(WIP) Ship's Acceleration Physics

[JREX53]

Ship’s Acceleration Physics

By JREX53

This mod is an attempt to make the ships in Silent Hunter 4 to react is a more realistic way. As we have all experienced, the rates of speed changes to be very unrealistic. Ships that go from a dead stop to 30 kts in less than 30 seconds or being able to turn on a dime will become a thing of the past. From my personal testing, in the beginning, I have observed ships not being able to maintain convoy positions and scattering at unrealistically slow speeds when using drag coefficients as the main choice to control ship acceleration.

This mod is a continuation of the work started by Swdw/Sam. Sam had informed me shortly after I started work on this mod that changes to drag should be minimized as it caused ships to act in weird ways. He also suggested that adjusting the engine power and engine rpm to get the timings to match realistic speed curves. He suggested using the engine power to get into the ballpark, then us the engine rpm to fine tune the desired results. He also suggested changing the propeller efficiency as needed. The main reason that he used the changing of engine power was because the power does NOT represent the true shaft power generated, as the other factors affecting acceleration, prop size, etc are not represented in the acceleration physics of the ships. He also discovered in his testing that the game engine slows the acceleration of the ship as it gets closer to rated speed.

So based on this information and a chart posted by Sailor Steve & Tater showing the speed curves for some of the British warships, I started over with this mod. There are several parameters that can be changed that will affect how ships behave. These parameters are: Mass, gravity center height, gravity center position, displacement, draught (draft), left/right drag coefficients, up/down drag coefficients, maximum speed, engine power, engine rpm, rudder drag coefficient, and propeller influence factor. In conforming to remain compatible with RFB, I have used their values for displacement, draught, (and in the case of the destroyers, minesweepers, and minelayers) the gravity center height. I have set the gravity center height for the other ships to 0.2, the Left/Right drag coefficient to 0.45, up/down drag coefficient to 0.3, rudder drag coefficient to 0.03, and propeller influence factor to 0.05.

This leaves parameters that can be adjusted to: maximum speed (only to match the config file), engine power, and engine rpm. The one remaining parameter that I have not tested is the engine’s max force.

I then started adjusting the engine power to get the civilian type ships (freighters, tankers, liners, etc.) to get their acceleration to more reasonable rates. I then timed the ships in a 90-degree turn to see how much speed they lost and how long it took for them to recover back to their maximum speed.

After completing the civilian type ships, I started on the destroyers, Japanese then Allied. I used the chart posted by Sailor Steve & Tater to get a ball park feel to the timings for the destroyers and the rest of the warships. (I was unable to find speed curves for the other nations involved in the game.)

The speed curves that resulted are based on the curves provided and by the age, displacement of the ship and the number of propellers driving the ship. I.e. twin-propped ships will take less time to reach a given speed then a single-propped ship, an older ship will take more time to reach a given speed and a heavier ship takes longer than a lighter ship.
My vision of the final product is that all the ships will act in as true a realistic manner as the real thing. This is probably not possible given the way the game engine uses the data that is inputted into its calculations. So given that we are limited into what parameters we can change and how they will cause the ship to react. We can only give a close approximation to how their movements are viewed in game.

Unfortunately, given this limitation we are forced to have unrealistic results in some phases of the ships movement through the water. It may result in the loss of too much speed in a course change, or the rate of acceleration may not be accurate at the start of an acceleration phase or even the end of an acceleration phase. My hope is minimize these affects in the game.

This version of Ship Acceleration Physics covers:
1.All Merchant, Tankers, and Passenger ships, both Axis and Allied ships.
2.All Destroyers and Destroyer Escorts on both sides. Note: Some additional modifications may be needed to the Destroyer Escorts in the future.
3.All Light Cruisers on both sides.
4.All Heavy Cruisers on both sides plus the Pocket Battleship Graf Spee.
5.All Carriers on both sides.

The next version will include the battleships, and any other ships/boats not done yet.

A special thank you goes to Skwas, for S3D, for without this magnificent program I would never have even thought of attempting this mod.

A special thank you also goes out to Swdw for his work on this process and his kind words in support of my endeavor.

A special thank you also to Vickers003 for allowing me to use his Sonar Target Fix mod in this mod.

Thanks also go to Philip Thomsen and Webster their work on this problem in both SH3 and SH4.

I also want to thank the beta testers for testing this mod and giving me feedback on problems
encountered and for their encouragement and support of my work.
These testers are:
399nkov
Wilcke
Rockin Robbins
Peto
Ablemaster
BillyBubble
Captgeo
fireship4

This version of the mod has been broken down into 2 separate downloads.

