Ship speed

[Mooncatt]

Hi guys,

Might be answering my own question here, but ill ask anyway.

I designed a new H class BB, gave it a top speed of 29knts. engine efficiency is 100% etc

problem lies in battle when my top speed is only 26knts . heres where I might answer my own question. I had moderate seas waves giving me -4.6% is this why I cant achieve my 29knts? 

im STILL doing design the H class. ive sank 1 BB but the other BB is undamaged and running, it only has a top speed of 24.5 knots. however ive got to get passed the DDs and that BC first 😕

Edited March 1, 2020 by Mooncatt

[flaviohc16]

you need a crapton of time to accelerate, especially in an h class bb

you need to go straight to do so

you need to have your ship pristine ( not have taken any serious damage ( 80%+ integrity)

then, with 100% engine efficiency you will come to the full design speed

[Shaftoe]

My biggest issue with speed (and movement in general) is that ships in UA:D can't use reverse speed to slow down quickly or move backwards. I hope this oversight will be rectified soon (definitely before Steam release).

[Cptbarney]

3 hours ago, Shaftoe said:

My biggest issue with speed (and movement in general) is that ships in UA:D can't use reverse speed to slow down quickly or move backwards. I hope this oversight will be rectified soon (definitely before Steam release).

yes pls, cus when the quad turrets come out along with ricchy and nelson like hull set ups i can then finally bow tank forevah lol.

Edited March 2, 2020 by Cptbarney

[arkhangelsk]

18 hours ago, Shaftoe said:

My biggest issue with speed (and movement in general) is that ships in UA:D can't use reverse speed to slow down quickly or move backwards. I hope this oversight will be rectified soon (definitely before Steam release).

Is that what they do in World of Warships? Because that's not what they do in real life. To suddenly reverse speed is to place a large load on the shafts (the more so since as you know, our ships are allowed way too much horsepower) and moving backwards makes for a much harder to steer ship. As a tactical option it's not AFAIK very realistic - ships use reverse basically only when putting themselves towards a pier.

[Woodrow]

I don't believe that is correct, a quick search yielded the following:

From the book: International Marine Engineering page 365:

"A most efficient method of direct reversing is employed by which the engine is automatically slowed down before the reverse action takes place.  By thus provided effective cushioning the wear and tear which is likely to occur by reversing is avoided."

Next from a business insider article regarding a near collision between a US & a Russian warships in 2019 titled 'Russia blames a US warship for a near collision, but a naval expert is poking holes in its story':

"Unlike a car, a ship doesn't have brakes, so the only way you can slow down is by throwing it into reverse," Bryan Clark, a naval affairs expert and former US Navy officer, explained to BI recently. "It's going to take time to slow down because the friction of the water is, of course, a lot less than the friction of the road. Your stopping distance is measured in many ship lengths."

Please note, that quote is from a former USN officer and expert.

Next, those who know of the Titanic are aware of the fact that the ship did a reverse while still at speed in an ultimately futile attempt to avoid the fateful iceberg.

Finally, the KMS Bismark, when she lost control of her rudder attempted to steer the ship using only her screws (which involved one screw going in full reverse while she was still at speed.  It should be noted that this maneuver was also attempted during her sea trials to see if this could be used.  Sea trials proved only small adjustments could be made this way and there was some regret for having three screws instead of 4.

Edited March 3, 2020 by Woodrow

[Shaftoe]

5 hours ago, arkhangelsk said:

the more so since as you know, our ships are allowed way too much horsepower

Which is exactly my point. This is a game, after all. And not having something so basic looks like an oversight, no matter what arguments could be conjured up to justify it.  

And while IRL it may be detrimental to the machinery, no amount of conjecture on forum would soundly prove that reverse will not be used to cut the speed in a critical situation. Whatever you may say, in reality - the option is there, and so it is logical (and expected) to give it to players in the game, to use (or not to use) at their discretion. 

Woodrow said the rest. And I find his arguments more convincing.

[arkhangelsk]

7 hours ago, Woodrow said:

"A most efficient method of direct reversing is employed by which the engine is automatically slowed down before the reverse action takes place.  By thus provided effective cushioning the wear and tear which is likely to occur by reversing is avoided."

