Das Boot or the American Fleet Boat

[Bilge_Rat]

Originally Posted by Gammelpreusse

That applies if the plane's only detection equipment is RADAR as well, not a RADAR signal detector.

a typical Naxos radar detector could detect allied aircraft at about 5 kms, which gives about 1 min warning.

the ASV MK II airborne radar, in operation in the atlantic in 42-43, would detect a U-Boat at 7-8 miles.

the SJ radar on U.S. Fleet Boats, could detect a large aircraft out to 20-40 miles.

you do the math...

[JamesT73J]

According to at least one source I've read (Cold War Submarines by Polmar and Moore) Doenitz knew as early as the late thirties that the contemporary type of submersibles had a limited future. As soon as Radar was advanced enough (and surface forces owned the surface) the type VII and IX were through.

Herbert Werner (Iron Coffins) was more critical, understanding that by 1943 the boats of the period were basically useless against the allied advances.

Hence the explorations into alternative designs as early as 1942.

[AVGWarhawk]

Originally Posted by Kromus

http://www.uboat.net/types/ixd.htm

Look for facts first.

Just FYI

Small VIIB was able to make 8700NM! and it was pretty close to 11000nm of US fleet boat range

Close only works in horse shoes.

[Gammelpreusse]

Originally Posted by Bilge_Rat

a typical Naxos radar detector could detect allied aircraft at about 5 kms, which gives about 1 min warning.

the ASV MK II airborne radar, in operation in the atlantic in 42-43, would detect a U-Boat at 7-8 miles.

the SJ radar on U.S. Fleet Boats, could detect a large aircraft out to 20-40 miles.

you do the math...

Well, I am not going to debate this topic to death, you are certainly entitled to your opinion, but the most important figure in your list is lacking, that beeing the efficiency of allied airborn based radar detection equipment.

[tater]

I think the US Fleet Type engine setup (diesel-electric) was unambiguously better, frankly. US boats could push 21 knots when not charging, but if you are dashing that fast, do you also need to be charging? Their 11,000 range was predicated on a 10 knots speed. It's not like u-boats ran around at 21 knots whenever they were surfaced—they needed to conserve fuel as well, presumably.

Did any post war boats use direct diesel propulsion on the surface? What %?

[Krauter]

As someone mentioned earlier in the thread, the two submarines are very hard to compare because each was designed to meet specific needs of it's theatre.

Thus it's like comparing (vague comparison coming..) a crocodile to a dinosaure. Sure they're related, but both predators come to meet different criterias of their region and age.

One point that boggles me is that yes, the earlier Type VIIA and possibly the Type VIIBs cannot really be compared to subs like the Gato, Porpoise, etc. But once the U-Boat operations started running out into the Atlantic Gap (now strictly talking of VII operations, not IX which could actually be compared to Gatos) the operational framework starts to look similar to that of the Pacific. Find, Fix and Destroy convoys and targets of opportunity in the middle of the ocean.

Thus, how do such subs such as the VIIC, VIIC/41 and the planned VIIC/42 compare to the Gatos and their contemporary American cousins.

Secondly, I understand the great difference that Radar makes for the Americans, but I'm really amazed to see that such simple (well not really simple..) things such as diving depth (really a Type VIIA can dive deeper then a Balao..) are greatly different between the two.

Question for you naval types: With the fleet boats larger size, would it not then offer a better chance at diving deeper then the smaller Type VIIs? What is the difference maker here?

I am really interested in the differences between the two campaigns and how they affected the ships that fought them, to this thread

Krauter

[tater]

Originally Posted by Gammelpreusse

Well, I am not going to debate this topic to death, you are certainly entitled to your opinion, but the most important figure in your list is lacking, that beeing the efficiency of allied airborn based radar detection equipment.

So the argument is that better radar gear would have been wasted? That is likely true, but it doesn't change the fact that the radar itself was fr more primitive.

Radar of course becomes the analog of active sonar on subs, a no-no since it broadcasts your position.

This goes to the overall failure of the u-boat since it faced a more advanced opponent. It's dangerous to use radar, so your search diameter is tiny (shears to masts or smoke of target... So doctrine then becomes lines of boats, but to make this work, the boats have to call home. Trouble is that the call home is just as detectable as using radar and gets DFed. U-boats had a tough time, really. If you operate alone like a Fleet Type and use radar, you run a grave risk. If you operate in the "chatty" way they actually did, you get detected from that (not even counting code-breaking) and run a grave risk.

It was one of those times in history where technology was "in between" sort of like the US Civil War, and doctrines needed to evolve. The USN boats were more of a true "silent service" which I think helped them a great deal (the IJN had excellent DF capability, for example, even though it took them a long time to get radar detection gear going at all). I imagine that the u-boats would have been less successful in tonnage doing it that way, but also would have sustained fewer losses.

Could it be the differances in tactics in the interwar period?

