Secret engines on the Mauretania
- Thread starter Tom Bates
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Michael H. Standart
Member
I don't know about any secret adjustments, though my understanding is that the top speed of the Maurataina was around 26-27 knots.
And the top speed of the Nimitz is not 60 knots. Not even close. She's in the 30+ knot range.
Conterary to some popular opinion, nuclear power does not give a ship some sort of magical capabilities. When you get right down to it, a nuclear powered vessel is a steamship plain and simple. The unique capability such a ship has is that she can sustain her top speed without having to worry about running out of fuel.
And the top speed of the Nimitz is not 60 knots. Not even close. She's in the 30+ knot range.
Conterary to some popular opinion, nuclear power does not give a ship some sort of magical capabilities. When you get right down to it, a nuclear powered vessel is a steamship plain and simple. The unique capability such a ship has is that she can sustain her top speed without having to worry about running out of fuel.
The same person who told the story was in the navy said the Nimitz top speed is 60 knots Michael you said She's in the 30+ knot range but 60 is above 30 i rest my case. the story i herd about the secret adjustments made to the engines on the Mauretania is (cunard was aware of the germans' intentions to set a new speed record so in 1928 the Mauretania is takeing out of service for seven weeks in order for top? secret adjustments made to the engines and top secret pumps and condensers installed..and her top speed was 32 to 39 knots)thank you for you time and i am looking for a empress of ireland thank you
tom bates
tom bates
Dave Gittins
Member
Who told you the story, Tom? Hans Anderson?
Michael H. Standart
Member
Tom, I'm sorry, but you have no case to rest. I was stationed on the USS Geroge Washington, which is a Nimitz class ship, I've been on the bridge, I've seen the brass plaque on the Engine Order Telegraph (Which give actual revolution and speed figures!) and I know what these ships are capable of. It's nowhere near 60 knots. Never has been, and never will be. Cut that by half and you'll be in the neighbourhood. I can't get more detailed then that.
Do the math yourself with these figures;
Length;1088ft Width;257ft Draft;37 feet and a mass of up to 102,000 tons at full load. The limiting factors are hull form and the actual horsepower available to push that mass through the water.
Propulsion is provided by two A4W reactors providing steam to geared turbines at 280,000 shaft horsepower which is close to identical for conventionally powered ships of the same type.
As to the story you "Heard about", beware of such. Mr. "I Heard" has a notoriously poor track record for accuracy.
Now if you have some documented sources for the claims regarding the RMS Mauritania, I'd be interested.
Do the math yourself with these figures;
Length;1088ft Width;257ft Draft;37 feet and a mass of up to 102,000 tons at full load. The limiting factors are hull form and the actual horsepower available to push that mass through the water.
Propulsion is provided by two A4W reactors providing steam to geared turbines at 280,000 shaft horsepower which is close to identical for conventionally powered ships of the same type.
As to the story you "Heard about", beware of such. Mr. "I Heard" has a notoriously poor track record for accuracy.
Now if you have some documented sources for the claims regarding the RMS Mauritania, I'd be interested.
David G. Brown
RIP
There is a limit to everything.
The maximum speed of a displacement hull vessel (like a big ship) is a function of its waterline length. The formula is 1.34 x SQ RT Waterline. A ship with a 1,000 ft waterline reaches this so-called "hull speed" at a bit over 42 knots.
Once a displacement hull vessel reaches its hull speed, applying more power simply "digs a hole" for the stern and results in little additional (if any) speed. Designers have found some ways to "cheat" on hull speed.
The U.S. Navy's famous 4-piper destroyers of the 1920s were extremely narrow and "nuttin' but engines" below decks. They could exceed their theoretical hull speed but only at an enormous expense in fuel. And, when they did, their fantails were reportedly in a self-dug hole more than 20 feet deep. Can't vouch for the size of the hole, but photos of them "at speed" show an alarming wall of water on either side of the stern.
Extremely narrow beam like those destroyers was tried on passenger vessels, but with limited success. Passenger ships require high superstructures, so quickly became too narrow for good stability. Also, the energy needed in terms of tons of coal for a 4-piper to exceed hull speed was far beyond anything a commercial ship could afford.
