...I highly doubt your propeller is cavitating.  It might be thrashing and sucking a bit of air -but that's an entirely different scenario.  Woukd a project like this lend itself to a propeller cut and twisted from flat sheet material?

Rich
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ScottW

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Re: Pondering propellers for a Jules Verne Nautilus
« Reply #5 on: July 30, 2022, 03:58:41 pm »

...I highly doubt your propeller is cavitating.  It might be thrashing and sucking a bit of air -but that's an entirely different scenario.
Ah, looks like I'm using the wrong word.
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ScottW

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Re: Pondering propellors for a Jules Verne Nautilus
« Reply #6 on: July 30, 2022, 04:10:07 pm »

Aircraft propellors are designed to work in air, not water.
And yet they can work well at lower RPM in the denser fluid on small models; for example these from Seaworthy Small Ships, https://seaworthysmallships.com/

Seaworthy Small Ships Draketail
https://youtu.be/R8Jv5SPkFlc


Seaworthy Small Ships' submarine
https://youtu.be/KWp0tP7l72k


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Akira

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Re: Pondering propellors for a Jules Verne Nautilus
« Reply #7 on: July 30, 2022, 04:13:43 pm »

Considering the time frame of your build,, I would suggest looking at the Disney Nautilus builds on line, particularly on the SubCommittee web site, as well as this site. it will give you a pretty fair approximation of what one might expect to find in your model.
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ScottW

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Re: Pondering propellors for a Jules Verne Nautilus
« Reply #8 on: July 30, 2022, 04:53:46 pm »

I would suggest looking at the Disney Nautilus builds on line, particularly on the SubCommittee web site, as well as this site. it will give you a pretty fair approximation of what one might expect to find in your model.
The most that one might expect to find inside my Nautilus model is the rubber band motor & some batteries for lights, it is not a radio control model.
My hull design is patterned after Jules Verne's description instead of Harper Goff's stylized interpretation for Disney.
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Akira

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Re: Pondering propellors for a Jules Verne Nautilus
« Reply #9 on: July 30, 2022, 05:06:31 pm »

"My hull design is patterned after Jules Verne's description instead of Harper Goff's stylized interpretation for Disney." I understand that, but my point remains. Look at the design, quite a few blades, 5 I believe, and quite shallow pitch.
Either way, must subs require a geared motor to turn the prop, otherwise the motor is over worked and the battery, if there is one, runs out very quicky. In that you are using rubber band power, that is not a concern.I might suggest considering making a prop out of a disc of metal, tin maybe. You can experiment with the number of blades and the pitch very easily. Having more blades is not a problem, just reduce the pitch.
Solder your prop to a shaft collar and easy on/off of your shaft for testing. Once you find the combination that works best for yor build, you could consider making a sturdier version.

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tonyH

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Re: Pondering propellors for a Jules Verne Nautilus
« Reply #10 on: July 30, 2022, 06:12:35 pm »

If the prop is too wide in the chord and too coarse the very high torque from the elastic band will spin the sub as much as the prop %) Can you take the drive line down away from the centre line, possibly by going from a circular cross section to an oval? This would increase the spin resistance.
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ScottW

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Re: Pondering propellors for a Jules Verne Nautilus
« Reply #11 on: August 16, 2022, 07:46:59 am »

I might suggest considering making a prop out of a disc of metal, tin maybe.
  Health problems with my hands, which the paid professionals have determined several things the problem is not yet still don't know what for sure it is, since the 1990s have pushed me out of a couple jobs & the less metal work I have to do the better.
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ScottW

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Re: Pondering propellors for a Jules Verne Nautilus
« Reply #12 on: August 16, 2022, 07:58:05 am »

If the prop is too wide in the chord and too coarse the very high torque from the elastic band will spin the sub as much as the prop %)

Indeed, the 25 inch long and slightly square-ish cross section sub built, generally, to plan in book, torque rolls a bit with a Traxxis RC deep vee black nylon prop of unknown pitch and about 2 inch diameter when powered by 2 loops of 3/16 inch tan sport rubber with around 300 winds.


Can you take the drive line down away from the centre line, possibly by going from a circular cross section to an oval? This would increase the spin resistance.
The answer to can I is yes.
The answer to will I is No.
That would deviate from Vern's description more than I care to.
Dive planes are going to be much larger than "scale" by book description (and twice as many of them too; the described single set of planes at midpoint is not practical by modern real world experience) and the large dive planes on 25 inch long PRS-1 do appear to give it resistance to torque roll. See attached image of it.  This Nautilus will have dive planes of similarly exaggerated proportion.
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ScottW

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Re: Pondering propellors for a Jules Verne Nautilus
« Reply #13 on: August 16, 2022, 08:06:38 am »

As an alternative small 3 blade propellors are available for the micro drones that are available now, 3 or 4 inch props will be common and are available as right or left handed rotation as drones need both.
Finally thought to go look at drone props.
Hmm ...
Quote
Prop Disk Diameter: 63.5mm
[/size][/color][/size]That's a little over 2 inches, that could be useful for a 20th century design idea I have.
[/color]
https://www.amazon.com/Gemfan-Propeller-1105-5500-Brushless-Quadcopter/dp/B08QVFKDVH/?th=1

Still want a 5 inch, 100mm to 120mm prop for Nautilus.

If similar comes in that size we may have a test article ...
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tonyH

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Re: Pondering propellors for a Jules Verne Nautilus
« Reply #14 on: August 16, 2022, 10:51:56 am »

https://www.youtube.com/watch?v=esvQae8hx3w Contrarotating props such as this? No torque effect?
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