i always set the patrol zone hexes to 'remain 1 day' - this greatly reduces the amount of normal damage they accrue, & greatly increases the amount of time they can spend at sea.
Are you sure? I don't think the code assumes no fuel is used unless a hexside is crossed. If you're at Cruise speed and loitering you're still moving in the hex. Same with damage. I assume you mean system mostly. I believe it's a function of number of phases plus randoms, not movement. FWIW, true in the real world too. Subs break standing still at the pier sometimes. Amazing what sailors can do when they set their minds to it.
If my assumptions are wrong somebody chime in.
say a sub's PZ is 3 hexes in a triangle, w/ each point 2 hexes distant from the others. If remain = 0 days, a typical USN fleet boat will travel at least 8 hexes each turn. If remain = 1 day, it'll travel only 2 hexes each turn.
So the 1-day boat is using only 25% of the fuel, & accruing ~25% of the random sys-damage, compared to the 0-day boat. They can patrol for 3-4 months before they auto-rtb for refueling, & they never run out of fresh eggs.
But I'd want to deploy 3 single-boat TFs to that 3-hex PZ, set to have 1 boat in each of the 3 hexes. I also think it's important that the subs move a bit, to increase their ability to look for targets. I didn't get good results setting subTFs to single-hex remain-on-station orders.
The above isn't quite correct. I went and researched this in the manual; it was in sections I rarely have looked at.
Fuel: you are correct that more fuel is used when changing hexes on whatever loiter schedule is used. But staying put in a hex still uses fuel as per 6.2.13:
"Whenever a ship moves in a TF, it draws on its Endurance, which in turn subtracts from the
amount of fuel carried. Fuel is expended when:
--Each ship in a TF that is not docked also expends a small amount
of Endurance every turn equal to 40 times the ship’s cruising
speed in hexes (i.e. it is assumed they are constantly moving at
cruising speed even if they aren’t moving to other hexes)."
In that sense loitering isn't "free". It's cheaper most likely though. In exchange you give up the chance to add to the odds of meeting a target. IT has to come to you IOW.
As for damage, changing hexes isn't a factor. Among the other ways system damage can accrue, there is this:
"6.5.1 OPERATIONAL DAMAGE AND REPAIRS AT SEA
Whenever a ship is at sea (not docked), it has a chance of suffering system damage due to
wear and tear on the ship. This damage can occur as the TF enters each new hex or remains
on patrol in a hex, and will immediately affect the TF’s speed for the rest of the turn."
IOW, staying put still provides a chance for things to break, a completely real possibility I might add.
There are very complex studies, some classified, in the ASW world where people with highly developed operations research backgrounds have modeled whether it is better to hunt for a target or to sit and wait for one to happen by. It's probability and modeling far above my abilities. Consider a fixed size field with X nodes and two objects in it, each able to move Y distance per cycle. Y need not be the same number, and in ASW won't be. In each cycle both objects can move in 360 different directions, but in a non-random manner as prior and present sensor data influences the choice. Of course, the sub can move in three dimensions as well. Then you throw in the real world factors of weather, geography (there may be reefs or islands), crew training, equipment maintenance, sensor accuracy, human error, etc. These are very complex models. The game doesn't try to match them. But it's not an open and shut question IMO that loitering is always, or ever, the best move. It might be. It might not be. Bu I don't think that letting fuel economy or random system damage control the decision is always wise.