Other methods of "cheating" hull speed have been found. Most often, they involve finding a way to increase the effective waterline length without increasing draft or the friction of the "wetted surface" of the hull. Another trick is to change the shape of the bow wave with "bulbs" and other odd shapes on the stem. Some designers have claimed they could get speeds of 1.4 or 1.45 times the SQ RT of the "at rest" waterline length.
Skin friction is a major problem in large, high-speed displacement vessels. One way to have increased Titanic's speed (and the other riveted construction ships of the era) would have been to reverse the directly of the overlap on the vertical butts between plates. Titanic's were lapped so the "step" of the overlap faced aft. This seems the logical way. However, the aft-facing step causes a burble in the flow of water, which creates drag. Facing the step forward causes water to "pile up" in the butt, which forms a smooth wedge to improve the flow of moving water along the hull. The gain is slight, but measurable.
The speed of naval ships is always considered as "secret" despite the fact that accurate numbers are available. And, navies often issue "disinformtion." I recall during the Gulf War that a U.S. Navy aircraft carrier departed the East Coast with fanfare. Seemingly hours later it was reported in action. Dividing the distance by the time required the ship to have made in excess of 55 knots. The rumor mill was full of stories that the carrier actually made speeds illegal on some freeways.
What the military did not say, however, is that the ship was "in action" only because its aircraft could fly exponentially faster and farther.
My river ferry is designed to "push" against the pier while boarding passengers. We don't tie up, just keep the engine in forward tt slow speed. Special pusher "knees" hold the vessel at 90 degrees to the pier. We have found a specific RPM at which this pushing works best. Logically, Mr. Spock, this has been dubbed "wharf speed."
--David G. Brown
The maximum speed of a displacement hull vessel (like a big ship) is a function of its waterline length. The formula is 1.34 x SQ RT Waterline. A ship with a 1,000 ft waterline reaches this so-called "hull speed" at a bit over 42 knots.
Once a displacement hull vessel reaches its hull speed, applying more power simply "digs a hole" for the stern and results in little additional (if any) speed. Designers have found some ways to "cheat" on hull speed.
The U.S. Navy's famous 4-piper destroyers of the 1920s were extremely narrow and "nuttin' but engines" below decks. They could exceed their theoretical hull speed but only at an enormous expense in fuel. And, when they did, their fantails were reportedly in a self-dug hole more than 20 feet deep. Can't vouch for the size of the hole, but photos of them "at speed" show an alarming wall of water on either side of the stern.
Extremely narrow beam like those destroyers was tried on passenger vessels, but with limited success. Passenger ships require high superstructures, so quickly became too narrow for good stability. Also, the energy needed in terms of tons of coal for a 4-piper to exceed hull speed was far beyond anything a commercial ship could afford.
Other methods of "cheating" hull speed have been found. Most often, they involve finding a way to increase the effective waterline length without increasing draft or the friction of the "wetted surface" of the hull. Another trick is to change the shape of the bow wave with "bulbs" and other odd shapes on the stem. Some designers have claimed they could get speeds of 1.4 or 1.45 times the SQ RT of the "at rest" waterline length.
Skin friction is a major problem in large, high-speed displacement vessels. One way to have increased Titanic's speed (and the other riveted construction ships of the era) would have been to reverse the directly of the overlap on the vertical butts between plates. Titanic's were lapped so the "step" of the overlap faced aft. This seems the logical way. However, the aft-facing step causes a burble in the flow of water, which creates drag. Facing the step forward causes water to "pile up" in the butt, which forms a smooth wedge to improve the flow of moving water along the hull. The gain is slight, but measurable.
The speed of naval ships is always considered as "secret" despite the fact that accurate numbers are available. And, navies often issue "disinformtion." I recall during the Gulf War that a U.S. Navy aircraft carrier departed the East Coast with fanfare. Seemingly hours later it was reported in action. Dividing the distance by the time required the ship to have made in excess of 55 knots. The rumor mill was full of stories that the carrier actually made speeds illegal on some freeways.
What the military did not say, however, is that the ship was "in action" only because its aircraft could fly exponentially faster and farther.
My river ferry is designed to "push" against the pier while boarding passengers. We don't tie up, just keep the engine in forward tt slow speed. Special pusher "knees" hold the vessel at 90 degrees to the pier. We have found a specific RPM at which this pushing works best. Logically, Mr. Spock, this has been dubbed "wharf speed."
--David G. Brown
Michael H. Standart
Member
<groan> Wharf Speed.
