Depth under keel when attacking convoys

[4saken]

What's the minimum depth you operate?It seems that anything less than 150m is suicide with my IX.Surfaced attack doesn't seem to work form me...I d rather be at periscope depth and dive fast as soon as i fire the torpedoes.

[Tessa]

Since the IX's are so large they are detected much easier by sonar, and harder to escape from if you get caught. I'm not really a type IX captain, preferring the VII's instead. Usually I'll be at 13-14m while aiming; though the periscope sometimes has to be fully extended you don't run into the problem where at periscope depth the water drop down/you end up in a large troff that exposes your tower and gets you instantly detected. Once the last eel is fired I'm already making my way away from the convoy/task force so that when the first torpedo hits I've hopefully managed to put at least a km or 2 between me and my firing position.

[4saken]

Thanx for that...At full speed or in silent running?

[desirableroasted]

Originally Posted by 4saken

Thanx for that...At full speed or in silent running?

That would depend on proximity of escorts, of course, but as smartly as you can manage. Also, you want as much depth as you can manage (even more important, in my book).

If you can be 150-180m down and 750-1000m away before the first escort shows up, then go to full silent running (silent running mode + under 2 knts), your chances of escaping without a scratch in 39-40 are excellent.

[danexpat]

There's a nifty diagram in the GWX manual that shows how depth of 175+ m provides evasion from early-war front sonar arrays. But the other important thing to remember is that ASW have the same hydrophone equipment you have. Silent running (just under 2 kts) at 180 m works like a charm early war -- in a Type VII anyway.

[raymond6751]

Deep and silent is good, but try to always have about 5 degree turns going on too. The enemy appears to have trouble locking on a curved position.

I tend to zig zag away from them, altering port to starboard every few minutes. Be aware that you are going so slow that for a while you are going straight during that switch.

If they are close, better to do a 10 degree turn in the same direction. When they pass over, switch to other tack and speed up a bit. The speed won't be detected if they just passed or dropped charges.

Remember the big turn when the charges are dropped overhead, and speed.
Also, know where the bottom is. You could be heading into shallow water.

[Missing Name]

"Tiefe unter Kiel - Eins, null, null, null." That's what I like to hear. But as long as the bottom is right at crush depth (~165m in my IXB), I'll be happy.

As for the approach: I sprint on the surface as long as possible, maybe only 2km away in poor weather and then dive. I like attacking from the front... fire the four fo'd torpedoes, turn a bit on silent running and fire the two aft torpedoes as the convoy passes over. Once they're away (or I can hear PING PING PING) I go one knot and dive to at least 80m.

[desirableroasted]

Originally Posted by 4saken

What's the minimum depth you operate?It seems that anything less than 150m is suicide with my IX.Surfaced attack doesn't seem to work form me...I d rather be at periscope depth and dive fast as soon as i fire the torpedoes.

Looking back, I see I didn't look closely enough at your real question, which is how much depth you want to have under you in a fight.

If I have free choice, I want enough to get into the "red zone" on my boat. Early in the war, I rarely need it, but later, oh yes.

For convoys, even early in the war, I would like 70+. That can mean trailing a convoy for a day or so until it reaches deeper water. I don't mind that.

However, sometimes you are assigned to the North Sea & just have to bite the bullet. Or you go to Narvik, where you can have 8 or so escorts after you in a 12m deep, 3000 meter wide fjord.