prop shrouds

[waterwar]

I am so happy that you have had so much ego boosting I can imagine many heads puffed up .
The reality hasn't changed

I would still like to have some solution that works well. I have an old outboard OMC and light orlando clipper v hull and don't want to lose speed or performance.

http://www.propguardmarine.com/test.html


http://www.propguardmarine.com/index.html


http://www.ronhalemarine.co.uk/superbasket/images/products/151/b_propguard.jpg

I am curious if any of you Experts have any opinions on this product
I can only laugh at some of the more ridiculous posts piece of work...



a bemused Stew

In actual fact, I repeat the question and expand on it...

 

[waterwar]

You should re-read your own post. There was not question but a lot of snooty remarks. The negative reputation points are a reflexion of what members think of you. Except for a bad attitude, you haven't answered or substantiated anything.

I would still like to have some solution that works well. I have an old outboard OMC and light orlando clipper v hull and don't want to lose speed or performance.


.Threads are allowed to evolve, go look that up now.
Propeller Shrouding works well look at the boat again as it dives! No grapes to watermelons: draft of surface vessels can be a limiting factor.Submarines have no such limitations for wheel size except for stream lining restrictions. Pump jet propulsion seems to used on most modern submarines. A simple bolt on prop guard can retrofit most recreational sized boats quite easily.Its no pump jet but a partial shroud. But it will keep a propeller from the common performance nicks and damage that routine occurrence in normal operation of pleasure craft. I realized that asking for an evaluation of an unpopular device was going to difficult.....


http://wn.com/Spearfish_torpedo

 

[gonzo]

I like that waterwar can't just post and wait for a response. He seems to work himself up, walk back to the keyboard, and write more self-pitying nonsense. It is amusing though.

 

[hoytedow]

Yes, all of us are perfect. Let us find the flawed one and stone him.

 

[hoytedow]

Ouch! That hurts! Stop it, guys! I didn't mean it! Ouch! Oof! I'm outta here!

 

[waterwar]

Hi bet you missed me

Responsibility
I am responsible for posting some rather disturbing information on weapon systems, and I make no excuses. In this accelerated age of communication the state of the art is happening everyday.
Anything that can be accessed by a simple person like my self was probably done countless times by someone else. Military secrets are inaccessible except when they are no longer secret.
Propulsion underwater is a prime example of this; changes occur and are met. That response is a military secret. Rest assured that the Free world is deployed at present. Many candidates were on the ‘board’ years ago. Cannons as one of many delivery systems possible employing exactly same ‘new’ principle. Have faith in the free world! Send Emails to complain about the Germans for selling fuel cell tech to the Chinese for their diesel - electric subs, not to me (actual transfer of forbidden technology).

I only wanted to get and use the best type propeller guard I could get
I know this sounds corny! But some very fine members of this board, professionals apparently have had a hand in the design of some underwater weapons.These men worked in secret and resent the facts I found on the internet. Many of these weapon platforms are still deployed, but none more deadly than the fine torpedoes that run silent run deep with huge explosive capacity with no warning.
* Pictured below: 2 Stingray launches, a MK 54 and the USN fleet torpedoes chart and the RFS Dmitry Donskoy (TK-208) is a Russian Navy nuclear ballistic missile boat (Typhoon class)
USN Virginia Attack Boat.(pump jet driven) it replaces the older, larger Los Angeles Class.
http://www.youtube.com/watch?v=tfZ6zCL38ic
In this 'fox and hounds hunt' (during the cold war) the largest fox was the huge 600ft Dmitry Donskoy. .The prize target of the American hounds (attack boats).Only one of these giants was made operational.
http://www.youtube.com/watch?v=Wlp1lUWqRYI&feature=fvwrel Dmitry Donskoy (TK-208)

 

[waterwar]

I like that waterwar can't just post and wait for a response. He seems to work himself up, walk back to the keyboard, and write more self-pitying nonsense. It is amusing though.

That's the only reason you are here as is everyone: to be amused.

Quote:
Originally Posted by viking north
Waterwar, the topic is a good one and has been ongoing one over the years, it's an interesting topic and worth some new input The problem i think was in your excitement to create debate you took the wrong approach by using the tool of confrontentation to create debate instead of querry. We're probably all guilty of this at some point in our life, it's usually a sign of higher levels of tetosterone thus the question on your age.Good for you if your levels are high but bad for you if you want meaningful debate. Thats why old guys mellow and become more patient and wise. So me thinks if it's not too late you could re tone your post and a transfer of info could possibly occur. Geo.

