Interesting propeller shape. Any idea?
 

688i propeller in RA
http://img.photobucket.com/albums/v3...mp00734068.jpg

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?

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.

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

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.

Well now that we started .. who cares about the sim .. I just want to know what it is good for :rotfl:
Looks like another google night.

Good luck on the search, this is a black topic.

Yeah .. it's perfectly allright .. I guess we all respect your oaths.

But I have found something. It's all matter of good search terms.

http://ci.nii.ac.jp/naid/110003873027/en

You can get whole PDF paper but it's mostly in japanese. Still the abstract says it all.

But it took me an hour.

Any link for that swastika like prop?

So it's not meant to add additional push force lol:)

Ohio propeller (and more):

http://images.google.com/images?hl=c...ropeller&gbv=2

:ping:

Great find, well worth the hour it took you.

:up::up:

Interesting abstract.....

I can not confirm nor deny....

Non sence... The little prop powers the turbo drive that lets it travel at the speed of sound underwater...:rotfl:

of course... The article could be right... I guess the large prop helps it stay quiet, and produce speed effectivly because of its shape... and maby the smaller prop does like the artical says... or is some kind of thing to fool a distroyers listening equipments... to make it sound faster than it is... could also be there to fool homeing torpedos... (noise fools them...) may add to its speed when staying quiet... but im just guessing...:yep: I could keep speculating...

Something to do with reducing cavitation and therefore enabling a sub to have higher speed at or near the surface ? :D
Just my guess.