RMweb Premium Reorte Posted March 31 RMweb Premium Share Posted March 31 2 hours ago, jjb1970 said: I don't necessarily disagree, but it raises profound questions about the news and whether we should assign much credibility to what is reported. The example I quoted of describing a ship as being Belize flag and UK registered is so egregious it begs the question of whether anything at all in the story was worth paying attention to. Reporting of this incident hasn't impressed, I am generally refraining from offering opinions on the incident (though not completely so) as I have only guesses to offer and see little point speculating. However TV news is about filling schedules and calling a few talking heads to basically speculate and offer opinions. Where this is especially disappointing is in specialised news sources. I get that the BBC doesn't have shipping reporters but I would expect journals which exist to report on shipping to have reporters with knowledge of shipping, but most don't. If news wasn't so influential it might not matter, but people form their opinions of the world based on news. At least they'll correct things if pointed out to them, and will be in trouble if they deliberately make stuff up. It's a good point about filling schedules, having to fill more time than ever really doesn't help the standards in the news in the slightest. 3 Link to post Share on other sites More sharing options...
Jeff Smith Posted March 31 Share Posted March 31 I generally follow CNN for news in the Americas but BBC for British and European. It is sometimes interesting to compare reporting from both sources on the same topic. Being from an aeronautical engineering background I see errors on both sides but strangely enough incident reports in the US often initially fail to identify the type of aircraft whereas the BBC usually include it. I realise that Joe Public might not care, unless of course it's a Boeing! 6 Link to post Share on other sites More sharing options...
Ozexpatriate Posted March 31 Share Posted March 31 (edited) 3 hours ago, Jeff Smith said: I realise that Joe Public might not care, unless of course it's a Boeing! On that topic - covered last night on SNL - just 10 seconds. Edited March 31 by Ozexpatriate 1 2 Link to post Share on other sites More sharing options...
Michael Hodgson Posted March 31 Share Posted March 31 6 hours ago, St Enodoc said: "I can't see who's in the lead, but it's either Oxford or Cambridge" John Snagge, 1949. Ah yes, we don't get pea-soupers like that any more! 1 2 Link to post Share on other sites More sharing options...
Michael Hodgson Posted March 31 Share Posted March 31 7 hours ago, jjb1970 said: Reporting of this incident hasn't impressed, I am generally refraining from offering opinions on the incident (though not completely so) as I have only guesses to offer and see little point speculating. Oh, I'm inclined to believe that the bridge probably was stationary when the boat made an unprovoked attack on it. 2 5 Link to post Share on other sites More sharing options...
billbedford Posted March 31 Share Posted March 31 I found this on YouTube: https://www.youtube.com/watch?v=BEzDh4RwpaM Which seems the most likely explanation I've seen. Who hasn't panicked and ignored the non-intuitive best course of action? O'corse the guy might be wrong. 3 1 Link to post Share on other sites More sharing options...
RMweb Gold Dagworth Posted March 31 RMweb Gold Share Posted March 31 10 hours ago, kevinlms said: the exception is mainstream sport, like top level football, which cannot be ignored. It can most definitely be ignored, I manage every day! Andi 2 10 Link to post Share on other sites More sharing options...
Titan Posted March 31 Share Posted March 31 1 hour ago, billbedford said: I found this on YouTube: https://www.youtube.com/watch?v=BEzDh4RwpaM Which seems the most likely explanation I've seen. It would seem that there were many effects that contributed. There was a slight wind pushing it towards the bridge too. Really not much, but with something as tall and flat sided as a container ship it does not take much to have an effect. The ship was probably being steered into the wind slightly to compensate, so when steerage was lost due to crash reversing the engine, the wind added to the propellor effect to turn the ship further towards the bridge. 2 Link to post Share on other sites More sharing options...