David, that was bad!
David, that was bad!
Shelley Dziedzic
Member
Dave- you may be just the man to exlain the Yourkevitch bulbous bow thing to me- how does that help stability and speed? Was this experimental on Normandie?
Yuri Singleton
Member
Ok, I worked with a former US Navy ordanence, person. He was on a nuke carrier called the George Washington I believe, back during the Vietnam War. (Could be wrong on the name.)
Anyway, he told me about a time that his ship was docked in Virginia back in the late 60's, and that evening there came word that all crews' leave was cancelled and all hands had to report to their stations immediately. So within about 3 hours, the ship left port just as the sun was going down. He said that he had never heard the engines running as loudly as they had that night, and that the ship was vibrating tremendously all night as well.
So the next morning he wakes up for his shift on the flight deck and discovers that the carrier is now cruising slowly near the coast of an island. Turns out, its the coast of Cuba. He showed me his own calculations of time, distance and speed. And the result was that the ship must have been traveling at over 60 MPH, (yes MPH, he did the numbers in MPH instead of Knots.).
Now, he told me that was the fastest he had ever known the ship to travel. That, or any ship. The only other time he witnessed a large ship travel so fast was when he was on another carrier off the coast of Vietnam and had to respond to a distress call in the Gulf of Tonkin or something. That ship was traveling at over 40 MPH that time.
Truth, or tall tale? I personally believed the guy's story because he seemed genuinly sincere about it. He wasn't the story telling type. But of course I have no way to know for certain.
Yuri
Anyway, he told me about a time that his ship was docked in Virginia back in the late 60's, and that evening there came word that all crews' leave was cancelled and all hands had to report to their stations immediately. So within about 3 hours, the ship left port just as the sun was going down. He said that he had never heard the engines running as loudly as they had that night, and that the ship was vibrating tremendously all night as well.
So the next morning he wakes up for his shift on the flight deck and discovers that the carrier is now cruising slowly near the coast of an island. Turns out, its the coast of Cuba. He showed me his own calculations of time, distance and speed. And the result was that the ship must have been traveling at over 60 MPH, (yes MPH, he did the numbers in MPH instead of Knots.).
Now, he told me that was the fastest he had ever known the ship to travel. That, or any ship. The only other time he witnessed a large ship travel so fast was when he was on another carrier off the coast of Vietnam and had to respond to a distress call in the Gulf of Tonkin or something. That ship was traveling at over 40 MPH that time.
Truth, or tall tale? I personally believed the guy's story because he seemed genuinly sincere about it. He wasn't the story telling type. But of course I have no way to know for certain.
Yuri
David G. Brown
RIP
Shelley -- I'm not a naval architect, so I can't give a definitive answer on how a bulbous bow works. I understand it changes the bow wave and the flow of water, but beyond that...I will defer to my betters.
A bulbous bow is not for stability. It is to increase speed and/or fuel economy on a large displacement hull.
Stability control is a different animal. Adjustable fin stabalizers are the the way it is done now. Titanic had bilge keels which helped to dampen roll.
Modern fin stabilizers are like stubby wings that extend at 90 degrees to the hull. A gyro sensing unit causes the fins to work opposite to the natural roll of the vessel. If the ship is rolling naturally to port, the fins try to counter by rolling the ship to starboard. The fins work much like ailerons on an airplane, although they look more like small rudders sticking out of the hull.
A little bit of stabilizing is a good thing, but too much can produce an uncomfortable, jerky ride. As I recall, too much control can also cause physical stress on the framework of the ship. Perhaps one of our big ship (large vessel, not captain) drivers can add more to this. Today's systems are pretty complex with computers to control both the angles of the fins and the speed of their response.
On some vessels the fins stick out beyond the side of the ship. This is most often the case on older yachts. Woe betide the captain who docks without retracting the fins on one of those boats. I know at least one stabilizer manufacturer that equips its units with sensors to detect boat speed. If the speed drops below a pre-set amount, the fins retract automatically.
Some inventors have tried to come up with ballast shifting systems in which water is moved to the high side to counteract rolling. In theory, this should work, but it's hard to get the water moving properly. I also recall that on the Eastland (the ship that rolled over in the Chicago River) they would roll barrels full of water from side to side to counteract listing caused by movement of the passengers.
