Type IXD2's 23700 NM does not compute!

Ducimus · 07-06-10, 06:44 PM

Something about the IXD2's often cited 23,700 NM @ 12 kts has always striked me as incredible.

I noticed wiki's article says: 12,750 nmi (23,610 km) at 10 knots.

Everywhere else says: 23,700 NM @ 12 kts.

But this is wiki were talking about, and not really considered a reliable source. But, it got me looking more closely. Now according to uboat.net:

an IXC is:
76.7 meters long, 6.7 meters wide, goes 13450 @ 10 kts, for 1540 total displacement.

an IXC/40 is:
76.7 meters long, 6.8 meters wide, goes 13850 @ 10 kts, for 1545 total displacement.

An IXD2 is:
87.6 meters long, 7.5 meters wide, goes 23700 @ 12 kts, for 2150 total displacement.

So.....
-an IXC/40 is only 0.8 meters wider, and 5 tons heavier then an IXC.

-an IXD2 is 10.9 meters longer, 0.7 meters wider, and 605 tons heavier.

So with an extra 605 tons, the extra range almost seems plausible....almost. But the thing is, i doubt all that 605 tons was occupied by fuel. IXD2's had two smaller backup engines normal type 9's didn't carry for example. So it still seems like quite a big jump in range.

--------------

Now compare the IXD2, with an equivlant long range attack submarine that could be thought of as a valid comparison.

So here's the IXD2 again:

- 87.6 meters long, 7.5 meters wide, goes 23700 @ 12 kts, for 2150 total displacement.

Followed by a Gato class:

- 95 meters long, 8.3 meters wide, goes 11000 @ 10 kts, for 2424 total displacement.

Mind you both of these boats carry 24 torpedos.

So a gato is, 7.4 meters longer, 0.8 meters wider, and is 274 tons heavier.

Now with wartime modfications of fuel ballast, a gato could go around, im guessing, 13,000 NM give or take. Even then with that additional range, internet sources (which tend to copy each other) mean to tell me that the TypeIXD2 that is 7.4 meters shorter, 0.8 meters skinner, and 274 tons lighter could go an additional 10,700 NM?

I find that a hard pill to swallow, also could it be more then a coicidence that 23700 kilometers converts to 12797 nautical miles? I strongly suspect that somewhere, some source mistakenly cited the KM range as a NM range, and the same mistake has been quoted all over the internet.

Anybody have some hard resources not on the internet to support or refute my hypothesis here?

Gorshkov · 07-06-10, 07:09 PM

Not so long ago I posted here Type IXB performance data taken from real commander's KTB entry found on U-boat Archive web-page. Look for some Type IXD2 U-boats KTBs there...maybe similar data were also made. Well, there were not so many Type IXD2 U-boats commissioned - only 29. Have a nice reading...

Speed measures and distances travelled (as for IXB in 1939):

- Cruising speed at 10 knots: 6 days 15 hours 36 minutes = 1596 nm
- Cruising speed at 9 knots: 21 days 14 hours 58 minutes = 4670.7 nm
- Chasing speed at 12 knots: 2 days 5 hours 33 minutes = 642.6 nm
- Chasing speed at 14 knots: 4 hours 35 minutes = 64.25 nm
- Chasing speed at 15 knots: 2 hours 32 minutes = 38.0 nm
- Submerged speed about 2.5 knots: 3 days 1 hour 46 minutes = 64.4 nm

http://www.uboatarchive.net/KTB37-2.htm

lurker_hlb3 · 07-06-10, 08:06 PM

"The Encyclopedia of Uboats, From 1904 to Present" by Eberhard Moller & Werner Brack

Page 103

Range 13450nm at 10kts / 63nm at 4kts

etheberge · 07-06-10, 08:24 PM

No that it's the Bible or anything but Clay Blair's The Hunters 1939-1942 says 24000 miles and he specifies that the IXD had double the fuel capacity as the IXC.

In my copy it's on page 501, in the footnote related to the first mention of U-177.

Ducimus · 07-06-10, 08:51 PM

Ok... so .. one source says one thing.
Another source says another thing,
and we have an extrapolation right smack in the middle.

Side note. I do wonder what Blair's reference was. Saying a boat has twice the fuel of the previous class of a long range boat is one hell of a claim.

etheberge · 07-06-10, 09:32 PM

Yes it's perplexing, it looks like you stumbled into quite the historical mystery.

Blair has a HUGE list of sources in the last volume (40 pages, very tightly packed

) but since the footnote in question isn't linked with one particular source I guess there's no way to know where the info came from.

Jan Kyster · 07-06-10, 08:18 PM

Lüth (U-181) reported to have 200 cbm fuel left for the return trip from well east of the Cape to Bordeaux, France = more than 5800 miles

Full tank 605 cbm, so a total of more than 17400 miles possible. Or 26 weeks....
Speed not mentioned.

