Gibraltar!
 

http://img90.imageshack.us/img90/4740/11fm1.jpg

I think you could say I'm in a bit of a pickle :hmm:

It's '44 and I'm drifting through the Straight in my brand new XXI at 200 rpm, exactly 260m. I had just attacked two convoys, one going into the Med(troop transport) and one coming out(three T3's and a troop transport), lost the pursuing DDs and then made my approach directly down the middle of the needle thin entrance. Satisfied I had lost all escorts and finished reloading all torps for the trek ahead, I began heading through @ 128x TC. At around midnight, I had not quite reached the point in my journey directly below the famed port when my 128x TC drops down to 8x! I'm in a XXI and not even going ahead slow, but set speed to coincide with 200rpm and I'm at 260m! This is my first attempt at passing through the straight because I wanted to wait until I had the XXI to attempt it, but how in the world did they find me? I know it's not sound(although my next attempt will be at 100rpm) and I'm extremely deep so how did their passive sonar pick me up?

I know the DDs passive sonar is like a cone ahead of the bow and that I try to avoid this area when approaching a convoy's lead DD, but c'mon, I'm usually at around periscope depth when I do this. Maybe I should drift down to 280m on my next attempt?

Another theory I had was that I'm approaching the problem the wrong way: instead of going down the middle where patrols are heaviest, maybe I should try going along the outskirts, in shallow water...Any input would be great.

why u going down the straits in 1944?? The Med is lost, no ports!

You must be brave or nuts ;)

Part of passive detection by the AI, is how many RPM's your turning.

By default, since the XXI has more Emotor power, it turns a higher RPM at most speed settings. (IE ahead slow, where your crusing at about 6 kts, is damn near flank speed on a standard uboat)

I wouuld manually set speed to say, 1 or 2 kts. That should lower your RPM's, and its about the best you can do short of modding the boat.


EDIT:

almost forgot, how calm the seas are also effects passive detection. If your trying to cross through gibralter and the wind is low, and seas are likecalm, the range at which they can detect you is increased. Similarly the heavier the wind, the rougher the seas, the less they can hear.

In real life, yeah it's plausable... but did they include this in the game?

yup.

From testing ive done awhile ago, im quite sure of it.

Awhile ago i was testing AI detection, and ran a series of tests messing with the wavefactor COEF, the state of the sea, and how fast the boats going.

To summerize i found that that by tinkering with the wavefactor coef, i could change how large or small the effect of waves upon their passive sonar is.

WIth waves presenting a small effect, i found that the stealth meter would go from green to red at a much farther distance then the stock game. By increassing the sea state from 0 to 15, i found that this distance shrank, but was still fairly far.


WIth thewavefactor coef presenting a mediem to large effect on their passive ablities, i found that they damn near had to step on me before they'd hear me. The rougher the seas, the closer they'd have to be to hear me.

If i remember correctly If you remove (0 out the wavefactor coef), the AI can practically hear a Rock Cod fart in the pacific from the atlantic.

Well as you can tell from the pic, the wind was about 6m/s. So judging from your advice, I should wait until wind is 10m/s+ and go about 100rpm?

Exactly, that's why I never look at my speed, but rather rpm when trying to evade/remain undetected.

Interesting,

By the way,
Which dial you look at to get the RPM?

thanx!
:oops: :hmm:

Goto into the conning tower and look right.

Wierdest thing happened, I went down to 275m @ 1knot(50rpm) and I kept going! While no ships were within range, I went back up to 275m at ahead slow, and while the dive planes were at 0, I went back to 1 knot, I started drifting deeper again! I went to 230, 220 and 190m and it seems that, while I'm in the red on my depth gauge and I'm going really slow, the boat can't keep itself up! Maybe a bug or maybe it's realistic but to remedy this, I went up to the yellow zone(160m) and continued on that way, so far I'm right under Gibraltar, going 50rpm(1knot) @ 160m and things seems to be going ok. A destroyer even passed directly over me...abeam! No ping, no nothing even though my silhouette was staring at him! I'll make an update If I get passed the straight.

