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Old 07-26-08, 10:08 PM   #16
Frame57
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No! Unlimited fuel will not give unlimited "Goose Juice". That will always deplete. Try a ten knot speed to get where you are going, else you have a fuel leak.
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Old 07-26-08, 11:03 PM   #17
pythos
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The boats in SH4 actually have a pretty well simulated hull drag model.

As a boat moves through the water it creates drag, this drag increases as the boat speeds up, but it also increases when it slows down. That's right, drag increases at slower speeds. The boat has an optimum speed for best speed and drag, this is where the drag is at its its lowest, and the boat is operating at the most efficient.

For instance. These are the speeds and ranges for a gato leaving port.
at 1/3 the boat had a range of 5585 NM, at 2/3, 11778 NM, Stand 15113 NM, Full 5548, and finally flank 3634 NM. So the optimal cruise for this boat is at standard speed, which is about 10 kts. This is also affected by weather and sea state, but not all the much.

The type XVIII is a very very clean hull design hydrodynamically. Compared to the long legged type IX, the hull of the type XVIII is very slick, which allows it to travel further per gallon of fuel than the less smooth type IX.

I am going to do a range test with the type XVIIII and post my results. Stay tuned.
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Old 07-27-08, 12:11 AM   #18
pythos
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Default Ok, so the hydrostatics for the typeXVIII stink.

I did a speed and range check, and yea, the boat is pretty awful as far as range it concerned.

Here are the results.
1/3: 15868 KM, at 7kts
2/3: 13243 KM, at 10kts
stand: 7126 km, at 15kts
Full: 5255 km, at 17kts
Flank: 4649 km, at 18kts.

Remember these ranges are in kilometers. The milage at the best range speed is 8569 NM, just over half the range of the Gato at standard (10kts).

It is in no way a long range boat. Probably another reason the boat was converted over to the type XXI standard.

As far as a hard hitting, "strike and fade" weapon this thing is top notch. You can quietly sneak in, fire your first salvo, engage the walter and dive deep, all the while reloading your tubes, going back to silent running at periscope depth, and make another attack. And you can do this over and over again, and as long as the walter holds out, and the number of torps you have, you can decimate a large convoy single handedly, without having to worry about depth charges. If you get pinged, you can dash away and re allocate your targets...on the other side of the convoy.

If the Walter drive did not have the bad tendency to blow up at the wrong moment, this would really have been a terrible weapon against the allied fleets.

Thank God the drive liked to explode.
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Old 07-27-08, 05:44 AM   #19
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All your above deliberations refers to optimal control theory, guys. In short, optimal speed/range value is an example of minimum energy trajectory solved by Bellman equation.
Of course it is quite hard to understand but it can clearly explain why the slowest sub speed doesn't offer the longest range.

http://en.wikipedia.org/wiki/Bellman_equation

Quote:
Originally Posted by pythos
If the Walter drive did not have the bad tendency to blow up at the wrong moment, this would really have been a terrible weapon against the allied fleets.
This is a big mistake! It should be as follows: "If the Walter drive had not had..." - Type three Conditional!

Last edited by Gorshkov; 07-27-08 at 07:03 AM.
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Old 07-28-08, 08:26 AM   #20
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Default XVIII is a Cheetah

As you all know, XVIII wasn't made for pacific theatre, and they were short legs for this wide area.
Simple problem to solve using larger fuel tanker on this big ship... but simply a bad theatre for them, historically ...

Here is the way I use the XVIII : it's like boom and zoom => cruising 11 knts to go to patrol area (11.000km range), then patroling at 1/3 (7 knts) on the desirated zone, until I have a proximity radio contact or, even better, until one of my sensor reveal me a potential target.

If it's a radio message for an incoming (not outgoing) contact, I plot an interception path to meet the target, only if I could do that without expending to much fuel to hunt.
This mean, no much than 200km (say 100NM) ( at full (17knts), if i couldn't intercept the target within 100NM, I simply forget it and wait for another one.
If it's easy to go to an interception point, I do my best to go there with minimal fuel consomption : If I can go there to 11 kts it's nicer than to go at 17 knts, so you simply have to plot a good path when it's possible.

Once a target pop up to my sensor, I immediately go to Walter propulsion.
If a target is caught by sonar, I have around 20 miles before watching it, so, moving at standard, surfacing, at 23knts right ahead to the target position, reading, during the way in, the right or left defilement on the sonar to lead the path of the target.

