RMweb Premium kevinlms Posted April 1 Author RMweb Premium Share Posted April 1 5 minutes ago, Darius43 said: Especially the examples of narrowboat handling compared to that of the container ship ‘cause they’re essentially the same, right? Cheers Darius Container ships are more predictable? 3 Link to comment Share on other sites More sharing options...
Hroth Posted April 1 Share Posted April 1 1 hour ago, Titan said: 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! 24 minutes ago, Darius43 said: Especially the examples of narrowboat handling compared to that of the container ship ‘cause they’re essentially the same, right? Cheers Darius Basically yes, the hull profile is more or less identical, flat bottom, straight sides, big prop flapping at the end! 1 1 Link to comment Share on other sites More sharing options...
RMweb Premium Sidecar Racer Posted April 1 RMweb Premium Share Posted April 1 1 hour ago, GrumpyPenguin said: 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 hour ago, Darius43 said: Especially the examples of narrowboat handling compared to that of the container ship ‘cause they’re essentially the same, right? Cheers Darius As has been said many times and on many threads , if a particular post doesn't interest you just move on . No need to make a fuss about it . 4 Link to comment Share on other sites More sharing options...
RMweb Gold Darius43 Posted April 1 RMweb Gold Share Posted April 1 1 minute ago, Sidecar Racer said: As has been said many times and on many threads , if a particular post doesn't interest you just move on . No need to make a fuss about it . As you may be able to see if you bother to read the thread from the beginning, this thread does interest me. I occasionally comment on aspects of engineering or things I don’t agree with, as so, it would appear, do you. Cheers Darius 1 1 Link to comment Share on other sites More sharing options...
Jeff Smith Posted April 1 Share Posted April 1 The gentleman who made the earlier referenced YouTube video has made a follow-up alluding to the sidethrust being more noticeable when the propeller is partly submerged - yes, makes sense! 1 Link to comment Share on other sites More sharing options...
Hroth Posted April 1 Share Posted April 1 Its not thread drift as such* but the use of examples from other areas to illustrate and explain some hydrodynamic problems... And all we have at this point is speculation while the process of taking the wreckage apart takes place. * Though drift, in the context of a nautical disaster is very appealing! 8 Link to comment Share on other sites More sharing options...
RMweb Premium jjb1970 Posted April 1 RMweb Premium Share Posted April 1 3 hours 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 side thrust effect is different to torque effect, there are multiple factors at play (immersion, shaft angle being two) but there is a serious safety issue with torque. Modern engines are tuned for low emissions, part of this involves a different response from turbochargers at low revs which combined with large and heavy low revving propellers has had the result of very sluggish response to telegraph commands when accelerating. As well as the obvious implications for ship handling it is a serious issue for the shaftline as engines are operating in the barred speed range for much longer than was ever intended by engine designers. 2 1 1 2 Link to comment Share on other sites More sharing options...
RMweb Premium Sidecar Racer Posted April 1 RMweb Premium Share Posted April 1 (edited) 38 minutes ago, Darius43 said: As you may be able to see if you bother to read the thread from the beginning, this thread does interest me. I occasionally comment on aspects of engineering or things I don’t agree with, as so, it would appear, do you. Cheers Darius As you may be able to see if you read it , I said a POST not the thread . Edited April 1 by Sidecar Racer 2 Link to comment Share on other sites More sharing options...
RMweb Premium PhilJ W Posted April 1 RMweb Premium Share Posted April 1 2 hours 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. The Packard Merlin engined P51D Mustang had a tailfin that was flat on one side and bowed out on the other (rather like an aircraft wing fitted vertically) to compensate for the torque of the engine. 4 2 Link to comment Share on other sites More sharing options...
Hroth Posted April 1 Share Posted April 1 2 minutes ago, PhilJ W said: The Packard Merlin engined P51D Mustang had a tailfin that was flat on one side and bowed out on the other (rather like an aircraft wing fitted vertically) to compensate for the torque of the engine. They could have done with that on the Sopwith Camel, which had an aggressive torque turn, though that might have spoiled a key combat advantage! Oops! Thread drift! 2 3 1 Link to comment Share on other sites More sharing options...
RMweb Premium jjb1970 Posted April 1 RMweb Premium Share Posted April 1 The Macchi C.202 Folgore fighter port wing was longer than the stbd wing to counter prop torque. Not sure if other designs did the same thing. 3 Link to comment Share on other sites More sharing options...