--David G. Brown
A bulbous bow is not for stability. It is to increase speed and/or fuel economy on a large displacement hull.
Stability control is a different animal. Adjustable fin stabalizers are the the way it is done now. Titanic had bilge keels which helped to dampen roll.
Modern fin stabilizers are like stubby wings that extend at 90 degrees to the hull. A gyro sensing unit causes the fins to work opposite to the natural roll of the vessel. If the ship is rolling naturally to port, the fins try to counter by rolling the ship to starboard. The fins work much like ailerons on an airplane, although they look more like small rudders sticking out of the hull.
A little bit of stabilizing is a good thing, but too much can produce an uncomfortable, jerky ride. As I recall, too much control can also cause physical stress on the framework of the ship. Perhaps one of our big ship (large vessel, not captain) drivers can add more to this. Today's systems are pretty complex with computers to control both the angles of the fins and the speed of their response.
On some vessels the fins stick out beyond the side of the ship. This is most often the case on older yachts. Woe betide the captain who docks without retracting the fins on one of those boats. I know at least one stabilizer manufacturer that equips its units with sensors to detect boat speed. If the speed drops below a pre-set amount, the fins retract automatically.
Some inventors have tried to come up with ballast shifting systems in which water is moved to the high side to counteract rolling. In theory, this should work, but it's hard to get the water moving properly. I also recall that on the Eastland (the ship that rolled over in the Chicago River) they would roll barrels full of water from side to side to counteract listing caused by movement of the passengers.
--David G. Brown
Dave Gittins
Member
"Sailors will say anything when they are ashore."
Captain Stanley Lord.
Captain Stanley Lord.
Michael H. Standart
Member
Tom, when I refer to documented sources, I'm talking about technical papers, data, journals, in short anything actually in writing from a credible source. Newspapers don't count BTW.
Yuri, I suspect your friend may have been pulling your leg a bit. I spent 20 years listening to Golly-Gee-Whiz-Whillikers-Wow stories like that from 'tween the decks, but the problem with the lot is that they can't get past the laws of hydrodynamics. With any given hull form, you can only get so much speed out for the power available. After that, you could double the horsepower and at best, get only one or two knots extra, and at that, at a horrible expence in fuel.
A lot of these stories come from people who have little knowladge or understanding of how and why ships work as they do. You would be absolutely stunned at how many Navy people don't know an awful lot about the subject outside of what is covered by their own ratings...which isn't as much as you might think.
And whatever ship this was, she couldn't possibly have been the George Washington. At that time, the name was carried by a ballistic missile submarine which remained in service until 1985. The current George Washington (CVN-73) was commissioned in 1992. For the Naval Vessels Register listing, go to http://www.nvr.navy.mil/nvrships/details/CVN73.htm
For the submarine which carried the name, go to http://www.subnet.com/fleet/ssbn598.htm
The only nuclear powered carrier in service at the time you mentioned is the USS Enterprise (CVN-65) You can see a little bit about her at http://www.nvr.navy.mil/nvrships/details/CVN65.htm
Yuri, I suspect your friend may have been pulling your leg a bit. I spent 20 years listening to Golly-Gee-Whiz-Whillikers-Wow stories like that from 'tween the decks, but the problem with the lot is that they can't get past the laws of hydrodynamics. With any given hull form, you can only get so much speed out for the power available. After that, you could double the horsepower and at best, get only one or two knots extra, and at that, at a horrible expence in fuel.
A lot of these stories come from people who have little knowladge or understanding of how and why ships work as they do. You would be absolutely stunned at how many Navy people don't know an awful lot about the subject outside of what is covered by their own ratings...which isn't as much as you might think.
And whatever ship this was, she couldn't possibly have been the George Washington. At that time, the name was carried by a ballistic missile submarine which remained in service until 1985. The current George Washington (CVN-73) was commissioned in 1992. For the Naval Vessels Register listing, go to http://www.nvr.navy.mil/nvrships/details/CVN73.htm
For the submarine which carried the name, go to http://www.subnet.com/fleet/ssbn598.htm
The only nuclear powered carrier in service at the time you mentioned is the USS Enterprise (CVN-65) You can see a little bit about her at http://www.nvr.navy.mil/nvrships/details/CVN65.htm
Tracy Smith
Member
And Scotty was NOT the Chief Engineer of this particular Enterprise, either......
