Engine bells and boat speed in RFB

[swdw]

Thought I should explain this because some people misunderstand what the correlation is between the engine bell ordered, and the actual boat speed. SO the speeds in RFB may have some people scratching their heads.

I know it seems ahead one third should be one third of the flank speed, but it's not. Here's the actual correlation on the EO telegraph.

Ahead standard is usually based on operating at a fuel efficient speed. This may not be the most fuel efficient speed, but a speed that gives good range and gets you there w/o taking too long. Standard is the designation for "standard cruising speed". Which of course caries for each ship type.

Ahead 1/3 and 2/3 are one and two thirds of a standard bell, not of flank speed. Even at that point it may not be exactly one third of standard. Lets say a boat does 8 knots at a std bell, one third of that is 2.6 knots, yet the boat may move at 2 or 3 knots per SOP.

Because of this you have to be careful when setting the speeds, they are not usually equal increments, and a full bell is usually about 80-85% of a flank bell, but varies base on the engine's horsepower curve and the efficiency of the propellers in a higher RPM. This has to do with getting a good strong push out of the engines w/o running into the area where you start to lose mechanical advantge because of friction losses, slippage, possible cavitation, etc. that will give you good speed w/o burning tons of fuel unnecessarily to do so. Flank is to be used when needed for specific reasons, not just because you can.

You can push a boat past flank by ordering maximum RPM's but this is to be done only under and emergency situation- i.e. flooding, imminent collision and things like that.

SH4 doesn't have a setting for that so we work with the rest.