RL question... speeding up and slowing down
 

Okiedookie, question here for the RL bubbleheads...

So your on a 6000 ton sub at moderate depth going 30knots and your captain orders all stop. How long does it take for the sub to actually come to a stop?

Ingame there are pretty good decellerations, but I'm thinking that a RL sub isn't made of paper... those things are huge and heavy and it would probably take a while to bleed off speed in RL..

Anyone have any experience that would like to share. Also... I'm thinking that it should probably take a 6000 ton sub a couple of minutes to reach "max" speed (though in about 30 seconds it would probably have achieved 2/3 of its max).

thanks
lb

It depends on the boat. Even boats of the same class have different screws and configurations (for example, dihedrals with external countermeasures) that can change that.

Tridents take forever to do any maneuver. 688s much less so.

Slowing down
 

If you just shut the throttles and coast-a long time- dead stop probably 30 minutes or more.. If you go from flank to all back emergency, on average 5-6 minutes and the noise and vibration is a bitch. You practice this a lot for loss of lube oil drill.

Ron Banks MMCM(SS), USN(Ret)

5 or 6 minutes? Dang.. you were on an OLD boat.

Hm... clear as mud huh?

Well if you can't talk about it because of "top secretcy" or whatnot that's fine. Though it doesn't seem like there's anything secret about it. Its just a matter of experience with large ships (of which I have none).

... okiedokie then... well lets open it up to ANY large ship about 6000 tons ( I guess a medium sized cargo ship would do?) Anyone with ANY experience with large ship maneuvering that can comment on how long it would take the ship to slow to... say 3 knots from full speed of say 15knots?

What were you time.
 

Bubblehead nuke;
Yes I was on an old boat, I am old, so what is your point? Was my number high or low. If you are going to tell me it took you longer, then on a real loss of lube oil you must have had to replace bearings.
Bubblehead I went on my first boat in the early 60s, most of those boats are gone now, but we got the job done.

Ron Banks MMCM(SS), USN(Ret)

A 4600ton frigate (M-class or Karel Doorman, RNLN) will go to top-speed (roughly 29 knots) in under 2 minutes and will stop itself in 1 boat length by going full reverse on the pitch of the proppellors. Been there, done that.

This should give you a nice view of the manouvrebility (dreadful word btw) of todays frigates.

Wow, full stop in one boat length... I can imagine all the split coffee. :lol: That's pretty impressive. What about without going to full reverse?

I guess strong boats can achieve nice accelerations .. but getting to full speed in something as dense as watter can take some time .. so I guess top speed will always be in minutes, but 0-10 kts can be achieved in seconds.

But I'm just guessing .. my biggest (and almost only) boat trip was Belgium-Britain traject :|\\

IIRC, our criteria was 30 seconds.. from the loss of lube oil siren till a stopped shaft and that was from a flank till a stopped shaft. The REAL PITA was HOLDING the shaft still. As the boat slowed you had to back off the throttles to compensate for the lower drag. You did not want to put it on the lock till you were pretty slow.

I have LOTS of respect for the older boats. The Skipjacks and Permit classes were tiny. Yes, they were lightyears ahead of some of the S-class boats but I have to tell you, *I* got claustophobic when I got to tour a few. The fact that they kept going and going and GOING was what impressed me. They had much smaller plants, smaller hulls, but the same sized if not larger hardware.

And hey, I am getting old. There was no slam involved sir.

Lets just say that when you stomp on the throttles there is nothing like feeling 6900 tons of sub accelerate (yes, you sometimes have to reach out and steady yourself). Even better is that the sudden increase of torque to the shaft rolls you about 10 degrees initially. It only goes away after ships speed makes the sail surface (not the sail planes but the vertical sail itself) more effective and it rightens the boat.

How fast can they accelerate? *IF* you are ordered to cavitate, Flank speed comes up REAL fast. It depends on how well the reactor operator and the throttleman cooperate.

You'd simply coast to a halt, we didn't do this normally, But the built-up inertia @ 29 knots, I reckon it'll take a while :)

and seldom do you want to make the massive noise of going from a flank bell to back emergency with the manuevering, conn cavitate order at the same time. Only events like the sternpmanes jammed on dive would cause one to do such a thing. Well that or Sammy Rickover getting his jollies on Sea Trials. The plant itself could torque the shaft to the point of breaking it. That is why as been mentioned here, the real key is the skill level of the ship control/engineering watch on duty.

I can recall being woke up while offwatch to come sit on the sternplanes for an anticipated drill for an inspection. Nothing more flattering than such an event, worth a box full of commendations.

That's what I'm thinking that most subs would do since they wouldn't want the extra prop noise going in reverse (unless an emergency like Rip mentioned). My gut says 4-5 minutes to bleed speed from 30 knots to 3 knots on coast.... but that's just taken outta thin air.

Shaft engineering has always amazed me. How to take a X ton shaft undergoing tremedous torque and RPMs, and punch it through a pressure hull with seals intended to withstand thousands of feet of water pressure... and do so without friction or noise. Its amazing what engineering can do. :cool:

Bet these new "shaftless" drives that General Dynamics is developing will simplify things though. http://www.darpa.mil/body/news/2005/tango_bravo.pdf