Cruising speed accuracy

[SonicB]

I've noticed that the relationship between cruising speed and accuracy has become even more significant to the meta now that it effectively replaces formation aiming bonuses. However I've been unable to find any real historical examples where reducing speed to an arbitrary let's-say-3/4 of battle speed meant a major increase in accuracy.

So I'm throwing this out to the fellow naval history buffs here. Was this ever a thing? If so, did it ever trump the tactical value of maintaining maximum speed, in the way it often does in this game?

Looking forward to your thoughts.

[madham82]

Yea I am not aware of any specific speed ranges, but I think an argument can be made for running at flank speed probably is not the most stable for gunnery. Interested to hear other's thoughts. 

[SonicB]

1 hour ago, madham82 said:

Yea I am not aware of any specific speed ranges, but I think an argument can be made for running at flank speed probably is not the most stable for gunnery. Interested to hear other's thoughts. 

I guess what prompted my question is reading a design history of the Queen Elizabeth class, and how they were built for 25kts to allow them to flank the main battle fleet when necessary, which was designed for a 21-knot maximum speed because it was intended to fight at this speed. If there had been a significant improvement in accuracy gained by maintaining lower speeds, surely this calculus of speed/armour/firepower would have been very different. Especially for battlecruisers, which mounted large calibre, long-range accuracy dependent weapons on very fast hulls.

My suspicion, from what I know of historical designs and hydrodynamics, is that the actual effect of flank speed on accuracy is very much dependent on sea state, rather than the blanket 15-30% effective malus we see in game. Many casemated guns were unusable in heavy seas at battle speed - what the game refers to as 'flank' - and certain ships were known to be 'wet' forward or aft to the point that it impeded the use of the main armament. Conversely, in calm or moderate sea states (1-3) I don't see how there should be any significant difference between full and flank - not that this game models 'calm' seas accurately in any event.

Edited November 20, 2020 by SonicB

[madham82]

7 minutes ago, SonicB said:

I guess what prompted my question is reading a design history of the Queen Elizabeth class, and how they were built for 25kts to allow them to flank the main battle fleet when necessary, which was designed for a 21-knot maximum speed because it was intended to fight at this speed. If there had been a significant improvement in accuracy gained by maintaining lower speeds, surely this calculus of speed/armour/firepower would have been very different. Especially for battlecruisers, which mounted large calibre, long-range accuracy dependent weapons on very fast hulls.

My suspicion, from what I know of historical designs and hydrodynamics, is that the actual effect of flank speed on accuracy is very much dependent on sea state, rather than the blanket 15-30% effective malus we see in game. Many casemated guns were unusable in heavy seas at battle speed - what the game refers to as 'flank' - and certain ships were known to be 'wet' forward or aft to the point that it impeded the use of the main armament. Conversely, in calm or moderate sea states (1-3) I don't see how there should be any significant difference between full and flank - not that this game models 'calm' seas accurately in any event.

Yea I remember reading that too, but I also think the British made a lot of bad assumptions about tactics before and during WW1. For one, the north sea visibility frequently meant the battle ranges envisioned were impractical. Even at Jutland, Beatty closed the range too much and gave up any range advantage. Their doctrine of rapid fire also gave up accuracy. So really they were not using their ships the way they were designed to fight.

That said, I think the sea state would be a big factor like you mentioned. I remember reading something about the Iowas having trouble with waves over the bow compared to British BBs. So would make sense to impact accuracy from the jarring of the ship which would force them to slow down. So it could just be accuracy was impacted due to the relationship of speed and seakeeping with the sea state. That might too complex for the game to calculate. 

[SonicB]

1 hour ago, madham82 said:

Yea I remember reading that too, but I also think the British made a lot of bad assumptions about tactics before and during WW1. For one, the north sea visibility frequently meant the battle ranges envisioned were impractical. Even at Jutland, Beatty closed the range too much and gave up any range advantage. Their doctrine of rapid fire also gave up accuracy. So really they were not using their ships the way they were designed to fight.

That said, I think the sea state would be a big factor like you mentioned. I remember reading something about the Iowas having trouble with waves over the bow compared to British BBs. So would make sense to impact accuracy from the jarring of the ship which would force them to slow down. So it could just be accuracy was impacted due to the relationship of speed and seakeeping with the sea state. That might too complex for the game to calculate. 

