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Author Topic: "Mare Australe" thruster has way too less power  (Read 5596 times)

RapsodyR55

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"Mare Australe" thruster has way too less power
« on: October 04, 2016, 17:44:45 »

Hey folks,
im a fan of this game and i work on a inland ship as captain.

i am struggling so much with the ship "Mare Australe"
The bow thruster has way too less power this feels like there's only 200HP of the required 650 HP
and the main engine works very well but srsly the truster is almost useless.
Real inland ships can Turn their ship incredibly fast using their truster but the Mare Australe has a very big problem doing this...
Is there any way of giving this engine some more power ?
Thanks in advanced ( if the forum is still alive ^^ )
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Traddles

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Re: "Mare Australe" thruster has way too less power
« Reply #1 on: October 04, 2016, 22:36:17 »

Hi RapsodyR55,
Whilst I have no knowledge of real Inland craft such as "Mare Australe" a rate of turn of 1030 per minute with thruster alone seems pretty fast to me. with helm hard over and thruster together I get a rate of turn of 1590 per minute, which also seems very fast movement. However, I bow to your better practical knowledge. What kind of rates would one expect from such a vessel?
Sadly, the Forum is just about still alive, but only just, which is a great pity. ::) :doh:

Kind regards,
Angus.
« Last Edit: October 04, 2016, 22:39:33 by Traddles »
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LucAtC

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Re: "Mare Australe" thruster has way too less power
« Reply #2 on: October 07, 2016, 00:28:59 »

Hello Angus and RahpsodyR55,
The Mare Australe's bow thruster engine has the specifications of a 365hp engine, and the attached thruster can deliver up to 48 kN thrust at no ahead speed.
Main engine is 1380 kW, at 2100 RPM and 24 km/hr.
Getting accurate and detailed data about bow thruster performance has been impossible for the ships I didn't know well, and I resorted to simply timing the turn rate under thruster alone, not knowing how much rpm the captain chose to set. I guessed full throttle, as it seemed to be quite common in these pre-ecofeeling days.
For the thruster engine power, I simply asked the make/model to a skipper of my friends who captains a similar ship, albeit a 9.50 m beam instead of Mare Australe 11.20 m.
Looking at Marin's report for new builds, it appears the bow thruster median of the AVV class M10 is 410 kW (557hp), 52% more power, a probable 15% higher turn rate, 125 deg/min with bow thruster alone instead of 109 in test conditions (i.e. flat water, full load,...)
Is it enough, I am not sure, perhaps do you have more accurate wishes? Given consistent data, I can with pleasure edit a new dynamics file.

Regards,
Luc

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Traddles

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Re: "Mare Australe" thruster has way too less power
« Reply #3 on: October 07, 2016, 12:01:15 »

Hello Luc,
Thank you for your interest in this discussion. I thought that I would have a try at improving the bow thruster performance. (Just to stop my brain completely ossifying.) You will see from my picture that I was able to bring up the details of the motor, a Cummins365, and the pumpjet bow propulsion. However I tried to increase the breakpower above the 1.7336kW shown and the max RPM of the bow propulsion, but in my very inadequate comprehension of this stuff I was unable to do so. I THINK I was on the correct track but just do not have sufficient knowledge to carry out any changes.
My sole object was to see just what I could do, or not do, and to take my mind off my main problems with my wife's illness.
It is great to hear from you again, and perhaps I could ask you to make the changes which you suggest to the .dyn files for this ship. I would be interested to see the resulting performance of the ship. I feel certain that RapsodyR55 would also be interested too, if he is still around that is.

Kind regards,
Angus.
« Last Edit: October 07, 2016, 12:08:08 by Traddles »
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Traddles

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Re: "Mare Australe" thruster has way too less power
« Reply #4 on: October 08, 2016, 11:37:56 »

I have checked "Deo Favente" to see how she compares in this manner with "Mare Australe". It seems she has a more powerful Cummins engined thruster which gives her a max rate of turn of 1250per minute, which fits with Luc's notes above. Together with maximum helm and full power on main engine this rises to 1640per minute. Very much more speedy than "Mare Australe".

