Cavitation Profiles

[Halcyon]

. . .

[FPSchazly]

I've heard this can be determined mathematically by examining the cavitation profile specified for each boat in the boat config file. Forgive the vague terms, I'm not sure of the specifics.

My point is it's not necessary to determine these empirically.

[-Pv-]

Do you have an example of doing this as you describe or the ID of someone who claims to have done this?

When I look at the cavitation numbers in the default submarines, they are all the same, but the exact depths/speeds are a little different for each sub I have used. So far, I've found no other way than experimenting, the easiest is to use the Navigation mission with each sub.
While I have started creating tables of my own, they are not detailed down to the knot yet.
-Pv-

[FPSchazly]

Did some digging.

http://www.subsim.com/radioroom/showthread.php?t=232919

It's just a linear formula y=mx + b, where x is the speed in knots and y is the depth in feet, with m equal to the first parameter (20) and b equal to the second parameter (-100). Were you testing the depths manually or using the new automated depth control?

Although 19 vs 20 are in fact not identical, they're very close. Honestly, when you're diving and the boat is at an angle, I don't know how useful the keel depth would be to determine cavitation given that the bow and stern would be at different depths. I'm not sure if the game takes that into account.

[-Pv-]

In all the default sub vessel files CavitationParameters=20,-100 is used yet the actual 3D sim values are slightly different from each other when tested.
There is more to this than the obvious.
-Pv-

[FPSchazly]

It could be related to the distance between keel and screw centerline.

[-Pv-]

^^^
Makes sense.

[Halcyon]

Did some digging.

http://www.subsim.com/radioroom/showthread.php?t=232919

It's just a linear formula y=mx + b, where x is the speed in knots and y is the depth in feet, with m equal to the first parameter (20) and b equal to the second parameter (-100). Were you testing the depths manually or using the new automated depth control?

Although 19 vs 20 are in fact not identical, they're very close. Honestly, when you're diving and the boat is at an angle, I don't know how useful the keel depth would be to determine cavitation given that the bow and stern would be at different depths. I'm not sure if the game takes that into account.

I tested by manually adjusting the ballast to go down 1 foot at a time. I went back and forth several times between +19 or +20 feet for several speeds to find which depth triggered the cavitation.

The slope intercept formula isn't linear in my testing. Maybe they round up or down for fractional depths...but that data is locked into the code and the only way you know for sure is manually testing.

As far as angles, my boat was level the entire time during testing because I left the planes at 0.

[-Pv-]

Nice
-Pv-

[Kazuaki Shimazaki II]

Maybe the real lesson here is to actually play it for real and not un-necessarily take your boat right to the theoretical limit. I remember doing similar things back in Dangerous Waters, and it is easier to do now that you are allowed knot-by-knot control. But should we be encouraging such "gamey" behavior?

[Kazuaki Shimazaki II]

I agree just being completely ignorant or cavalier is gamey. However, neither do real submariners go "According to theoretical calculations, my submarine will cavitate at 10 knots at under 99 feet. I am now exactly 100 feet, so I will order 10 knots. When I get to exactly 113 feet, I will order exactly 11 knots."

You do such things in a game (I did too, in DW) because it is completely predictable in this regard and really your boat is free. If your lives depended on it, most likely you'll wait till say 150 feet before putting the 10 knots on, just in case.

So I suggest it might be more immersive and realistic if you just ran with a basic idea of roughly where the line is and play it safe from there.

[-Pv-]

If cavitation charts are no good to you, ignore them.
-Pv-

[Capt Jack Harkness]

It could be related to the distance between keel and screw centerline.

Isn't the depth shown actually the vessel center line rather than keel?

[FPSchazly]

In the game? I have wondered that based on the "Conditions" tab. It's supposed to be from the keel.

[Halcyon]

In the game? I have wondered that based on the "Conditions" tab. It's supposed to be from the keel.

Looks like it goes off the bottom of the rudder.

https://s26.postimg.org/fu7fvc6mh/cw1.jpg
https://s26.postimg.org/70gje8jnt/cw2.jpg

[subcritical]

If we just had a good throttleman we wouldn't have cavitation unless it was ordered! Maybe a game improvement to have a cavitate button? And in real life, at least 20 years ago, it was a basic calculation. The calculation works for steady state to steady state speed, not transiting from one speed to another. That depends on how aggressive the throttleman is.

-sub

edit: corrected spelling of cavitate!

[Bubblehead Nuke]

If we just had a good throttleman we wouldn't have cavitation unless it was ordered! Maybe a game improvement to have a cavitate button?


YES!. Devs.. This please!

As a qualified throttleman I can ASSURE you that we would NOT cavitate on a bell change unless ORDERED to do this. If cavitation was to occur the EOOW would notify conn that they were cavitating. They would then acknowledge the report and order us to continue to answer the bell.

If you got the bell change with the a ring of the engine order telegraph (a cavitate button I guess) that would indicate a order to answer the ordered bell without regard to cavitation.