All of that's true - that said, ship designers from Dreadnought on did have solid data on how accurate turbine-driven battleships were at 20-21kts. Reciprocating engines could reach that speed, but the fact that turbine engines could sustain that speed indefinitely during combat was a pretty major reason most navies went to turbines for their battle fleet, including the German fleet.

I looked up a few papers (can't link others because they're closed repositories) and though results for 16kt+ speeds are very limited, the general consensus seems to be that hull stability generally improves logarithmically with speed up to the displacement speed of the hull and then is constant after that. I would extrapolate that the devs made one or more of these incorrect assumptions when deciding cruising speed was so much better for accuracy:

- 1. Engine vibration at top speed impacts accuracy; this was moderately true of reciprocating engines but not of turbines.
- 2. Higher speed causes slamming, stuffing of the bow, unpredictable roll and inoperable weapon mounts; this is true in very high sea states but not most.
- 3. (Most likely in my view) overcoming the hull speed limitation (aka 'cruising speed') requires more power and creates more drag and wake (true) and this adversely impacts ship stability (false.)

In terms of the game engine, we already have a flat accuracy modifier for sea conditions, so I don't see it as hugely complex to have that also affect the scale of the cruise speed buff - or more accurately the flank speed debuff.

Edited November 20, 2020 by SonicB

[disc]

Yes, prescribed battle speed for some ships was sometimes much less than maximum speed.

Biggest example of this I can think of are some of the big French "contre-torpilleur" type of destroyers. The Le Fantasques could reach over 43 knots on trial, and 40+ knots at more realistic displacements. In formation, the ships could travel at 38-40 knots. "Raiding speed" was 38 knots. Combat speed was only 28 knots, a value where all the ships in the class had minimal vibration for gunnery. The other contre-torpilleurs appear to have been similar. The Vauquelins achieved a sustained speed of 37 to 39.5 knots at Normal displacement on trial, a formation speed of 37 knots, a "raiding speed" of 34 knots, and a combat speed of 30 or 31 knots. Again, the combat speed was intended to give steady gunnery.

[madham82]

4 minutes ago, disc said:

Yes, prescribed battle speed for some ships was sometimes much less than maximum speed.

Biggest example of this I can think of are some of the big French "contre-torpilleur" type of destroyers. The Le Fantasques could reach over 43 knots on trial, and 40+ knots at more realistic displacements. In formation, the ships could travel at 38-40 knots. "Raiding speed" was 38 knots. Combat speed was only 28 knots, a value where all the ships in the class had minimal vibration for gunnery. The other contre-torpilleurs appear to have been similar. The Vauquelins achieved a sustained speed of 37 to 39.5 knots at Normal displacement on trial, a formation speed of 37 knots, a "raiding speed" of 34 knots, and a combat speed of 30 or 31 knots. Again, the combat speed was intended to give steady gunnery.

Good information. Any examples of this with capital ships? I can definitely see how tin cans could have real issues with stability due to their construction and displacements vs speed. Wondering if heavier and better built (and theoretically more stable) BB/BC could operate at higher relative speeds without loss of accuracy. 

Edited November 20, 2020 by madham82

[SonicB]

2 minutes ago, disc said:

Yes, prescribed battle speed for some ships was sometimes much less than maximum speed.

Biggest example of this I can think of are some of the big French "contre-torpilleur" type of destroyers. The Le Fantasques could reach over 43 knots on trial, and 40+ knots at more realistic displacements. In formation, the ships could travel at 38-40 knots. "Raiding speed" was 38 knots. Combat speed was only 28 knots, a value where all the ships in the class had minimal vibration for gunnery. The other contre-torpilleurs appear to have been similar. The Vauquelins achieved a sustained speed of 37 to 39.5 knots at Normal displacement on trial, a formation speed of 37 knots, a "raiding speed" of 34 knots, and a combat speed of 30 or 31 knots. Again, the combat speed was intended to give steady gunnery.

Thanks, that's very helpful. I've mostly been concentrating on battleships and battlecruisers for my examples, but it's a good point that destroyers have much larger engines relative to displacement and are smaller and faster, and therefore should be more affected by sea state and vibration.

[SonicB]

2 minutes ago, madham82 said:

Good information. Any examples of this with capital ships? I can definitely see how tin cans could have real issues with stability due to their construction and displacements vs speed. Wondering if heavier and better built (and theoretically more stable) BB/BC could operate at higher relative speeds without loss of accuracy. 