Angus.
« Last Edit: October 08, 2016, 11:43:00 by Traddles »
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LucAtC

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Re: "Mare Australe" thruster has way too less power
« Reply #5 on: October 08, 2016, 17:51:17 »

Hello Angus,
There is also the possibility that Rapsody R55 used a former version, evenyually less powerful? I remember having changed the bow thruster at the same time than making that of Deo Favente.
It was certainly linked to the azimutal capacity, be it by redirecting the flow/wash from a non-pivoting screw or some Schottel solution, retractable SPR or Pumpjet, Scania Veth-Jet ...  and I could have increased the power at the same time.

The brake power (erroneously written as breakpower) in question is the maximum power delivered to the thruster propeller by the engine during the editing session, slightly less than 2 kW in your example. It is somewhat irrelevant in the case of a "JetPropulsion" vs "Propeller", due to the power computations being mainly based on the speed ahead. Due to the fuel consumption being forsaked, further formulas tuning was also abandoned by our friend math/physicist.
The thrust of the JetPropulsion is determined exclusively as a function of RPM, trimmed by the speed, designed in two graphs. Unlike other propeller designs, prop design, diameter and pitch are disregarded which makes designing freely apparently much faster, perhaps then less accurate.

Perhaps we could wait for RapsodyR55's details about his wishes, before editing the dynamics?

Kind regards,
Luc
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RapsodyR55

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Re: "Mare Australe" thruster has way too less power
« Reply #6 on: October 15, 2016, 20:32:58 »

Hello Dear Luc and Angus
Sorry for my very late reply guys.

Iv'e pleen playing around on this ship where im working at.

Emtpy without any playing factor like wind,water-speed etc, the thruster can easily get the ship 360° around within a minute.

Loaded without any playing factor the ship gets around in
1 minute and 13 seconds.

And believe me i did not use the main engine.

This is also the reason why "Mare Australe" feels very uncontrollable to me.

The specs of this ships are the following.
Length : 110M
Width : 11,45M
Draught : around  3,5M usually
Thruster engine power : 650HP
Main Engine Power : 1600HP

If you guys like i could make some Recordings as well.

It would be very awesome if the specs of Mare Australe could be adjusted.

Quick Edit :
This thruster system is like how Luc said "Schottel" its called a "Tunnel Thruster" which can turn 360° around







« Last Edit: October 15, 2016, 20:38:39 by RapsodyR55 »
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Traddles

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Re: "Mare Australe" thruster has way too less power
« Reply #7 on: October 15, 2016, 23:13:47 »

Hi RapsodyR55,
From your description of your ship I can see your point about "Mare Australe". A complete 3600turn in 1m13s when loaded is quite amazing to me. Let us wait to see if Luc responds, as I feel certain he will. Your bow thruster at 650hp is almost double the power of the modelled thruster on "Mare Australe" which is a Cummins 365hp engine. Thank you for coming back on this, it is appreciated. Your vessel at 110M length and 11'45M beam is 18m longer than "M A" but of similar beam. Thus to me, as an ignorant retired deep sea man, it is all the more remarkable.

Kind regards,
Angus
« Last Edit: October 15, 2016, 23:22:49 by Traddles »
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LucAtC

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Re: "Mare Australe" thruster has way too less power
« Reply #8 on: October 16, 2016, 23:43:44 »

Hello,
The file attached should replace the existing one, the latter to be saved somewhere before replacing, in the following folder, if the default paths have been applied.
C:\Program Files (x86)\Vstep\ShipSimExtremes\Projects\ShipSimExtremes\Data\Entities\Dynamics

Mare Australe being shorter than your ship, the bow thruster lever and the pivoting torque are shorter as well, but the yaw resistance being smaller too, both rates of turn should be similar.
The mass moment of inertia in yaw has been reduced (20-22%), as if the load was better distributed, and the thrust of the bow thruster designed to simulate the 650bhp power, that is all I changed.
Of course, changing yaw resistance and inertia also changes the steering response, which I didn' test, that is up to you.
Also, recordings of the rate of turn vs time, given throttle setting would improve the simulation, just as the speed ahead or astern under bow thruster alone, at your chosen setting, or any other available data, speeds, timings, etc. I can try to reflect the specifications as well as I can, but taking the scaling into account.
Once we all agree about the model, it could be published in the community patch?

