could US subs dive/surface so fast?

[Laffertytig]

ive noticed that compared with gwx in SH3 i can dive/surface a lot faster in SH4. also were US subs able to surface/dive when not moving like in SH4?

[seaniam81]

The american subs were pretty quick in getting under some reading I've done suggests around 30-50 seconds for a dive. My reading also suggests it took a lot longer to surface, mostly on perpose to stop hull poping. And yes a boat could dive and surface with out forward speed. It took a lot of compressed air and was noisy but it could be done.

[mrbeast]

IIRC crews trained to crash dive in around 30 seconds, at least that was the target it also depended on the type of sub. Something big such as the USS Narwhal took longer and was one of the reasons why large cruiser type subs were abandoned in favour of fleet boat types.

[mookiemookie]

The american subs were pretty quick in getting under some reading I've done suggests around 30-50 seconds for a dive.

Everything I've read suggests this also.

[Laffertytig]

yeah that would be for a sub runin at flank then doin a crash dive, not for a sub on the surface or at periscope depth at all stop. in SH4 u can go from periscope depth to 90 metres in 2 min then back up in 2 mins, just like an elevator!

the main reason skippers didnt wait to see the torps hiting was so that they had time to go deep. stayin at periscope to should be a risk but not so in SH4. i know in SH3 the major mods all fixed this to more realistic levels so that it took more time to dive and surface but it look like noone has done this sith SH4 yet.

i would do it myself if i knew what files to change, anyone got any ideas?

[Wilcke]

This is an interesting topic, I suppose that since mechanically the sub can come to periscope depth so quickly without the "noise" and alerting the escorts, one could just do it a bit slower and hold at various depths instead of just hitting the old "P" button.

When using the Trigger Maru mod its bit more realistic in that once your torpedoes are on their way its best to just go deep evade and plan a reattack for a couple of hours later from a new position.

Would be cool if one could implement the "hull plate popping" and have the escorts key in on that. There is always something to work on.

[Ducimus]

My reading leaves me to believe that 30-35 seconds was the goal, with 40ish being the average.

[Powerthighs]

An interesting tidbit I just read in Submarine! (page 14) by Ned Beach:

"Trigger, in common with her sisters, always 'hangs' on a dive at about thirty-five feet. ... Will she ever break through? ... Forty feet. She's going under at last. Fifty feet. We're under!"

Just wondering if this hesitation is modeled (I'm guessing no) or if anyone has heard of it before.

[Laffertytig]

yeah ducimus for crash dives at fast speed, not at all stop! the reason why this is really obvious in SH4 is the vast majority of attacks are made from periscope depth at very slow speed because i can never seem to get close enough on the surface.

the 1st thought should be to get as deep as possible but currently u dont have to worry bout that as u can get down to 90 metres in 120 seconds which defo aint right. im surprised that RFB hasnt altered this as it goes for realism, has TM made any changes to this?

i guess i could just restrict how fast i dive but sureyl there must be a way to fix this. ive just been playin GWX 2.0 and they have it spot on, it takes a lot longer to dive and surface (not crash dive)

[seaniam81]

IIRC TM did change the dive speeds for a crash dive from flank and from standing still.

[Laffertytig]

well he has then thats another reason to try TM then although RFB is still doin the business for now.
ive found out what file i need to mod so if anyone has any info on how fast a US sub could surface/dive at very slow speeds that would be great

[swdw]

IIRC TM did change the dive speeds for a crash dive from flank and from standing still.
True, but as mentioned earlier, the dive times in TM are even faster than the ones in RFB which is the opposite of what Laffertytig is looking for.

And BTW Lafferty, if you read the earlier post you'll see why this isn't fixed in RFB yet. till looking where to make the needed changes.

