Ship Simulator
English forum => Ship Simulator Extremes => General discussions => Topic started by: The Ferry Man on September 03, 2010, 20:33:05
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Practicing my Reversing out of Calais a la Pride of Dover method (revrersing out of the harbour and swinging there) I have found the PoR Dynamics in reverse to be... odd. i checked again in the Atlantic (mainly becauise the odd dynamics caused me to hit the arm) and I got the same.
What I find is this:
- I am in reverse, at a few knots
- I engage the rudder at a asmall angle, to turn the vessel clockwise
- I get the PoR at the angle I want, and 0 the rudder
I am currently doing this in the Atlantic (following MVSmiths advice about getting to know your boat)
I killed the rudder whilst she was turning at a rate of 10' per minute this was a few minutes ago
she is currently still turning with a rate of 26' per minute
I am pretty sure the Thrusters do something similar, as when I turn, after using the bow and thruster to move off the berth, she developes a anti-clockwise swing, and won't reverse in a straight line
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I have the same problem, when backing onto a berth in Dover she swings uncontrollably in one direction (with both thrusters on full in one direction she swings in the opposite direction), and putting the thruster to the other side doesn't solve the problem :-\
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Well she is still doing 26' per minute... :doh:
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Have you guys checked the wx conditions, she may being pushed by the tide in dover/calais as it can be tricky
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wx conditions?
I also tried it in the Atlantic
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Have you guys checked the wx conditions, she may being pushed by the tide in dover/calais as it can be tricky
Wind and tide don't have any effect in ShipSim ;)
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In what direktion do the props on PoR spin then, that also afects her dynamics. :)
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When both propellors are on the same RPM/% astern, and the rudder is amidships with full power on the thrusters in the opposite direction trying to stop the swing, she shouldn't continue turning at 20 degree a minute :P
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If someone made a badly mistake when building her and set the props to spin in the same direktion :doh:
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But she is fine until you make her turn... then she just cannot stop...
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Sound strange :doh:
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But she is fine until you make her turn... then she just cannot stop...
Same story for Red Jet 4 - once she's at full speed, it takes an eternity to stop her again even when the engines are in full reverse.
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Have you guys checked the wx conditions, she may being pushed by the tide in dover/calais as it can be tricky
anyone know where you can check the weather(wx) conditinons since they dont seem to have a weather indicator in this game.. i agree with everyone the por handling duynamics are off while in reverse. i tried spiing her off her home dock using twin screw which didnt work as well as it should and also using bow thruster totally got her in some awkard swing drift and i couldt stop or straighten her out using bow thruster rudder all the tricks.. totally ran her into the dock
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Wind and tide don't have any effect in ShipSim ;)
really??? i almost beg to differ with that in the first mission tourist tales the journey driving orient star down river bound for sea. several different times she would seriously drift down the channel. id aim her high get on a good course mid ship rudders and id look and see the bow and stern blowing the same directing at about 2 knots in certain places.. i believe the wind has something to do with it just like in real life
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Hello Capt L. Henry,
Really, there is no wind effect and no current effect. The ships can be moved by waves due to some asymmetries of the waves, giving this impression. The drift in the channel can only be due to the shallows.
Regards,
Luc
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What about the reversing problems?
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I am not sure of the version that has been published, my answer cannot be 100% as long as I don't know that. It should be of 24/08/10.
There is a small asymmetry too in the RPM and pitch curves of PoR, and there are problems with the keyboard controls, particularly that the keyboard controls of the bow thruster act on the stern thruster (and etc). You will not be aware of it too much, because both have the same characteristics and are symmetrically placed vs the centre of the ship. You can only be aware of it dynamically if you really pay attention.
So, PoR thruster 1 (in options) is the bow thruster, 2 is the stern thruster, but also left is right and right is left.
It could also happen that using the throttle keyboard controls, the thrusters will start : You should not only call the chief, but try to reset them as often as needed. Perhaps is it only for me, I use a G11 belgian azerty keyboard and don't know if it also happens for regular keyboards.
The propellers are CPP, rotating inwards, ahead is CCW for the starboard propeller (so left hand screw) and CW for the port one (right hand screw seen from behind).
It is a normal arrangement to maximise the turning effect due to the propwalk when backing. For propellers relatively close to the centre line, it also means that the thrust ahead that helps you turn due to the eccentricity of the propeller is thwarted by the propwalk in forward, meaning not much of the eccentricity effect, eventually fully hiding the fact that the propeller is to the side. Not a big problem, as the full flow of the propeller acts on the rudder, restoring your manoeuvrability. Another advantage is that you can more easily make way on one propeller if needed.