And this quote is describing what ship? BTW, when I search for International Marine Engineering, I get a series of books - it looks more like some magazine, so which volume would this quote be in?

7 hours ago, Woodrow said:

"Unlike a car, a ship doesn't have brakes, so the only way you can slow down is by throwing it into reverse," Bryan Clark, a naval affairs expert and former US Navy officer, explained to BI recently. "It's going to take time to slow down because the friction of the water is, of course, a lot less than the friction of the road. Your stopping distance is measured in many ship lengths."

Since this is a modern American ship, it uses controllable pitch propellers. Do you know why they are considered so cool? Because in being able to reverse their pitch, you don't have to reverse the shaft's rotation to reverse! Unfortunately, I'm pretty sure WWII ships don't have that, just as they don't have gas turbine engines.

The Titanic ... I know the reverse engine narrative is traditional, but personally I find David G. Brown's explanation in The Last Log of the Titanic more convincing as to why the Titanic did NOT reverse engines. Basically, reversing engines will disrupt the water flow around the propeller, making it impossible to steer. Ah, wait, here's a version of it https://www.encyclopedia-titanica.org/last-log-of-the-titanic.html sparing me from having to type a wall of text:

Quote

 

No "Crash Stop"

According to Fourth Officer Boxhall, First Officer Murdoch changed the orders to the two outboard propellers from AHEAD FULL to ASTERN FULL, requesting what sailors call a "crash stop." This is a violent maneuver that can damage the ship's engines, drive shafts, or propellers. For that reason, it is reserved only for the worst of emergencies. Testifying in London, Boxhall said the engine order telegraphs read "full speed astern" when he stepped into the enclosed section of the bridge.

Unfortunately Boxhall's recollection seems faulty. Titanic never attempted the crash stop that people on land still believe was the obvious way to prevent the ship from slamming into the iceberg. Reverse thrust from the propellers would have eliminated the ability of the single rudder to steer the ship. Murdoch knew this. Under full reverse power the ship could not have pivoted to the right, but would have begun a sideways slide into the iceberg2.

The toil of those sweaty men feeding the fires in the ship's boiler rooms was by red warning lights and clanging bells moments before the accident. "Shut the dampers," sang out Leading Stoker Frederick Barrett. He and Second Engineer James H. Hesketh had been talking in Boiler Room #6 when the alarms clanged and the lights on the stoking indicators changed from white to red. Chatter among the men stopped in mid-sentence as they turned to this unexpected work. Closing the dampers on the furnaces was an ordinary precaution to reduce the fires to prevent generating excess steam pressure while the engineers stopped the engines. There were safety valves, of course, but these were not foolproof and had been known to stick on occasion. Nobody wanted to risk building up excessive steam pressure.

The command to close the dampers came just prior to impact when Titanic was perhaps 700 feet from the berg. Closing the furnace dampers is yet another indication that a crash stop was never performed. Full reverse power would have required as much steam as possible from the boilers. Shutting the dampers would have been the worst possible thing to do during a crash stop. Instead, stokers would have been asked to rake the coals in their furnaces to increase steam output from the boilers in order to get maximum power out of the engines.

Titanic's engines and associated drive shafts and propeller blades were designed to withstand an instant shift from forward into reverse at harbor speeds. They might have had strength enough to withstand the strain of instant reversal at 22.5 knots, but only if every part from cylinder to tail shaft was totally free of defects. Ships have been known to snap shafts and propeller blades during crash stops. If nothing broke on Titanic, a crash stop would have caused a rumbling shudder to convulse through the after third of the hull.

In 1951, the U.S. Navy aircraft carrier Tarawa was passing through the Straits of Messena. A passenger ferry suddenly cut across the warship's bow. "All back emergency!" was the instant commande and the carrier's engines began pounding in reverse. The stern of the ship began jumping up and down, some of the crew later said the jumps were six feet or more. The collision was avoided. Next morning, dozens of the carrier's crew were sporting slings, casts and neck braces from being flung to the deck by their ship's successful "crash stop." So much china was broken by the maneuver that it was necessary to put into port to buy more in order to feed the crew. Within a few weeks, the ship itself was drydocked to repair damage done to the at least one propeller shaft.

