How long is a real ship wake?

[LoBlo]

So we've all used wakehomers now and again. They are great weapons and allow a "fire and forget" tatics to any sub. Just shoot, and let them fish sniff out the trail.

But question is? How long is a real life ship wake? The question comes up whenever we see a wakehomer latch onto a ships trail, but the ship is at least 6-7nm past that point.... are ship wakes really 6miles long? Longer? Can a RL wake be seen some 15minuters after a ship has past?

Anyone with sea experience that can offer their observations?

[XabbaRus]

The Russians seem to think so. They have non-acoustic sensors on the Akulas and Viktors that are believed to be for tracking the wake turbulence of ships and subs that have been through the area some time before.

Not much is known about them. All I know is that the abreviation is SOKS.

[LuftWolf]

If it makes you feel any better, LoBlo, the size, mass, and speed of the target plays a large role in determining the length of the ship's wake.

A FFG under 10kts generates a very short wake, and at 5kts and slower practically no wake. A supertanker at 12kts or a large warship above 25kts generate extremely long wakes in game.

Wakehomers work, at least partially, by using a very short range high frequency sonar to detect bubbles left in the water in a ship's wake.

I would imagine that the four screws and and massive hull of a Nimitz class at 30kts would generate enough disturbance in the water to still be detectable 10-15 minutes after the ship had passed, maybe more, but that's only using heuristical thinking, I'm not absolulely certain.

In any case, the wakehoming behavior in the game always seemed fine to me (except that it can track submarines if the depth is the same depth as the submarine, which is crap, but can easily be taken out using a combinations of the database and doctrines).

Cheers,
David

[LoBlo]

Yeah, I'm looking more for quantitative numbers. Intuitively bigger ships = longer wakes and faster movement = longer wakes, but in the context of a combat model, "how long is it" is the question at point.

I mean for example, here's a picture of a carrier
http://upload.wikimedia.org/wikipedi...rican_navy.jpg
http://yaleglobal.yale.edu/display.image?id=5353
http://apsey.org/ximages/navy_csg.jpg
http://www.navsource.org/archives/02/74.htm (about 2/3 down the page is a good wide angle photo.

So its impossible to tell the true speed of the ships in the photos, but from the looks of it appears that the wakes (given that a carrier is around 1000ft or about 6/10 or a mile long) are extending approximately... 4 - 5 miles behind the ships.

Perhaps some better pictures are in order if anyone has been available. But we've all seen the in-game wakehomers lock onto a ship from 10nm... is it feasible? What game engine aspects control the length of a ship wake anyway?

[Kapitan]

In game it depends dont realy know, but in real life the wake can stay in the water for several hours by that time the ship is 30 to 40 miles away, also depends on type of propellor and also the ships wieght.

[Nexus7]

Sorry for putting "transversal" questions but:

1. why would you use a wakehoming instead of an active/passive
2. length of the wake, according to the answers so far, can be very very long... and the width?
3. does the fish need to enter the wake with an angle in order to effectively acquire?

[shift-E]

[quote=Nexus7]Sorry for putting "transversal" questions but:

2. length of the wake, according to the answers so far, can be very very long... and the width?

as far as I could ever tell, the width of the residual wake (the whitish bubbly remains of it) never seemed to exceed the actual beam of the ship..... in my experience (Tico CG's, Spruance DD's, and even one HMAS Anzac-class FFG) about 50 feet...

[johan_d]

http://www.steelnavy.com/WavePatterns.htm

http://images.google.nl/images?q=shi...=&start=0&sa=N

[SeaQueen]

Originally Posted by Nexus7

Sorry for putting "transversal" questions but:
1. why would you use a wakehoming instead of an active/passive

Mostly because they're easy to use and they have no wires to worry about, so you can shoot and scoot away as fast as you can before the ships you shot them at start buzzing around like angry hornets.

[LoBlo]

And they are no countermeasures that can fool them. You don't have to worry about decoys (as long as the torp has found the wake you wanted.)

On a side note: I've done some digging into Kapitan's comments and he's actually right on. Check out these space views of ships wakes. From space some of these things are seen to be a 200km long.

http://disc.gsfc.nasa.gov/oceancolor...b/oss_94.shtml

So it seems like the effects of the turbulence say around for a while. The obvious followup questoin would be: But how long is the turbulence significant enough to be detectable by a sonar sensor? The only people that probably know are the engineers that build the torps in the few place... and the navy brainiacs that are working to counter them.

[LoBlo]

Originally Posted by Kapitan

In game it depends dont realy know, but in real life the wake can stay in the water for several hours by that time the ship is 30 to 40 miles away, also depends on type of propellor and also the ships wieght.

30-40 miles?... ...I'm going to have a hard time believing that.

[Kapitan]

Ships traveling at 15mph which is only about 17 or 18 knots will do 15 miles in one hour so in two hours how far has that ship gone?

The wake works on these factors.

Nuber of blades on propellor and size
Speed the propellor rotates
Wieght of the ship
Draft of the ship

This is something im learnding for my officer course.