Once I see the smoke (using PE here) I finalize the approach, staying enought away to avoid detection (remember to send a "convoy" message to the base when you could do, it will help you and give you more objectives, increasing the immersion).
During that time, I manage to position myself, very easily with walter sytem, ahead of the convoy path.

So the final word is this : only use the walter propulsion when you already have caught a contact on you sensor, never before.
This way you could make around 4 patrol with your H2O2 (reloading 2 or 3 times).
This is actually my first patrol with XVIII, just finished to use all of my torps and half of my fuel, still 84% of H2O2, 45.000 tons in 10 days, south of Java for patrol area.
Stock SHIV (XVIII is implayable with RFB) only external view (for the show)

Fortunatly, there is lot of refueling point, but XVIII is really short leg in fuel for pacific theatre.
Amazing boat anyway.
With 1/4 of type IX torpedo as reload, once you found a convoy, he is in very bad trouble, whatever the escort, all major ships are condamned.

It's harder to find them than to sink them, but usual uboat commander will be really surprised at the speed all things will occurs, about 3 to 4 time faster than usually.
That's need to be pretty accurate and to think 3 to 4 times speeder than in a conventionnal WWII submarine.
But this is not because you have a so good weapon, you become a terrific commander, this ship need to be properly handled to be used correctly.
It's simply not a "magic boat", and you have to learn to do the job in 3 to 4 time less time than other submarines.
Here, experimented submariners will do a much bigger difference than average ones.
Even if it's much more easier to evade problems, it's also harder to engage, as the window is shorter to fire at targets.

This XVIII / XXI are the first modern submarines, in term of performance, the way they are built, and doctrine used with them.
Americans, russians, english and french used this technology at the end of war to built new generation submarines.
We could say XVIII (more likely XXI) completely changed the face of submarine warfare after the end of WWII.
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Old 07-28-08, 09:12 AM   #21
The Fishlord
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If you're really pissed off about having this...There's a great Type XXI mod here. It gives a snorkel, deck guns, and a new skin to the Walther. (And removes the turbine).

http://www.subsim.com/radioroom/show...ied+type+xviii

NOTE: Putting ROW #3a over the mod will remove the deck guns, keep the snorkel, and add the walther back in. If that's your deal, go ahead with overwriting it.
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Old 07-30-08, 12:43 PM   #22
Gorshkov
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My five cents about Type XVIII U-boat endurance: I never tested it in the game but I have recently checked her real data on the Internet. Here you are:

- surface range on diesels: 5200Mm@12kts
- underwater range using batteries: 45nm@4kts
- underwater range using Walter turbine: 202nm@24kts


Also for comparison you have the following data:

Type XXI:

- surface range on diesels: 11150nm@12kts
- underwater range using batteries: 340nm@5kts

Type IXC:

- surface range on diesels: 11000nm@12kts
- underwater range using batteries: 63nm@4kts

Type VIIC:

- surface range on diesels: 6500nm@12kts
- underwater range using batteries: 80nm@4kts

As you can see it is obvious that Type XVIII U-boat was not designed as ocean-going submarine! It was simply direct Type VII boat successor and thus developed solely with ATO in mind. This sub should have shattered Allied convoys around Britain with impunity thanks to her amazing submerged speed.
So I think your blaming on Type XVIII U-boat is unfounded! This sub was good in concept (aside of unreliable propulsion but I assume this was successfully solved in our fictional game reality) and would be very deadly. One thing UBT developers missed is wrong TMO they assigned this U-boat. In short, huge Pacific distances exclude medium range subs as effective tool of warfare. Note US fleet subs were very large boats as for Atlantic standards. They were in 1500t/2500t displacement class, not even produced by European countries during war. That is why you still meet all these troubles with limited range navigating Type XVIII boat...but this is not Type's XVIII fault per se!

Simply Type XVIII should belong to SH3 and Type XXI sub should go into UBT...





Last edited by Gorshkov; 07-30-08 at 03:22 PM.
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Old 03-05-12, 03:07 AM   #23
zygoma
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Default refueling?!?