Turning astern, the propwalk is added to the eccentricity (if I dare say so), and it helps your ship to turn, QED.
Also, there is not necessarily much course stability when making way astern, and the steady rotation of 26°/min can be realistic. Once the ship turns either way, you must steer, why would you think you shouldn't? There is no guarantee that the ship course will be straightened while astern. More importantly, the whole steering system should be able to match the yaw up to (down to) the manoeuvring speed, but the rudder is very close to the pivot point and doesn't receive much help from the propeller. Also, the rudder as a foil is working in a reverse direction, and its stall angle is smaller, so that great angles are worse than angles smaller than the stall angle.
Coming back to the propeller, RPM and pitch vary simultaneously, as if controlled by a combinator, and the propellers keep turning slowly when the pitch is 0.
Regards,
Luc
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Hello Capt L. Henry,
Really, there is no wind effect and no current effect. The ships can be moved by waves due to some asymmetries of the waves, giving this impression. The drift in the channel can only be due to the shallows.
Regards,
Luc
well if the ships can be moved by waves.. then in other words that is an effect of current. due to the fact that current is what creates waves. and i guess i understand the shallow thing but i was far from the shallows so it still makes no since
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For your information and to stay factual, at least at sea, it is the wind that creates the waves, not the currents. But wind against current increases the steepness of the waves indeed, and your interpretation is ok for me. 8)
Regards,
Luc
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OK, just tested it again in the Atlantic, and she reverses fine until she reaches 5 knots - then she starts turning anticlockwise - currently on 34' per minute and rising.
she is also turning in the opposite direction to last time when I used the rudder.
?
*Whilst I was typing she has gone up to 43' per minute
Edit: I then tried the bow thruster to counteract the turning - it just mad it start turning the other way Bow thruster was switched off when it reached 10' per minute in the clockwise direction, and it just continued increasing its RoT - now at 42' per minute.
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Why should such a large ship go more then 5 knots astern ???
It's not very realistic or safe.
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Why should such a large ship go more then 5 knots astern ???
It's not very realistic or safe.
http://www.marinetraffic.com/ais/default.aspx?mmsi=232001710¢erx=1.765498¢ery=50.96703&zoom=10&type_color=6
If you look very carefully into Calais, you can see a track Pride of Dover shows her going 10 knots astern
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I think also the dynamics of the PoR are much more real in (unpatched) 08 then SSE
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http://www.marinetraffic.com/ais/default.aspx?mmsi=232001710¢erx=1.765498¢ery=50.96703&zoom=10&type_color=6
If you look very carefully into Calais, you can see a track Pride of Dover shows her going 10 knots astern
Well this one is not exactly the size of the PoR.
But I know that many companies wouldn't allow a speed like that unless it's really necessary.
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Well this one is not exactly the size of the PoR.
But I know that many companies wouldn't allow a speed like that unless it's really necessary.
Think you havent seen the manoevers of ferrys in the size of the Pride at mare mediterrane??
Marseille, Genova, Livorno, Sardegna for example.
Class and type: Superfast I class fast ropax ferry
Tonnage: 23,663 GT (gross tonnage)
Displacement: 5,717 metric tons deadweight (DWT)
Length: 173.50 m (569 ft 3 in)
Beam: 24.00 m (79 ft)
Draught: 6.41 m (21 ft 0 in)
Installed power: 4 × Wärtsilä-Sulzer 12ZAV40S diesels
34550 kW
Speed: 27.9 kn (51.67 km/h) maximum speed
Capacity: 1400 passengers
686 berths
830 cars
1850 lanemeters
Or manoevers of the Colour Magic and Fantasy, World biggest Ferries
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Hello TFM,
PoR in SSEx reaches 12 knots astern after 2 minutes if kept at full astern, and can easily be steered to keep its heading even at this speed.
At speeds more than 6 to 8 knots astern, steering is needed with very small rudder angles to stay on course, from 0.5° to 1.5°. The ship is then course unstable, it means that if you don't steer, she will begin to yaw.
Under 8 knots, the ship should steady her heading without help, and you can learn how to control the ship thanks to the yaw indicator and the rudder angle, as the ratio yaw rate/rudder angle to match the yaw is the basic data you must keep in mind, it depends mostly on the speed. But the course stability is (too) good under 8 knots.