Source:
Jordan Vause: U-Boat Ace, The Story of Wolfgang Lüth

Btw. found a sea distance calculator: http://e-ships.net/dist.htm

07-06-10, 06:44 PM	#1
Ducimus Rear Admiral Join Date: May 2005 Posts: 12,987 Downloads: 67 Uploads: 2	Type IXD2's 23700 NM does not compute! Something about the IXD2's often cited 23,700 NM @ 12 kts has always striked me as incredible. I noticed wiki's article says: 12,750 nmi (23,610 km) at 10 knots. Everywhere else says: 23,700 NM @ 12 kts. But this is wiki were talking about, and not really considered a reliable source. But, it got me looking more closely. Now according to uboat.net: an IXC is: 76.7 meters long, 6.7 meters wide, goes 13450 @ 10 kts, for 1540 total displacement. an IXC/40 is: 76.7 meters long, 6.8 meters wide, goes 13850 @ 10 kts, for 1545 total displacement. An IXD2 is: 87.6 meters long, 7.5 meters wide, goes 23700 @ 12 kts, for 2150 total displacement. So..... -an IXC/40 is only 0.8 meters wider, and 5 tons heavier then an IXC. -an IXD2 is 10.9 meters longer, 0.7 meters wider, and 605 tons heavier. So with an extra 605 tons, the extra range almost seems plausible....almost. But the thing is, i doubt all that 605 tons was occupied by fuel. IXD2's had two smaller backup engines normal type 9's didn't carry for example. So it still seems like quite a big jump in range. -------------- Now compare the IXD2, with an equivlant long range attack submarine that could be thought of as a valid comparison. So here's the IXD2 again: - 87.6 meters long, 7.5 meters wide, goes 23700 @ 12 kts, for 2150 total displacement. Followed by a Gato class: - 95 meters long, 8.3 meters wide, goes 11000 @ 10 kts, for 2424 total displacement. Mind you both of these boats carry 24 torpedos. So a gato is, 7.4 meters longer, 0.8 meters wider, and is 274 tons heavier. Now with wartime modfications of fuel ballast, a gato could go around, im guessing, 13,000 NM give or take. Even then with that additional range, internet sources (which tend to copy each other) mean to tell me that the TypeIXD2 that is 7.4 meters shorter, 0.8 meters skinner, and 274 tons lighter could go an additional 10,700 NM? I find that a hard pill to swallow, also could it be more then a coicidence that 23700 kilometers converts to 12797 nautical miles? I strongly suspect that somewhere, some source mistakenly cited the KM range as a NM range, and the same mistake has been quoted all over the internet. Anybody have some hard resources not on the internet to support or refute my hypothesis here?

07-06-10, 08:24 PM	#4
etheberge Watch Officer Join Date: Nov 2007 Location: Montreal, QC Posts: 345 Downloads: 614 Uploads: 10	No that it's the Bible or anything but Clay Blair's The Hunters 1939-1942 says 24000 miles and he specifies that the IXD had double the fuel capacity as the IXC. In my copy it's on page 501, in the footnote related to the first mention of U-177. __________________ 11 War Patrols / 56 ships sunk or damaged for 212,022 tons Zero casualties throughout the war Scuttled on 8 May, 1945 in Sonderburg Bay, after German surrender

07-06-10, 09:32 PM	#6
etheberge Watch Officer Join Date: Nov 2007 Location: Montreal, QC Posts: 345 Downloads: 614 Uploads: 10	Yes it's perplexing, it looks like you stumbled into quite the historical mystery. Blair has a HUGE list of sources in the last volume (40 pages, very tightly packed ) but since the footnote in question isn't linked with one particular source I guess there's no way to know where the info came from. __________________ 11 War Patrols / 56 ships sunk or damaged for 212,022 tons Zero casualties throughout the war Scuttled on 8 May, 1945 in Sonderburg Bay, after German surrender

07-06-10, 07:09 PM	#2
Gorshkov Commodore Join Date: Mar 2007 Posts: 604 Downloads: 139 Uploads: 0	Not so long ago I posted here Type IXB performance data taken from real commander's KTB entry found on U-boat Archive web-page. Look for some Type IXD2 U-boats KTBs there...maybe similar data were also made. Well, there were not so many Type IXD2 U-boats commissioned - only 29. Have a nice reading... Speed measures and distances travelled (as for IXB in 1939): - Cruising speed at 10 knots: 6 days 15 hours 36 minutes = 1596 nm - Cruising speed at 9 knots: 21 days 14 hours 58 minutes = 4670.7 nm - Chasing speed at 12 knots: 2 days 5 hours 33 minutes = 642.6 nm - Chasing speed at 14 knots: 4 hours 35 minutes = 64.25 nm - Chasing speed at 15 knots: 2 hours 32 minutes = 38.0 nm - Submerged speed about 2.5 knots: 3 days 1 hour 46 minutes = 64.4 nm http://www.uboatarchive.net/KTB37-2.htm

07-06-10, 08:06 PM	#3
lurker_hlb3 Admiral Join Date: Apr 2005 Location: San Diego Calif Posts: 2,290 Downloads: 187 Uploads: 12	"The Encyclopedia of Uboats, From 1904 to Present" by Eberhard Moller & Werner Brack Page 103 Range 13450nm at 10kts / 63nm at 4kts

07-06-10, 08:51 PM	#5
Ducimus Rear Admiral Join Date: May 2005 Posts: 12,987 Downloads: 67 Uploads: 2	Ok... so .. one source says one thing. Another source says another thing, and we have an extrapolation right smack in the middle. Side note. I do wonder what Blair's reference was. Saying a boat has twice the fuel of the previous class of a long range boat is one hell of a claim.

07-06-10, 08:18 PM	#7
Jan Kyster Ace of the Deep Join Date: Oct 2006 Posts: 1,151 Downloads: 152 Uploads: 0	Lüth (U-181) reported to have 200 cbm fuel left for the return trip from well east of the Cape to Bordeaux, France = more than 5800 miles Full tank 605 cbm, so a total of more than 17400 miles possible. Or 26 weeks.... Speed not mentioned. Source: Jordan Vause: U-Boat Ace, The Story of Wolfgang Lüth Btw. found a sea distance calculator: http://e-ships.net/dist.htm