[scrag]

US Boats in the Pacific AOR dived slower than there German counterparts in the Atlantic - one reason for this was the better radar and much longer distances in the PAC Vs. LANT. Consider that the Germans were faced with a massive Air ASW threat which forced them to dive faster or to eventually design a boat that was better submerged than surfaced (the 21 class). The game(s) reflect this pretty well. Even at Flank it takes a while to get down. Referencing Ned Beach's issue we still experience problems at times - particularly coming to PD and passing a layer. A temperature gradiant can add or subtract thousands of pound of weight which can cause a "stall" and have the ship stuck at a less than optimum depth. Might be a real pain in the but to model that and frankly probably not worth the time or required processing.

[Ducimus]

A "dry" crash dive in TM, being on the surface at around 8-9 kts, takes anywhere between 43 to 47 seconds, depending on boat type.

[Laffertytig]

thats all good and well but from all stop (or for arguments sake PD) to 90 metres it takes around 2 mins which is ridiculous. im talkin about RFB and vanilla here and someone said your mod if even faster than this.

Ducimus, if your mod does sive faster than vanilla id be very interested to know what setting u changed and by how much to increase the dive speed.

[CaptainHaplo]

This probably needs to move to the mod side of the house - but the MBT flood speed is what controls the speed of diving from the surface. Increase it, and you get a rock that can drop like crazy. Decrease it, and you get a fat lady that cant even get to the bottom of a backyard pool in an hour of trying.

The thing is - I am not positive - but I think this also controls the speed of depth changes. I have played with the values alot in for the Nuke sub mod, and it seems to be the factor used.

The biggest problem is balancing realistic dive times from the surface with the depth change times with one number.

[beartooth91]

I haven't brought this up before because 1) there wasn't a topic to do so, and 2) I'm not sure what can be done about it game-wise:

I am an ex-Navy Nuke submariner (USS Pintado SSN-672 '87-90), and US subs - including WW2 fleet boats normally surfaced without air. When submerged, boats are normally trimmed to have a slightly negative buoyancy (so going to all stop to preserve the batteries isn't realistic either). Just prior to surfacing, the order "Prepare to surface without air" is given and the boat is driven to the surface with propulsion. At this point, the main deck is awash and the shortly thereafter, the Low Pressure Blower is started which blows the remaining water out of the ballast tanks. My reading indicates our WW2 fleet boats surfaced the same way - I believe, the LP Blower in those days was called the Turbo Blower. If memory serves, it took Pintado 10-20 minutes to reach a normal surface running trim after the LP Blower was started.
Just my 2 cents here.

beartooth91

[Laffertytig]

i cant see this file affectin depth charges as there is a seperate file for this. if the MBT flood speed affects dive time then what do u think the "diveBT flood affects then?

probably better lettin this thread die as we have established subs obviously couldnt dive/surface this fast at very low speeds. i have another similar thread on the mods forum, if people could respond to that thread instead of this one that would be great

cheers

[Wilcke]

I haven't brought this up before because 1) there wasn't a topic to do so, and 2) I'm not sure what can be done about it game-wise:

I am an ex-Navy Nuke submariner (USS Pintado SSN-672 '87-90), and US subs - including WW2 fleet boats normally surfaced without air. When submerged, boats are normally trimmed to have a slightly negative buoyancy (so going to all stop to preserve the batteries isn't realistic either). Just prior to surfacing, the order "Prepare to surface without air" is given and the boat is driven to the surface with propulsion. At this point, the main deck is awash and the shortly thereafter, the Low Pressure Blower is started which blows the remaining water out of the ballast tanks. My reading indicates our WW2 fleet boats surfaced the same way - I believe, the LP Blower in those days was called the Turbo Blower. If memory serves, it took Pintado 10-20 minutes to reach a normal surface running trim after the LP Blower was started.
Just my 2 cents here.

beartooth91

Thanks for the information, I have only been driving these virtual subs for about a year and I always wondered about the Dive/Surface abilities. Now I have a better picture!

Who knows how our sim is coded in replicating this dive/surface activity.

