[TEC] Tweaking submarine ranges

[Peto]

An important point to remember is that 10--12 knots was a pretty typical "long haul" speed for the fleet boats. They could be running 80-90 but only running 2 engines. If the battery wasn't too low and they were ok with a slow charge they wouldn't even fire up #3, they'd just kick in the mule which was a smaller diesel they had for tasks other than propulsion. Kicking in the other mains did increase speed but the gain became smaller with the 4th engine only providong a couple more knots (not sure of exact numbers here).

It seems to me that most accounts I read talk about making Japan from Pearl in about 10 days. I think that's aproximately 12 knots (again not positive--sorry). The longest non-stop run of a Gato was made by the Redfin from Panama to Australia without refueling. If I recall correctly, they finally fueled at Potshot (Darwin) and were nearly dry.

I guess what I'm saying is that in reality, 50% power for a fleet sub doesn't really translate as 21/2. I think running all 4 diesels at best economical means produced a speed of about 18 knots. More meant they were pushing the engines hard.

Hope this helps somehow... :hmm:

[swdw]

I think you're misinterpreting what they mean by economical.

Could be wrong, but here's how I interperet this.

Economical does not mean 80-90 isthe most fuel efficient of all the running combinations possible. What it means is this is the what the navy considered the best load/speed for normal full load/speed (flank operation with full electrical load). It's economical because it gives longer life for parts, better MBT (meantime between failure), requires less maintenance costs, fuel costs at "full load", and for cost vs performance increase it's not worth it to run the diesels at 100-100 as the full load/speed conditions.

So to me, this doesn't mean it burns less fuel at 80-90 than running at a standard bell, but that the normal full load should be 80-90 of the emergency rating for longest life.

[LukeFF]

Originally Posted by swdw

I think you're misinterpreting what they mean by economical.

Could be wrong, but here's how I interperet this...

You're right. My oopsie on this one. I should have keyed in on the "for emergency use" part of that paragraph. Thanks for the explanation.

[Capt Jack Harkness]

Well in the book Wahoo, Richard O'Kane mentions a "cruising" speed of 17kts running 3 engines at 80/90 from Mare to Pearl.

I think the real problem is the lack of proper engine room controls...

[Joe Armstrong]

If we review USF 25(A) – The US Sub Doctrine Manual 1944 Paragraph 1122 and 1123 it would appear the best speed we could obtain would be around 16 kts, but to obtain the optimum range of 12,000 we would be required to reduce the speed considerably. If there was a refueling base close it would make since to go full out to that location but after leaving that point 2 to 3 kts would make more since to conserve fuel because of the fast runs required to get in front of some targets.

Information on this can be obtained from http://www.history.navy.mil/library/online/ss-doc-1.htm

[Fincuan]

Originally Posted by Joe Armstrong

If there was a refueling base close it would make since to go full out to that location but after leaving that point 2 to 3 kts would make more since to conserve fuel because of the fast runs required to get in front of some targets.

2-3 knots is an extremely inefficient speed. Ingame(using TMaru) the optimum cruising speed is around 9.5 knots in a Gato or a Balao and a little less in the other Fleet boats and the S-class. AFAIK it might have been a few knots higher in real life, but definitely not much less.

[Peto]

Originally Posted by Fincuan

2-3 knots is an extremely inefficient speed. Ingame(using TMaru) the optimum cruising speed is around 9.5 knots in a Gato or a Balao and a little less in the other Fleet boats and the S-class. AFAIK it might have been a few knots higher in real life, but definitely not much less.

I don't think they are using 2-3 as a cruising speed to and from patrol areas. But once in the patrol area, it was typical to use Very low speeds. It only required 1 engine for propulsion and 1 to charge the batteries which enabled the boat to be on station for over a month. Cruising at 9 knots in the patrol area would have seriously curtailed the amount of time on station.