Kind regards,
Luc
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Traddles

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Re: "Mare Australe" thruster has way too less power
« Reply #9 on: October 17, 2016, 11:16:02 »

Hello Luc,
I have tested the new dynamics you have made, and the difference is quite remarkable. I get a 3600 turn using thruster alone at full power in 1m 40s. However it must be very carefully used at this rate as it is not easy to stop the turn!! Steering is much more sensitive, but by careful use of the helm, is easily controllable. Max speed ahead comes out at 12.8/9 knots.  Overall, I like the change you have made, which comes very close to the performance which RapsodyR55 describes for his own vessel.
I would like to express my thanks for your work on this ship, and your ongoing interest in the details of the ship & the game itself.

Kind regards,
Angus.
« Last Edit: October 17, 2016, 11:35:15 by Traddles »
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RapsodyR55

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Re: "Mare Australe" thruster has way too less power
« Reply #10 on: October 17, 2016, 13:45:03 »

I will test this today once this ship has been anchored near our loading spot( where today has been an explosion with an chemical product near an unloading ship! God help the crew and people over there )

Like angus said once turning the ship at full throtle it is a tough job to stop the ship from turning but thats exactly what happens here too so thats okay.

Kinds Regards,
RapsodyR55
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RapsodyR55

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Re: "Mare Australe" thruster has way too less power
« Reply #11 on: October 17, 2016, 18:57:50 »

wow these adjustments changed the whole ship.
its really good maneuverable now excellent work and the way the settings are now are really good.
but one thing just one thing botters me.. the bow thruster engine's Acceleration is... slow :P for a Mid-RPM engine is the acceleration too slow it takes about 7 - 8 seconds to be at full throttle, our engine is at top RPM in about 3 seconds, also an Mid-RPM engine.
it doesnt really have to be adjusted but when maneuvering into lock's and small docks etc, you'll need an fast acting thruster ( in my opinion and i needed it much ).
but guys truly i thank you so much its a really nice simulator now i appreciate it.

Kind Regards,
RapsodyR55
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Traddles

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Re: "Mare Australe" thruster has way too less power
« Reply #12 on: October 18, 2016, 16:39:21 »

Hello again Luc,
I have had second thoughts about my first report. :doh: I tried an actual mission of Jans, "Charges and repairs", which has a few acute turns for "Mare Australe". These turns were almost impossible to make using the helm alone, even at slow speed. Applying more than about 50 of helm causes the ship to start a very fast turn which cannot be stopped even by applying full reverse helm. I did say that the steering was very sensitive, but with more than a few degrees of helm applied it is virtually uncontrollable. :o
I am sorry to say this Luc, as your work on the thruster is very good, again provided too much power is not applied for too long a time. Overdoing it produces the same kind of unstoppable rotation of the ship as does the helm.
Kind regards,
Angus.

P.S. Not liking to be beaten, I have been persevering and find that with patience & practice it is possible to handle "Mare Australe" fairly well, without crashing her badly. ::) :doh:
A.
« Last Edit: October 18, 2016, 22:43:24 by Traddles »
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LucAtC

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Re: "Mare Australe" thruster has way too less power
« Reply #13 on: October 20, 2016, 22:54:43 »

Hello,
Please find a new MareAustrale.act file to replace the previous one. In this version, the bow thruster acceleration has been increased in RapsodyR55's way, and the steering controllability has been hopefully improved by changing the rudder parameters. At the same time, the hull turning drag has been changed, as if the stem aspect had been changed.
The lift coefficient of the rudders is consistently smaller, but at higher maximum angle of attack, the useful range of the rudder angle for steering is increased, while very large angles should still work well.
She should be easier to be steered, without too much manoeuvrability loss I think. Anyway, I hope that you will enjoy the changes, don't hesitate to suggest new ones.

