Ship handling characteristics & errors

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[steve149c]

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Hi all,

Only been playing the game a matter of hours - but there are great problems with the basic ship handling techniques.

(1) Put a ferry at 20 knots, set power to zero and try and turn - it doesn't. In reality it will because the vessel still have water flowing over the rudder

(2) Red jet's ensign is wrong - it is supposed to be a Red Ensign, not a British Union Flag!!

(3) Ferry - Ferries use a constant speed engine, usually in the region of 550 - 600 RPM, it is the pitch of the rudder that changes.

(4) Ferries have two rudders - which are independant of each other - this should be present.

(5) Time for ferry to gather speed is too slow - when you push the power on a ferry will accelerate to about 9 knots in about 30 seconds, it is also not a steady power to speed increase, E.G. 10% power will produce 4 knots, 90% 22 knots and 99% 22.5 knots. It is based on the theory - to double your speed you require an exponential increase in power. IE for 2 knots you require twice the power of 1 knot, but 4 knots requires 16 times the power of 1 knot.

Will keep playing and hopefully find the solutions

Thanks

Steve
Chief Officer - British Merchant Navy

[ADDUBYA]

(ref. #'s 1 &4) I believe the Red Eagle has voith schneider cycloidal drive not rudders, so really with no power you would not be able to turn. I agree with your other observations though.

[mporter]

(ref. #'s 1 &4) I believe the Red Eagle has voith schneider cycloidal drive not rudders, so really with no power you would not be able to turn. I agree with your other observations though.

Agreed, but the same is true of other ships with conventional rudders.  And as soon as the ship is put into reverse the rudder acts in reverse, even though the ship is still making headway. Something that would be really nice but seems unlikely to happen is making handling characteristics depend on the ships' characteristics instead of being arbitrary, as they are now.

Cheers,
Michael

[J3nsen]

(1) Put a ferry at 20 knots, set power to zero and try and turn - it doesn't. In reality it will because the vessel still have water flowing over the rudder

That one! I hate when i not can turn! Bad thing!

[steve149c]

Not really, it is a simple algorithum for the computer to work on. If a ship with a standard rudder is making headway then the rudder works are normal, if she has stern way on then the rudder operates in reverse. This would mean that you could get the ship to move sideways by running the ship with headway, rudder hard over and engine running astern, depending on the prop you would get the Transverse thrust from the prop to counter the turn, and she will move sideways

Steve

Ship handling is more of an art than a science

[LucAtC]

Hello steve149c,
Well, there is probably no simple algorithm to tweak Quest3D, so that hydrodynamic forces acting on a ship could be integrated and that the ships manoeuvring capabilities would be realistic: That would have been solved indeed when the add-on was published.
Nevertheless, one can only fully agree to the remarks you made in your post, (with a small question mark for 5.) and hope that a patch will solve these problems.
Could you please also elaborate on your last post, I dont quite get it (and sorry it can be my understanding of English)

... you could get the ship to move sideways by running the ship with headway, rudder hard over and engine running astern, depending on the prop you would get the Transverse thrust from the prop to counter the turn, and she will move sideways

Steve

Ship handling is more of an art than a science

Regards,
Luc

[steve149c]

Hi all,

Sorry, yes I will try.

Ok a propellor. You have to imagine it as a wheel on a cart, if the wheel fell off the cart whilst moving, then the wheel rolls in the direction of turn.

A propellor acts the same way, but the grip is down to the difference in pressure between the top of the rotating circle and the bottom (Large ships this can be 7 or 8 metres). This produces a pheonominom (Or something spelt like that) called Transverse Thrust.

Transverse Thrust is present all the time when a propellor is turning, but it's effect is proportional to the speed of the vessel. Thus a single screw (propellored) ship running ahead with a propellor (clockwise turning) will have the bow canted to port. Run the same screw astern and the bow goes to starboard, as its changed direction. At sea on single screw ships we use this to our advantage.

Run the ship ahead slowly on a clockwise turning screw, put the rudder hard to starboard, thus the bow swings to starboard, and the stern to port. At the same time run the screw astern, this pushes the bow to port and the stern to starboard. The combine forces are greater on the starboard bow and starboard stern, thus the ship will move bodily sideways for a few moments.

One a ferry, or twin screw ships this is not the case. Twin screws conuter rotate, ie usually inwards over the top to the center line (looking from the stern, the left one clockwise, right one counterclock wise). So we use Torque instead. Imagine your hips, push forward with your right arm, and back with you left. Your nose moves to port (left) and your bum to starboard (Right). This is exactly the same with the engines. Couple this with a bow thruster and you can dance!!