Since none of the seven-hundred Titanic survivors described such a memorable event, and because the firebox dampers were ordered shut, the engineers could not have performed a crash stop3. They just closed the throttles to the engines to stop them from pushing the liner forward. In sailor terms, Titanic was "shooting," or coasting forward without power when it contacted the iceberg.

 

As for steering with the engines, it is clearly already permitted. I find myself quite able to steer even when the Rudder damaged symbol is illuminated.

3 hours ago, Shaftoe said:

Which is exactly my point. This is a game, after all. And not having something so basic looks like an oversight, no matter what arguments could be conjured up to justify it.  

And while IRL it may be detrimental to the machinery, no amount of conjecture on forum would soundly prove that reverse will not be used to cut the speed in a critical situation. Whatever you may say, in reality - the option is there, and so it is logical (and expected) to give it to players in the game, to use (or not to use) at their discretion. 

I think ultimately, the horsepower problem would be solved by either a very stiff tariff or a cap on horsepower. It would also essentially resolve the problem of the very much hated speed malus for the battleships, so it'll be implemented.

And I think we need to be intellectually honest. That feature will simply not be limited to only a critical situation. People will abuse the crap out of it just like World of Warships as soon as it is installed, and I see no reason to include it when right now we don't even have collisions (we need to get formation handling working brilliantly before we can even think of having collisions, though).

No wait, tell you what. How about I agree to having it, and you agree that if we have it, the speed bar will be a mass of red after you use it to represent all the damage the shaft suffered.

Edited March 3, 2020 by arkhangelsk

[Shaftoe]

10 minutes ago, arkhangelsk said:

No wait, tell you what. How about I agree to having it, and you agree that if we have it, the speed bar will be a mass of red after you use it to represent all the damage the shaft suffered.

1. While damage may occur, it is not necessarily going to be so significant and immediate. Therefore, this approach is extreme and therefore unacceptable. If you want to minimize potential abuse (which is a fair point by itself), then just apply significant penalties to accuracy of deccelerating ships, while minimizing evasion benefits of such maneuvers. Therefore, they will be useful to quickly slow down from full speed to cruising speed (to get accuracy bonus sooner), and to more easily avoid timely detected incoming torpedoes. However, they won't work quite like "WASD hack" you're so afraid if.

2. Don't get me wrong, but your agreement is not required. 

[Woodrow]

To arkhangelsk, I easily found two more historical books regarding the use of full reverse from a full head of steam in the direct attempt to avoid torpedoes in war time.  One book called "British Destroyer vs German Destroyer:Narkiv 1940"

https://books.google.com/books?id=jw5kDwAAQBAJ&pg=PA67&lpg=PA67&dq=reverse+engine+to+avoid+torpedoes&source=bl&ots=nopNKsdws0&sig=ACfU3U0ycq9wHcdH2k9AYuzFTq3mWXtcVw&hl=en&ppis=_c&sa=X&ved=2ahUKEwiWwsC70_7nAhVKrZ4KHfyWCOUQ6AEwEXoECA0QAQ#v=onepage&q=reverse engine to avoid torpedoes&f=false

And "Notes on Naval Progress"

https://books.google.com/books?id=i8byk1kcbtwC&pg=RA2-PA111&lpg=RA2-PA111&dq=reverse+engine+to+avoid+torpedoes&source=bl&ots=WdW1YqXR80&sig=ACfU3U2_xMpAclq0MzZVIl6c56mYrxHF3A&hl=en&ppis=_c&sa=X&ved=2ahUKEwiWwsC70_7nAhVKrZ4KHfyWCOUQ6AEwDXoECAgQAQ#v=onepage&q=reverse engine to avoid torpedoes&f=false

This discusses a Corvette going to full reverse in 90 seconds with a from full speed of 12 knots, of course she didn't go full reverse, but the effect was to reduce to 3-4 knots in that time.  Google is surprisingly easy to find these historical examples of such uses in war-time, which is what we are trying to do with this game, simulate this extreme maneuvers to survive.  I seriously doubt a Captain at the time, upon sighting a torpedo would find the risk of some damage to outweigh the risk of eating a torpedo outright.  Properly done, these manuevers would just put extreme wear on the engine components.  Another way to think about it, most warplanes had War Emergency Power (WEP) throttle setting, this would put extreme wear on the engine, but was used just for those cases and then documented in the maintenance log should the plane survive.

