[derstosstrupp]

Originally Posted by VonHoffman

Does trim change that much with attitude? If you simply point the boat up/down using the planes and forward speed, then I can only see trim changing due to temperature differentials or even minor variation of pressure due to the different depth of each end of the boat?

If the tanks are not totally flooded, then I can also see the shift in mass making a small change, but surely not that much? Once the boat levels it will be back in trim again?

I do agree that near/on the surface the boat needs to rock a lot more with the waves. It's almost completely immune to the sea state.

Trim for U-boats referred strictly to attitude changes. These were offset by transferring small amounts of water between the forward and aft trim tanks. This needed to be done daily as part of the trim dive, and became necessary due to any weight changes forward vs aft. Say carrying a sack of potatoes from end to end as a simple example. It’s also why, when submerged, moving about the boat was only by permission of the chief engineer because it would upset the trim (which is why the crew had “diving stations”).

I agree in terms of buoyancy being a function of many different factors including temperature, salinity, plankton content, own weight etc. That’s what the regulating tanks (what Wolfpack calls trim tank) were used for. However no significant changes were made here typically since weight changes were maintained in the dive logbook and the control room mate added the necessary water to compensate already on the surface. Different concept than trim though.

So the bulk of trimming (“einsteuern”) was shifting the water between trim tanks and also possibly adding/subtracting water from regulating tanks to make up for any miscalculations in weight, such that, at Kleine Fahrt and periscope depth, depth could be maintained with minimum hydroplane input on an even keel. But in rough seas this whole process was made exponentially more difficult because the sea churns on the surface and just below it, wreaking havoc on a submarine trying to maintain depth.

I advocate for true trim tanks in Wolfpack because the dive officer role becomes easy to master quickly. So some more complexity here I think would be welcome.

Now, that being said, there is an argument to be made for leaving that element out, because the assumption would already be possibly that the boat has undergone its daily trim dive by the time you spawn in, but regardless, it would be a nice touch to have to do a quick trim dive before you go about your engagement.