[WIP] Improved Ship Physics

[merc4ulfate]

Those unruly hit points must be what I ran into ...

I had 11 fish in a freighter and it would not go down.

I reverted back to ISP 1, reloaded a save at that location and time re-fired at the ship and it went down in two fish.

ISP 2 changes or cause a miss somewhere so that fish have less value or something.

11 fish and not sinking on a medium composite is just unheard of. I waited three days at least and it just sat there dead in the water.

[waffle]

Indeed something with how in RFB ships sink based the flooding model and not the old hp system. Sounds like Torpx is already on top of it tho with the crashspeed variables

[TorpX]

Originally Posted by merc4ulfate

Those unruly hit points must be what I ran into ...

I had 11 fish in a freighter and it would not go down.

I reverted back to ISP 1, reloaded a save at that location and time re-fired at the ship and it went down in two fish.

ISP 2 changes or cause a miss somewhere so that fish have less value or something.

11 fish and not sinking on a medium composite is just unheard of. I waited three days at least and it just sat there dead in the water.

I agree. It is a nonsensical result. The torps and shells are the same, but I did change the CrashSpeed. In the stock files, the values for the surface ships are all either .5 or 1, same with RFB. I had changed them to .1 to eliminate sinking in heavy seas. I didn't think it would impact sinking from weapons. Holed compartments should still flood the same, after all. Maybe the crews were able to pump out water as fast as it came in?

I did some more testing with the merchants. Of the 10 selected, 7 were able to go 24 hrs in 12 m/s waves without problems. Two sank, but I think it is partly a matter of stability, and I can fix that. The Hog Island type 'A' lost speed and seemed to be taking on water after ~20 hrs., but was still going at 24 hrs. This ship has a low freeboard, and is a likely candidate for trouble in rough seas.[This with a CrashSpeed of 0.5]

Indeed something with how in RFB ships sink based the flooding model and not the old hp system. Sounds like Torpx is already on top of it tho with the crashspeed variables

Well, I was pretty sure it had to be the CrashSpeed; I didn't change anything else in the damage dept. I guess I will change the Naka class CL, since I can't think of any good reason why a light cruiser should have more hit points than the Yamato.

[waffle]

Very cool, thanks for being awesome torpx!

[TorpX]

Originally Posted by waffle

Very cool, thanks for being awesome torpx!

Well, maybe not.

While I was testing the sea-keeping, I decided to torpedo some of these ships. Of ten ships, 2 sank with one torp, 4 sank with greater effort, and 2 not at all (2 were not hit). That seems to eliminate the CrashSpeed theory.

My next hypothesis was that changes in the ships' mass was the problem, but that didn't seem to pan out, either.

I did manage to get my test ship, a Nagara Maru, to sink, finally, by changing the submerged displacement and draft to zero. I don't really know what's going on with this.

In the stock files, most ships have a defined mass, and undefined displacement/draft, but a few do. In RFB, most ships have a undefined mass, and a defined surface displacement/draft. It isn't clear why this is so (at least not to me). I will pretty much have to start from scratch on this.

Without any rhyme or reason in this, I may have to test each ship, to make sure they will sink.

For those who were using, or want to use ISP 2.0, I would recommend either going back to ISP 1.1, or deleting the 'Sea' folder from ISP 2.0 before you enable it.

[TorpX]

More testing today............

I think I've figured out why some ships are reluctant to sink.

I set up 6 ships in another mission, 4 merchants (at least 3 of these are in the 'we no sinky' club, the Hog Island (which would sink ok), and a Kuma light cruiser to round out the group.

First, I set the submerged draft to a value close to the surface draft. Then I fired 2 torps at each. Only the Kuma sank. I repeated the mission to see if the Kuma CL would sink with one torp and found it seems designed to sink. Note that RFB doesn't alter the Kuma; it has only 400 hit points.

Then, I increased the submerged depth on all the ships to stock level, and hit them with two torps again (except just one for the Kuma). All but the Akita Maru sank. Gave it another; still floats.

Looking at the Akita, I increased the sub. draft from 12 to 15m, and repeated the mission. Two torps and they all sank, though not all quickly.

It seems that the submerged draft must be high enough to have the water over the ship's side. If not, it will sink down part way and stay there. I'm not sure if there is any substantial disadvantage to having it higher than necessary. I'll have to do some more testing here.

In ISP 2.0, I had set the values pretty close to the surface draft. The idea here was to have heavy seas change the way the ships maneuvered, but didn't know it would have an impact on the sinking mechanics. For ships with little freeboard, this doesn't seem to matter, but with others, this would seem to be critical.