E.G. Starboard engine 50% ahead, port engine 30% astern (This figure changes for each ship) and Bow thrust to starboard. The ship moves bodily sidewards to starboard. By changing the bow thrust you can change the heading. Altering the engines makes her move astern or ahead. There is no real need to use a rudder on a ferry.

Hope that this has helped and not too many headaches.

I'll try and get some diagrams.

Cheers

Steve 

[LucAtC]

Hello Steve149c,
Many thanks for having given these explanations. Well, the question was addressed some time ago, and for sure, your explanations were very clear.
I asked this question because, in your post, you didnt mention the bowthruster, and that is why it was for me difficult to understand the sideways thrust, but now I see what you were meaning, thanks again.

Well, sometimes, written explanations are tricky, and I dont understand the following:

... Run the same screw astern and the bow goes to starboard, ....

Run the ship ahead slowly on a clockwise turning screw, put the rudder hard to starboard, thus the bow swings to starboard, and the stern to port. At the same time run the screw astern, this pushes the bow to port and the stern to starboard. The combine forces are greater on the starboard bow and starboard stern, thus the ship will move bodily sideways for a few moments.
.......

To come alongside a quay with the "bad" side (ie starboard with a clockwise screw in fwd), at the last moment a turn to port is initiated with the rudder, and this girational motion is cancelled through backing.
There is seemingly a slight contradiction in the text, but that can happen quickly in writing, more easily than in doing.
Regards,
Luc

[Stuart2007]

I follow all that. Thanks steve.

My Q. If you run engines astern- the ship stays in a straight line as transverse thrust is not modelled. If however you put the rudder over to port it brings the bow to startboard.

Surely this is not right? There was a topic ages back on this and I don't think there was ever a conclusive answer.

Would like to  know, once and for all, if you would be so kind...!

Stu

[steve149c]

Hi Stuart,

Ok running an engine astern (Single screw) - the ship should in reality cant to either port or starboard, depending on the direction of the prop. The rudder is effectively useless running astern as there is very little water flow over it.

Also a minor point, but using your rudder running astern at speeds above 4 or 5 knots can damage the point where the rudder is attached to the ship.

As for your question Stuart, yes the modelling is incorrect. However for the Redjet 2, Pilot boat - it is correct. These use "Buckets" and jets of water. No transverse thrust.

Hope this helps

Steve

[Stuart2007]

Thank you Steve.

When I first came on this forum I thought I knew quite a lot about shipping, from my fringe involvement with the industry... how wrong I was.

I must pay more attention next time I'm on board a ship... What a good excuse for another trip to Dover or Pompey-Spain


Stu

EDIT: Steve- I notice that pic you posted of one of the Stena HSS- that's not your ship is it?

[stanny1230]

Does anyone know how to reverse a Raptor.

[thethanatos]

I just purchased the game and I am incredibly disappointed in the handling charactaristics of most of the ships. Crabbing on single screw vessels seems to be nonexistant, some vessels accellerate and turn too fast to be realistic. Titanic should not be able to do a 180 degree low speed turn in 10 mins for example. Split throttle on twin screw vessels should be able to turn the bow but doesnt seem capable of doing so.

Rudder input while having way on the ship doesnt work without throttle input stupid and impossible assuming no current coming from astern at equal speed. The "jarring" from wave impact doesnt slow the vessel down at all that I can see. I am a small boat sailor since I was 12, I have been a liveaboard on a 44' ketch and I was a sailing instructor in Miami for a while and I have found that this game does not live up to any realistic standards IMO. I am so unimpressed that I am seriously considering getting a refund through my CC company for poor quality.

I also feel that I need to comment since I am already on a soapbox that having all the addon ships and scenery locked into company production instead of allowing the players do design their own will probably sink this game. There really is not enough content packed with the game itself or the addons to justify the lack of modding ability. I would have liked to have seen sailing  vessels as well as great lakes navigable waters. Were I aware of the small size of the areas and the innacurate handling of the larger vessels in particular I would never have purchased this "game". I did play the demo and the small boat handling other than the fact that there is no steering on a rudder equipped boat with forward way on and the poor handling of twin screws was a very poor example and did not give enough information to make an educated purchase.

[Stuart2007]

Oh dear Not a happy chap.

