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Author Topic: testing simulator  (Read 436 times)
Shukaikan
Forum member

Posts: 1

2006
Money earned: none
« on: May 17, 2017, 20:30:19 »

I start studying for my ship handling licence on Brazil, so I decide test this simulator in some manoeuvres using the VLCC and I found in some manoeuvre, the ship acting too different from it suppose to act. Like the manoeuvre "Half astern to dead in the water", after she is putting in 6 kts, rudder amidships, she is putting half astern, rudder amidships until dead in the water. If this ship is right hand propeller, I expect she about 80 to 90 degree to starboard from the start heading when she is dead in the water (no wind, no current and no shallow water), and this didn't happened. The start heading was 263 and the final heading 287 (only 25 degree to starboard).

So, if I can do a suggestion, is first, give more ship's detail, like, kind of propulsion, kind of propellers and drafts.

Another thing is about the chart, we should be able to save the positions on the chart, to make a history and increase the possibilities for this simulator.
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LucAtC
Ship Simulator Developer
Global Moderator

Posts: 2073


France
Registered Extremes user


2008
Class:  - Current rank: RookieClass: Motorboat - Current rank: RookieClass: Cargo - Current rank: Third officerClass: Passenger or yacht - Current rank: Second officerClass: Tugs - Current rank: Second mate

2006
Money earned: 0
« Reply #1 on: June 10, 2017, 21:30:22 »

Hello Shukaikan,

I imagine that your suggestions are about ShipSim Extremes, you would have more infos if you registered it in order to gain access to all the forum boards.
The game has never been intended to serve as a professional simulator, quite to the contrary, because of the simultaneous development of the Vstep professional Nautis simulator. Diverting too much time to develop SSE was in fact not really doable, and not necessarily desirable.
Nonetheless, enough attention was given to the ship handling characteristics, taking into account that SSE had to remain a game. That is why the engine simulation remained at best sketchy, there was no wind nor tidal streams, no shallow water effects, etc.

About the stopping distances, reach and deviation from the initial course, I used the IMO values of the standards of manoeuvres and criteria, 15 lengths from full speed ahead less the shaft and transmission delays. The lateral deviation and rate of turn due to the side-thrust effect of the propeller have been derived from various sources, for instance the existing SNAME literature or various proceedings of maritime conferences.

Latitude was designed to show a final heading change around 45°, starting at 15.2 kts @ 74RPM full ahead, full astern (decreasing at 6 RPM/s) disregarding shaft stopping delays.  The engine was "supposed" to be a "8RT-Flex84T 27160kW", powering an 8.08m CW FPP at 74 RPMmax.
Latitude's displacement is 203016 mt at 18 m draught, Loa 314 m, Lpp 298 m and B 45.6 m, ruddder 82 m², Vmax 16.23 kts.
Then, a quick test :
2000 m after initiating the manoeuver, Latitude is still sailing at 4kts, 15° from her initial heading at a 5°/min CW yaw rate.
Her final heading change is 38°, only at a residual 14°/min turning rate to starboard.
The mean astern propeller walk was set at around 6°from the axis of rotation, and zero ahead, to avoid the necessity of permanent steering while making way (or the need of an autopilot).

What are your sources concerning a 90° final heading change in the conditions you describe, meaning a very strong side effect? It remains nevertheless credible to increase the final heading change to 90° if you wish so, but not from half astern at 6 kts and no initial turning rate. It can easily be done through an increase of the propeller walk, as that doesnt change the other turning data too much.

Please don't hesitate, suggestions are welcome !

Regards,
Luc
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