ship stopping distances

i wanted to run some numbers by you to see what is the most realistic ship slowing times in your opinion

i tested the battleship kongo from a 20 kt speed doing evasive manuvers and at a 15 kt speed and it will stop by just turning off its engines and drifting for the stoping test

these are the numbers i got for three different settings i tried:

stopping test one:
from 15 kts - 11 kts = 2 minutes
from 15 kts - 10 kts = 3 minutes 15 seconds
from 15 kts - 9 kts = 6 minutes
from 15kts - 8 kts = 10 minutes 10 seconds
from 15 kts - 7 kts = 15 minutes
from 15 kts - 6 kts = 20 minutes 30 seconds
from 15 kts - 5 kts = 26 minutes 45 seconds

evasive manuvers test: it slows from 20 kts to 10-12 kts when turning

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stopping test two:
from 15 kts - 11 kts = 4 minutes 30 seconds
from 15 kts - 10 kts = 7 minutes
from 15 kts - 9 kts = 10 minutes
from 15 kts - 8 kts = 13 minutes 45 seconds
from 15 kts - 7 kts = 18 minutes 20 seconds
from 15 kts - 6 kts = 24 minutes 15 seconds
from 15 kts - 5 kts = 32 minutes

it slows from 20 kts to 12-14 kts when turning


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stopping test three:
from 15 kts - 11 kts = 4 minutes 30 seconds
from 15 kts - 10 kts = 7 minutes
from 15 kts - 9 kts = 10 minutes
from 15 kts - 8 kts = 13 minutes 45 seconds
from 15 kts - 7 kts = 18 minutes 20 seconds
from 15 kts - 6 kts = 24 minutes 15 seconds
from 15 kts - 5 kts = 32 minutes

it slows from 20 kts to 14-15 kts when turning

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acceleration test for all three versions above:
from 1 kts - 5 kts = 15 seconds
from 1 kts - 10 kts = 1 minute 5 seconds
from 1 kts - 15 kts = 2 minutes 50 seconds
from 1 kts - 17 kts = 4minutes
from 1 kts - 20 kts = 6 minutes 15 seconds


in your opinion, which is the most realistic slowing speed in evasive manuvers and in your opinion, which is the most realistic slowing down speed from turning off engines?

[Rockin Robbins]

Question: is the same set of adjustments going to affect acceleration and deceleration? I would think (non-researched opinion that could be dead wrong) that deceleration would be considerably faster than acceleration. Tater could really help here I think, with some real ship numbers.

I'm thinking a 20 knot ship should go about 15 knots when maneuvering, decelerate like #1 and take over 30 minutes to go from 1 knot to 20 knots. So I would say acceleration like #3 and deceleration like #1. And of course, the limited controls will probably make it impossible!

That's my opinion right now, subject to correction by hard numbers from real surface craft.

Originally Posted by Rockin Robbins

Question: is the same set of adjustments going to affect acceleration and deceleration? I would think (non-researched opinion that could be dead wrong) that deceleration would be considerably faster than acceleration. Tater could really help here I think, with some real ship numbers.

I'm thinking a 20 knot ship should go about 15 knots when maneuvering, decelerate like #1 and take over 30 minutes to go from 1 knot to 20 knots. So I would say acceleration like #3 and deceleration like #1. And of course, the limited controls will probably make it impossible!

That's my opinion right now, subject to correction by hard numbers from real surface craft.

actually no, i CAN control deceleration and acceleration seperately however my test doesnt include reversing engines.

drifting is controlled by one set of values and acceleration has its own value.

as for stopping its like a train, once you get a large mass in motion its a lot harder to stop it quickly power wise than it was to get it in motion.

thats why a train needs brakes on all the cars but only one or two engines to get it going. (an object in motion wants to stay in motion)


EDIT: i also added the acceleration tests i got for all 3 versions above

[Sailor Steve]

On the other hand, a train doesn't have an equal weight of water pushing against it all the time. Ships do decelerate relatively quickly (relative to cars and trains, that is) but the slower the ship is going the less the drag, so it might drop from 15 to 10 knots in a lot less time than it takes to drop from 10 to 5 knots. Funny, that is very much how your tests look.

I think test one is closer to reality, but that's just what I think, not based on any hard facts.

On the other hand, there is no way Kongo is going to accelerate to 5 knots in 15 seconds. Should be more like 5 minutes. To 20 knots should take 30 minutes or more. I'll get some numbers from home and put them up tomorrow.

Originally Posted by Sailor Steve

On the other hand, there is no way Kongo is going to accelerate to 5 knots in 15 seconds. Should be more like 5 minutes. To 20 knots should take 30 minutes or more. I'll get some numbers from home and put them up tomorrow.

yes i know, the game is hard coded that way. every ship gets a free jump start to 5 kts in way too quickly a speedup. 10-15 seconds is about as slow as i can get but its better than the 2 seconds it takes in stock lol.

my biggest problem is turning and the amount of speed that is lost. what do you think about the turning deceleration speeds?

Originally Posted by WEBSTER

my test doesnt include reversing engines.

i figured stopping by reversing engines would be about the same as acceleration speeds so i figured i would assume they are the same but i will check this at a later time.

[jmardlin]

They wouldn't be because reversing engines even at back emergency only uses about 2/3's ships power. So stopping distances should be slightly longer. But not by much because the screws are much more efficient running backwards because of less turbulence in the water.

[vanjast]

Webster, I found this in the 'attic', and might be useful information.

[Sailor Steve]

Originally Posted by jmardlin

They wouldn't be because reversing engines even at back emergency only uses about 2/3's ships power. So stopping distances should be slightly longer. But not by much because the screws are much more efficient running backwards because of less turbulence in the water.

Drag helps as well. Reversing the engines to stop the ship should make a big difference.

Here are the numbers I promised. The first is a graph made for a naval wargames study back in 1929. Kongo should be in the same area as Repulse.


This is an actual acceleration board from a WW2 aircraft carrier. Sorry I can't remember which one, but at the time I wasn't in a position to record where stuff I was downloading came from.