Edited March 3, 2020 by Woodrow
Forgot to add the individual I was addressing in the post.

[arkhangelsk]

Quote

Eskimo had positioned itself abeam to fire a torpedo at Georg Thiele and thus was vulnerable; the British ship steamed full ahead to within 100yd of the shore to avoid the four torpedoes fired from Hans Lüdemann and then had to reverse engines.

The British ship evaded the torpedoes by accelerating to full speed. It reversed engines to avoid hitting the rocks. As for your other source, it is written in 1897 and concerns a thought exercise rather than something that even used a real ship to see if it works as well as some dreamy theoretician thinks.

I'll also point out that Vitiaz's loading is only 3000 SHP and Eskimo's is only 22000SHP/shaft (which is low for a WWII shaft). A WWII fast battleship would be loaded to 40-50000SHP per shaft, and the monstrosities this game allows (at least for now) would be loaded even more heavily.

The overstress caused by immediate shaft reversal from top speed cannot be compared to something like War Emergency Power, which is only a fractional overload. When you suddenly reverse you are decelerating the shaft at a multiple of the rate it normally accelerated, fighting all its momentum in trying to halt its rotation and into contra-rotation.

I won't go as far as to say there are zero circumstances that a real captain would try it. But it would have to be a "life or shaft" or a "if we don't do it, the ship's going to stop moving anyway (because it is about to ground)" situation. Even a torpedo won't convince him to do it because he might just get to keep his engines even after taking a hit. Besides, just you see, pal, the moment this thing gets installed, players are going to use it because:

3 hours ago, Shaftoe said:

they will be useful to quickly slow down from full speed to cruising speed (to get accuracy bonus sooner)

Yeah, this is the kind of casual thing real human players will use such features for. 

Given such realities of human players, and since I try to approach these things from a realism standpoint, I'll say the balance of advantage is with either just not allowing this kind of fringe move or exacting heavy, realistic penalties.

I suggest that people that need to stop might try hydrodynamic braking. That way you can save your engines and I've been told at high speeds, it is even a better stopper. Plus, you can try it right now, simply by cutting engine power and hitting full rudder. Your ship will slow, plus its nose will get out of the way.

[Cptbarney]

iowa going from 35.2knots to a full stop.

https://www.guinnessworldrecords.com/world-records/fastest-speed-recorded-for-a-battleship/

and yeah its guinness, but snce they need to gather accurate records for world events and also records its still a viable source of info.

also theres no real reason not to add a reverse mode into the game.

[Shaftoe]

50 minutes ago, arkhangelsk said:

Yeah, this is the kind of casual thing real human players will use such features for. 

Given such realities of human players, and since I try to approach these things from a realism standpoint, I'll say the balance of advantage is with either just not allowing this kind of fringe move or exacting heavy, realistic penalties.

I suggest that people that need to stop might try hydrodynamic braking. That way you can save your engines and I've been told at high speeds, it is even a better stopper. Plus, you can try it right now, simply by cutting engine power and hitting full rudder. Your ship will slow, plus its nose will get out of the way.

Before coming to my points, let's address something. While you are free to express your opinion just as everybody else, I would caution you from trying to impose it as the single correct point of view. After all, sometimes people like Cptbarney and Woodrow make convincing arguments against your position - let's respect that.

Now, to my points... The game was announced as a realistic naval game. Therefore, your idea of keeping arbitrary restrictions simply contradicts the very premise of this game. Whatever you may think of "casual players" and their choices, you are not entitled to make decisions for them, including limiting their right to choose. 

