Maybe it's just me, but when they're doing their dive test, and they're supposed to be diving to 62 feet, it seems to me that they maintain that 7 degree down angle a lot longer than what it would take to reach 62 feet. In fact, when they show the boat suddenly list to starboard, it looks like they've already passed 62 feet, and they're still going down even as they right themselves.
Any sub vets have an opinion on this?
Been quite a while since I've seen it. Don't remember the details of how long they were going down nor whether they flooded then blew the Negative tank.
If in the confusion of the list they did not blow the Negative, they would have kept going down with about 7 tons of negative buoyancy.
The list itself was created by a very real problem of having a vent valve stuck.
There are multiple "Main Ballast Tanks" or.. MBTs.
MBT 1 and 7 are large and are forward and aft
MBTs 2 and six however are subdivided port and starboard as further subdivided laterally as well. So you would have MBTs 2a,2b,2c,and 2d... as well as 6a,6b,6c,and 6d. tanks a&c would be to starboard and b&d would be to port. these are the "saddle tanks" the bulges to the hull seen around the middle of the sub on either side.
a vent valve sticking on any of those subdivided tanks would throw the sub out of trim and cause a list as it would shift the center of buoyancy to that side. These valves (2 a-d and 6a-d)do have an emergency vent valves located in the tank top with stems extending through the pressure hull into the control room for hand operation in the event the main vent valves are damaged.
MBTs 1, 2a, 2b, 2c, 2d, 6a, 6b, 6c, 6d, and 7.
So what about number 3, 4, and 5?
MBTs 3, 4, and 5 were tanks not exactly necessary to have the buoyancy to surface, they were additional reserve buoyancy and thus they were able to be converted into additional Fuel oil tanks.
They are known as Fuel Ballast Tanks (FBTs) 3, 4 and 5.
Once the fuel is used up in the NFOTs (Normal Fuel Oil Tanks), the fuel in the FBTs are transferred over into the NFOTS and the FBTs transformed back into Sea Water Ballast tanks, the additional buoyancy giving the sub additional freeboard while surfaced and greater speed with less hullform drag in the water.
without watching the film again I cannot comment on your original point of the question concerning timing, But I would chalk it up to Film-making convention as they needed time to play out the scene in question. In reality, the crew would have just immediately corrected the situation as a non-event, and kept going about their duties.
I joined the Navy to see the world, only to discover the world is 2/3 water!
Oh, I had already chalked it up to artistic license. Time has little meaning in film.
I just wanted an expert opinion on just how far they had deviated from realism, since it looked like they were already pretty close to 62 feet when they started to list, and they kept going down. And yes, she gave the command to "blow Negative to the mark," so we are left to assume that someone did it.
I must have watched this movie at least a hundred times, and this is the first time it occurred to me that they seemed to be diving an awfully long time for such a shallow depth. I also just recently noticed, in the scene where Lt. Pascal walks the plank, that Nitro is wearing a wooden leg.
Thanks for the tutorial. I didn't expect that much information, but I'm not one to turn down a chance to learn something new.
Never such a thing as too much information is there? the day you stop learning is the day you decide to become a Liberal. LOL.
Regardless of the time it took and their going deeper than 62 feet (periscope depth)... there is another problem with the whole scene from a pure point of realism (yes... this is a Comedy I know)
In a properly trimmed and compensated boat, flooding all MBTs will not result in the boat sinking into the deep. It will only settle lower into the water until it is fully submerged but it WILL STOP sinking at that point. Properly compensated and with fully flooded MBTs will reduce the buoyancy of the boat to a NEUTRAL state. Not a Negative state. Just Flooding the MBTs will result in slowly settling lower in the water till fully submerged then stop.. to continue on down requires forward motion from main propulsion and the use of the dive planes to angle the boat and drive it down to depth while Neutrally Buoyed.
This is the reason for the Negative Tank. Flooding the Negative tank in addition to the MBTs results in a Negative Buoyancy of 7.51 tons. the sub will submerge like the hunk of iron it is. IN order to stop the dive and level out at some predetermined depth, Negative must again be blown dry to restore Neutral buoyancy.
Now here is the problem with this scene... One of the MBT's failed to open it's vent and did not flood, keeping air trapped in that tank. This will prevent the sub from going to neutral buoyancy in addition to the problem with trim. Even with the Negative tank fully flooded, this will not reduce the vessels buoyancy to neutral much less negative.
I don't remember which exact tank it was but each of the possible tanks vary by only a tiny amount so it doesn't matter. Say it was MBT 2c that failed to open and flood. That tank holds 32.25 tons of seawater when flooded. This means they will be light.. Positively buoyed to the tune of just over 32 tons. This means that a corresponding amount of the sub itself will not submerge (the top of the sail and the Periscope shears) Even with Negative fully flooded they would still have a positive buoyancy of 24 and a quarter tons. Negative cannot compensate for a fully blown dry MBT saddle tank. The sub would have listed over to one side but would have never been able to submerge at all. wallowing on the surface like a waterlogged... log.
I joined the Navy to see the world, only to discover the world is 2/3 water!