Jeff Smith Posted March 31 Share Posted March 31 Having watched the video I can see that this is a likely explanation from someone with relevant knowledge. However I don't understand the sideways thrust explanation. Surely, assuming the propeller is fully submerged, the side thrust in the upper arc would be counteracted by thrust the opposite way in the lower arc.....in other words each blade as it rotates would push first one way then the other.... 1 Link to post Share on other sites More sharing options...
RMweb Premium jjb1970 Posted April 1 RMweb Premium Share Posted April 1 My recommendation for those interested in what happened is to wait for the NTSB to report. 1 4 Link to post Share on other sites More sharing options...
Jeff Smith Posted April 1 Share Posted April 1 Preliminary in 6 months, final in 2 years...... 1 Link to post Share on other sites More sharing options...
RMweb Premium jjb1970 Posted April 1 RMweb Premium Share Posted April 1 Not necessarily, the NTSB can work quickly and issue preliminary findings. If the causes are as obvious as the various media talking heads think and given that the voyage event recorder was transferred immediately after the incident it may not take long. 2 Link to post Share on other sites More sharing options...
RMweb Premium J. S. Bach Posted April 1 RMweb Premium Share Posted April 1 4 hours ago, Dagworth said: It can most definitely be ignored, I manage every day! Andi If the Birds win the Series or the Ravens the bowl, that is all that I wish to hear about. After the fact! 2 Link to post Share on other sites More sharing options...
RMweb Premium J. S. Bach Posted April 1 RMweb Premium Share Posted April 1 21 hours ago, Darius43 said: Tuned in to get the latest thoughts on the bridge and instead get:- - hatred of the BBC - hatred of journalism - a brief history of friendly fire Time for a thread lock I think until the big crane starts its act. Darius Thread drift, don't you just love it! 1 2 Link to post Share on other sites More sharing options...
RMweb Premium kevinlms Posted April 1 Author RMweb Premium Share Posted April 1 On 31/03/2024 at 14:37, Darius43 said: Tuned in to get the latest thoughts on the bridge and instead get:- - hatred of the BBC - hatred of journalism - a brief history of friendly fire Time for a thread lock I think until the big crane starts its act. Darius Things have started to happen, sections have been removed - a long way to go. https://edition.cnn.com/2024/03/31/us/francis-scott-key-bridge-collapse-sunday/index.html 1 2 1 Link to post Share on other sites More sharing options...
Tumut Posted April 1 Share Posted April 1 Hello All, like most cargo ships, even of this size, it is a single screw for propulsion, and side thrusters for manourvering. Both modern Container ships, and Cruise Liners (which are built on Container style ship hulls), they are wide beam with a flat bottom, hence stable, and able to transit some shallow harbours. Regards from Australia. 3 Link to post Share on other sites More sharing options...
eastglosmog Posted April 1 Share Posted April 1 7 hours ago, Jeff Smith said: Having watched the video I can see that this is a likely explanation from someone with relevant knowledge. However I don't understand the sideways thrust explanation. Surely, assuming the propeller is fully submerged, the side thrust in the upper arc would be counteracted by thrust the opposite way in the lower arc.....in other words each blade as it rotates would push first one way then the other.... From my days navigating narrow boats, the side thrusts are not equal. From what I can remember, the lower arc does not counteract the upper arc exactly because of the greater water pressure on the lower arc giving greater thrust. 1 4 Link to post Share on other sites More sharing options...
RMweb Premium jjb1970 Posted April 1 RMweb Premium Share Posted April 1 A single screw ship will have some degree of side thrust from the propeller, which is speed dependent, usually corrected by the rudder. At manoeuvring speed the rudder correction is generally not great. In the event of a black out the steering gear may be fed from the emergency switchboard (emergency generator) however I have no idea whether that was the case on this ship as the requirements are related to installation size and allow for split supply from the main switchboards. 1 1 Link to post Share on other sites More sharing options...
RMweb Gold Gilbert Posted April 1 RMweb Gold Share Posted April 1 20 hours ago, 2750Papyrus said: One of yesterday's boat race reporters didn't know which oarsman was bow and which stroke. This morning's news told us that Oxford had won. But the Oxford stroke was on what is normally bow side - work that one out.. 1 2 Link to post Share on other sites More sharing options...
