Quote:
Originally Posted by Sailor Steve
In any case, the mass will be the weight of the boat plus the weight of the water on board, so the submerged displacement will indeed be much more than the surfaced displacement..
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I think you might be confusing mass and weight.
The mass of the boat is the mass of the boat and the basalt, however
the weight of the boat is the mass of the boat minus the mass of the
water displaced multiplied by the force of gravity (this value is always 1 on
earth so we can ignore it).
When any boat is not sinking or rising it's weight is zero because the
mass of displaced water is equal to the mass of the boat.
When a boat is sinking that means it's mass is greater than the mass of
the water displaced. In a u-boat the weight of the boat can not exceed
the spare capacity of the basalt tanks after they are filled to neutral
buoyancy.
The VIIC can change it's weight by about 135 tonnes (2x 25m^3 tanks,
2x32m^3 tanks and the ~20m^3 tank ) and can change it's displacement by 118 tonnes.
That means that the VIIC will never weigh more than ~16 tonnes in water.
Under normal operation this value would likely be a deal lower than 16 tonnes.
You are quite right to worry about momentum tho.
Momentum is a product of the mass of the two boats and not the weight.
The sun, for example, has almost no weight, but plenty of momentum.