A yacht is not defined by the vessel but by the care and love of her owner.
Agreed. Except for me, we are not idiots here. These are in great part professionals with centuries of combined knowledge.
__________________
Cheers,
Hoyt
http://www.weathercenter.usf.edu/weathersticker/
http://arctic.atmos.uiuc.edu/cryosph....new.some.html

Sub Tommy

you've broken my Heart by retracting you post how quaint?

how could you now the cat will eat em' all

"Life is like a field of newly fallen snow.
Where I choose to walk every step will show."
Author: Denis Waitley

Meanwhile Life marches onward. But I have questions as to the validity of the anti shroud position but I am no expert. Stew

 

[CatBuilder]

Yes, all of us are perfect. Let us find the flawed one and stone him.

http://www.youtube.com/watch?v=MIaORknS1Dk&feature=fvwrel

 

[waterwar]

..

At low speeds thrust will be increased, but this can't overcome the increased drag from the duct at higher speeds.

Some of the advertising for these add-on ducts for outboards is a bit misleading, as they tend to compare static thrust, sometimes described as bollard pull.

Ducts work well at increasing low speed thrust, and can improve the ability of something like a ski boat to lug inexperienced skiers out of the hole, but as soon as the boat gets above a few knots, performance will fall off when compared to an open prop.

Jeremy

Thank you for meaningful imput.

Waterwar: if you have an old OMC outboard and are talking about joining the big dogs in speeds, you must be delusional. The boat is a crapper too. You want speed, you need new technology and lots of money. I can sell it to you, but show the money first. BS is plentiful and free.

No, I just don't want to chop the kids up! Go figure....

I suspect there can be cases where the addition of a shroud may improve top speed of a boat which has a badly matched propellor to start with. But I haven't seen any independently tested examples. It such a case a properly matched propellor without a shroud would probably have even higher top speed.

This is a smart true professional.

Thank you for your expert analysis all insights have been informative.
I certainly think that the state of the art may hopefully be pushed.Your astute observation of the patent rights expiring hopefully will promulgate even more innovation. We need one system that works.and guarding a prop from damages and or causing them to others.


.once again thanks for your views
Stew

This is the topic sink or swim!

I feel that some more mention should be documented as the 'test' was flawed as pointed out but in defense of fairness, I found these disclaimers on a vendor website;


''Prop Guard is the ultimate in prop protection, providing both protection and enhancements that every boater is sure to desire. Made up of two joined polypropylene rings (duct type guard) it provides protection for the propeller and a measure of safety for people and animals in the water.

This model fits most outboards from 25 hp through 30 hp. Usually you will see an increase in performance at low speeds and little or no decrease in performance at top speed.

This model fits most outboards from 9.9 hp through 20 hp. Usually you will see an increase in performance at low speeds and little or no decrease in performance at top speed

This model fits most outboards from 4 hp through 9.8 hp. Usually you will see an increase in performance at low speeds and little or no decrease in performance at top speed.''


I think we all and myself finally that there will be a loss of speed at high speed using anything that cause drag like a guard.
The point being that some will still want to use one.and want the best .


Just for fairness .
thanks stew

I am not in this for profit or for gain, Lets be clear on this point I am in no way or affiliated with any manufacturer!

In general, anything that reduces the magnitude of tip vortices will increase efficiency, so producing more output power for a given input power. A simple ring around the tips of the prop will do this to some extent.

Adding a convergent duct around the prop (like the Kort and Rice nozzles) tends to increase the velocity ratio across the prop disc and duct combination, so increasing the mass flow rate and generating more thrust for a given diameter (with a commensurate increase in the power absorbed by the prop). In effect, a prop in a convergent duct behaves somewhat like a larger diameter open prop.

The tradeoff comes when comparing the efficiency improvement that comes from the reduction in vortex magnitude with the power needed to overcome the additional drag created by the duct. As has already been mentioned, the break-even point tends to be just a few kts; a ducted prop is unlikely to be more efficient than a properly sized and pitched open prop above about 10 to 15kts or so.