RMweb Gold Darius43 Posted April 1 RMweb Gold Share Posted April 1 Meanwhile, somewhere near Baltimore… Cheers Darius 3 1 1 Link to comment Share on other sites More sharing options...
billbedford Posted April 1 Share Posted April 1 2 hours ago, Hroth said: They could have done with that on the Sopwith Camel, which had an aggressive torque turn, though that might have spoiled a key combat advantage! The Camel had a rotary engine, which made the torque a whole lot more than on later aircraft. 2 hours ago, Hroth said: Oops! Thread drift! Yup 1 2 1 Link to comment Share on other sites More sharing options...
stewartingram Posted April 1 Share Posted April 1 We had a very long discussion about torque steer on our old Rover 800 forum..... 1 1 Link to comment Share on other sites More sharing options...
Mol_PMB Posted April 1 Share Posted April 1 Thread drift may be less dangerous than container ship drift. 1 2 7 Link to comment Share on other sites More sharing options...
Classsix T Posted April 1 Share Posted April 1 1 hour ago, Mol_PMB said: Thread drift may be less dangerous than container ship drift. You're new here aren't you? (Dons steel helmet) C6T. 10 Link to comment Share on other sites More sharing options...
Hroth Posted April 1 Share Posted April 1 8 minutes ago, Classsix T said: You're new here aren't you? (Dons steel helmet) C6T. Yep, wars have started over less.. 1 Link to comment Share on other sites More sharing options...
Classsix T Posted April 1 Share Posted April 1 Just now, Hroth said: Yep, wars have started over less.. Indeed. I'm just wondering which will happen first...one or two (you know who) members wading in or thread-lock. C6T. 2 Link to comment Share on other sites More sharing options...
GrumpyPenguin Posted April 1 Share Posted April 1 5 hours ago, Sidecar Racer said: As has been said many times and on many threads , if a particular post doesn't interest you just move on . No need to make a fuss about it . There is a world of difference between a fuss and a comment - further scope for thread drift ? TBH, the "out-anoraking" quite amuses me & I wondered if anyone would bite - bite they certainly did. 1 Link to comment Share on other sites More sharing options...
RMweb Premium J. S. Bach Posted April 1 RMweb Premium Share Posted April 1 3 hours ago, Mol_PMB said: Thread drift may be less dangerous than container ship drift. 2 hours ago, Classsix T said: You're new here aren't you? (Dons steel helmet) C6T. Well, certainly very much cheaper to repair, anyway🤔! 3 Link to comment Share on other sites More sharing options...
RMweb Premium melmerby Posted April 1 RMweb Premium Share Posted April 1 31 minutes ago, J. S. Bach said: Well, certainly very much cheaper to repair, anyway🤔! Talking about $3billion total cost. That's a lot of thread drift.............😕 2 Link to comment Share on other sites More sharing options...
Guest Posted April 2 Share Posted April 2 20 hours ago, Darius43 said: Especially the examples of narrowboat handling compared to that of the container ship ‘cause they’re essentially the same, right? Many narrowboat accidents are because they are crewed by some blokes on a stag do. Link to comment Share on other sites More sharing options...
Hroth Posted April 2 Share Posted April 2 (edited) 1 hour ago, 30801 said: Many narrowboat accidents are because they are crewed by some blokes on a stag do. I wonder how they solved that one? I expect a crane would have been used there, just refilling the lock would result in filling the boat too! At least its a broad lock with room to work. A narrow lock would be trickier.... Just a thought, I wonder where it was? The floor of the lock chamber is "dry" so its got to be the top lock of a staircase for that to be achieved. It might not have been a stag do either, if it were short crewed by inexperienced users (one or two people working the boat) they may not have noticed the stern was caught up on the cill until too late and that water was coming over the bow coaming... Edited April 2 by Hroth 1 Link to comment Share on other sites More sharing options...
RMweb Premium PhilJ W Posted April 2 RMweb Premium Share Posted April 2 48 minutes ago, 30801 said: Many narrowboat accidents are because they are crewed by some blokes on a stag do. 7 minutes ago, Hroth said: I wonder how they solved that one? I expect a crane would have been used there, just refilling the lock would result in filling the boat too! At least its a broad lock with room to work. A narrow lock would be trickier.... Looks as if the stern of the boat caught in the lock sill. 4 Link to comment Share on other sites More sharing options...
eastglosmog Posted April 2 Share Posted April 2 8 minutes ago, Hroth said: I wonder how they solved that one? I expect a crane would have been used there, just refilling the lock would result in filling the boat too! At least its a broad lock with room to work. A narrow lock would be trickier.... At the risk of being accused of more thread drift - at least it would remain upright and you could get a rope round the bows to lift it. 1 Link to comment Share on other sites More sharing options...
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