Suggestion: Instability at Periscope Depth

[derstosstrupp]

I think it would be great to make the boat a little more unstable at periscope depth, and well nigh impossible to hold over wind speed 9. The more I play with the wind speeds the more I am starting to think they approximate Beaufort scale winds based on the resulting waves I am seeing. And periscope depth was out of the question over about sea state 7 (where winds are often 9).

Many people complain that the dive officer does not have enough to do and that the role is too easy to learn/perform, and this would be a welcome challenge, the very same challenge that the chief engineer in reality faced when trying to hold periscope depth during an attack. I have read many accounts of skippers screaming down at the chief engineer for letting their scope pop up too high or dunk at a critical time.

The current ability to simply just dive and get a speed estimate even in very rough seas is a massive exploit and needs to change in my opinion.

[Lignite]

I agree. It would seem a fairly common theme through memoirs of the guys that were there that holding exact depths was not an easy task and required constant attention. I too would like to see some slight changes to buoyancy (nothing crazy) that require some planes and/or trim tank work. Not easy for solo players, but hopefully the bots can make up for that (dive officer bot is not particularly necessary in the current state, I can set it and take care of it solo). Just my opinion.

[mobucks]

Realistically, no sub Captain would ever even attempt a periscope attack with seas that high. It is just a game though.

Personally I don't even bother joining servers with high seas. Seems like a waste of time.

[Fidd]

Trim-tanks to affect longitudinal balance, especially after torpedoes are fired, or with changes of depth, are I think the missing component here. From the little I've read - and I'm no expert - one of the chief causes of boats being forced to the surface, or deeper than they intended to go, was the boat becoming out of trim. This could occur from depth charges exploding beneath the boat, causing the front or aft end to decend rapidly into the aerated water beneath. The crude pitch changes required to regain control necessitating major trim changes. If this process got away from the dive officer, they could find themselves unable to cease a rise or descent of the boat.

A need to operate such trimming would make attaining and maintaining periscope depth harder and more time-consuming, and to potentially make vertical operation of the boat more demanding.

[VonHoffman]

Does trim change that much with attitude? If you simply point the boat up/down using the planes and forward speed, then I can only see trim changing due to temperature differentials or even minor variation of pressure due to the different depth of each end of the boat?

If the tanks are not totally flooded, then I can also see the shift in mass making a small change, but surely not that much? Once the boat levels it will be back in trim again?

I do agree that near/on the surface the boat needs to rock a lot more with the waves. It's almost completely immune to the sea state.

[derstosstrupp]

Originally Posted by VonHoffman

Does trim change that much with attitude? If you simply point the boat up/down using the planes and forward speed, then I can only see trim changing due to temperature differentials or even minor variation of pressure due to the different depth of each end of the boat?

If the tanks are not totally flooded, then I can also see the shift in mass making a small change, but surely not that much? Once the boat levels it will be back in trim again?

I do agree that near/on the surface the boat needs to rock a lot more with the waves. It's almost completely immune to the sea state.

Trim for U-boats referred strictly to attitude changes. These were offset by transferring small amounts of water between the forward and aft trim tanks. This needed to be done daily as part of the trim dive, and became necessary due to any weight changes forward vs aft. Say carrying a sack of potatoes from end to end as a simple example. It’s also why, when submerged, moving about the boat was only by permission of the chief engineer because it would upset the trim (which is why the crew had “diving stations”).

I agree in terms of buoyancy being a function of many different factors including temperature, salinity, plankton content, own weight etc. That’s what the regulating tanks (what Wolfpack calls trim tank) were used for. However no significant changes were made here typically since weight changes were maintained in the dive logbook and the control room mate added the necessary water to compensate already on the surface. Different concept than trim though.

So the bulk of trimming (“einsteuern”) was shifting the water between trim tanks and also possibly adding/subtracting water from regulating tanks to make up for any miscalculations in weight, such that, at Kleine Fahrt and periscope depth, depth could be maintained with minimum hydroplane input on an even keel. But in rough seas this whole process was made exponentially more difficult because the sea churns on the surface and just below it, wreaking havoc on a submarine trying to maintain depth.

I advocate for true trim tanks in Wolfpack because the dive officer role becomes easy to master quickly. So some more complexity here I think would be welcome.