Spoken like a true professional

One point I wanted to add: in order to double the speed of a submerged object you have to more or less cube the power.
The powerful Otto fueled engine developed by Sunstrand from WW2 German inspired technology has not come with out a price.
This 'envelope push' did result in an accidental explosion for them.long ago in development phases. .
I would hope that this trend toward using a liquid monopropellant for the military would not continue as the *fuel is horrific stuff to handle. Unfortunately its resemblance to rocket fuel is not by chance. By definition it provides its own oxidizeras did the rocket fuel of old rocket(V2). Handling even the improved Otto fuel is tricky,and hopefully never endangers the submariners who perform their duty. I wish that the electric engine could be utilized instead with advanced batteries like lithium or seawater battery technology.

The military wanted the otto fueled engine. Electric was never fast enough.. The ultimate goal was always an engine: that would be prototype for a submarine. Exactly what the WW2 Germans had planned for otto fuel.

I want to dedicate this 'string' to 'all who brave the peril of the sea.'
particularly the submariners.

Stewart Loeblich

"What we do for love goes beyond good and evil" Friedrich Nietzsche

In actual fact, I repeat the question and expand on it...

Go figure... so go do what you do if its constructive at all.I doubt it
I know you have amassed a lot of points gee you must really be a real expert? Funny all I see in your numerous posts are abbreviated snipes, exclamations and other drivel: not worth my time,or anybody's else too!
cheers Stew.

I broke a Taboo something that would actually save lives: human and animal....

I will visit again soon and reply to ones that are on subject.
Personal comments will no longer elicit any response

*People who do such are irreproachable and a waste of time, and merely post to see their own name in print!



Vows made in stormy waters are forgotten in calm ones.

What's the problem with a real topic?

 

[waterwar]

sub tommy

'If you can't make cents'

How about some Change then?
OOOOh that would bad right?

Lake Powell solution for large inboard by an independent boater...
http://www.youtube.com/watch?v=_f08CLcK8TM


Sign the Petition Here:
http://www.thepetitionsite.com/10/save-the-manatee

As one can see there are many different designs out there to 'guard' a propeller
I came to this board not to play point games. Games are for children to play!
Try to act like an adult on your side of the computer.
Thanks again to the Professionals who aided in selection of one of thes 'bubble machines' that seem to at least be more efficient and durable (high impact plastic) than then metal ones.For instance the wire cage affairs are presumably true bubble machines I assume? but I guess it would waste of time for an educated opinion?

I am not qualified to do such. The highly skilled and competent architects of weapons are experts in propellers, as was quite evident in their posts. They have done an excellent job shown by the modern weapons deployed . Their imput to analyze this propeller guard is admirable
Such fine detailed, intelligent one. That is rare these days to find such a resource for free.... Tommy
Cheers and top of the Morn to you too!
Stewart
https://sites.google.com/site/preservethemanatees/
* Propguard is represented below first as yellow version.the very last is a red one (smaller), run 100 to 200$. High impact resistant Plastic.
While the sixth candidate below runs 550 to 600$ depending if you want it painted... jeez? Metal has disadvantages sometimes....
A lot of money for wire cage! IMHO a bubble machine?



https://sites.google.com/site/preservethemanatees/

http://www.thepetitionsite.com/10/save-the-manatee/

 

[waterwar]

Once one of these things lock onto you it's just re arranging the deck chairs on the Titanic boys. Back in the old days with outdated equiptment tuned by us tecks who knew our stuff we'd out kill anyone in war games amoung the Nato nations. A sub was not the place to be,Imagine what these hunter killers can do now with modern gear and active submurged underwater tracking devices. In her belly was two massive homing torpedoes (yes they had rings,why i don't know but it keeps me on the repetitive topic) each one probably capable of taking out an aircraft carrier, certainlly crippling it enought to hold it in one spot, imagine what it could do to to a 60 or 70's era sub. No thank you as far as i'm concerned any sub mission ( with or without prop rings)is a one way trip with a modern version of this bird. Pretty pictures of subs are just that pretty pictures. And thats my last post here as i'm guilty as anyone keeping it going long past it's expirey date. geo.

Here's just one of the professionals his expertise and experience is evident to all. Notice his interest in 'rings' ,funny thing guys my dad was in the 'loop' too.
I always wondered about the rings too, my learned engineer friend, everyday as I look at the Mk 48 torpedo (aluminum model) given to my late father for his contribution to the 'fish's' development.

 

[waterwar]

I can't make any sense out of what's going on with this thread. I'm getting disjointed PM's, weird rep comments, somebody's off their med's.

I'm outta here.