Thanks

[ssbn627g]

I haven't brought this up before because 1) there wasn't a topic to do so, and 2) I'm not sure what can be done about it game-wise:

I am an ex-Navy Nuke submariner (USS Pintado SSN-672 '87-90), and US subs - including WW2 fleet boats normally surfaced without air. When submerged, boats are normally trimmed to have a slightly negative buoyancy (so going to all stop to preserve the batteries isn't realistic either). Just prior to surfacing, the order "Prepare to surface without air" is given and the boat is driven to the surface with propulsion. At this point, the main deck is awash and the shortly thereafter, the Low Pressure Blower is started which blows the remaining water out of the ballast tanks. My reading indicates our WW2 fleet boats surfaced the same way - I believe, the LP Blower in those days was called the Turbo Blower. If memory serves, it took Pintado 10-20 minutes to reach a normal surface running trim after the LP Blower was started.
Just my 2 cents here.

beartooth91


I don't remember trimming with slight negative bouyancy. What I remember the goal being is a 1/3 trim. Memeory might be a bit off, but it was ahead 1/3, 1 or 2 degree down angle, hands off the planes and helm with no depth drift or course drift.

But the surfacing without air is right.

[Sailor Steve]

On the other hand:
"The main ballast tanks are partially blown to surface normally."
http://www.maritime.org/fleetsub/chap18.htm#18C

As to trim, WW2 fleet boat doctrine says this:
"Submerged operations are usually carried on with the submarine in the state of neutral buoyancy."
http://www.maritime.org/fleetsub/chap18.htm#18B

Of course perfect neutral bouyancy was impossible to maintain without use of the dive planes and/or pumps, so "hovering" was indeed impossible, and depth-maintenance difficult while silent running.

[Laffertytig]

so the GWX and NYGM mods pretty much have things spot on then in SH3. if it was possible to fix in SH3 then it must be possible in SH4 as well, it just a matter of time i guess

[beartooth91]

On the other hand:
"The main ballast tanks are partially blown to surface normally."
http://www.maritime.org/fleetsub/chap18.htm#18C

As to trim, WW2 fleet boat doctrine says this:
"Submerged operations are usually carried on with the submarine in the state of neutral buoyancy."
http://www.maritime.org/fleetsub/chap18.htm#18B

Of course perfect neutral bouyancy was impossible to maintain without use of the dive planes and/or pumps, so "hovering" was indeed impossible, and depth-maintenance difficult while silent running.

"At the sounding of the signal, three blasts of the diving alarm, or the passing of the word "Surface, Surface, Surface," the various actions necessary are performed.
The bow planes are placed on ten degrees dive and rigged in automatically unless the conning officer gives other instructions. A report, "Bow planes rigged in," is made to the conning officer. Speed is increased to about 6 knots to give maximum lift. Due to the up-angle on the ship, the increased speed makes the inclined surface of the hull effective and the resultant lift raises the ship. The stern planes are used to limit the up-angle to about 5 degrees. The up-angle may be increased by blowing the bow buoyancy tank. Blowing the safety tank increases the positive buoyancy. However, this is not usually done.
The main ballast tanks are partially blown to surface normally. After surfacing, the high-pressure air is secured and the blow is completed with the low-pressure blowers."



And with regard to the 2nd link and quote: I believe that's a very general description. Perhaps its different for WWII fleet boats, but, on my boat it was pretty much common knowledge that all stop for long periods you would very slowly sink.

[beartooth91]

As to trim, WW2 fleet boat doctrine says this:
"Submerged operations are usually carried on with the submarine in the state of neutral buoyancy."
http://www.maritime.org/fleetsub/chap18.htm#18B


Read the above link, but several sentences down:

"The state of exact neutral buoyancy is probably never attained, but the approximation is near enough to allow depth control to be exercised easily by the diving officer. In all normal submerged operations, the submarine is underway at relatively slow speeds. This horizontal motion through the water enables the surfaces of the diving planes to correct the effect of any slight positive or negative buoyancy and also to increase or decrease the submerged depth at the order from the conning officer."

