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Seawolf pumpjet

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Seawolf pumpjet

Postby hakkikt » Sat Jul 18, 2009 7:09 pm

Probably of interest for RC too, but mine is primarily static, so this goes in here.

After some research on the net, I find (not too unsurprisingly, given the sensitive nature of the information) that what the Seawolf pumpjet looks like is not clear at all, even approximately.

From what I hear about pumpjet design,
1. it is imperative that stator and rotor have different blade numbers, and both should be prime numbers to avoid vibrations;
2. pumpjets come as either the pre-swirl or the post-swirl version, depending on where they have their stators (in front of the rotor or behind it, resp.). Pre-swirl gives better quietness (=subs), and post-swirl better torque balancing (=torps).

My conjecture:
All models (and their RC adaptations) have stators in front of and behind the rotor, and typically the same number of blades for all. This seems to be incorrect.
Since Seawolf is optimized for quietness, it probably has a pre-swirl design. Assuming that the number of blades is higher than that of a normal propeller (typically 7), the next higher prime number would be 11. Stator blade no. must be different, that means it should be 7 or 13.

Any thoughts of the community on this?

The attached photo shows the Mk. 50 torpedo, which has a post-swirl design with 11 blades on the rotor and 13 on the stator.
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Postby junglelord » Sat Jul 18, 2009 10:37 pm

I could throw some interesting ideas out there.

I have worked on Canadian Mililtary Sonar, so I have some eduation.
I also have a personal and professional interest in geometry, engineering, biological tissue engineering and structure, Buckminster Fuller, Tensegrity, a wide range of study of structures and engineering princples, from many angles.

The Prime Number Code is a very interesting book.
The Sacred Geometry of the spiral vortex is a key. Anyone know about Viktor Schauberger? I know the military does.

The different numbers between the prop and stator are I believe, related to the way the ratios of the Prime Number Code and Sacred Geometry connect, think Spirograph possibly to determine the final geometry of the water flow. Schauberger vortex technology might be a key.

To diverge from those concepts of symmetry, consider that while sacred geometry is symmetrical, consider that in nature, crystals, for example exhibit Asymmetry. I think its possible that these ratios of Prime Numbers and not having the same number of blades as being one and the same.

I wonder if they have tried a Tesla Turbine Drive?
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Postby hakkikt » Sun Jul 19, 2009 2:55 am

I recognise you now, Mr. Tesla... what an honour to have you with us.

May I most humbly offer the thought that having 2 different numbers of blades is not the same as having 2 different numbers of blades that are prime numbers?
A 6-bladed rotor and a 12-bladed stator should produce vibrations much easier than, say, 7 and 13.
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Postby junglelord » Sun Jul 19, 2009 4:22 pm

Thats why I mentioned the prime number code.
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Postby hakkikt » Mon Jul 20, 2009 4:36 am

Thank you for mentioning that, Mr. Tesla. :)

A point that I would be interested in is: how did the layout and blade count of the Caswell/Merriman Seawolf RC conversion kit come about? Is it based on RL info, or is it is something that was chosen because it looks sharp and credible (sure does), and works fine in a model?
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Postby junglelord » Mon Jul 20, 2009 10:48 am

He said he tried several blade combinations with a amp meter in a test bucket. He chose the combination with the best thrust with the lowest current draw. That simple.
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Postby Kerry Addington » Mon Jul 20, 2009 11:51 am

Can't resist a bow to anyone taking on the challenge of finding accurate information about Seawolf.
No US nuke boat class is less visible to the public domain modeler.
Scaled Seawolf propulsors that are visible, besides the 1/44 you mentioned, are the 1/48 beauty David Merriman created for a customer ( green attached ), and that same design was the inspiration for the superslick 1/96 scale unit Pete Piekarski made for his Virginia class Submarine Works kit ( see parts attached ).
This is a an excellent piece proven very thrusty in tests on my SSN-22. I have no idea how closely it resembles the prototype in shape,blade count or quietness.
Good luck,
Kerry

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Postby junglelord » Mon Jul 20, 2009 9:26 pm

That is super slick.
8)
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Postby hakkikt » Wed Jul 22, 2009 3:30 pm

This stuff looks sharp, great engineering, and I believe anytime that these pumpjets can move a lot of water. But I doubt that the blade count is that of the real thing... even numbers are a no-go.
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Postby sam reichart » Wed Jul 22, 2009 6:57 pm

looks a lot like Matt Thor's SSN-21 pumpjet...which I believe David worked on as well.
what were once vices are now habits
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Postby Albion » Thu Jul 23, 2009 3:05 am

hakkikt wrote:I recognise you now, Mr. Tesla... what an honour to have you with us.

May I most humbly offer the thought that having 2 different numbers of blades is not the same as having 2 different numbers of blades that are prime numbers?
A 6-bladed rotor and a 12-bladed stator should produce vibrations much easier than, say, 7 and 13.

Is known as blade passing frequency. Best to stick with odd numbers of blades and stator vanes. Obviously prime numbers work quite well

at the wrong speed 6/12 would be very unpleasant
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