prop shrouds

[waterwar]

I didn't mean to ignore you sir. I do understand the size issue of the prop is always the bigger the getter. So a bigger bare prop will beat a smaller sized pumpjet ....my wife will love this one

But practicality demands the prop can only be so large does it not?


Recreational craft, with limited draft limit the prop can only be so large does it not? You can’t mount 3 foot propellers on most recreational craft. You can put any size you want in large vessels with cowling drag overcome with unlimited power.* http://wn.com/Spearfish_torpedo That’s applicable grapes to watermelons! Please understand the that the parameters change when you add have size limitation, as you do on pleasure craft. That’s applicable grapes to watermelons.

additional military links dated years old info.
http://www.navy.mil/navydata/cno/n87/usw/issue_14/torpedoes.html

http://www.ussjamesmadison627.com/viewtopic.php?f=17&t=295

 

[DCockey]

I didn't mean to ignore you sir I do understand the size issue of the prop is always the bigger the getter So a bigger bare prop will beat a smaller sized pumpjet ....my wife will love this one

but practicality demands the prop can only be so large does it not?

Not what I meant at all, assuming your response was directed at me.

 

[waterwar]

Re-reading the introduction to the AIAA paper above it occurs to me that the paper may not consider the drag of shroud directly since it is for wind and water "turbines" for which the forces acting on the device are of secondary importance. Note that these types of "turbines" behave similar to propellers in that the amount of flow through the device is not determined a-priori.

I see applies to air not water turbines.

I am glad that you truly are doing the research that I am not qualified to do. I think that there is a lot of research done but behind ' doors'
Stealth and pumpjet are integrated systems apparently in underwater propulsion it seems.and the military application is obvious
having a quiet silent electric drive enable modern subs to be super stealth.
..
cheers
stew

Re-reading the introduction to the AIAA paper above it occurs to me that the paper may not consider the drag of shroud directly since it is for wind and water "turbines" for which the forces acting on the device are of secondary importance. Note that these types of "turbines" behave similar to propellers in that the amount of flow through the device is not determined a-priori.

I am sorry, I see I misunderstood . I'll step aside and let you exchange info with your peers who are more learned and wise than me. I've had enough today
good nite.
Stew

Its rocket science now as the 'cavitation' weapons have arrived.This unfortunate development proves one of my points that noise is no longer inhibiting a very fast weapon from being deployed. The Soviets (Chinese and Irananians) have illustrated so poignantly. The presence of ultra quiet subs with noisy but fast rocket weapons ups the peril in the high sea for all who ply them.
No vessel avoids this unfortunate scenario; surface or deep below,there is little time for countermeasure deployment at 300 knot plus...incoming.

stewart loeblich

 

[gonzo]

Noise never did. For example, bullets.

 

[waterwar]

Noise never did. For example, bullets.

Noise certainly does stop many weapon systems depends.

For example Panzerfaust in WW2 when fired was very loud and left cloud of smoke pinpointing the position of the soldier immediately. the resulting retalitory fire from the rest of the attacking Soviet army made it suicide to fire practically.

The examples are endless actually.and not the point of this thread...
What is important is exchange of information that accomplishes a true goal.... not chatteric
I will keep this thread open for that chance for free useful information exchange as open source for those who might want a shroud system application.

Re-reading the introduction to the AIAA paper above it occurs to me that the paper may not consider the drag of shroud directly since it is for wind and water "turbines" for which the forces acting on the device are of secondary importance. Note that these types of "turbines" behave similar to propellers in that the amount of flow through the device is not determined a-priori.

I do want to thank you for your efforts sir.
I also wish to thank any of you in advance, who would care to contribute a meaningful post.

Most of the outboards amongst my friends and relatives are small, typically around 10 hp. None of them have shrouds. If the outboard is more than a few years old the propeller is usually more or less dented. To my experience, all small boats and all small outboards eventually hit a rock (at low speed because you know you're in shallow water). It's more fair to compare the efficiency of a dented unshrouded prop with an undented shrouded prop.
Erik

Very astute point that is like my old prop its OE, and been polished by time and nicked. .

 

[seeds]

This is great stuff! I'm gonna go grab some popcorn and watch the show unfold...lol

 

[waterwar]

on guard and vigilant

USS New Mexico is the first picture she is a Los Angeles class attack nuclear submarine
The second picture is a stingray torpedo (helicopter mounted in this case).
The third photograph is also a US fleet torpedo Mk50 (I believe no other info was provided)
The fourth picture is of China's Xia class of nuclear ballistic missile submarine

 

[gonzo]

This turned into a "post pictures and make unrelated comments thread". I would like to see any support for the original proposition. I think Waterwar, using his own word, is "chatteric".