Example: When conn ordered ahead flank for torpedo evasion we would get the OET to Ahead Flank with 3 rings of the OET bell. That was our clue to stand on the power.

[ETR3(SS)]

YES!. Devs.. This please!

As a qualified throttleman I can ASSURE you that we would NOT cavitate on a bell change unless ORDERED to do this. If cavitation was to occur the EOOW would notify conn that they were cavitating. They would then acknowledge the report and order us to continue to answer the bell.

If you got the bell change with the a ring of the engine order telegraph (a cavitate button I guess) that would indicate a order to answer the ordered bell without regard to cavitation.

Example: When conn ordered ahead flank for torpedo evasion we would get the OET to Ahead Flank with 3 rings of the OET bell. That was our clue to stand on the power.I can confirm this from my time as helm. Cavitation will occur if you go too fast for a given depth though, and that may be what they're modeling. Watching the screw go from All Stop to All Ahead Flank at 500 ft, the in game Throttleman cranks open the Ahead Throttle without regard to cavitation occurring due to putting too many turns on the screw too quickly. But in this instance no cavitation occurred when it should have in real life. So I think it's safe to say the cavitaion model is a simple depth vs speed profile.

Also that Throttleman should blow the ORSE team away with his ability to go from Ahead Flank to All Stop Stop the shaft, all in under 3 secs. :haha:

[subcritical]

Qualified TH here also. Crash backs from Flank were awesome! We did a bunch of these on the way into the shipyard in which the shaft was being replaced!

[-Pv-]

The ramification of what's suggested here in the last few posts is you will not get the turns requested unless:
1) You pressed the additional "whatever" button.
This has the additional ramification that the software has to decide if it will give you the nearest lower bell or the nearest lower absolute knots speed.
OR:
2) The depth for the requested speed is sufficient to prevent cavitation.
This has the ramification if the software will automatically increase the bell response OR the nearest lower exact knot response automatically as the boat dives.

-Pv-

[subcritical]

Yes, precisely. This is a more realistic scenario, while maybe being too complicated for the desired game play. I personally would like it.
1) the button would be the cavitate button. All forward bells are implied as do not cavitate (unless you get the 3 rings). I can't remember if Flank followed that rule or not. All backing bells are cavitate, unless told otherwise. In the software under normal changes the forward speed would need to follow the cavitation profile until the ordered bell (or speed) is reached. If the cavitate button is activated then you answer the bell aggressively.
2) if I understood correctly you mean that as you change depth the subs speed may or may not need to change. That would be correct, as you go deeper, maneuvering can answer a higher speed until the ordered bell (or speed) is reached. Likewise if you are going shallow, lower the answered turns to prevent cavitation.

[-Pv-]

Keep in mind one of the game challenges is cavitation. If the enemy subs were also equipped with auto cavitation prevention, they would never cavitate unless they are aggressively attacked or thought they might be.

Right now, they sometimes cavitate by accident just as a real player might while learning or in a moment of inattention.

In Full Auto not only would you never cavitate under auto control (I suggest the possibility of a "Full Auto" button- in which the sub would never cavitate unless instructed to by "Full Auto" = off) and the enemy subs would never accidentally reveal themselves and would only cavitate when under escape power.

Maybe disable this feature under max skill level. I suspect having this feature would require some major adjustment to AI enemy tactics logic.
If the concept of an "accidental/incidental" AI cavitation is retained, while under player "Full Auto" there should also be the possibility of the player crew making a mistake, providing an incentive to turn FA off to afford the player the opportunity to use the skill to prevent it entirely.

-Pv-

[ETR3(SS)]

Yes, precisely. This is a more realistic scenario, while maybe being too complicated for the desired game play. I personally would like it.
1) the button would be the cavitate button. All forward bells are implied as do not cavitate (unless you get the 3 rings). I can't remember if Flank followed that rule or not. All backing bells are cavitate, unless told otherwise. In the software under normal changes the forward speed would need to follow the cavitation profile until the ordered bell (or speed) is reached. If the cavitate button is activated then you answer the bell aggressively.
2) if I understood correctly you mean that as you change depth the subs speed may or may not need to change. That would be correct, as you go deeper, maneuvering can answer a higher speed until the ordered bell (or speed) is reached. Likewise if you are going shallow, lower the answered turns to prevent cavitation.Flank followed the rule too. I think we may have to look at a complete overhaul of the ships speed mechanics in game to get closer to reality. In the mean time a cavitation profile chart for each boat, and learning that profile, would also put you closer to reality as well. Before qualifying OOD you had to qualify EOOW, so an officer would learn early on the operational constraints in regards to speed vs depth for cavitation.

[-Pv-]

Right now, creating your own charts for the subs you "fly" the most is relatively easy, just very tedious. Some do it knot for knot for depth, but I tend to use a half-dozen relatively easy to remember ranges. Takes less time to create.

What this thread was originally created for is a central place for players to POST the cavitation charts they have discovered for the various subs they fly and post them here for others to use which would be useful to all beginner commanders to help them over the learning curve and as part of their make-believe "certification" course.

-Pv-