Interesting propeller shape. Any idea?

[Castout]

688i propeller in RA


Hmm I think the unconventional shaped propeller is meant to optimize on speed but does it offer any other advantages?

I thought it was the Russian submarines which are fitted with propeller shaped to give them maximum speed(push power) while the US submarines are fitted with propeller shaped for optimum noise performance(least noise).

If this is the shape of a propeller for optimum speed how is the shape of the propeller designed for optimum(lowest) noise performance?

Is this propeller(as shown in the picture) realistic to be fitted in 688i class SSN?

[Dr.Sid]

As the propellers go, nobody who knows will tell you.

But on Microsoft maps there was picture some time of Ohio propeller. That propeller was for sure designed for stealth. And it is based on ww2 design, where the tip of the blade is extended back, so it looks like huge 7 bladed swastika.

I have never seen something like this though. Not on any model, any picture, not in any books on submarine design.

But it totally gives sense. Limiting part of the screw is the propeller tip. The tip moves at maximum possible speed (not to cavitate) and the rest of the blade moves slower then it could. The second screw could rotate faster with same tip speed .. and accelerate that not so well used middle part of the propeller disc. It would be something like propeller which tips moves slower then the blades (ultimate dream of any propeller designer).
Also the second propeller could be counter-rotating, which could help even more. It does not look so from the picture, but AFAIK it is DW's limit and DW can't do counter-rotating propellers.

So it would improve effectiveness - it could achieve better acceleration at same power, and it would need less power to achieve same acceleration. That means it could be even more silent.

Sure it would complicate a gearing, I mean a lot.

We have made Oscar-I in –RA- Add-on, with two coutry - rotating propellers on one shaft.

Also TU-142 Bear have coutry - rotating propellers.

Other business what is it in any way is not connected to awful physics of the engine.

But visually, it is looked very well.

[Bubblehead Nuke]

I have made comments about the curvilinear shape of the screw before. It has to do with controlling cavitation formation. A screw on a boat is not like a screw in a chunk of wood. Nor is it like a wing, it can not 'stall'. There are many many reasons it is shaped like it is. What you see there is the rough shape. There are many things about the surface of the screw and exact shapes that are the real secrets.

The smaller propeller in the back spins ar the same speed and direction as the main propeller.

my other post: http://www.subsim.com/radioroom/show...ear#post967416

[Dr.Sid]

So that small prop actually used ? On 688 class ?

[Bubblehead Nuke]

Originally Posted by Dr.Sid

So that small prop actually used ? On 688 class ?

This is not really a prop... and it does not do what you think is looks like it is doing.

Yes, it is there, and it is probably used on all 688's now. I can not tell you what it was called as it was (and for all I know still is) a classified item. I know our boat was testing working hardware of the original concept design. I can tell you for a FACT I know what it is, what it is there for, and how it works.

The reason for it goes beyond the scope of a sub sim.

[TLAM Strike]

Wasn't there a 688 boat fitted with a contra rotating prop? Also a Permit had one too USS Jack I think. Albocore had one at one point as well.

And yes DW can do contra rotating props the DPRK's P-4 class SSM in LWAMI has one.

[Bubblehead Nuke]

The Albacore still has one. It is a sight to behold. The X planes were a little starnge to me.

The screws for the Jack are at the Albacore park. They are interesting in they are MIGHTY small in my opinion.

No 688 had counter rotating screws. I do believe that one had a propulsor instead of a screw to test the then new Seawolf gear.

[Bill Nichols]

Originally Posted by Bubblehead Nuke

The Albacore still has one...

Yes, but I don't think she's going anywhere anytime soon!




BTW, lots more Albacore pics here:

http://www.ussalbacore.org/html/virtual_tour.html

[Dr.Sid]

Cool ..
Notice how the planes pairs are offset. The upper right (and lower left) ones are a bit more forward. It's so their axises wont collide. And they must not collide with the propeller shaft either. I'd really like to see this part from inside.

Edit: Old man ? OLD man ? I've just turned 34, and that makes mi OLD ? :rotfl:

[Bubblehead Nuke]

Originally Posted by Dr.Sid

Cool ..
Notice how the planes pairs are offset. The upper right (and lower left) ones are a bit more forward. It's so their axises wont collide. And they must not collide with the propeller shaft either. I'd really like to see this part from inside.

:rotfl:

Nothing to see, they cut the steering rams in order to put the after access in the engineroom.

One other interesting thing they had was a rudder on the back of the sail.