To further elaborate on my point, if it is possible in reality, then it should be featured in this realistic game. People (who are not naval experts - just players who want to have fun) should have the means to do what they want, regardless of how stupid you think their actions may be. The game itself should "teach" them what decisions work, and what don't. How to go about something, and what not to do. If use of reverse to slow down is not going to be very useful (or will even be potentially dangerous), then people should be the ones to figure it out, whether by reading a tutorial, or by making this mistake in game. We all paid money for it, based on premise of realism, and objectively, our reality is not constrained by some arbitrary limitations - like the kind you insist on having. And since this is not a multiplayer game, there are no viable justifications for implementing such arbitrary limits - especially against expectations of the community.

You wanted to be "intellectualy honest"? Fine. Then accept this: UA:D is a complicated strategy game. People who buy such games are usually quite sophisticated, capable of learning and willing to do so. They don't need arbitrary protection from reality and consequences. They can handle it. And if there are some not very effective or even potentially dangerous solutions in reality, then we as players should have them at our disposal, with all the risks therein. After all, that's the "realism" we paid big bucks for. 

Edited March 3, 2020 by Shaftoe

[arkhangelsk]

6 hours ago, Shaftoe said:

The game itself should "teach" them what decisions work, and what don't.

As a general premise, I agree with this position. That's why ultimately I settled to agree, but with a heavy, realistic penalty that would hopefully sell people into never doing it again. A tiny little inaccuracy malus simply does not do that (many won't even read the tiny line of text where it is represented), and while technically it should be a RNG for the shaft breaking, you can't do RNG things in game because people would save-scum. So all you can do is exact a "fixed" penalty.

BTW, I send these arguments up to be critiqued. If they are winners, I win. If they have weaknesses, I learn. (To be honest, I was surprised even Eskimo was there to bushwhack me).

Edited March 4, 2020 by arkhangelsk

[Shiki]

It does have to be pointed out that there are instances where American battleships were capable of throwing themselves into accelerate - reverse - accelerate, all within a matter of minutes. Though the particular incident's name escapes my mind, one of the Standard-type turbo-electric drive battleships was able to execute an immediate full-power reversal of the screws in order to avoid hitting her predecessor in the line, and apply acceleration again within moments in order to avoid the steam turbine-driven ship behind her (which herself was trying vainly to stop). I don't profess to be an engineering or hydrodynamic expert - I took ballistics - but the main problem from my understanding is the time it takes to switch from forward to astern turbines. Turbo-electric drive and diesel-electric drive ships don't have this problem, since at no point are turbines involved in the physical movement of the ship - electric motors are capable of switching from flank ahead to full astern at the drop of a hat.

So add a penalty, but remove it for diesel and turbo-electric drive systems? That would seem to be the answer to the issues (not being able to execute a reverse, and the potential damage to the shafts).

[Woodrow]

I'm very curious arkhangelsk can you provide historical examples where shafts had snapped under such maneuvers?  When you disagreed with my historical examples posted earlier, you mentioned SHP as the driving factor.  I disagree with this, mainly on the premise that properly designed systems will have matched components.  That 3000 SHP destroyer will not have a shaft and screw that would be appropriate for say a battleship of a much larger power output.  Put into terms of cars, you could drop the clutch with a matched system with say 200 BHP for a quick takeoff (not so great for the transmission of course).  Swap that V6 out to a V8 putting out 450 BHP and you will destroy the transmission and or the rear diff (in a RWD car).  But, do the same for a car with a matched drivetrain and you can do that with much reduced risks.  Now where you have issues in ships is if the screws are still spinning at full speed and you fail to slow them down (through engine braking or backing off the power and allowing to slow) and them slam them directly into reverse, you will have problems, but most likely those problems would occur in the gearing section (though equally likely as severe as a snapped shaft).  You also have to remember basic maneuvering, ships use reverse to slow down.  Nice wiki article link for that: https://en.wikipedia.org/wiki/Astern_propulsion

Done, common maneuver with its own specific flag signal to display that this maneuver is occurring to other ships.   Again, I await the references for snapped shafts done under this maneuver and the circumstances in which they occur.