 

[waterwar]

gonzo

the name is self explanatory

You are the very reason I coined the term;"chatteric"

If you have some contribution... that would advance something, other than brash comments, that are the defining feature in counterproductive activity ......go sell a boat to a top dog wannabee or whatever you do

 

[Jeremy Harris]

Interestingly, the centre picture is the torpedo (Stingray) that I worked on through it's initial design and development in the late 70's, early 80's. It does have a pump jet, primarily to keep the noise signature down so that its sensors can work effectively. It's not that efficient though, and needs a heck of a lot of battery power to get the weapon up to speed. The pump jet was chosen for this weapon on grounds of low noise and relative ease of control (low torque reaction), not because it was a particularly efficient high speed propulsion option. Getting the high power needed from the sea water battery system to meet the needs of the pump jet was a significant challenge during development.

We're just going to re-hash old debates from now on, I fear. The facts regarding the physics and hydrodynamics of pump jets are very well understood, most are in the public domain and have been summarised in posts here. There's nothing mysterious about them, they meet the needs of providing fairly quiet high speed propulsion for vessels where this is the most important design criterion well, albeit at the expense of propulsive efficiency at speed. This deficiency isn't really a problem for a nuclear powered boat where there is more than enough power to spare.

Jeremy

 

[hoytedow]

Wink! Wink!

http://en.wikipedia.org/wiki/Dwarf_Livebearer

 

[waterwar]

Interestingly, the centre picture is the torpedo (Stingray) that I worked on through it's initial design and development in the late 70's, early 80's. It does have a pump jet, primarily to keep the noise signature down so that its sensors can work effectively. It's not that efficient though, and needs a heck of a lot of battery power to get the weapon up to speed. The pump jet was chosen for this weapon on grounds of low noise and relative ease of control (low torque reaction), not because it was a particularly efficient high speed propulsion option. Getting the high power needed from the sea water battery system to meet the needs of the pump jet was a significant challenge during development.

We're just going to re-hash old debates from now on, I fear. The facts regarding the physics and hydrodynamics of pump jets are very well understood, most are in the public domain and have been summarised in posts here. There's nothing mysterious about them, they meet the needs of providing fairly quiet high speed propulsion for vessels where this is the most important design criterion well, albeit at the expense of propulsive efficiency at speed. This deficiency isn't really a problem for a nuclear powered boat where there is more than enough power to spare.

Jeremy

Thank you very much sir, your expertise in weapons development is admirable and your observations are correct as to identity.
I thought Ii had a label that would accompany the jpg.'when posted...
I will end this thread: if the the subject has finally ended and no useful exchange is evident.




I posted the slow Stingray, as it had been mentioned in a prior post, for illustrative purposes.

cheers

Stewart

Wink! Wink!

http://en.wikipedia.org/wiki/Dwarf_Livebearer

Yes, Hoyt
you know the routine,I see very well! The poor hapless Least Killifish is now poised above the gaping house cat's mouth. So the rest of you better behave and stay in your seats,or else I drop the hapless innocent into the very jaws of death...

Thank you again for the reminder! You are a true sport! and a credit to this fine Board

Tip of the hat to you sir!

*Least Killifish smallest of all livebearers,this tiny relative of the guppy' hails from our own shores, and is in great abundance in pristine freshwater environments.
I get mine from Crystal Springs

 

[Jeremy Harris]

I posted the slow Stingray, as it had been mentioned in a prior post, for illustrative purposes.

Just one correction. Stingray isn't particularly slow for a lightweight air launched torpedo, but I'm not going to tell you just how fast it is on a public forum. To the best of my knowledge that's still classified but I can confirm that, just as with most weapons still in service, the speeds often quoted from public domain sources are rarely correct.

I can confirm that it needed more power to reach a given speed than it's predecessor, that was of similar size but used contra rotating open props of greater diameter. Unfortunately, these open props, although very efficient, created a lot of noise, making passive target detection impossible.

Jeremy

 

[waterwar]

T thank you very much sir. I am wrong about the Stingray torpedo being slow, sorry. I didn't mean to downplay this fine weapon's speed . I too was hesitant about speeds and posting them.
However, as it became apparent that the world was shocked by the new 'cavitation' weapons,several years ago and speeds of the free world's weapon systems were 'leaked'
the new weapons are 300 knot plus almost five times the speed of most propeller driven weapons.
the Mk 48 has a 120 (knots) more or less.
As you know that is our heavy torpedo'...I am sure that the Stingray is not slower, than its older brother, so to speak.
As for speeds of subs i don't see posted, I'll keep mum on that regard respectfully.

cheers To a true professional, I commend you on your personal contribution to underwater propulsion systems.

thanks

 

[waterwar]

Pictures will be ID'ed

I will edit and add identifying labels to all pictures.
Please bear with me I am busy at present! Thanks for your patience.
regards
Stewart

have to go catch more fish damn cat ate em all