(WIP) Ship's Acceleration Physics

JREX53 · 04-27-09, 09:38 PM

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.

04-27-09, 09:38 PM	#1
JREX53 Frogman Join Date: Jan 2006 Posts: 300 Downloads: 353 Uploads: 13	(WIP) Ship's Acceleration Physics 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. __________________ Jim Last edited by JREX53; 08-24-09 at 09:58 PM.