I'm doing tests with bank angle. Now that really brings 'piloting' into it. Now I understand why they have 2 men driving the sub.
By my guess, there are 4 major forces effecting bank:
1) hydrostatic stability. Since center of buoyancy is higher then center of gravity, sub 'wants' to stand sail up even at zero speed.
2) hydrodynamic stability. Center of side-drag is similar to center of buoyancy for 688 .. near the centerline of the column-shaped body, or even higher because of the sail. Because of that, when water flows from the side of the sub, it will bank away from the water flow direction. This happens even in simple turn - in right turn sail banks to the right. Also if sub dives straight down, this helps keep the sail up. Sail is kind of flag so it turns to opposite of 'wind' direction.
If the sub surfaces straight up, this force would force the sail down (to 'flag' behind the main body). In this case hydrodynamic stability fights against hydrostatic stability.
3) screw rotation. Forces the body to rotate in opposite direction.
4) planes input. Used to fight all these effects.
Now amount of individual effects is quite mystery to me. I could compute at least hydrostatics quite well, but I would need to know where exactly point of gravity lies in 688. I don't know that. This too affects hydrodynamics. Screw effects ? No idea. At what vertical speed is the hydrodynamics stronger then hydrostatics ? No idea.
Planes effects .. is it possible to turn the sub upside down ? Can planes fight over hydrostatic stability ?
Anyway this really complicates all maneuvers. Simple right turn for example will bank the sub to the right which will make the banked rudder to pitch sub down. I know this really happens, but again, the amount is unknown.
Any ideas ?
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