If 1 DD just happens to go over the top of you, your screwed. The Active pinging that all DD's do at 14 Knts and under will get you. Its max depth is 300m. Being under TC you may have very well done the above and not been aware that you had done so.

The thing that gets me is that the Devs did the incorrect thing with the Type XXI. You see its Prop is far bigger than any other Uboat. Being so its there for must turn at a slower RPM. I wont go into properler theory here but to basicly say that the bigger a prop the slower it turns. This does not equate to a slower speed BTW. Its all due to pitch, how many blades an so forth. Anyway the Type XXI's prop RPM's is to fast.

So therefor the noise it generates is now to loud. Technicaly the Type XXI is cavitating at all speeds over 4-5 Knts. They may have used the correct RPM's for the Electric motor's, but they sure as hell didn't allow for the reduction gear (Gearbox). The most typical ratio on light craft is around the 1:1.5 mark, but on heavier craft its common to get ratios up to 1:2.3, sometimes higher (thats 1 revolution of the Prop to 2.3 revolutions of the motor)

Not a bug. its acutaly fairly realistic. Whats unrealisitc is a sub maintiaining depth without forward motion of some sort. At least thats my understanding of it.

You dont see this behavior very much in VII boats, but you see it alot in the larger boats like the IX and XXI. Basically the deeper you go, the higher your absolulte minimum speed is to maintain depth. So if you go down real deep, and creep along at 1 kt to be as quiet as you can, you'll slowly lose depth.

While i cant prove it, my overall experience has been the longer you stay deep creeping along at 1 or 2 kt, the harder it is to surface. Ive had a few situations where it got particuarlly intresting because i felt i coudlnt speed up the screws to recover depth without being heard, and i coudlnt gain depth because i coudlnt increase my speed.

Its quite intresting when your boat is at a 30 degree incline, bow up, stern down, dogpadding. :D It also makes turning manuvers impossible to do, because any reduction in forward momentum makes the boat drop another couple meters.

Usualy going at ALOT faster speed and ordering to surface (but stopping the asent at say 130 meters) will recover from it. Ive had one situation where i orderd to surface (but stopping it at a comfortable depth) at least twice in one encounter, and got to the point where that didnt work anymore and had to blow ballast.

I managed the VIIC through the Gib, very easy in later 1942, i got ordered to head to Brest port so had no choice but to head threw it. And yes i hugged the sides spotted two destroyers in the distance they never spotted me, though i did get hassled alot from PT boats., and nearly got sunk when i thought it was safe to surface hit the 256x and within 5 sec a destroyer was spotted so had to dive and slowly do the last few miles out of there.

I wouldn't do it though in 1944, even if i did have a XXI

Well I made it through, sort of.
http://img82.imageshack.us/img82/9941/26fw.jpg
I went along at about 2kts the whole way at around 200m(this time I didn't drift deeper) and got pinged on two different occasions. The first time I got away by maintaining speed until he went into his run across my bow and setting ahead slow as my new speed to get passed the depth charges, returning to 2kts after about 200m away from the line of DCs, I let loose a decoy and continued on with about 5 DDs and 2 elco's circling the decoy. Same thing happened the second time with the same result. I seem to have found a new way to escape DDs without turning or going deeper!

About 2 minutes before this screenshot was taken, I was going at snorkel depth(16m) and running at ahead one-third when some aircraft missed me with their bombs, put the snorkel down and I'm moving at ahead slow @ 16m. Repairs are finished(hull's still @ 100%) and so I'll continue on until nightfall to put the snorkel back up(those aircraft probably just saw me as I've got the radar fix and the snorkel was barely out of the water).

On my way back I think I'll try moving along the southern coast of Africa to avoid the heavy traffic.

http://img151.imageshack.us/img151/9110/30ue1.jpg
I think I can safely say heading through Gibraltar was worth it... :arrgh!: Even though there probably will be naysayers saying I could have just waited for them to get through the straight.
I spotted two passenger liners in one of those long straight line convoys the very same day I took the map screenshot...I'll give updates.