Now, at least in my cold war days, a slight negative buoyancy was preferred I suppose, because at periscope depth, you'd rather sink vs broach and flap your fairwater planes at the Soviets - in the event of a loss of trim control.

[Laffertytig]

yeah i just tested this again with the new GWX mod for SH3. it takes around 9 mins to get down to 90 metres at all stop and u actually sink if u stay at 0 knots:)

spot on

[Ducimus]

The problem with adjusting dive times in SH4, is the mechanics dont behave quite the same way as they did in Sh3.

For instance, the MBT_Flood i have specified in some boats could probably make a type 9D2 in Sh3 crash dive at about the same rate as a sinking rock. Here, i get a reduction dive time from 1min and 10 seconds to 45 seconds. Similarly, going to flank speed and then diving in Sh3 acutally speeds up the process. In SH4, it seemingly slows it down - last i tried it anyway.

[scrag]

Aloha again,
Today's surfacing methods as well as depth control is different than yesterdays. US boats use water flow to damn near overcome most issues. PD is different and albeit more difficult on 88's than 37's or the 21 boats. 637's you could develope a feel for the boat easier than a 688. 688's you are usually a bit behind the problem and often we trim heavy so not to broach - which of course requires more speed and hence a bigger feather which leads to being seen - not good. Another factor not discussed is the direction of the Seas - put your stern into a sea state (ie turning) you are likely to come up. 21 and 774 class boats the computer does a lot of the work - though quick intervention is required to prevent broaches. Surfacing on a 688 is simply Prepare to surface us getting to PD and then broaching the ship (again with speed) and then running the blower. Less sea preasure to overcome the quicker your tanks are in a surfaced condition. I believe in WWII that US Fleet boats had both valves for venting and flooding the MBT's and that the tem "riding the vents" described being a more riskier albeit faster crash dive state. Today's US Boats only have the Valves at the top of the tanks.
Fleet Boats also had the ability to use more tanks to achieve a trimed condition and were generally able to use these reserve tanks to maintain depth control or speed the diving process. Boats then and now had to achieve a satisfactory 1/3 trim (trim dive) to ensure that the ship (like a plan) was in a semi balanced state- so your stores and weapon load out woudl affect all this and went into the calculations by the Ships Diving Officer and checked by the Diving Officer of the Watch. Other effects on trim is salinity in the water as well as temperature (previously discussed). It is more complex than it looks - guys who have punched holes take it in stride but when you have to explain it to those who have not it makes it more cool as it really is very involved. As far as game play goes - getting it close is good enough - the problem with WWII books is that unless you find an author that explains some of this then often the full effect is lost in translation.

[Sailor Steve]

As to trim, WW2 fleet boat doctrine says this:
"Submerged operations are usually carried on with the submarine in the state of neutral buoyancy."
http://www.maritime.org/fleetsub/chap18.htm#18B


Read the above link, but several sentences down:

"The state of exact neutral buoyancy is probably never attained, but the approximation is near enough to allow depth control to be exercised easily by the diving officer. In all normal submerged operations, the submarine is underway at relatively slow speeds. This horizontal motion through the water enables the surfaces of the diving planes to correct the effect of any slight positive or negative buoyancy and also to increase or decrease the submerged depth at the order from the conning officer."

Now, at least in my cold war days, a slight negative buoyancy was preferred I suppose, because at periscope depth, you'd rather sink vs broach and flap your fairwater planes at the Soviets - in the event of a loss of trim control.
I did read the whole article. My point was simply to answer those who insist on negative or positive with the official statement that neutral was the (seldom obtained) goal.

I agree with negative as the accepted norm, to the point that I'm a huge fan of of NYGM's 'Anti-Hummingbird' mod, which makes the boat start to sink at very low speeds or All Stop.