Thanks.
The new math behind the boat itself should be pretty accurate now, simulation of the ballast tanks & blowing system is based on the math of real world computer controlled ballast tanks. And the boat's behavior on the surface almost (90%) matches what's known about the real thing from german and british documents. (slightly different tactical diameters and times to turn at different velocities)
For the historical technology of the boat I have great help from the former (1950s) chief engineer of a Type VII and some others who are amazingly deep into this stuff.
My goal was to create a simulation based on the different ways used by ship designers to estimate vessels - and that works now by just feeding it with the correct data of the boat and estimations where no exact data is known.
I've started with the simulation of the diesel engine itself, shaft & propellers, the different drags, the rudder, a new buoyancy system, the ballast tanks, vents and compressed air installation and finally I'm busy with the pumps right now.
But all this stuff doesn't make the game itself complicated for the player if he doesn't want it - the only difference to the usual faked or over simplified approach is that a serious calculation of the physics behind the boat and its systems lets it act more like the real thing automatically. …and I can give the player control to some details if he wants that, like control of the ballast tanks and the flooding & drainage installation - if the player doesn't wants to touch that then that's no problem at all because the "crew" will do it for him anyway.
From the boat's simulation itself I'm at a point where I think that only tiny details could be improved in future desktop versions but I also think that most of that will be unfortunately out of my scope and I would really need to hire someone for this task who is a professional in hydrodynamics, someone who is doing real world ship calculations all day. (I doubt I will ever be able to afford such a person).
Anyway, developing this part of the simulation was boring and often extremely frustrating, can't count how often I felt like a prehistoric man who is trying to understand the drawings of a fusion reactor - but in fact I was someone from Utopia trying to understand the stuff of people 60-250 years ago… damned nerds.