Now, that being said, there is an argument to be made for leaving that element out, because the assumption would already be possibly that the boat has undergone its daily trim dive by the time you spawn in, but regardless, it would be a nice touch to have to do a quick trim dive before you go about your engagement.

[VonHoffman]

Yes - I would certainly like to see more technical depth to the tanks.

I know some time ago there was discussion about adding the saddle tanks rather than the simplified trim tank we have now. I'd like to see that whole area improved (even make it an option for easy vs. realistic tank configuration).

How do you trim the sim? I flood both fore and aft ballast tanks then use the trim tank to obtain neutral buoyancy at 20-30 m below the surface in a level condition. I'm guessing the boat is "magically" trimmed given the tanks we have?

[derstosstrupp]

Originally Posted by VonHoffman

Yes - I would certainly like to see more technical depth to the tanks.

I know some time ago there was discussion about adding the saddle tanks rather than the simplified trim tank we have now. I'd like to see that whole area improved (even make it an option for easy vs. realistic tank configuration).

How do you trim the sim? I flood both fore and aft ballast tanks then use the trim tank to obtain neutral buoyancy at 20-30 m below the surface in a level condition. I'm guessing the boat is "magically" trimmed given the tanks we have?

That’s how I do it as well yeah. Typically at the start of an engagement I will do a trim dive and adjust the tank to achieve neutral at dead slow speed. And the ballast tanks should be completely flooded always on diving.

[VonHoffman]

Originally Posted by derstosstrupp

That’s how I do it as well yeah. Typically at the start of an engagement I will do a trim dive and adjust the tank to achieve neutral at dead slow speed. And the ballast tanks should be completely flooded always on diving.

Yes - I leave them open for a few minutes after diving to be sure they're full.

That raises another question: when blowing the tanks, do you wait until near the surface? Do you blow them quickly or slowly?

I did some testing and the external water pressure seems to be factored into how much compressed air is required to empty the tanks. If you blow the tanks when deep it requires far more compressed air than if you blow them near the surface (great!!!).

The only thing I couldn't quite determine is if blowing them slowly is more efficient than blowing them quickly? My guess is there is a maximum rate the water will leave the tanks, and it might be possible to compress the tanks with air, thereby losing air when the tanks finally empty and the pressure equalizes with the atmosphere??

A low-pressure blow, cutting the compressed air before the tanks are completely empty, would therefore reduce the compression in the tanks, and save compressed air as well by not using more air than necessary?

I need to do some more testing!

[derstosstrupp]

Originally Posted by VonHoffman

Yes - I leave them open for a few minutes after diving to be sure they're full.

That raises another question: when blowing the tanks, do you wait until near the surface? Do you blow them quickly or slowly?

I did some testing and the external water pressure seems to be factored into how much compressed air is required to empty the tanks. If you blow the tanks when deep it requires far more compressed air than if you blow them near the surface (great!!!).

The only thing I couldn't quite determine is if blowing them slowly is more efficient than blowing them quickly? My guess is there is a maximum rate the water will leave the tanks, and it might be possible to compress the tanks with air, thereby losing air when the tanks finally empty and the pressure equalizes with the atmosphere??

A low-pressure blow, cutting the compressed air before the tanks are completely empty, would therefore reduce the compression in the tanks, and save compressed air as well by not using more air than necessary?

I need to do some more testing!

I try to follow the historical surfacing procedure:

1. Steer dynamically to periscope depth using hydroplanes. All depth changes are made dynamically.

2. After checking all clear with the scope, great speed ahead, forward planes hard up, aft up 5, and start the blowing (full turns of wheel all the way).

3. As soon as the tower comes up, stop blowing. While still on electrics, head up to the bridge and make sure all clear.

4. If all clear, finish blowing and switch to diesels. Historically, they finished blowing using diesel exhaust from one engine, thereby saving on compressed air. But in the game your compressed air refills quickly so no need to worry as long as you initiate blowing from periscope depth.

[Onkel Neal]

I completely agree, holding the boat at PD should take a fair amount of effort. I want to tackle this tweak when the game is closer to complete, the devs like to fix stuff that stays fixed after updates, so for now I'm being patient. But yes, you have the right idea.