Kind regards,
Luc
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Traddles

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Re: "Mare Australe" thruster has way too less power
« Reply #14 on: October 21, 2016, 11:58:38 »

Hello Luc,
This last .act file is quite superb in my opinion. It is now possible to steer "Mare Australe" with a degree of accuracy which is great. The acceleration of the thruster engine, as RapsodyR55 wished for, is also excellent. Altogether the ship is now very easy and enjoyable to handle both on a steady course and in tight manoevring situations. I thank you sincerely for your efforts on our behalf.
Just as a matter of some interest, ( I hope ::)) I have added a new .lgt file to the ship which has the three stern lights for a vessel pushing another one (a barge for example). A little extra added interest, possibly, for the professionals like RapsodyR55.

Many thanks again, and my kind regards,

Angus.
« Last Edit: October 21, 2016, 12:03:48 by Traddles »
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RapsodyR55

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Re: "Mare Australe" thruster has way too less power
« Reply #15 on: October 21, 2016, 21:17:11 »

This ship has been perfected ^^
the thruster is perfect, as well as the manouvering does now.
i like the ship it is now, Old main engine good thruster Oh and ofcourse the new lights from Angus ^^
if you guys want to go some further then you should upgrade the power of the main engine's screw.
when you set your rudder Full PS and you set the main engine at 100% then it feels like there's a loss of power at startup, when i execute that situation here i wouldve been at 90 Degrees in no time :P but thats tricky because i have to Catchup the turn as well :P

Greetings RapsodyR55,
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LucAtC

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Re: "Mare Australe" thruster has way too less power
« Reply #16 on: October 22, 2016, 18:06:20 »

Going further is possible, I think, that is why the initial yaw resistance and its corresponding "added mass" have been changed in the attached file. The result should improve the startup response indeed, because it eliminates a good part of one of artefacts introduced to ease stopping the ship, in this case her yaw.
The various resistances have indeed been generally increased for very slow and small movements in order to suppress "creeping" around stop. The reason are the rather blunt/insensitive controls and the difficulties to check the ship movements in the simulation versus reality, and also the time needed to moor the ship.
For each movement of each ship, a trade off had to be made to eliminate creeping without it being too apparent, more or less successfully, of course.

If you see other weaknesses, please don't hesitate to mention them, happy to be of some help.
And as usual, untested!

Kind regards,
Luc
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ACR

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Re: "Mare Australe" thruster has way too less power
« Reply #17 on: December 08, 2017, 13:23:10 »

i know this is an older thread but i,m a little bit stunned here.

i,m just a recreational skipper but have since some years a boat in a marina at an inland channel and often see inland cargoships manouver .

i never in my life saw a performance here advised up to a 360deg circle in one minute with bow thruster only .

not much videos found but this seems to be a common bowthruster performance of an inland cargo .

https://youtu.be/wfD9NXt3tRw

the guy admits his 110 meter ship circles 360deg in 60 seconds at a dead stop and common maths show that with a 110 meters ship the bow has to travel 690 meters !!!  ( 110×2×pi 3.14 ) to make a full circle with bow thruster only ...

travelling that distance in 60 seconds means the bow reaches a transverse speed of 11.5 m/s  ( 690÷60) or 41.4 km/h ( 11.5 ×3600 ÷1000 )  or 22.4 knots .

really ? ;-)))

finally i,m surprized that this guy has a medium speed engine as a thruster when you google whatkind of engines are referred to be medium speed engines .

i,m not sure if you worked in the right direction ...

best regards




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LucAtC

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Re: "Mare Australe" thruster has way too less power
« Reply #18 on: December 10, 2017, 00:17:14 »

Hello ACR,
Your surprise is understandable, and there is no easy answer. But please let us look at the distance travelled by the bow thruster. This distance is more like Pi x Diameter, and the center of the circle is somewhere near to the centre of lateral resistance of the rather rectangular lateral aspect, closer to 105m, 2 to 3 m from the bow, isn't it? 330 m, 5,5 m/s or 20 km/h? Which is already quite a lot , I agree, andthe curve described is not exactly a circle, because she is also swaying.