[waffle]

hmmm interesting thanks for the updates torpx!

[TorpX]

I've done some more testing with this mission.

I've set the submerged draft of these ships to '0', and found they will often sink with 1 hit. I was concerned that maybe they were too vulnerable, so I ran the mission with RFB alone, and found similar results. The Kuma was a little odd in that a hit in the stern area was survivable, but not in the bow, or middle. Two would finish it quickly.

I'm satisfied that this will fix the no sink issue, but I'll do some final checks when I'm ready.

Also, I'm doing some testing with new turning schemes. The reason being to reduce the constant helming problem. I found a set of numbers that worked ok with the Nagara Maru, but I'll need to test it with a fair cross section of vessels before I can consider it a go. It uses a very low LR drag, so I have some doubts. In past tests I noticed some squirrely behavior with this sort of thing. I'll just have to see how it goes.

***

About the 'Warship Damage Model', I mentioned the other day, I was searching my drive and found it. There may be more than one version, but I think this is the only one I have. It is labeled "RFB_WDM_17Jan09". I was excited to find this, but there was no readme or documentation inside; perhaps it was overwritten or lost. Anyway, looking inside I found only one ship; the CL Agano. I guess it was a project, that was never completed.

[waffle]

How goes things torpx!

Currently running with isp 2.0 without the sea folder included and everything has been going smoothly.

[TorpX]

Time for another update!

I meant to post this a few days ago, but I'm still busy working on this.

I think the sinking issue is solved. I still have to do final tests, but I don't anticipate any problems. I'm tinkering with the stability of the ships now, so I want to test sinking after I've made the changes. There is no problem with the ships being unstable; rather the reverse, the GC values I used in v2.0 seem to make the ships too stable. I want them stable in calm weather, but they should roll about some in rough seas. Unfortunately, there is no formula I can use to calculate/predict results. I must use trial and error, so this is a tedious process.

I've finished with a new turning scheme. It should help the 'constant helming' issue significantly. I think this is worth some elaboration:

There are 3 basic factors I had in mind here,

1. power and acceleration

2a. turning circle

2b. turning speed

Note, that I divided turning into two parts. To a large extent, improving these are contradictory objectives. I tried very hard to reach targets that would allow realistic performance in all these aspects, but try as I might, I could not get the numbers to stretch that far. I could have any 2 out of 3, but not all of them. In v2.0 I made the turning circle a priority and didn't worry too much about the turning speed.

Later, retesting some merchants produced some discouraging results. Not all ships suffer the same speed loss in turns. It is more dramatic in big, underpowered ships like old battleships and merchants. Of course, this leads to the very unrealistic slow-downs when ships do the 'constant-helming' thing. I could forget about realistic power/accel. and simply "dial up" the power of slow ships, but I certainly don't want to do that, nor are the other choices very appealing.

After much thought about the problem, I decided on a two-pronged approach: Reduce the rudder drag and speed loss for larger ships, especially capitol warships and merchants, and consider turning circles to be secondary here. For the escorts, ASW ships, and most smaller ships, make the turning circles tighter and realistic, and consider turning speed secondary.

The large ships (and the merchants, especially) are underpowered, and need to have the best possible turning speed. If they are configured to turn tight, they slow down badly, and they cannot get back up to speed, quickly. These ships benefit most from using a minimal rudder drag.

The escorts, most of which are faster, ships do not slow as badly as the merchants, and can accelerate quickly coming out of a turn. I consider it more important for these ships to have a tighter turning circle. Obviously, this helps them lay out DC patterns.



In terms of game numbers, I've found that lowering the LR (left-right) drag does not produce a linear effect; As one tries low values below 0.1 and even more so below 0.05 there is little improvement in the turning circle. At '0', all control is lost; the ships slides sideways and slows down drastically. For the Nagara Maru, 0.02 seemed to be the threshold for stable turning. In terms of the circle diameter, there is no appreciable benefit of .02 over .05. I chose to keep the LR at 0.05 or above.

The rudder drag and prop factor are the other side of the coin. The prop factor, in itself, doesn't seem to cause any speed loss, but trying to use a zero drag with a high prop factor leads to unstable turning, where the ships turns past the desired course. By experimentation, I found I could use a rudder drag as low as 0.0025 with a prop factor of 0.5, provided the LR drag was not too low. For tighter turns, it is necessary to increase both the rudder drag and prop factor.

I haven't had time to do any specific tests related to the performance of these ships when 'constant-helming', but I am hopeful that they will be able to keep up their speed a lot better. Of course, this isn't a complete fix, but, perhaps, the next best thing.