[Aktungbby]

QUESTION: does wolfpack incorporate reality into use of the U-boat periscope as occurred in WWII? http://www.uboataces.com/periscopes.shtml

At 6 knots, (out of 7 knots max when submerged) it caused excessive vibration which rendered it almost impossible to use. This was dampened by using an extension bracket to reduce the unsupported length and the pointed end was redesigned to minimize the forward hydrodynamic resistance. Nevertheless, vibrations still occurred, but to a much lesser degree. The other problem was fogging of the lenses. Since the damp atmosphere of the U-boat caused fogging, it was especially important that the tube was not only watertight, but was airtight as well. Any fracture on the airtight casing caused by a depth charge attack would result in fogging of the tubes.

https://www.subsim.com/radioroom/sho...d.php?t=189585

Originally Posted by Sailor Steve

On the other hand there is anecdotal evidence that raising the periscope at more than 3 knots would cause enough vibration to render the image unviewable. As I said, it's my understanding that damage wasn't the problem so much as not being able to see anything due to vibration. That said, I really don't know the exact parameters and problems.
I always slow down to use the periscopes, but that may just be me.

https://maritime.org/doc/uboat/index.htm

125.) The "sparing" use of the periscope (see Section I, B, No. 31); i.e., the raising of the periscope, at frequent intervals and for a brief space of time, to surface level, So that the periscope appears no bigger than a fist, and almost constantly awash, begins at a distance of approximately 4,000-5,000 m from the enemy, according to the state of the weather and the conditions of light. It is a mistake to keep the periscope down for any length time when the enemy is near. In that case the submarine is not less visible an during the "sparing" use of the periscope; but it can itself see nothing, and is therefore in greater danger. Consequently, the submarine should carry out frequent observations of short duration; but, in all circumstances, they should be repeated again and again.

126.) The periscope should only be raised when the submarine is traveling at low speed. Before raising the periscope, it is therefore necessary to reduce the speed. Otherwise, if the sea is calm, the wake of the periscope can easily be seen, besides which the periscope of a submarine traveling at speed will cause splashes, and a conspicuous feather ["Wasserfahne"].

127.) If special reasons require that the speed be temporarily increased, for example, in order to reach a position more suitable for launching an attack, the periscope must be lowered until the top of it is at least 1 m under the surface. When the submarine is at the depth for attack, the periscope should not, however, be further lowered to an extent greater than it is absolutely necessary, in order not unnecessarily to lose time in raising it again.

[Bilge_Rat]

A periscope vibrating is basic physics at work, think of a flagpole in a high wind. An extended scope is a long metal tube, metal, but still flexible. As the sub moves forward, water pressure pushes the tube aft, but you can only bend the tube so far before it snaps back to its original position at which point the process restarts. Of course in RL, the effect is more dynamic, but the result is that the faster the sub goes, the higher the vibration effect.

[VonHoffman]

What the wake looks like at 6 kts...

https://www.marineinsight.com/case-s...h-a-submarine/

@Onkle Neal: sounds great! Look forward to it!

When I'm attacking or maneuvering to get closer I lower the periscope until it is constantly under water then keep lowering for another 2-3 seconds or so. This allows for the motion of the boat and the wave action to clear the periscope while still being able to see under the water.

I always stop the boat before using the periscope when close to enemy ships unless I'm already looking at them in which case I'll raise, get a sight-picture, then lower it again. It's never above the surface more than a few seconds in that instance. I find it helps if the seas are not flat calm. I'll raise the scope so it keeps going awash for minimum visibility from the surface (again, while stationary).

[Fidd]

I think it's very reasonable for the boat to be in-trim when players first spawn in. Adding this little complexity for when the boat changes in pitch angle and/or there are significant weight changes, would be a welcome addition. What I'm more interested in, is seeing more difficulty in maintaining periscope depth, and in particular much more interplay between nearish depth-charge explosions, and changes to the boats pitch attitude due aerated water after an explosion, especially beneath the u-boat. As there are a fair few incidences of such depth charge attacks causing a u-boat to lose control of depth-keeping, to the point that it breached the surface, it would seem well worth modelling said difficulty in depth keeping when under DC attack?