One final note, I agree that under these maneuvers in the game and accuracy malus should be appliedin addition to when crew is simulated, there should be a malus there too, dependent on how drastic the manuever was conducted.

[disc]

Most ships can "crash stop." This might be defined as reversing the prop revolution in an attempt to stop the ship from speed.

1. On a steam engine, changing the valve timing will reverse the engine, which will have a powerful braking effect on the prop shaft.
2. For a steam turbine ship, the great majority have reverse turbines. Steam is cut off to the main turbines and introduced to the reverse turbines. On many (most?) ships there is no reverse clutch, so it does not need to be clutched in -- always attached to the prop.
3. Electric transmissions can rapidly switch from full reverse to full ahead; usually the limiting factor is heat dissipation.
4. Diesels use air-injection to brake, similar to reversing steam engines. I do not know if this was possible on the vessels of our era, but I suspect it was given that many used air-blast fuel injects.
5. For a controllable-pitch prop, changing pitch will work. Likewise, a turnable prop pod can spin.
6. Rudder cycling will slow the ship, though I am not sure it is particularly useful.
7. Water brakes were trialed on US battleships -- and probably a bunch more commercial ones -- but they didn't work very well. Here's a picture of one on USS Indiana.

Edited March 4, 2020 by disc

[disc]

Full speed crash stops are typically performed on trial runs. I do not know about potential damage to the drivetrain, but I suspect it would be unlikely unless many repeated stops were made. Cavitation on the props would be the big concern, I think.

• For the trials of the 224,950 tonne steam-turbine tanker Esso Malaysia: Traveling at an initial speed of 16 knots, a crash stop took 17.6 minutes with an ahead reach (distance traveled forward) of 4389 meters. A turn at 16 knots would have an ahead reach of only about 900-1000 meters.
• For the 26700 deadweight-ton single-screw steam-turbine tanker Esso Lima, a crash stop from full speed (presumably about 10-18 knots) required 8 minutes with an ahead reach of 1463 meters. The prop was stopped within 32 seconds of crash-stop initiation, and it was in full astern RPM by 1 minute 37 seconds.

There are issues with crash stops. Turning is typically faster, easier, and requires less ahead-distance. Stopping can take time to enact: With steam turbines closing and opening the throttles may take ~20 seconds. Stopping will markedly reduce directional stability. For the Esso Malaysia, the ship ended up 503 meters to starboard and perpendicular to the original direction of travel. Not ideal. Additionally, the ship will take a long time to reaccelerate to its original speed, unless it has extremely powerful engines.

Crash stops can be useful, however, when there is insufficient room to maneuver, or when the ship is already traveling slowly. Principles of Naval Architecture gives a figure of 6 knots as a cutoff for single-screw ships. I suspect it would be higher for multi-screw ships with powerful astern power.

Edited March 4, 2020 by disc

[Shaftoe]

5 hours ago, arkhangelsk said:

As a general premise, I agree with this position. That's why ultimately I settled to agree, but with a heavy, realistic penalty that would hopefully sell people into never doing it again. A tiny little inaccuracy malus simply does not do that (many won't even read the tiny line of text where it is represented), and while technically it should be a RNG for the shaft breaking, you can't do RNG things in game because people would save-scum. So all you can do is exact a "fixed" penalty.

BTW, I send these arguments up to be critiqued. If they are winners, I win. If they have weaknesses, I learn. (To be honest, I was surprised even Eskimo was there to bushwhack me).

There are numerous factual evidences contradicting your position. Apparently, reversing can be done without wrecking ship's propulsion. Therefore, "heavy" penalties you are advocating for are not necessarily "realistic". If players constantly switch between flank and reverse, then I agree - some damage might occur due to reckless use. However, you make it sound like damage should occur immediately upon engaging reverse to slow down, so I cannot agree with you. From where I stand, it looks like all you did is merely changed format of the same unacceptable arbitrary limitations. 

Edited March 4, 2020 by Shaftoe

[arkhangelsk]

2 hours ago, Shaftoe said:

There are factual evidence contradicting your position. Apparently, it reversing can be done without wrecking the entire ship. Therefore, "heavy" penalties are not necessarily "realistic".