The americans most likely subscribed to the traditional theory of submarines, their role was to sit at periscope depth outside of the enemy home harbor and sink ships of the line as they sailed out for one big battle. The idea was that they were like torpedo boats that could hide for a bit, not roaming underwater death machines.

The germans thought this way as well, but due to the foe being much more obvious and the tactics based much more on attacking escorted supply convoys submerged and getting away underwater, the focus was indeed on long term underwater ops and a deeper diving depth would be needed.

Still cant for the life of my figure out why radar would be a bad idea. If you suspect air activity in the area than switch it off, why deprive yourself of a tool?

[Piggy]

Yeah Ive always found that a bit odd that the fleet boats max depth was well under that of u-boats...

However, could the explanation simply be that the germans had a lot of prior experience with submarines, at war.

What were the diving depths of WW1 U-boats?

Edit: According to U-boat.net the UB III's (most produced of WW1) had a max depth of ~250' (75m).. so not very deep. These boats are quite similar to VII's.

http://www.uboat.net/wwi/types/index.html?type=UB+III

[tater]

Could the VIIA actually dive deeper? Balaos dove far in excess of rated depth and survived, and post war boats which were little different went deeper still.

I think like radar in actual use, this is more necessity than anything else—not of design, but practice. Had the US faced better ASW, our boats would have gone deeper and deeper since when the alternative is certain death, risking a deeper dive is a chance worth taking.

As was said, comparisons are hard due to the situations faced. Seems like the added range and stores in the Fleets would have proved very useful since simply getting to sea was often troublesome for u-boats. Once there, duration on station would be desirable, right? I assume the allies paid special attention to patrolling approaches to u-boat bases. Were they successful in sinking many that were coming or going from port?

[Gammelpreusse]

Originally Posted by tater

So the argument is that better radar gear would have been wasted? That is likely true, but it doesn't change the fact that the radar itself was fr more primitive.

Radar of course becomes the analog of active sonar on subs, a no-no since it broadcasts your position.

This goes to the overall failure of the u-boat since it faced a more advanced opponent. It's dangerous to use radar, so your search diameter is tiny (shears to masts or smoke of target... So doctrine then becomes lines of boats, but to make this work, the boats have to call home. Trouble is that the call home is just as detectable as using radar and gets DFed. U-boats had a tough time, really. If you operate alone like a Fleet Type and use radar, you run a grave risk. If you operate in the "chatty" way they actually did, you get detected from that (not even counting code-breaking) and run a grave risk.

It was one of those times in history where technology was "in between" sort of like the US Civil War, and doctrines needed to evolve. The USN boats were more of a true "silent service" which I think helped them a great deal (the IJN had excellent DF capability, for example, even though it took them a long time to get radar detection gear going at all). I imagine that the u-boats would have been less successful in tonnage doing it that way, but also would have sustained fewer losses.

Excellent post and lots of good points. Nothing to add, really, as the rest goes too much into speculation.

[Krauter]

For diving comparisons I`m just assuming the designed crush depth of 200m for VIIAs (220 i believe for VIIC's). Whereas the Balaos was somewhere around 600-650ft.

If I am wrong by all means correct me. Because with the arguments that Balaos could go under the 650mark, the argument that VII's went under the 200m mark is perfectly plausible as well.

Edit: In regards to your earlier post on this page tater.. it's kind of like a damned if you do damned if you don't situation . I have somewhere in a book at home a quote which I will post later on a description of the U-Boat Kaleun. These men are truly magnificent example of bravery and courage

[Ducimus]

Originally Posted by Kromus

http://www.uboat.net/types/ixd.htm

Look for facts first.

Just FYI

Small VIIB was able to make 8700NM! and it was pretty close to 11000nm of US fleet boat range

Acutally, the range of most US fleet boats was much farther then the figures cited due to wartime modificaitons. The number for a fleet boat is actually closer to 15,000NM

[tater]

I read in Friedman that the limiting factor on Fleet Type depth was actually the trim pump (which was based on a German design) seeing as it's not just the hull, but also every penetration that might leak. They made a new type of trim pump in 1944, and were much better off. I think the actual crush depth was beyond 675 feet.

It's tough, as I don't think either side destructively tested real boats, it was all sort of theoretical, whereas in practice, skippers on both sides went well below "sanctioned" depths.

You also have to be careful with production stats vs wartime use. US battery specific gravities were changed from the peacetime value upwards, increasing storage capacity, for example. So the time at 2 kts in the manual would be wrong if based on the lower sg. I'm sure there is loads of that on both sides.

[Bilge_Rat]

AFAIK, the deepest dive of a type VII (that came back up) was U-331 in november 1941. After it sank HMS Barham, it dived to 250 meters (820 feet).

The Balao class could dive to 600 feet and one accidently dived to 1011 feet and survived, although the hull was so damaged, it was taken out of service.

http://www.usschopper.com/Chopper%20...e%20Report.htm