Allied Forces Thread

**Fisherking** · 01-20-2011, 23:08

Here is the advantage. The lead escort plays leapfrog with the convoy staying far enough a head to use passive sonar...which means rushing a head and then very slow.
If we use active pinging before we see the subs it give away our location.
The subs will pick up the sound of the convoy much quicker than that of a single ship and see the smoke before we see the sub if we don’t have something forward.

The lead ship is listening for submerged subs and looking on the surface and as an advanced radar picket. It is more advance warning than hunter and it only works during the day.

Subs can pick up a convoy by sound and hone in from about 20 miles. The preferred location would be in front of us. They won’t expect us to use passive sonar and they can not lay still in the water.

Does that sound riskier than holding positions and doing nothing?

No gap we go from here to England.

**Sarmatian** · 01-23-2011, 14:58

Sorry guys, thought this was going to be a bit broader IH. I don't have the knowledge about such specific issue and technology and don't have the time to learn now. I'll have to withdraw from the game...

**Peasant Phill** · 01-23-2011, 15:05

Originally Posted by Sarmatian

Sorry guys, thought this was going to be a bit broader IH. I don't have the knowledge about such specific issue and technology and don't have the time to learn now. I'll have to withdraw from the game...

I don't have the specific knowledge either. Just read a few wiki articles now and then and perhaps a few interesting websites. I can't say I have read much on this subject. Common sense and the inclination to ask questions is all it takes to be a worthwhile contributer as far as I'm concerned.

Originally Posted by Fisherking

Subs can pick up a convoy by sound and hone in from about 20 miles. The preferred location would be in front of us. They won’t expect us to use passive sonar and they can not lay still in the water.

Unsurprisingly, after some further thought the plan appears to be sound. If subs can detect us from 20 miles away, from how far could we detect them?

**Fisherking** · 01-23-2011, 17:43

By eye- maybe 12 mi.

By radar- in theory about 24 nautical mi (but subs are low in the water and choppy seas can hide them almost all together. Under normal conditions 1941, 6 to 10 N.mi.

Passive sonar- sub on surface using engines about 12 N. miles, submerged on electric motors but not silent running 3 to 5 nautical mi. It can tell direction but not range. Active sonar is needed to determine range.

These are only rough figures and conditions could make it much shorter ranges.

References that may help:
http://en.wikipedia.org/wiki/36th_Es...8Royal_Navy%29
http://en.wikipedia.org/wiki/Battle_...2%80%931945%29
http://www.uboat.net/index.html
http://www.convoyweb.org.uk/index.html

As to knowledge base; I know a lot more about subs than I do about escorts so don’t feel so alone.

**Peasant Phill** · 01-23-2011, 22:15

In other words, they can 'see' us from farther out than we can. I was under the impression that we had the better equipment. This makes it a lot more complicated.

**Fisherking** · 01-24-2011, 08:52

Yes, at this stage of the war they had advantages in being able to find us before we could find them. That doesn’t mean they can get into an attack position without us knowing they are there. If we find them we can make it very unpleasant for them.

The subs were also faster on the surface than the ships we have. But they need 5 hours on the surface to charge their batteries in order to operate submerged.

They can not fight us on the surface however, and submerged they are slower and can’t keep up with the convoy. It also depletes their batteries.

The greatest danger is for a night surface attack where they get among the convoy its self. During the day we can keep them far enough away, if we are diligent, that they can’t do much harm. At night it is radar and star shells that can help us most.

If I read the chart correctly the convoy we are escorting is SL 89. The article makes it sound like nothing happened prior to convoy HG 76 but if you look on convoy. net you see there were two ships lost west of Ireland from SL 89.

It could be that the escorts were exchanged off southern England but I don’t know, and it will depend on how the boss runs the game.

Something important to remember is that the merchant ships should be in a box formation and zig zag on the mean course. At twilight it is a good idea to make a radical course change to defeat any U-boats laying in ambush ahead of us.

Also remember that to launch a torpedo the U-boat has to work out a complex geometry problem using estimates of speed and course before they can fire. It will take them several minutes to complete, so altering course and speed frequently reduces the chance that their target solution will find a target.

We are not totally without long range attack weapons either. Subs don’t zigzag until an escort is above them. One of our ships carry torpedoes that can be set deep enough to target a sub at periscope depth. Those torpedoes are quiet enough that the sub can’t hear them coming until it is too late.

**King Kurt** · 01-24-2011, 13:14

Some good technical stuff recently on the thread. The only thing I would disagree with is Fischerking's comment on U Boat speeds. I would have said that our vessels were a similar speed to a surfaced U Boat - about 15/16 knots. moreover a surfaced U Boat's speed is probably more affected by the sea state. If the sea is rough, their low freeboard would mean that full speed might mean the conning tower being swamped.

as for detection - we have 2 tricks up our sleeve - aircraft (from gib in this instance) and Enigma code messages