SH3 -- should I be able to run on batteries on surface? - Page 2

Sailor Steve · 03-09-12, 12:23 PM

Quote:

Originally Posted by aj906

But at 4 knots (as your latter post implies) this will not be a problem.

Absolutely true. I was only answering his idea that it should be better.

Quote:

And, with batteries engaged, it is not like you would want to do much more than about that for the sake of economical cruising.

True. That said, you're only going to get six-to-eight hours doing that and then you'll have to recharge them. Since the engine doing the recharging has to run at full speed it will actually cost more fuel than if you just ran at 4 knots on the diesels. Unfortunately the game has this wrong and you can actually save fuel by travelling on batteries. Also they will recharge even if you are out of fuel. SH4 fixed this.

Quote:

Also, if it is such an issue - and I'm not for one minute questioning you - why would it be a viable option related by veterans? Perhaps their recollections refer to mill-pond conditions only and I missed that implication

I was unaware of submarines using batteries for long-distance travel. Decks-awash surface approaches, yes, especially where silence is important. Maneuvering in port, yes. But travelling? I've not read those accounts.

aj906 · 03-18-12, 04:06 PM

According to U-Boat Far From Home. The epic voyage of U-862 to Australia and New Zealand:

"One shaft was kept running at half speed coupled to a diesel while the batteries were charged using the diesel dynamos. The remaining shaft was coupled to the motor with current from the batteries. With this arrangement the greatest range could be covered while proceeding at approximately 7 knots."

Mittelwaechter · 03-18-12, 05:53 PM

As far as I understood the most efficient (fuel vs.range) way to sail the U-Boot was using one diesel directly, making revolutions for about 8 to 10 knots.
With the necessity to recharge the batteries, they used your quoted setup for recharging, sacrificed 1 or 2 knots but kept the fuel vs. range efficiency as high as possible. The low charging rate may have been a welcomed feature either, to keep the overall lifetime of the batteries up.

Running the second diesel to recharge the batteries would have used definitively more diesel fuel.

Mittelwaechter · 03-18-12, 08:32 PM

Post under reconstruction...

Mittelwaechter · 03-18-12, 09:12 PM

Do you remember the dialog between Kriechbaum and the Kaleun about the bad weather conditions? Kriechbaum explains they are making 'no speed over ground' any longer and the Kaleun orders to dive?
This is the reason why the U-Boote had a better over all range using the e-motors in combination with the diesels.

Just switching regularly between the two propulsion methods to enlarge the range doesn't make any sense, because there is a certain energy loss in transforming fuel into current and back to kinetic energy to power the propellers - even with German machinery.

But under certain - more or less regular appearing - circumstances, this deficit is overcome by the fact to travel at all instead of only burning fuel.

aj906 · 03-20-12, 02:06 AM

Thanks for the posts and thoughts. I only added the bit above just as a point of interest. Hope people didn't take it as a shot across the bows

zygoma · 03-25-12, 12:59 PM

Wow, great answers -- both the easy answer, of "Can't do it in SH3" and apparent "undocumented features" that allow charging on the surface with no fuel

Lots more discussion than I anticipated, and interesting to see some background. Steve's mention of hydrodynamics and the link made me wonder, since it's related: for surface running, since these boats weren't designed to do any planing, will setting the depth such that the longest possible section of the boat is at the waterline result in the greatest possible speed (at least before the disproportionate amount of engine power needed to overcome the design hull speed)?
I'm really enjoying seeing how the game dynamics both mimic and diverge from real-life boat ops, too.
Thanks, all.
Zygoma
May the number of your surface operations exceed your number of dives by one, at the end of your career.

03-18-12, 04:06 PM	#17
aj906 Helmsman Join Date: Mar 2008 Posts: 107 Downloads: 5 Uploads: 0	According to U-Boat Far From Home. The epic voyage of U-862 to Australia and New Zealand: "One shaft was kept running at half speed coupled to a diesel while the batteries were charged using the diesel dynamos. The remaining shaft was coupled to the motor with current from the batteries. With this arrangement the greatest range could be covered while proceeding at approximately 7 knots." __________________ Gott weiß ich will kein Engel sein...!

03-18-12, 05:53 PM	#18
Mittelwaechter The Old Man Join Date: Apr 2007 Posts: 1,304 Downloads: 35 Uploads: 0	As far as I understood the most efficient (fuel vs.range) way to sail the U-Boot was using one diesel directly, making revolutions for about 8 to 10 knots. With the necessity to recharge the batteries, they used your quoted setup for recharging, sacrificed 1 or 2 knots but kept the fuel vs. range efficiency as high as possible. The low charging rate may have been a welcomed feature either, to keep the overall lifetime of the batteries up. Running the second diesel to recharge the batteries would have used definitively more diesel fuel. __________________ 10 happy wolves rear 90 blinded, ensnared sheep. 90 happy sheep banish the wolves. Arrest the 1% - https://www.youtube.com/watch?v=dQ6hg1oNeGE Last edited by Mittelwaechter; 03-18-12 at 06:11 PM.

03-18-12, 08:32 PM	#19
Mittelwaechter The Old Man Join Date: Apr 2007 Posts: 1,304 Downloads: 35 Uploads: 0	Post under reconstruction... __________________ 10 happy wolves rear 90 blinded, ensnared sheep. 90 happy sheep banish the wolves. Arrest the 1% - https://www.youtube.com/watch?v=dQ6hg1oNeGE Last edited by Mittelwaechter; 03-20-12 at 03:17 AM.

03-18-12, 09:12 PM	#20
Mittelwaechter The Old Man Join Date: Apr 2007 Posts: 1,304 Downloads: 35 Uploads: 0	Do you remember the dialog between Kriechbaum and the Kaleun about the bad weather conditions? Kriechbaum explains they are making 'no speed over ground' any longer and the Kaleun orders to dive? This is the reason why the U-Boote had a better over all range using the e-motors in combination with the diesels. Just switching regularly between the two propulsion methods to enlarge the range doesn't make any sense, because there is a certain energy loss in transforming fuel into current and back to kinetic energy to power the propellers - even with German machinery. But under certain - more or less regular appearing - circumstances, this deficit is overcome by the fact to travel at all instead of only burning fuel. __________________ 10 happy wolves rear 90 blinded, ensnared sheep. 90 happy sheep banish the wolves. Arrest the 1% - https://www.youtube.com/watch?v=dQ6hg1oNeGE

03-20-12, 02:06 AM	#21
aj906 Helmsman Join Date: Mar 2008 Posts: 107 Downloads: 5 Uploads: 0	Thanks for the posts and thoughts. I only added the bit above just as a point of interest. Hope people didn't take it as a shot across the bows __________________ Gott weiß ich will kein Engel sein...!

03-25-12, 12:59 PM	#22
zygoma Loader Join Date: Sep 2006 Posts: 84 Downloads: 66 Uploads: 0	Wow, great answers -- both the easy answer, of "Can't do it in SH3" and apparent "undocumented features" that allow charging on the surface with no fuel Lots more discussion than I anticipated, and interesting to see some background. Steve's mention of hydrodynamics and the link made me wonder, since it's related: for surface running, since these boats weren't designed to do any planing, will setting the depth such that the longest possible section of the boat is at the waterline result in the greatest possible speed (at least before the disproportionate amount of engine power needed to overcome the design hull speed)? I'm really enjoying seeing how the game dynamics both mimic and diverge from real-life boat ops, too. Thanks, all. Zygoma May the number of your surface operations exceed your number of dives by one, at the end of your career.