RMweb Premium Sidecar Racer Posted April 1 RMweb Premium Share Posted April 1 (edited) 11 hours ago, Jeff Smith said: . However I don't understand the sideways thrust explanation. Surely, assuming the propeller is fully submerged, the side thrust in the upper arc would be counteracted by thrust the opposite way in the lower arc..... It may be similar to torque reaction in an aircraft causing pull on take off . From the net , The primary reason the 172 wants to move left during the takeoff roll is due to torque. The propeller, rotating clockwise, causes the aircraft to rotate in the opposite direction (counter-clockwise). I don't know if full power is applied to a ship to get it under way but if so it could cause a similar effect , I'm sure @jjb1970 can help out here . He has , 😎 Edited April 1 by Sidecar Racer Posted without full read . 2 Link to post Share on other sites More sharing options...
Hroth Posted April 1 Share Posted April 1 (edited) 4 hours ago, eastglosmog said: From my days navigating narrow boats, the side thrusts are not equal. From what I can remember, the lower arc does not counteract the upper arc exactly because of the greater water pressure on the lower arc giving greater thrust. And with narrowboats in particular, the upper tip of the propeller is verging on cavitation as its within inches of the water surface, thus having less grip on the water than the lower tip. If you knew what hand your prop was, you could also use it as a side thrust (in forward or reverse) to get the boat alongside when mooring up... Allegedly... Edited April 1 by Hroth 1 Link to post Share on other sites More sharing options...
Titan Posted April 1 Share Posted April 1 (edited) The propellor effect is down to the interaction of the prop wash with its surroundings. On the top side of the propellor the wash interacts with the hull, and in shallow water like this on the bottom side of the propellor it interacts with the river bed. This creates all sorts of funny pressure differentials and eddies that tend to push on the stern. This means that the torque of the propellor has little effect, it is other forces at play. As noted above, this can be particularly noticeable on narrow boats as the bottom of the canal is often only a little bit deeper than the draft of the boat! So it is no surprise that the Dali, a long ship with a flat bottom in (relatively) shallow water behaves like a scaled up narrow boat! Edited April 1 by Titan 1 Link to post Share on other sites More sharing options...
Michael Hodgson Posted April 1 Share Posted April 1 1 hour ago, Sidecar Racer said: It may be similar to torque reaction in an aircraft causing pull on take off . From the net , The primary reason the 172 wants to move left during the takeoff roll is due to torque. The propeller, rotating clockwise, causes the aircraft to rotate in the opposite direction (counter-clockwise). I don't know if full power is applied to a ship to get it under way but if so it could cause a similar effect , I'm sure @jjb1970 can help out here . He has , 😎 The contra-rotation effect of a single engined aircraft against its propeller in air would be a lot more signifciant than the equivalent effect in water of a propeller on a container ship. Of course, a Cessna needs to apply disproportionately more thrust relative to its weight to reach take-off speed before the end of a runway than a big ship needs to leave port. 1 Link to post Share on other sites More sharing options...
GrumpyPenguin Posted April 1 Share Posted April 1 7 minutes ago, Michael Hodgson said: The contra-rotation effect of a single engined aircraft against its propeller in air would be a lot more signifciant than the equivalent effect in water of a propeller on a container ship. Of course, a Cessna needs to apply disproportionately more thrust relative to its weight to reach take-off speed before the end of a runway than a big ship needs to leave port. I've not been here for long but I soon learnt that thread drift was a RMW speciality, as is members "out anoraking" each other with minor detail. Now, it's comparing the behaviour of llight aircraft with big ships........... 1 Link to post Share on other sites More sharing options...
RMweb Gold Darius43 Posted April 1 RMweb Gold Share Posted April 1 Especially the examples of narrowboat handling compared to that of the container ship ‘cause they’re essentially the same, right? Cheers Darius 3 Link to post Share on other sites More sharing options...
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