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View Full Version : Estimate speed via wake size... How?

Wild_Cat_NL
04-11-2007, 11:29 AM
I've no clue how to estimate speed via wake size, could some one please explain this with some more details along with when and when not to try this...

Wild_Cat_NL
04-11-2007, 11:29 AM
I've no clue how to estimate speed via wake size, could some one please explain this with some more details along with when and when not to try this...

Klocka1992
04-11-2007, 11:55 AM
Wake is the water that is pushed away from the bow when driving a ship. It is the white spraying water in the bow(front end) of the ship. It's real easy, Bigger Bow wake=More speed, and vice versa. If you are going to torp a ship that you see is gong fast guess the speed and then you divides the ship top speed with 2, Example (top speed of 10 knots divedes by 2 = 5 knots, estimated speed by you 7 knots and then take the number most to the middle, in this case 6 knots. DONE!http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif

/GS

psychp0
04-11-2007, 12:19 PM
Easiest thing to do is to calculate it yourself. No really, it's EASY.

Put a mark at the front of a target with the pen. Start the stopwatch. At 3 minutes 15 seconds put another mark at the front of the same ship.

Now, provided you are in METERS, use the ruler to draw a line between the two marks.

The resulting number is their speed in knots. SO, of they have gone 900 meters (or .9 km) their speed is 9 knots. If they have gone 1.2 km, their speed is 12 knots. VERY VERY simple and takes but 3 min 15 seconds of plotting.

davejb1167
04-11-2007, 01:23 PM
Put a mark every minute, multiply distance measured by compasses by 60 - 0.1 miles = 6kts, 0.2 miles = 12 kts.... midway between 0.1 and 0.2 points = 9kts, and so on. Easy to get within 1-2 kts, then let your solution run for a minute to check the target and your torp solution don't move at different speeds... if the target lags the solution your speed needs winding back a knot or two, if the target moves faster then add a knot or two.

This is the imperial measurement version http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

RoughRaider1
04-11-2007, 02:52 PM
I believe the wake is the wave left behind the vessel. The spray in the front is just that, bow spray. When you go past a marina you'll see signs that say.."watch your wake" because they rock the docked boats violently.
Displacement hulls make larger wakes in relation to thier speed. But a vessel with a larger displacement could generate a larger wake going slower then one of less displacement going faster.

Wild_Cat_NL
04-11-2007, 03:58 PM
Thx... but ehmmm I'm not quite following you, on how you calculate things.

I understand the part about ship speed and bow wake size. Slow going ship, small wake. Fast going ship, big wake.

Taking the top speed of the ship and dividing it by 2. Sure, if you say so... But why divide it by 2?

Then you give an example, what I don't understand... Might be a good example, but I don't see where your going with it nor do I see any logic in it.

So ehmmm, that leaves me back to square one.
Can you estimate the ships speed by just looking at the wake size?
Or do I first need to calculate the ships speed in knots by doing some drawing and measuring like how psychp0 or davejb1167 explain things... Then have a good long look at the wake size and recall it from memory the next time I encounter a ship with a similar wake size...

More details, please... want to learn more, but the given replies don't make sense to me and how the are linked to wake size.

FYI I'm not using the metric system.

opalias
04-11-2007, 06:11 PM
I don't know how to do this in game, but the reason wake size and speed are related has nothing to do with the size of the ship. The rate that a wave propagates in water is fixed. Thus, a stationary boat emits a ring, which can be thought of as a 180 degree wake, a boat moving at a speed greater than zero leaves behind the characteristic V, the narrower the V the more water the boat has moved through in the same period of time, following that model, a boat moving at infinite speed leaves a single line behind it. Thus if you know the right constants, which i don't, you can calculate speed based on the angle of the wake.

yngvef
04-11-2007, 06:38 PM
I have the collectors edition of the game with the separate recognition manual. It states the length of all ships.

I simply use a stopwatch to see how much time a ship uses to pass through my crosshairs (target lock off). The closer you are to 90 degrees AOB, the easier the measurement is (but it works quite well at AOB as low as 50-60 degrees). Then you divide the length of the ship with the time it takes to run a length; which gives you meters per second which you can multiply by 2 to get a rough estimate in knots, or you can multiply with 1.94 to get it REAL accurate (not really necessary).

Example: A Takao heavy cruiser passes through your sights in 20 seconds. It's 204.5 meters long. 204.5 meters / 20 seconds = 10.2 m/s. Multiplied by two, you can easily see the speed is roughly 20 knots, or you can do it the more complicated way: 10.2 X 1.94 = 19.8 knots.

Using this technique, I've hit almost every target with manual TDC at distances up to 2000 meters. Works like a charm, and you don't have to use map contact updates. Also, on known ship classes with known length, this would work quite well in real life too. I don't know how the skippers in WW2 did it, but this works quite well for me http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

This process requires a handheld stopwatch (because the ingame watch resets when you stop it, making it too difficult to use for this in my opinion, a simple calculator, and the recognition manual that tells you the length of the ships.

Hope it helps http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

TO devs, mods, or whoever capable of doing this: The length of ships should be stated in the in-game recognition manual, and the manual should not reset to the first boat in the list every time you close and open it.