In fact, the length of Mare Australe is overall 92 m, beam 11.05 m, displacement 2100 mt. The distance from the bow thruster to the CoM is 36 m, the offset is 1.25 beam or 14 m, hence a 50 m radius and 314 m circonference, 5.23 m/s. The bow thruster engine which was deemed 365hp in the first file, was upgraded to 800 kW (!) after I was made aware of more recent conceptions and "hugely and unbelievably more powerful", bow thruster engines. And her maximum rate of turn is anyway less than 265°/min, I didn't agree to give more power to the bow thruster than to the main engine.
Medium speed probably not, for issues of mass and costs for such an intermittent use.
I agree with you that it seemed incredible, that is also why I didn't change Deo Favente characterisitics, because I have friends who own similar ships, but I also cannot deny people who are so affirmative. Saying that something doesn't exist cannot in general be proven (is it not somehow in relation with Karl Popper's theory?). For the other many ships that I didn't know of, I had to resort to computations and design/analysis software, then tedious trials in the simulation environment, thanks to a great editor. Then, the projected dynamics were beta-tested by our knowledgeable friends to be finalized, as far as possible due to the limitations of ShipSim Extremes state at the time, particularly some not yet developed features of the ship controls.
And yes, errare humanum est, isn't it?
Best regards,
Luc
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cegmail

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Re: "Mare Australe" thruster has way too less power
« Reply #19 on: December 10, 2017, 09:45:09 »

I don't know where the video was made (in the U.S.A.), but if this is on a river where there is current and you are moving upstream, then the speed with which the ship turns is always faster because of the advantage of the current. Usually the engines of the bow thruster have more power in a push barge than in a normal motor ship. This is to be able to sail with the barge only to be able to move it at a loading or unloading area without the help of a motor ship or pusher.

cegmail
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ACR

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Re: "Mare Australe" thruster has way too less power
« Reply #20 on: December 10, 2017, 16:59:28 »

thats interesting gents!

 from a geometrical point of view i would say in a deadstop- bowthruster only scenario the shiplenght is the radius and not the diameter of the circle . not perfectly because you are correct the stern swings away and the bow thruster is not located at the very bowtip but the shiplenght being the diameter of the circle would only apply in a scenario bowthruster and at the same time sternthruster in opposite direction .

what do you think ?

even taking the shiplenght as the diameter - the bow of a 110meter ship would have to swing at more than 20 kmh transversal AVERAGE speed to make the circumfence of a three sixty in 60 second - lets remember that at the first seconds the thruster has to overcome inertia of the ship but the clock is ticking  . ( like luc calculated cirrectly )

you imagine the wake the bow would create being pushed TRANSVERSAL at this speed thru water ?

thats why i believe a 360deg swing of a 110 meter ship in 60 seconds is completely off any reality .



whats your opinion ?





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LucAtC

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Re: "Mare Australe" thruster has way too less power
« Reply #21 on: December 11, 2017, 23:10:06 »

Yes and no, your reasoning is correct, but results without computations is just fuzzy guessing, isn't it?

The issue is that of the distance between the static pivot point and the CoM, which is the mass moment of inertia divided by the product of lever (i.e. distance from bow thruster to  CoM) by the mass of the ship, 11.64 meter for Mare Australe as it was designed.
The static pivot point is a valid centre of rotation as long as the water resistances are small compared to the external forces exerted on the ship. This is the case until the maximum yaw rate is approached, or the maximum sway speed for the said movement.
More in detail, the ship displacement  as loaded is 2100 mt, beam 11.05 m, length 88 m, distance from bow thruster to CoM is 36.40 m lever, and the mass moment of inertia is 889434 (mt, m), a radius of gyration in yaw some 20.58 m(sqr of 423.54), less than that of a solid rectangular parallelepiped, of course.
So, the radius of the pseudo-circle is 48 m at start, defining the initial yaw acceleration (moment of the thrust divided by inertia in rad/s²), until the yaw settles due to the water resistance (the dot act file gives the figures in plain text).

As the mass moment of inertia of a 110 m ship, given her loading, her dimensions and that the distance from her thruster to the bow can be viewed at the painting on the hull, timing the initial acceleration gives easily a good guess of the thrust. Is 360°/min credible or not? You have all the elements .... I had to increase the thrust of Mare Australe up to 140kN to reach 270°/min, loaded as she is. I think that it was way too much, but an almost empty barge with a powerful thruster could probably do it, the more it was pivoting at start.