One download is for stock and RFB only, for those people who play strictly Stock and/or RFB without RSRDC – File name: SAP_v0.5_Stock-RFB-Only.rar.
Links:
SUBSIM: http://www.subsim.com/radioroom/down...o=file&id=1313

FileFront: http://www.filefront.com/14385855/SA...k-RFB-Only.rar

A second download for Stock and/or RFB with RSRDC – File name:
SAP_v0.5_Stock-RFB-RSRDC.rar
Links:
SUBSIM: http://www.subsim.com/radioroom/downloads.php?do=file&id=1314


FileFront: http://www.filefront.com/14385861/SAP_v0.5_Stock-RFB-RSRDC.rar

I hope you enjoy!

This mod is installed by JSGME.

[vanjast]

You do know that Webster's done this already...?
Maybe you should speak to him, you guys can exchange ideas

[JREX53]

Yes I know Webster has done it... I have accomplished mine in a different, and I feel better, way.

[Sailor Steve]

I'm glad to see more than one person working on this. The chart posted by tater was (I think) originally posted by me, quite some time ago. I've often wondered how accurate it is. It says it was created for 1929 war games. Was this an official Royal Navy war game, and were the curves created by naval experts of that time, or was it created by people like us for a homemade wargame? I know you don't know the answer to that question any more than I do. I was just putting it out there. Either way it doesn't really matter - there is no other information available. My problem with it is that I think destroyers should have a much better base acceleration. What slows them all down is that if a torpedo is spotted the captain or OOD first has to give the order, then the lee helmsman has to signal the engine room to make the change, then the lead engineer has to shout the order to the man at the throttles, and then he actually has to move them. With a fast warship I think the bigger problem is the time delay between the spotting of the incoming torpedo and the actual increase in power. This is also the problem with them reversing so quickly - a collision is likely to happen not because a small fast ship can't stop in time, but because the collision might well happen before the engines are even reversed!

My interest comes from a long history of tabletop miniatures naval wargaming. I've been working on my own rules for twenty years now, and have never quite gotten them finished, precisely because I keep obsessing over these questions. All I've ever had to go on were a thorough study of power/weight ratios and collected data on everything I could find. Not much, really. The only piece of real information I've ever seen was this placard from the engine room of a WW2 aircraft carrier, and I don't even remember which one it came from!

[vickers03]

@JREX53
does your mod influence the way ships are heard
on the sonar?
that has always been a problem when playing with
the engine power and rpm.

well good luck with it.

FYI the drag coefficients in my mod have nothing to do with the engines power, they are for giving ships realistic inertia.

the biggest problem i found with the game is that it only speeds up or slows down in somewhat straight lines so you cant get a true acceleration "curve" but you can get a slight arch going.

[Soundman]

Originally Posted by Sailor Steve

I'm glad to see more than one person working on this. The chart posted by tater was (I think) originally posted by me, quite some time ago. I've often wondered how accurate it is. It says it was created for 1929 war games. Was this an official Royal Navy war game, and were the curves created by naval experts of that time, or was it created by people like us for a homemade wargame? I know you don't know the answer to that question any more than I do. I was just putting it out there. Either way it doesn't really matter - there is no other information available. My problem with it is that I think destroyers should have a much better base acceleration. What slows them all down is that if a torpedo is spotted the captain or OOD first has to give the order, then the lee helmsman has to signal the engine room to make the change, then the lead engineer has to shout the order to the man at the throttles, and then he actually has to move them. With a fast warship I think the bigger problem is the time delay between the spotting of the incoming torpedo and the actual increase in power. This is also the problem with them reversing so quickly - a collision is likely to happen not because a small fast ship can't stop in time, but because the collision might well happen before the engines are even reversed!

My interest comes from a long history of tabletop miniatures naval wargaming. I've been working on my own rules for twenty years now, and have never quite gotten them finished, precisely because I keep obsessing over these questions. All I've ever had to go on were a thorough study of power/weight ratios and collected data on everything I could find. Not much, really. The only piece of real information I've ever seen was this placard from the engine room of a WW2 aircraft carrier, and I don't even remember which one it came from!

Pretty interesting, yet intense material here Steve. 20 years shows a lot of dedication to detail, or procrastination, I'm not sure which ! I admire your "stick to it ivness" (is that a word ? lol)

As for Jrex and Webster, hats off to both of you for even making an attempt at this painstakingly detailed can of worms you are delving into. We certainly have a very dedicated bunch of folks here. God bless all you modders!