No need to say, don't make a mistake when steering, if you go at a speed that your thrusters cannot control, otherwise you will throw the ship in a turn difficult to counteract.
When turning astern at speed, some caution is needed to keep the control of the ship. But that is not specific.
And I was perhaps not enough clear : Don't use the thrusters if you try steering astern, they are not at all reliable now, wait for the patch that will correct the controls. Try to use exclusively the wheel steering as it is now, both rudders together, until you can control the ship at any (reasonable) speed inside Dover or Calais. I think that leaving Beneluxhaven without thrusters is possible, but very difficult.
Regards,
Luc
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Thanks for the info Luc, most appreciated, but I am still getting dodgy stern movements - reversing with engine set at -23% giving a speed of 4.3 knots astern, had the rudder at 0.9', and she was turning fine with a RoT of 2/3' per minute. I have reset the rudder back to 0, and her RoT has gone up to 17' per minute and rising?
Edit: now 24' per minute
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Thanks for the info Luc, most appreciated, but I am still getting dodgy stern movements - reversing with engine set at -23% giving a speed of 4.3 knots astern, had the rudder at 0.9', and she was turning fine with a RoT of 2/3' per minute. I have reset the rudder back to 0, and her RoT has gone up to 17' per minute and rising?
Edit: now 24' per minute
Ahoy Ferry Man,
Untill the patches are released it seems that the only way to come out of that strange behaviour is to use the engines to steer. If she swings to port to fast, stop port engine and slowly give throttle in forward direction till she's steady with zero angle per minute.
That would be, for the moment the only solution I will use.
Maybe you can try it out too?!
Kind Regards
Aad
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Ahoy Ferry Man,
Untill the patches are released it seems that the only way to come out of that strange behaviour is to use the engines to steer. If she swings to port to fast, stop port engine and slowly give throttle in forward direction till she's steady with zero angle per minute.
That would be, for the moment the only solution I will use.
Maybe you can try it out too?!
Kind Regards
Aad
Thanks Aad, that could be a useful solution :thumbs:
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hello ferry man,
pride of calais and pride of dover use a bow rudder when they manoeuvring astern out of calais, like the spirit class (pride of free enterprise, herald of free enterprise and spirit of free enterprise). when they are out of the port, they use the bow rudder to the left, they reduce their speed and they go forward with the principal stern rudder to the right. so they are very stable when they go astern. they don't use their thruster. so it is impossible to reproduce excactly the same with the pride of rotterdam because she hasn't a bow rudder like p&o ferries built after (european pathway (pride of canterbury), european highway (pride of kent), european seaway and european causeway (pride of burgundy)). in the eighties the port of calais was very small and they can't manoeuvring inside when they were berth 5 and after berth 6, but during these years, the port has been extended, so for the following built ferries they didnt need to have a bow rudder because the could manoeuvring inside the port.
sorry for my very poor english
regards
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Hi Seafrance, your English is very good
Thanks for the explanation :thumbs:
I know the Spirit class also had a Bow prop, but this was not added for the PoD/C
As you say, Calais Port now is large enough that the manoeuvrability of a bow prop is not needed, so the more fuel efficient Bow Bulb is used
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Tested the PoR and the Ferryman is complete right, she is unmanouverable in reverse.
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If she's reversing and starts to take the stern to port, give it a kick ahead on the stbd engine to null that turning effect - I wouldn't expect the thrusters to be of much use above 4knots anyhow really.
When operating small commercial vessels with twin screw in real life, I generally find that they hold course upto about 5knots and then if they start to steer off course, that is unrecoverable without either a reduction in power on one engine or a kick ahead on one or both of the engines to bring it back into alignment.
-Alex
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If she's reversing and starts to take the stern to port, give it a kick ahead on the stbd engine to null that turning effect - I wouldn't expect the thrusters to be of much use above 4knots anyhow really.
When operating small commercial vessels with twin screw in real life, I generally find that they hold course upto about 5knots and then if they start to steer off course, that is unrecoverable without either a reduction in power on one engine or a kick ahead on one or both of the engines to bring it back into alignment.
-Alex
As I stated before:
http://80.95.161.114/shipsim/forum/index.php?topic=20788.msg281467#msg281467
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As I stated before:
http://80.95.161.114/shipsim/forum/index.php?topic=20788.msg281467#msg281467
Yeah, my point being that it happens in reality - not sure about a large ferry, but if smaller vessels are anything to go by, this particular dynamic isn't a fault that should be fixed by a patch!!
-Alex