Have fun,
Luc
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ACR

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Re: "Mare Australe" thruster has way too less power
« Reply #22 on: December 12, 2017, 01:42:41 »

hey luc !

you are pretty correct every ship turnes around its pivot point . but i think in our scenario ; ship zero fwd speed , no input from aft rudder/engine , bowthruster only the pivot point is pretty far to the stern .

please look at this explanating pdf from vetus , a major producer of bowthrusters and see how far in the stern the pivot point of a ship is with zero fwd speed and thruster only operation .

https://www.exalto-emirates.com/attachment.php?id_attachment=75

that again show us what huge distance the bow would have to travel for a 360deg with bow thruster only .

another question : is the editor you can change the ship dynamics available to the public or only for developers ?
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LucAtC

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Re: "Mare Australe" thruster has way too less power
« Reply #23 on: December 13, 2017, 00:55:58 »

Hello ACR,

That the ship turns around a pivot point is a tautology, as such meaningless. In our scenario, the static pivot point distance is fixed by the ship's measurements, mass, mass moment of inertia, position and force of the thruster. When Vetus explains how to calculate the thrust needed, it says that the thrust must balance the wind force when the ship is bridled at the stern, leaning at a quay, whatever.
There is not the slightest link with the static pivot point, the center of instantaneous rotation, a virtual point resulting from inertia and external forces acting on the ship. Didn't you read too hastily, did you?

Let us take the ship as in your reference, scaled arbitrarily, with a 10 mt displacement M (dty 1). Her mass moment of inertia, i.e. Iyaw=M x (4² + 10.44²)/12 or 104161.33 if it was a blunt parallelepiped, probably too much, as it gives sqr(Iyaw/M)=3.23 m as radius of gyration, but let us take it for granted.

Computing the distance moved by the CoM as a lateral movement and as a rotational one, then eliminating time, angle of rotation and thruster force shows that the mass moment of inertia is the product of mass times distance CoM to thruster times CoM to static pivot point.
CoM to static pivot point is =10.416133/4.56, 2.28 m behind the CoM.
Now, a 60 kgf thruster...
The initial lateral acceleration is for instance 600N/10000kg or 6 cm/s² and the corresponding rotational acceleration is 4.56*600/104161.33 rad/s² or 90°/min.s (90 degree/min each second, 4 s to reach 360°/min, if at all posible, while disregarding the yaw water resistance)
The higher Iyaw for a given displacement, the more the pivot point lies to the stern. The lighter the ship, the closer to the CoM.
You could do the same for the 110 m ship, with comparable hypotheses, just take 60% of the moment of inertia as computed above, for a better approximation.
Also, as a side note, the pivot point is nowhere to be found in the ships parameters, it is the zero drift angle point when the ship turns, nothing more, nothing less, and is only fixed relative to the ships frame of reference when in steady turn.
The editor is not available to the public, of course, you certainly knew it and can guess also why it is so, but it is possible to find by googling many good textbooks about ship hydrodynamics, not forgetting a revision of classical mechanics and Newton laws.

Regards,
Luc
« Last Edit: December 13, 2017, 01:01:16 by LucAtC »
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ACR

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Re: "Mare Australe" thruster has way too less power
« Reply #24 on: December 13, 2017, 13:30:27 »

how can we disregard water resistance ?

not intending to argue about this and your calculations about inertia are indeed very good as far as i can follow but from recreational skipper experience with displacement yachts 12-15 meters i often chartered in terherne before i owned an own boat : at a dead stop with only bow thruster at least such a boat turns more or less around the stern .

assuming a 110 meter ships reacts the same the bowsection by calculation would need to develop an incredible transverse speed like discussed .

in other words : an user creates an account to describe himself as the captain of such a vessel and tells you the real performance of an inland cargo , has a medium speed engine as bowthruster and also wants you also to increase the power of the main engine and effectivity of the rudder since in real he would be "in no time at 90deg " giving hard rudder and full power at such an 110 meter  inland cargo .

do you smell it ? it smells like teen spirit ...

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