Trim weight

[Iron Budokan]

Thank goodness not everything in the game is modeled! This passage is from Buchheim's novel, The Boat:

If a hundredweight of potatoes is moved from the control room to the bow compartment when the boat is submerged, bow heaviness results. To compensate this, water has to be pumped from the control room to the stern cell--only half the weight of the potatoes, though, because the water for the trim cell is taken from the opposite end of the boat. The foreship is thereby made lighter by one half the weight of the potatoes. If a hundredweight of potatoes were taken from the E-motor room into the bow compartment, the trim calculation would, of course, be different. In that case water would have to be pumped from the bow to the stern.

Sheesh, talk about micromanagement!

[Puster Bill]

That is why just about every submarine had to do daily trim dives: To make sure that they had all the numbers right. Invariably, something would have been done wrong, or not accounted for. Just too many variables, at least in pre-computer days. So, every day the boat would be submerged (slowly!) so that the LI could 'balance' the boat.

[Iron Budokan]

I wouldn't mind having to do trim dives modeled to the extent if you don't you might run into trouble the next time you dive. This could be cumulative. Maybe you don't do a trim dive for three weeks. God, imagine the trouble you could get into you when your watch officer sees a plane and screams, "Alarrrmmm!"

[AVGWarhawk]

Who would have thought that a sack of potatoes could ruin a whole day if not compensated for?

[_Seth_]

What if Bernard was on the toilet, releasing the last 14 (!) days of crap into the ocean? Wouldnt the boat pop to the surface like a cork? Or was toilet-patrols only allowed when surfaced?

[Jimbuna]

Trimming the boat was an art that took a long time to master

[Iron Budokan]

You're not kidding especially when you're talking about those kinds of tolerances (only a hundred pounds!) compared to the entire weight of the boat itself! Wow.

No doubt about it, it's a tightrope of sorts...

[Iron Budokan]

A quick calculation shows that a hundred pounds of potatoes is 0.05 tons. Seemingly nonexistent compared to the 865 tons of a submerged VIIC! That's only a difference of 0.0058% between stabilization and falling to crush depth.

Again....wow!

[Myxale]

The ever so famous "Prüfungstauchen" is pure mojo!:hmm:

[Brag]

Originally Posted by _Seth_

What if Bernard was on the toilet, releasing the last 14 (!) days of crap into the ocean? Wouldnt the boat pop to the surface like a cork? Or was toilet-patrols only allowed when surfaced?

Now, stop it! I almost fell off my chair laughing :rotfl: :rotfl:

[Brag]

Originally Posted by Iron Budokan

A quick calculation shows that a hundred pounds of potatoes is 0.05 tons. Seemingly nonexistent compared to the 865 tons of a submerged VIIC! That's only a difference of 0.0058% between stabilization and falling to crush depth.

Again....wow!

Neutral bouyancy is a delicate balance, even the salinity of water will affect it. Some U-boats in the Baltic had problems in the spring time when a lot of fresh water from the rivers ran into the sea.

When I had a sailboat in San Francisco Bay, when sailing up the San Joaquin river, my boat would sit a good 10 centimeters lower in the fresh water than at sea.

[Iron Budokan]

That's true. Even a sunny day affects the salinity of the ocean, driving off evaporation and increasing the salt content, thereby affecting the specific gravity of the sub itself. In Das Boot (the novel, not the film) Buchheim tells how every day they tested the density of the ocean water because it had such a big factor on trim weight.

It's much more complex than just flooding trim tanks, that's for sure. Much more complex than I originally imagined....a LOT of chemistry and physics involved. Pretty cool.