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#21
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Joe wrote:
Bull Feathers! When the conning officer says hard to Starboard...He wants the ship to turn hard to starboard. That is true now, and has been since some time around 1910 in the U.S. There is no wheeled ship in the world that ever set op the helm ass backwards. That would be confusing and dangerious. This is an issue of some contention among old time boat enthusiasts. I've heard a lot of people, inclduing a few that knew a lot about maritime history, say that backwards steering used to be fairly common. However I don't think it was ever "the standard" and I don't think that it's the reason for "reverse helm orders." For one thing, there are too many boats & ships surviving from that time period with their steering intact. For example, Edson has been in business for a long time and they never made any "reverse" or "tiller-order" steering mechanisms. OTOH who knows wether some crusty old geezers rigged their wheels to steer like a tiller because they liked it that way. DSK |
#22
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Are you saying that the rudder effrectiveness is not reduced if the
engine is stopped? Cheers DSK wrote: |
#23
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On an old cornish working boat I sailed you had the wheel behind you.
Even on that boat the wheel turned the head normally. Cheers DSK wrote: Joe wrote: Bull Feathers! When the conning officer says hard to Starboard...He wants the ship to turn hard to starboard. That is true now, and has been since some time around 1910 in the U.S. There is no wheeled ship in the world that ever set op the helm ass backwards. That would be confusing and dangerious. This is an issue of some contention among old time boat enthusiasts. I've heard a lot of people, inclduing a few that knew a lot about maritime history, say that backwards steering used to be fairly common. However I don't think it was ever "the standard" and I don't think that it's the reason for "reverse helm orders." For one thing, there are too many boats & ships surviving from that time period with their steering intact. For example, Edson has been in business for a long time and they never made any "reverse" or "tiller-order" steering mechanisms. OTOH who knows wether some crusty old geezers rigged their wheels to steer like a tiller because they liked it that way. DSK |
#25
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Nav wrote:
Are you saying that the rudder effrectiveness is not reduced if the engine is stopped? I'm saying that many of the statements made about why the Titanic hit the iceberg, with regard to her rudder's ineffectiveness, are incorrect. As for "engine stopped" that is not a very useful terminology... you mean shaft stopped & locked? Applying throttle in reverse? Spinning in reverse with forward way on? *If* the Titanic's central shaft had been either stopped & locked, or spinning in reverse with forward way on, then of course her rudders effectiveness would have been reduced. However neither of those cases apply for several reasons, the main one being that her central shaft had no reverse and could not have been stopped & locked. Regards Doug King |
#26
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![]() "Nav" wrote ... For example, the order "port 20" did not mean turn the ship to port 20 degrees. What did it mean? SV |
#27
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![]() DSK wrote: Nav wrote: Are you saying that the rudder effrectiveness is not reduced if the engine is stopped? I'm saying that many of the statements made about why the Titanic hit the iceberg, with regard to her rudder's ineffectiveness, are incorrect. Such as? As for "engine stopped" that is not a very useful terminology... you mean shaft stopped & locked? Applying throttle in reverse? Spinning in reverse with forward way on? *If* the Titanic's central shaft had been either stopped & locked, or spinning in reverse with forward way on, then of course her rudders effectiveness would have been reduced. However neither of those cases apply for several reasons, the main one being that her central shaft had no reverse and could not have been stopped & locked. If the engine were stopped the rudder effectiveness would have been reduced. I think that is most likely true, why do you disagree with it? If it were reversed, effectiveness would be even lower. Cheers |
#28
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I'm saying that many of the statements made about why the Titanic hit
the iceberg, with regard to her rudder's ineffectiveness, are incorrect. Nav wrote: Such as? Such as yours. If the engine were stopped the rudder effectiveness would have been reduced. OK, tell us what you mean by stopped. Then tell us about the Titanic's engineering plant and how they would have "stopped" the central shaft. ... I think that is most likely true, why do you disagree with it? Oh, just a silly whim on my part, no doubt. Years of marine propulsion engineering have nothing to do with it. If it were reversed, effectiveness would be even lower. That's a mighty big "if." As above, please explain how they would have put the central shaft in reverse. In any case, the ship was going full speed, the loss of the prop stream across the rudder would not reduce the rudder's effectiveness very much. DSK |
#29
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![]() DSK wrote: I'm saying that many of the statements made about why the Titanic hit the iceberg, with regard to her rudder's ineffectiveness, are incorrect. Nav wrote: Such as? Such as yours. If the engine were stopped the rudder effectiveness would have been reduced. OK, tell us what you mean by stopped. Then tell us about the Titanic's engineering plant and how they would have "stopped" the central shaft. The engine would be stopped by opening the steam bypass valve. That might not stop the propellor but that's not the issue here. Now are you still saying that stopping the engine has no effect on rudder effectiveness ... I think that is most likely true, why do you disagree with it? Oh, just a silly whim on my part, no doubt. Years of marine propulsion engineering have nothing to do with it. So you think an engine in neutral has no effect on rudder? If it were reversed, effectiveness would be even lower. That's a mighty big "if." As above, please explain how they would have put the central shaft in reverse. In any case, the ship was going full speed, the loss of the prop stream across the rudder would not reduce the rudder's effectiveness very much. Do you know what slip is and how it would affect the rudder? What would have been a likely value of slip for the central propellor of the Titanic at full speed? It's strange but every time I've taken the helm of a displacement boat the loss of helm authority when the engine is throttled back has been most obvious. Perhaps it's your engineering expertise that makes the difference. Cheers |
#30
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OK, tell us what you mean by stopped. Then tell us about the Titanic's
engineering plant and how they would have "stopped" the central shaft. Nav wrote: The engine would be stopped by opening the steam bypass valve. That might not stop the propellor but that's not the issue here. Please tell me what ships you've steamed where the engine could be stopped by "opening a steam bypass valve." Also please tell me where the steam is bypassed to... are you suggesting dumping main steam directly into the condenser? Another point I'd like you to explain is how do you stop the engine and not the shaft. Push in the clutch, maybe? Now are you still saying that stopping the engine has no effect on rudder effectiveness No, I'm saying that 1- a ship running at full speed is not going to stop & lock the shaft in less than a minute, 2- if it did then the water flow over the rudder would still be quite strong (ie 20+ knots), 3- in the specific case of the Titanic, the central prop had no reverse and thus no way to stop the shaft. Did you pay any attention at all to my post explaining some of the basics of the Olympic class ships propulsion plant? Do you know what slip is Yes. ... and how it would affect the rudder? Sure. Is it supposed to be rocket science? Are you insisting that a ship going 20+ knots is suddenly not going to answer her helm because of the loss of the prop stream? It has been suggested that if the Titanic's central prop had been spun in reverse, the cavitation would have greatly diminished her steering response... now that is a stronger case, except that it's simply not possible when there's no reverse on the central engine. ... What would have been a likely value of slip for the central propellor of the Titanic at full speed? I don't know, but it wouldn't be hard to figure out. The stats for the engine's RPM and prop pitch are public. It's strange but every time I've taken the helm of a displacement boat the loss of helm authority when the engine is throttled back has been most obvious. Yes, and I'm sure you have lots and lots of experience driving 800+ ships at 20+ knots. They handle *very* differently than a sailboat with under auxiliary power. If you're claiming that a vessel cannot be steered without a prop stream over the rudder, then how do you manage to control your boat's heading when under sail? .... Perhaps it's your engineering expertise that makes the difference. Perhaps. DSK |