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Seamanship Question #16 [Props again]
2 points
After hitting the lottery for big bucks, you have nearly completed your 150' new sailing mega yacht. Included on your new toy are both a bow and stern thrusters--for side-to-side control.. What sort of prop would you want if you were concerned about precise speed control, and being able to back down nearly instantaneously? Money is, of course not a concern. |
#2
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Bart Senior wrote:
2 points After hitting the lottery for big bucks, you have nearly completed your 150' new sailing mega yacht. Included on your new toy are both a bow and stern thrusters--for side-to-side control.. What sort of prop would you want if you were concerned about precise speed control, and being able to back down nearly instantaneously? Money is, of course not a concern. Hydraulically controlled variable pitch. BTW is this 150' yacht equipped with a rack of racing dinghies and a retractable artificial beach? Fresh Breezes- Doug King |
#3
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2 points to you Doug!
And if it was up to me, I'd at least want a a fold down dock on the back for those dinghies. DSK wrote Bart Senior wrote: 2 points After hitting the lottery for big bucks, you have nearly completed your 150' new sailing mega yacht. Included on your new toy are both a bow and stern thrusters--for side-to-side control.. What sort of prop would you want if you were concerned about precise speed control, and being able to back down nearly instantaneously? Money is, of course not a concern. Hydraulically controlled variable pitch. BTW is this 150' yacht equipped with a rack of racing dinghies and a retractable artificial beach? Fresh Breezes- Doug King |
#4
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There's no need for variable pitch -which is why you don't see it in
mega yacht thrusters Cheers FT. DSK wrote: Bart Senior wrote: 2 points After hitting the lottery for big bucks, you have nearly completed your 150' new sailing mega yacht. Included on your new toy are both a bow and stern thrusters--for side-to-side control.. What sort of prop would you want if you were concerned about precise speed control, and being able to back down nearly instantaneously? Money is, of course not a concern. Hydraulically controlled variable pitch. BTW is this 150' yacht equipped with a rack of racing dinghies and a retractable artificial beach? Fresh Breezes- Doug King |
#5
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Nav wrote:
There's no need for variable pitch -which is why you don't see it in mega yacht thrusters Cheers FT. I believe the discussion regarded the Main Engine, not the thrusters |
#6
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otnmbrd wrote: Nav wrote: There's no need for variable pitch -which is why you don't see it in mega yacht thrusters Cheers FT. I believe the discussion regarded the Main Engine, not the thrusters I thought it was 'bout the whole propulksion package 'cos he mentioned dual thrusters. If just about main engine that's a really boring question. Cheers |
#7
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The larger the vessel the more difficult it is to
manuever and stop. I wanted to be clear the issue in this question was with respect to backing down. The thrustors provide good side-to-side control and eliminate that factor from the question. Could it have be written more clearly? The variable pitch allows the throttle to be set and forgotten while pitch controls linear thrust--magnitude and direction. There are no worries about engine stalling while changing gears, or cables jamming or snapping, all of which have happened to me in the past, and each of which could be bad news docking and manuevering a mega yacht. Bart Senior Nav wrote otnmbrd wrote: Nav wrote: There's no need for variable pitch -which is why you don't see it in mega yacht thrusters Cheers FT. I believe the discussion regarded the Main Engine, not the thrusters I thought it was 'bout the whole propulksion package 'cos he mentioned dual thrusters. If just about main engine that's a really boring question. Cheers |
#8
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Doug,
There's no need for the complication of variable pitch. A reversing motor (electric or hydraulic) is all that is needed. Hence for this size vessel you see symmetric 4 blade props. The small increase in efficiency gained by having variable pitch is not worth the extra complication. Cheers DSK wrote in message ... Bart Senior wrote: 2 points After hitting the lottery for big bucks, you have nearly completed your 150' new sailing mega yacht. Included on your new toy are both a bow and stern thrusters--for side-to-side control.. What sort of prop would you want if you were concerned about precise speed control, and being able to back down nearly instantaneously? Money is, of course not a concern. Hydraulically controlled variable pitch. BTW is this 150' yacht equipped with a rack of racing dinghies and a retractable artificial beach? Fresh Breezes- Doug King |
#9
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Farr1220 wrote:
Doug, There's no need for the complication of variable pitch. Well, sure. There's no "need" for the boat at all. ... A reversing motor (electric or hydraulic) is all that is needed. And that's simpler than a CPP? ... Hence for this size vessel you see symmetric 4 blade props. Sometimes 5 blade. ... The small increase in efficiency gained by having variable pitch is not worth the extra complication. Bart wasn't asking about efficiency, he was asking about controllability. An electric drive may be on par with the controlled pitch for quick & easy reversing, but they're much less common... the ones I know about have a bad reputation for being troublesome. As for a hydraulic motor, if you think these are efficient and trouble-free then I suggest you get some experience with them. It would be at the bottom of my list for almost any power application. Actually CPPs are slightly less efficient, ideally, than conventional props becuase of the bulky hubs. However, in real world conditions, they often achieve greater efficiency by being able to trim the prop to match sea/wind conditions to engine load. Fresh Breezes- Doug King |
#10
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As a sailor you should be more concerned with trimming sails. Leave the motors to the likes of Captains Shen and otn. Captain Neal (a member of an elite group) "DSK" wrote in message ... Farr1220 wrote: Doug, There's no need for the complication of variable pitch. Well, sure. There's no "need" for the boat at all. ... A reversing motor (electric or hydraulic) is all that is needed. And that's simpler than a CPP? ... Hence for this size vessel you see symmetric 4 blade props. Sometimes 5 blade. ... The small increase in efficiency gained by having variable pitch is not worth the extra complication. Bart wasn't asking about efficiency, he was asking about controllability. An electric drive may be on par with the controlled pitch for quick & easy reversing, but they're much less common... the ones I know about have a bad reputation for being troublesome. As for a hydraulic motor, if you think these are efficient and trouble-free then I suggest you get some experience with them. It would be at the bottom of my list for almost any power application. Actually CPPs are slightly less efficient, ideally, than conventional props becuase of the bulky hubs. However, in real world conditions, they often achieve greater efficiency by being able to trim the prop to match sea/wind conditions to engine load. Fresh Breezes- Doug King |
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