[waffle]

Sounds great thanks for the update torpx!!!

[hugh]

Sorry if this is a stupid question but I'm guessing you popped those changes into the downloadable version of 2.0?

Keep up the good work.

[TorpX]

Originally Posted by hugh

Sorry if this is a stupid question but I'm guessing you popped those changes into the downloadable version of 2.0?

No, I will have that, and other improvements, in v2.1 as soon as I can finish the work. It would take too much time to add incremental improvements week to week. I'm working on it at a goodly pace, and I hope to have it done in about a week.

Today, I spent testing the stability of ships in moderately rough seas. I've finished Japanese ships, and am working on US ships now. After I finish with this last series of tests, the work will be nearly done. I could have simply set the GC (center of gravity) low and have them very stable, but I want them to pitch and roll a fair amount in rough weather. This is a tedious process, involving small changes and observation, repeated over and over. There is really no way to blaze through it.

I do think people will be pleased with the final result.

***

A few days ago, I was doing tests with the AI Uboat9 and the AI Sen Toku, so they can be added to the fixes. I found out the game seems rather fussy about how these vessels sink. Depending on the changes I made, I might torpedo one, and sink it, but not get credit in the log, OR, torpedo it, and get credit for it 'going down', but have the thing floating there hours later.

Does anyone know just how the game handles this?

Also, I've found that when I put the JPGunBoat01, and JPGunBoat02 (these are small armed riverboats), in a mission they will show up, but not be ID'd by the crew (no auto targeting lock on), and not show up in the map contacts. They will shoot back ok, and can be sunk, but no way to get credit for them. This still happens, even with just RFB + RSRDC alone. Does anyone know why this would occur?

[TorpX]

Just a brief note here - I am finished with the ship stability tweaks and have only a few tests to do, so I can update and edit the documentation.

[TorpX]

ISP v 2.1 is now in the downloads section, ready to go!

ISP v 2.1

I'll briefly discuss a few things, that I either did not fully explain before, or just added recently.

Or course, the sinking issue is fixed.

I tweaked the GC values of all the ships, so they had, as well as I could observe, a realistic level of stability.

I also changed the mass of all the merchants. I only realized this recently, but RFB used the GRT rating of the merchants as the displacements. Meaning a 1250 GRT freighter weighs, and has a displacement of, 1250 t. However, the GRT is only a standard cargo capacity, and has nothing to do with the mass, or weight. Lacking any better guidelines, I went back to the stock mass values, which made for heavier, and more sluggish ships.

I changed the ranges of the S-class some. The reason for this is that I believe the reference I used, Norman Friedman's work, contains figures that are in error. I'll explain what I mean. Freidman gives the following figures for the S-18 and S-42:

S-18
3,420 nm @ 6.5 kn. Normal
8,950 nm @ 9.5 kn. Maximum

S-42
2,510 nm @ 6.5 kn. Normal
10,000 nm @ 8.1 kn. Maximum

So, what's wrong with these figures? Well, to begin with, the maximum ranges (using FBT's), are given at a higher speed. The extra weight would increase the draft, and lower the cruising speed. Looking at the other figures given, I found the weights for the fuel (in long tons):

S-18
53.93 normal
97.14 max

S-42
59.03 normal
150.94 max

So, how can a S-18 increase it's cruising range by 161%, with only 80% more fuel, and boost their speed in the bargain? The answer is it can't. The most reasonable explanation is that the cruising speed figures were transposed, and should read:

S-18
3,420 nm @ 9.5 kn. Normal
8,950 nm @ 6.5 kn. Maximum

S-42
2,510 nm @ 8.1 kn. Normal
10,000 nm @ 6.5 kn. Maximum

I tweaked the Sim.cfg file values. Mainly, lowering the thermal layer attenuation values. People have been saying that the thermal layer offers almost a cloak of invisibility, and looking at the figures, I could see why that might be the case. I put in a spare file with the old v 2.0 values, in case people want to use those.

I tried to do a quick test of the turning/constant helming issue, but the game didn't cooperate. I put two lone merchants on a straight course (one ~ 10 mi. behind the other so I could test them separately. I fire torpedoes in front and tracked their movements. Instead of doing the constant helming thing, they turned to the track, kept turning and basically reversed course. This was not due to anything in my mod, as this was a control test with RFB + RSRDC alone. Maybe I'll try again, later. I went back and checked the mission, and these were 'veteran' merchants. That may make a difference.

Perhaps people who use the mod can get some data on this in the coming weeks.



Happy Hunting!

- TorpX