[WIP] Fleet Boat Engine Hour Mod

[Rosencrantz]

Hi!

I don't see any reason why Fleet Boat Engine Hour Mod could not be used together with any other mod or stock. What becomes to S-class I can't say anything yet, as I lack exact real life data about enignes fitted, their performance, and especially standard operating procedures.

As I'm still in the middle of the building process, I can't say much more. However, here is few quotes from real Navy documents, and conclusions I have made:


The Fleet Type Submarine Main Propulsion Diesel Manual, Chapter 9 Engine Performance and Operations, page 182: "The economical speed for most Navy type diesel engines is found to be from 70 percent to 80 percent of the rated load or output. Thus, we speak of running the engines at an 80-90 combination which will give the engine itself much cleaner and in better operating condition. The 80-90 means we are running the engine with 80 percent of rated load at 90 percent of rated speed."

My conclusions: Because a single diesel engine running at 80 percent of it's rated speed used probably about 6 - 7 times of fuel compared to engine running at 50 percent of it's rated speed, I'm positive that fuel consumption was not Navy's problem number one before, during or after the war. It was prolonged periods in engine overhaul what they tried to avoid as much as possible. This is the real reason why standard Navy procedure was to put less engines on the line running at higher speed to gain requierd speed. That 80-90 combination was not just a theory, we can see here:

USS Wahoo, Third War patrol, Report of, Jan 16, 1943: "2306L Completed runs. Set course for area at two engine speed (80-90). Still in company with our escort."

Conclusions: When Wahoo departed Pearl for the third war patrol, they put two engines on the line running at 80-90 combination. As Wahoo had 4 x Fairbanks-Morse Model 38D8-1/3 9-cylinder engines running four generators with emergency output of 1120 kw at 720 rated speed, 900 kw at 650 rpm, and with overspeed trip setting of 800 rpm, this means they were using 2 x 900 kw to run the boat when leaving Pearl.

But what was the actual speed they were running at? Because there is no clear connection to propeller rpm and actual speed in ships (compare to cars, for example) because of conditions are always different (wind, sea state, cargo on board, ship's material conditions and so on...) we can only try and make good estimations. If someone is interested in, I can write more. Now I have to get on with my every day job... sorry.


-RC-

[Jan Kyster]

Originally Posted by Rosencrantz

But what was the actual speed they were running at?

We can gather statistically data... example:

From same patrol log, Enclosure A, Subject 13. Miles Steamed:
Steamed 6454 miles enroute Brisbane to Pearl, plus appr. 100 miles at full power during attacks and counter-attacks. Total 6554 miles.

Subject 14. Fuel Oil Expended: 92,020 gallons; 14.1 gallons per mile.
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No status for Fourth War Patrol. Possible forgotten in the excitement?

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Fifth War Patrol Log, Enclosure A,

Subject 14. Miles Steamed:
Enroute to area: 2,964
In Area: 803
From Area: 3,061

Subject 15. Fuel Oil Expended:
Enroute to Area: 8.68 gal. per mile.
In Area: 8.58 gal. per mile.
From Area: 15.8 gal. per mile.

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All reports have these summaries. Just waiting to be filled into an Excel sheet!
Even speeds can be calculated as we know distances from maps and dates are in the logs...


but is it worth collecting these data?

[Rosencrantz]

Hello, Jan!

You asked:

but is it worth collecting these data?

Even if I think every data is worth of collecting, I think data gathered from war patrol reports tell basicly about changes in fuel consumption due different weather conditions or different operation tempo. Reading war patrol reports definitely gives us a good picture how much fuel consumption varied from patrol to patrol. In SH4 we are however dealing with simulation, which certainly has some real life aspects (reduced speed in bad weather for example), but also which lack many of them.

What would be good thing to have is for example original speed/endurance/fuel consumption table for Gato-class submarine. I know these tables exist, but I haven't been able to get them.

However, with data availible we can calculate theoretical speed for Wahoo at two engine speed in ideal conditions. I'll take this guestion up in my next post, because now I have to get back to work again...


-RC-