-Tom

Rules of engagement have been determined; tommy
The kindly and all so wise webmaster has removed some posts.on his own behest, others at mine.
regards
stew
Safety on and below the water is an important issue in a marine environment
Man Fined, Ordered to Give Up Boat After Killing Manatee
February 3, 2011
Contact: Craig Pittman craig@sptimes.com
with Caryn Baird www.tampabay.com

The angler recognized the boat roaring past him in the manatee refuge. It belonged to one of his neighbors in Brevard County. It was going much too fast. Then the boat slammed into a manatee, a collision so violent that the boat jumped out of the water. The manatee's fluke was still sticking up from behind the motor. The manatee thrashed wildly as blood spread across the rippling waves. The boat sped away. The angler, horrified, called the authorities to report what his neighbor had done. It turned out this wasn't the first time he had violated the speed rules.

Now the boat owner, Joseph Miata Jr., has become only the second person in nearly 40 years to be successfully prosecuted for killing a manatee. Miata, 62, of Merritt Island, was sentenced Wednesday to a year of probation and a $600 fine. In addition, he must forfeit his blue and white 1987 Mach One, the boat that struck and killed a manatee that was nursing a calf. Manatee advocates hope that Miata's case--and especially the loss of his boat--will deter other boaters from violating the rules designed to protect manatees from being run over.

"That's bound to get their attention," said Pat Rose, executive director of the Save the Manatee Club.

Miata's prosecution should benefit more than manatees, Rose added: "Somebody like that is not only putting manatees at risk but also putting other boaters at risk." Miata, in a brief conversation with a reporter Wednesday, suggested that his sentence for killing a manatee seemed unfair compared to the sentences handed out to boaters who kill people. But in a subsequent call his attorney, Corey Cohen, said Miata thought the sentence was fair. "He was okay with forfeiting the boat in exchange for getting on probation," Cohen said. The manatee that Miata killed was one of 83 run down by boats last year — down from the record 97 manatees killed by speeding boats in 2009. Since the Endangered Species Act became law in 1973, the only other boater to be successfully prosecuted for killing a manatee was Jimmy Malmsten, a fishing boat captain from Stuart. In 1984, Malmsten's boat accidentally hit a manatee calf. "It looked to me like it was dead," Malmsten later told a federal judge. "I heard it was good eating. I just took a couple chunks out of it." The judge ordered him to pay a $750 fine and sentenced him to six months behind bars, followed by a year of probation. Because Malmsten kept the meat to feed his wife and four children, investigators had the evidence to charge him. Most of the time when manatees are killed by boats, there is little or no physical evidence showing who did the deed or even where it happened. In Miata's case, the key was the eyewitness, said Officer Justin Morgan of the state Fish and Wildlife Conservation Commission. Miata's crime occurred about 8 p.m. on July 11. His neighbor, identified only as J.P. in federal court papers, said that while his own boat was anchored and he was fishing near Kiwanis Island in the Sykes Canal Manatee Refuge, he saw Miata's boat zoom past and clobber the manatee. J.P. not only reported the incident to the state wildlife agency, but when two investigators — one from the state and one from the U.S. Fish and Wildlife Service — showed up to interview him, the witness took them out in his boat to show them where it happened.

When the investigators told him he'd killed a manatee, he said he hadn't realized what he had hit before he zoomed away. But Miata's passenger, a relative identified in court papers as K.B., told them that "Miata was aware what had been hit after looking back at the thrashing manatee," the plea agreement says. Special Agent Neil Gardner of the Fish and Wildlife Service said the investigators also knocked on doors around Miata's canal-front neighborhood and "we heard more than an earful about this gentleman and how he operated his boat." Miata pleaded guilty in November to taking an endangered species, a federal misdemeanor. If there's a lesson in his case, his attorney said, it's a simple one: "The lesson is to slow down," Cohen said. "Slow down and follow the law."

https://sites.google.com/site/preservethemanatees/

Divers and swimmers well know the risk of sharp propellers blades also!
I have snorkeled and scuba dived for years, I was born in the Keys.
The terror of close encounters happen everyday for humans and manatees
. Prop shielding won't stop blunt force trauma to animals or humans
Please Slow down and respect all warning signs and buoys!

 

[waterwar]

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

This truth is self evident thank you very much for pointing this out!

 

[gonzo]

If you are truly disclosing secret government information as you claim, I guess it is time to report you to the DHS. You are claiming to be a traitor and perhaps a terrorist.

 

[Submarine Tom]

Gonzo, you've moved!

Congratulations.

What's changed then?

-Tom