How/where does one refuel in a mission? And if it's possible, can one also take out a new cage of eels to continue a mission from someplace? I don't see options after I dock besides "Continue Mission" and "Dock at XX XXXXXX?"
Inquiring noobs wanna know......
- -. -..- . ... --... ...--
-.. . -.- .-.. --... .... -. -.--
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Old 03-05-12, 04:04 AM   #24
Hinrich Schwab
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Quote:
Originally Posted by zygoma View Post
How/where does one refuel in a mission? And if it's possible, can one also take out a new cage of eels to continue a mission from someplace? I don't see options after I dock besides "Continue Mission" and "Dock at XX XXXXXX?"
Inquiring noobs wanna know......
- -. -..- . ... --... ...--
-.. . -.- .-.. --... .... -. -.--
Go to any friendly port that is not your home port and select "refit" when the menu appears once you are in docking range.
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Old 03-05-12, 04:14 AM   #25
Hinrich Schwab
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Historically, the Type XVIII never saw the light of day. Construction was halted halfway through in favor of the Type XXI. The Type XVIII is sort of a not-so-hidden Easter egg and a "what if" scenario. However, it is no long range boat. Its diesel endurance is comparable to a Type VIIB with its most fuel efficient speed being around 7.5 knots. 12 knots is not the most fuel efficient speed. The Walter Drive is necessary to maintain depth below 180m. The e-machines are less effective and consume too much battery power to maintain for very long.

What the Type XVIII excels at is submerged high speed approach and high speed submerged evasion. The drive may be extremely noisy, but with a flank speed rate of 28kts, escorts really cannot do much other than run around desperately trying to get a fix before they have to accelerate past washout speed to follow. Even if the escorts are all over you, depth charges do not fall fast enough. The odds of a hit are slim, if you are Johhny-on-the-Spot.

Good thing, too. Historically, the 80% H2O2 fuel is obnoxiously volatile and equally corrosive. A good hit to a fuel cell would rupture it and you would blow yourself up. This reality and the expense of the fuel is why the XXI boat came into being. Germany could not afford to make this thing work fast enough.
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Old 03-05-12, 06:55 AM   #26
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Quote:
Originally Posted by Gorshkov View Post
This sub should have shattered Allied convoys around Britain with impunity thanks to her amazing submerged speed.
If it had worked perfectly as it does in the game. A big what-if. Every nation that experimented with the Walther engine concept after the war eventually abandoned it as too dangerous.
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Old 03-08-12, 04:02 PM   #27
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I just finished my first patrol with the XVIII and I'm pretty satisfied with the results... It's the first time I've come back to port with absolutely no hull damage, probably for a couple of factors. About 56k of ships sunk which is pretty low, but I was able to nail a 10k warship that would have gotten away otherwise using what I'm calling "Super SPEED" for a nice follow up shot, got close enough for a follow up homing torpedo... try dodging that.

It reloads like a beast and if a ship is still going fast with escorts... who cares. Super speed till you get about 600 or closer meters with gas torpedo set to fast, there is no dodging that either! You cannot catch a fast ship underwater with a IX... If you can't surface because a lot of escorts are around to get more speed, typically kiss it goodbye. Especially a warship convoy.

You want to pull out a torpedo and put in a homing torpedo, no problem... it's like a instant request by comparison.

For the distance issue I'm having good results at 1/3 speed, can get around Australia and back.

The deck gun is a shame, because it is fun to jump in that gunner seat and start unloading on a helpless ship without using a torpedo, but I've got 25 torpedoes... no external reloads, they are all at my fingertips. I'll take it as a trade off for a near invincible ship.

Like I said, no damage... I'll sometimes take a nick from a plane... even if I dive I may take a % or 2 of damage. The thing dives way faster without even having to press c for a crash dive. It seems to get spotted less. It also looks smaller hence a smaller target for cannon fire and bombs.

So, where I'll usually take out a few ships with guns really tacking on to my tonnage, it was a pretty fun experience... and I used only like an 1/8th of my hydrogen peroxide! Don't think I'll run out of that stuff.

Well, that's what I can think of off hand... Also I didn't lose crew experience or my awesome torpedoes as someone else stated earlier. They gave me two homing torpedoes and several pattern running torpedoes. I don't use the pattern just program them for a straight run.
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Old 03-08-12, 04:04 PM   #28
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Hinrich, FYI, I get the "refit" option at my home base too.
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Old 03-08-12, 04:07 PM   #29
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Just thought of something else... I get sonar contacts while on the surface using this boat! Because of that under hull design? Whatever the reason, that rocks!!!!!
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Old 03-08-12, 04:09 PM   #30
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Another thing, you can recharge your batteries without losing speed. I tried stopping the recharge and it did not effect my speed while on diesel.
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