[JREX53]

Sailor Steve,
Tanks for your comments. Sorry about the graph, if I had known that you were the one to post it I would have given you credit for it. As far as being able to answer your questions, the only answer I can give is "I don't know."

Good luck on your endeavor I hope you can get your project completed, I would be interested in seeing your results.

[JREX53]

Originally Posted by vickers03

@JREX53
does your mod influence the way ships are heard
on the sonar?
that has always been a problem when playing with
the engine power and rpm.

I am not sure how it influences the way ships are heard, if you want to test it out and let me know, I would be more than willing to add your fix, with the proper credit of course.

The only parameter that I have really change has been the engine power not the rpm.

[JREX53]

Originally Posted by WEBSTER

well good luck with it.

FYI the drag coefficients in my mod have nothing to do with the engines power, they are for giving ships realistic inertia.

the biggest problem i found with the game is that it only speeds up or slows down in somewhat straight lines so you cant get a true acceleration "curve" but you can get a slight arch going.

Thank you Webster.

Concerning the drag coefficients, I feel that they should be the same for all the ships. That way drag is acting on all the ships to the same degree.

I agree with your last point to a certain degree.

[JREX53]

Thank you Soundman for your encouragement. I hope people understand how much work goes into working on mods. Especially a mod like this, a lot of testing, and for me, writing down a lot of numbers.

[NEON DEON]

Maybe after this mod is complete we could have Fleet boat drag racing.

Ok T3 does the quarter mile in 6.7

Seconds!

no

Minutes.

[JREX53]

Neon Deon,

According to my spreadsheet it takes the T3 to go from 1 kt to 18 kts in approximately 14 mins and 10 secs.

I will look into it though.

Thanks

Originally Posted by JREX53

Thank you Webster.

Concerning the drag coefficients, I feel that they should be the same for all the ships. That way drag is acting on all the ships to the same degree.

I agree with your last point to a certain degree.

i dont know whos mod you looked at or maybe you just think you know whats in my mod but you say things that sound like you havent really looked at it or if you did it must have been a prereleased version or something before i finished it because ALL my ships DO have the same drag coeficient.

you say your doing something different yet it sounds like an exact redo of my mod?????

i dont mind if thats what your doing because its all about making the game better but like you said, its a hell of a lot of work to do all those files so i want to be sure you understood what i had in my mod and what it did so you have a better place to start with your own settings.

did you actually download and test my mod since i posted it here at subsim?

[JREX53]

Originally Posted by WEBSTER

i dont know whos mod you looked at or maybe you just think you know whats in my mod but you say things that sound like you havent really looked at it or if you did it must have been a prereleased version or something before i finished it because ALL my ships DO have the same drag coeficient.

you say your doing something different yet it sounds like an exact redo of my mod?????

i dont mind if thats what your doing because its all about making the game better but like you said, its a hell of a lot of work to do all those files so i want to be sure you understood what i had in my mod and what it did so you have a better place to start with your own settings.

did you actually download and test my mod since i posted it here at subsim?

You were right, I am sorry. I went back and looked at your final release ad yes you did set the drag as a constant for all ships. I had made my statement on what you were saying when you first started working on your mod.
Which brings to mind a statement I had made to you about not using drag coefficients to control ship acceleration. It was in your Ship Stopping thread:

"Originally Posted by WEBSTER
Quote:
Originally Posted by gimpy117
this would really change the game. ships can't just accelerate to avoid torpedoes as well anymore and V&W destroyers (or the Japanese equivalent) can't come screaming in at 35 knots to ram you after traveling with a convoy at 7 knots.

well there is a hard coded issue where all ships get a free jump to 0-5 kts in 10-15 seconds and from 5 kts up you can actually control what they do, so they still can move out of the way on you but a bow shot should clip them in the rudders unless your too far away. but this is still better than stock where they go 0-5 kts in 2 or 3 seconds.
Webster,"

And I said then

"That isn't exactly accurate. I have been able to get merchant ships to only make 5 to 6 knots in the 1st minute, and to get them so that they don't reach their top speed for up to 20 minutes by just changing the engine HP and engine RPM.

As a suggestion, I would not use just the drag coefficients to cause the speed changes. You lead yourself open for weird things to happen in game. "

Which would mean, to me, that I gave you the idea to not use drag coefficients to control your ships, but yet you have not mentioned the fact, in your readme, that I had an influence on how you did your mod.

Frankly I don't really care if you did or not, but it would have been nice.