As a matter of "law" (principle), I agree that if heavy penalties are not realistically justified they shouldn't be put in. In fact, one reason I continue this discussion is to come up with the "perfect penalty". I'm just not so convinced that's "no penalty" or something insignificant like speed malus is the correct answer.

One of the problems is the basic definition of what kind of reversal we are talking here:

2 hours ago, disc said:

Most ships can "crash stop." This might be defined as reversing the prop revolution in an attempt to stop the ship from speed.

Yes, sure, most ships can indeed reverse themselves in some way to some degree. However, in the examples he mentions:

2 hours ago, disc said:

• For the 26700 deadweight-ton single-screw steam-turbine tanker Esso Lima, a crash stop from full speed (presumably about 10-18 knots) required 8 minutes with an ahead reach of 1463 meters. The prop was stopped within 32 seconds of crash-stop initiation, and it was in full astern RPM by 1 minute 37 seconds.

While I won't mind a solution where we can avoid immediate engine damage if players are willing to first stop the engines, wait 32 seconds (or maybe even longer if the ship's moving faster) and then engage reverse, how popular do you think would it be? Would it even be worth having such a limited feature?

Further, @disc is kind of confirming what I've briefly mentioned in my previous post - in most cases this is a move of very marginal advantage, and turning by far the more effective alternative in most situations.

Basically, you will do just as well telling yourself that an appropriate amount of reverse is applied when you click on the Zero in the speed selector.

3 hours ago, Woodrow said:

I'm very curious arkhangelsk can you provide historical examples where shafts had snapped under such maneuvers?  When you disagreed with my historical examples posted earlier, you mentioned SHP as the driving factor.  I disagree with this, mainly on the premise that properly designed systems will have matched components. 

Actually no, but an example of clear damage was already provided in the previous post:

Quote

In 1951, the U.S. Navy aircraft carrier Tarawa was passing through the Straits of Messena. A passenger ferry suddenly cut across the warship's bow. "All back emergency!" was the instant commande and the carrier's engines began pounding in reverse. The stern of the ship began jumping up and down, some of the crew later said the jumps were six feet or more. The collision was avoided. Next morning, dozens of the carrier's crew were sporting slings, casts and neck braces from being flung to the deck by their ship's successful "crash stop." So much china was broken by the maneuver that it was necessary to put into port to buy more in order to feed the crew. Within a few weeks, the ship itself was drydocked to repair damage done to the at least one propeller shaft.

In present UA:D terms, that sounds like "Engine 1 damaged". Given this and that there is an expert opinion, I think that's enough to reverse the burden of proof. One problem is that "crashbacks" at sea are rare, and the accounts not very detailed. Of course, where damage was recorded there's a clear overload, but where damage was not it is not clear if that's because the maneuver was gentle, the ship was tough or whether they just didn't record the damage. For example, did Eskimo reverse by transitioning first into a Minimum RPM regime, or did she reverse by just engaging reverse turbines or using the reverse gearbox? Can't tell that from the little blurb of text.

P.S. You can't easily tell how much damage the shaft took, either, because shortly afterwards, Eskimo was snuffed by a torpedo and had to go in for extensive repairs anyway. I do notice though, that the below says "could not respond to further rudder or engine orders". If this is literally true, something broke.

I agree partially the matched components factor, but in the end, steel just doesn't get that much stronger compared to the explosive growth in shaft horsepower. 

3 hours ago, Woodrow said:

Done, common maneuver with its own specific flag signal to display that this maneuver is occurring to other ships.   Again, I await the references for snapped shafts done under this maneuver and the circumstances in which they occur.

The discussion (at least as I read it) started in the context of emergency reversals to boost the tactical maneuverability of ships. This is a different kettle.

From a realism perspective, of course ships can go in reverse but one reason why there is such a flag is because of the loss of directional stability and controllability in the reverse regime so this is basically telling everyone to get out of the way of a ship driving around like a drunk. Which does not make it that useful of a feature in a tactical fight. The first thing I see it being useful is for extracting your ship after a collision, but we need ships to collide first.

Edited March 4, 2020 by arkhangelsk