There have definitely been a ton of examples where destroyers have not kept up with capital ships and cruisers in inclement weather and had to be detached. What I don't know is whether the reason was simply 'destroyers can't do this speed in this weather' or 'destroyers can't do this speed and fight in this weather.'

[madham82]

1 minute ago, SonicB said:

There have definitely been a ton of examples where destroyers have not kept up with capital ships and cruisers in inclement weather and had to be detached. What I don't know is whether the reason was simply 'destroyers can't do this speed in this weather' or 'destroyers can't do this speed and fight in this weather.'

Typhoon Cobra (?) that Halsey sailed his fleet into is probably a good study of this. The issue is ability to deal with the waves as I understand it. Those smaller ships simply just can't plow through the waves as fast or hold up to the constant wave action (either causing structural failures or capsizing the ship). If you had a choice of which ship to be on in a storm, you pick the biggest one lol. 

[Cptbarney]

We lack visuals for rough, harsh, extreme, calm, smooth, moderate and turbulent seas, depending on the sea type and also wind should also determine the best speed to be at, but also accompanied by visuals so peeps now why.

[madham82]

1 hour ago, Cptbarney said:

We lack visuals for rough, harsh, extreme, calm, smooth, moderate and turbulent seas, depending on the sea type and also wind should also determine the best speed to be at, but also accompanied by visuals so peeps now why.

What kind of impact would wind make on accuracy in relation to ship speed? I would think wind speed would be a separate value impacting accuracy, independent of the ship's speed. Wind direction would need to accounted for as well. 

[Cptbarney]

12 minutes ago, madham82 said:

What kind of impact would wind make on accuracy in relation to ship speed? I would think wind speed would be a separate value impacting accuracy, independent of the ship's speed. Wind direction would need to accounted for as well. 

I was thinking more for shells than for ships, the only ships i can think it would effect in-general would be smaller ships. I guess high wind speeds could also make the sea very choppy and wavy as well, so the two tie into each other. If wind is strong enough and engine aren't powerful enough compared to mass being shifted around it could affect the ship not sure how much however.

[madham82]

39 minutes ago, Cptbarney said:

I was thinking more for shells than for ships, the only ships i can think it would effect in-general would be smaller ships. I guess high wind speeds could also make the sea very choppy and wavy as well, so the two tie into each other. If wind is strong enough and engine aren't powerful enough compared to mass being shifted around it could affect the ship not sure how much however.

Ok I follow you now. You know now that I think about it, the stability characteristics (can't remember what they are called in the designer) have factors for various weather conditions. So it seems they are taking into account these factors. 

[SonicB]

On 11/20/2020 at 8:47 PM, madham82 said:

Ok I follow you now. You know now that I think about it, the stability characteristics (can't remember what they are called in the designer) have factors for various weather conditions. So it seems they are taking into account these factors. 

That's true, and I believe (could be wrong) that stability also affects the amount of cruising speed bonus, so they are kinda indirectly related.

The issue I wanted to raise in this thread, though, is that the end result of these calculations seems pretty unrealistic and arcadey, at least for large ships and light sea conditions. HMS Dreadnought was designed to fight at 21 knots. It seems pretty ridiculous that in a calm sea she's magically ~20% more accurate at 16 knots. Especially given the science I posted earlier indicating that if anything, stability actually increases with speed.

On the other side, as I've mentioned anon and as @madham82 and @disc alluded to above, we have seas in this game that look like consistent 20-30 foot waves (a sea state 5-6), and small cruisers or destroyers at full speed seem to be able to fire with impressive accuracy when their guns are literally underwater and the ship is broaching and stuffing all over the place in a way that would be difficult even to steer straight.

I guess in the absence of any historical accuracy-vs-speed data to the contrary (are any of the folks who used to post detailed gunnery info still around?) it stands to reason that the cruise bonus really should be tied to heavy weather conditions (and the size of the bonus related to hull size) to be remotely plausible. Not that I'm expecting any chances since they've now tied this game mechanic closely to the new formation system.

[Fairweather]

21 knots for the QEs may have been because the rest of the battle fleet could only do 21-22kts? Hood's gunnery officer reported that above a certain speed (mid 20s I think) vibration in the spotting positions/DCT became "excessive", presumably making accurate shooting more difficult. I think I remember reading something similar regarding vibration on Invincible and Inflexible at the Falklands too.