EDIT: I just noticed that you mentioned not using the metric system, but the conversions are quite simple. 1 foot = 0.304 meter and 1 nautical mile = 1852 meters. Knots = feet per sec / 1.69.

HOWEVER, you don't have to play the game in metric to use my method even though the recognition manual uses metric units. The math is still correct even if you play the game in cubits, feet, furlongs, yards or whatever you fancy http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif. I find the "multiply by two"-method easier than the "divide by 1.69".

yngvef
04-11-2007, 07:36 PM
Also, if you don't have the printed recognition manual, I'm sure someone crazy could be persuaded to write down the length for all ships in the game. I could, but not now as it is late where I am.

Good hunting http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

Klocka1992
04-12-2007, 06:55 AM
the reason to divide it by 2 is that it is not common sense for a battleship driving in 33 knots when escorting carriers almost all ships drive at half or little ovar half speed. The method i showed you only works when you are not dedected. And sorry for for missjudging "wake" but helllo im driving 100% realism here And i cant press F11. Have fun,http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif

Its more fun to use manual tdc, its makes you feel that you completes something.

/gs

Wild_Cat_NL
04-12-2007, 12:57 PM
Thx alot yngvef!

Yet an other way to calculate/estimate the speed of a target.

I've tried it a few times. But sadly I didn't score a hit yet. But, I came very close and that is much closer then I normally did when I tried to gestimate/calculate the speed in a very short time period.

So I wonder, can this only be applied when doing 0 knots?

04-12-2007, 02:00 PM
uhhhhh... yeah that sounds like a real cakewalk ! i was gonna say big wake=fast, small wake=slow . you are firing a spread of torps right?

Wild_Cat_NL
04-12-2007, 02:07 PM
Not having a recognition manual is a bit of a pain... Nor do I know how I could obtain one so I can print it and build my own. Is there one supplied on the DVD? If not, could I find one online.

So for now, I would like to know if the ingame recognition manual uses a fixed scale for all boats shown with the measuring scale line right under the boat.

I looked up the Takao heavy cruiser in the ingame recognition manual. I could see it had 5 steps in the measuring scale (or what ever its called in proper english) Its 204.5 meters based on yngvef his information. I could place about 6 and 1/3 steps of measuring scales under the ship ... 204.5 / 6.33 = 32.3 (rounded it up to 33)

So I used this information on a Medium European Composite Freighter. 3 and 3/5 Measurments Scale I could line up under it. 33 * 3.6 = 118 meters... is this correct? or am I close to its acctual size?

Correct or not... I scored a hit never the less.
Even tho I didn't see any hole where it hit, it sunk by a single torp hit.

04-12-2007, 02:45 PM
the book says its 121.9 mtrs

Wild_Cat_NL
04-12-2007, 04:15 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by subhadar:
the book says its 121.9 mtrs </div></BLOCKQUOTE>

Thx... Those few meters that i'm off wil not hurt my speed calculation.

I'm sticking with my 33 meters steps for the measurement scale.

I'm already having great deal of fun with it. Even tho I don't have the exact lenght of a ship. I now able to come up with numbers that are close enough and so far... I'm no longer missing.

I do have to go 0 knots, when I do the speed measurement to make it accurate... Still have to figure out how to make this work when moving.

Klocka1992
04-12-2007, 04:31 PM
Spray and pray.

yngvef
04-13-2007, 02:56 PM
Yes, I forgot to mention that the sub has to be stationary or near stationary for this technique to work. Especially if the boat you are targeting are close because the change in angle caused by the movement of your sub is greater the closer you are.

I just assumed people stood still when targeting ships because I almost always do http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif my mistake...

luviera, I'm glad you found it somewhat useful http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

yngvef
04-13-2007, 03:14 PM
Finally, remember to fire the torpedoes at "slow" setting until the patch 1.2 has arrived... There is a bug that "fast" torpedoes are running too slow and pass behind the ship.

RoughRaider1
04-13-2007, 08:33 PM
Your right about the wake when looking down on it from above and measuring the spread of the V and that it will not change due to the size of a ship but only it's speed. I was thinking about the actual wake wave height itself. I can assure you the size of the ship or rather it's displacement has a very large impact on the wakes wave height but the speed determines the shape of the V reguardless of the ships displacement.
A slower ship will have a wider looking V and a faster one a narrower V. The actual speed the wake travels may actually be constant too, but it looks narrower with a faster ship because the ship has traveled farther before the wake disapates making it look longer and narrower.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by opalias:
I don't know how to do this in game, but the reason wake size and speed are related has nothing to do with the size of the ship. The rate that a wave propagates in water is fixed. Thus, a stationary boat emits a ring, which can be thought of as a 180 degree wake, a boat moving at a speed greater than zero leaves behind the characteristic V, the narrower the V the more water the boat has moved through in the same period of time, following that model, a boat moving at infinite speed leaves a single line behind it. Thus if you know the right constants, which i don't, you can calculate speed based on the angle of the wake. </div></BLOCKQUOTE>