Tell me on what observations to ou base these statements? Being a sailing instructor is all well and good, but maybe doesn't qualify one for commenting upon ocean going multi thousand tonne ships?

Excuse the frank sarcasm, but as a pilot (light) I would never expect MSFS to be 100% accurate for flight dynamics, so perhaps it is not right to expect SS to be likewise.

I think if vstep were to produce a sim/game that was (close to) 100% accurate then people might be a little disappointed that it would take years of practice before they could manouver the ships- just like the years of training for the real world. Maybe.

[TerryRussell]

Sorry chaps, but for most of the ferries, no forward thrust=no steering. Any vessel that uses the voith schneider  or similar propulsion method has no steerage without thrust. It's just like any vessel that has an outdrive or outboard motor.

Examples are Red Jet, Red Eagle, Ocean Star.

In fact some of the vessels DO steer so long as they have forward motion. The steerage is less efficient and that reflects reality. Examples are P6, Pioneer, etc.

I know that not all the vessles are strictly accurate, but with the NH release, they are a lot closer.

Ship Simulator is probably closer to reality than any other simulator I've tried. With each new release it improves.

I only clock up about 200-300 hours at sea each year, so perhaps I'm not as experienced as some contributors (although I have been going to sea for around 50 years). The largest vessel I have owned and skippered was a mere 65 feet and my current vessels are 24 foot (my favourite) and 32 foot. But, I think I have some experience of these things.

[Captain Baines]

I've always felt when I saw animations on film or TV that nearly always the behaviour of movement was inaccurate. Mostly because the mass properties of objects seemed to be ignored. Since such properties are calculated through basic Newtonian physics, and doing such mathematical calculations is what computers do best - at lightning speed, I never understood why the makers missed such essential aspects. I can only guess that the artistic skills to design the animated things, or animals, don’t combine very well with a proper background in physics. They are at different sides of the spectrum. I've seen some improvements over the last years. Maybe because the makers of the graphics engines used for these animations/simulations are starting to incorporate support for a better simulation of such properties into their product so their users need less knowledge/skills about these properties to use them in their simulations.

Act-3D proudly announces about version 4 of Quest3D: "NEW: Newton Physics engine".

Didn't they have one at all in the previous versions or is the engine in this version "improved"?

It also says: "Select between physically accurate physics or performance optimized physics"

Which have been my thoughts exactly about the behaviour of the ships in Ship Simulator. Simply make a user setting with which you can choose between highly realistic behaviour (but often slow) or a more playable (game type) behaviour. I felt this was lacking from the game while in my opinion it should be so relatively easy to incorporate it.

And although the Ship Simulator 2008 project probably was designed on a previous version of Quest3D I'd expect it to be possible to load it in version 4 and add accurate Newtonian physics to the models. Then an update WITH such properties can be created. Slap such an update on the Vstep website and Bob's your uncle.

[nzlpilot]

Ummm an interesting thread which sadly has some misconceptions.

I am sure that the Red Jet is not a voith but a water jet.  I'm not too sure but high speed ferries are rarely voith driven. 
Also a voith does not need thrust applied.  It applies the thrust depending on the angle of attack of the blades.  Most Voiths run at a constant speed and it is the angle is altered by the controls.  A tractor tug normally has levers for ahead and astern for both units (and can almost be driven conventionally) and a single wheel to apply transverse thrust (to both units). By combining all three controls you can move a tug sideways and gain quite significant speed!

Jets also need water through them to turn.  Often there is enough water, even when engines at idle to turn a vessel a vessel when operating the buckets.  But at speed and engines at idle (unlikely though) there is very little turning moment.

A CPP propellor when stopped and the vessel underway is very likely to distrupt the water flow and the rudder will not be effective.  In fact even bring an engine from full to dead slow will cause handling headaches until the hull speed is the same as engine speed.  Its a well known problem with CPP vessels and one that catches out many a ship handler.  Also the direction of the CPP must be known as a right handed CPP propellor acts opposite to a normal right handed propellor when going astern.

Maximum transverse thrust when going astern is when the vessel still has some headway on (about 2 - 3 knots).

Normal propellors, when stopped, and the vessel making headway will be effective to a degree but depends on the speed of the vessel. Below about 3 knots it will not make much difference.  But rudder cycling can bring a vessel to a virtual stop and is used to slow vessels down very effectively.

Hope this helps. 
I may be wrong here and stand to be corrected 
Jon