question on TM fuel

[jazman]

Originally Posted by manucapo

Ive notice that on Trigger Maru
there is this fuel consumption thing that tells you how much you can go with your current fuel and speed
it is accurate that in the fact that if it says you can go farther than the distance to your last waypoint
you will get there , or atleast thats what i noticed
but according to the thing
you get the best fuel consumption at 2/3 speed, i always thougth that the slowest you go you consume less, but the thing doesnt seem to say that
i was thinking maybe this is a mistake with the equation it uses to calculate this , so whats the deal?
whats the best fuel efficent way of going
with batteries ?
and with diesels?

Slower isn't always better.

http://en.wikipedia.org/wiki/Power_band

The tradeoff is: are you working the engine in its power band, and not going too fast, generating lots of drag?

The optimal for our subs here is...about 2/3 ahead. You'll notice that's not really 2/3 of your top flank speed.

[seafarer]

This table gives the USS Missouri's fuel consumption versus speed - while it's steam power, the principles still apply.

Go too fast, the energy required to move through water greatly increases fuel consumption (power vs. speed is not a linear function). Go too slow, you burn less fuel per unit time, but take so much longer to cover a given distance that you end up consuming a huge amount of fuel.

[pythos]

Many of these boats were designed hydrodynamicly to have an optimum cruise around 10 to 11 knots. This is the speed regime where the drag produced by the hull is at it's minimum, allowing the engines to operate more efficiently. Slower than this, the hull builds up a resistance to movement, due to the increase in drag behind the boat. Above these speeds the hull is fighting both the incoming water, and the water trailing behind the hull.

It is very much like the VG characteristics of an airfoil, or airplane, just one a larger and slower scale. It is the point where lift generated and drag generated are equal. On most aircraft the best glide speed, or the speed at which the minimum altitude lost, for a given distance, is also the optimum cruise speed. Which is suprisingly slow. 70 knots on a cessna 172 at max gross weight.

By that you can see that aircraft are actually operated ineffeciently cause they are operated at speeds way above their best glide.

[howler93]

Using TM in Gatos and Balaos (not sure if this matters), 9kts seems to give you the greatest range.
I once ran out of fuel on my 5th patrol while heading back to Midway Fuel certainly needs to be monitored

Howler