Steeper dive angle in the control room please

[Letum]

Originally Posted by IanC

That animation is kinda funny lol...
But I don't understand your point, you saying a boat diving at 45 degrees will reach 220 meters in 6 seconds?

edit: btw you sure that boat animation is at 45 degrees? Looks a little steeper to me.

Yes, it is precisely 45 degrees at the steepest point.
It's not about the speed. Even slowed down to the correct speed, the
dive still looks utterly crazy.
I only have it going fast because no one wants to watch a .gif for 10 mins.
As soon as the boat reaches 45deg. it needs to pull up at an
impossible rate or it would go straight down to crush depth.

Originally Posted by JU_88

I presume a submarine must gain speed in steep dive, just like an aircraft gains airspeed in this way.

No, gravity does not give a uboat much speed at all because the u-boat
never has much weight.
Even with all tanks flooded it will only weigh about 10 tonnes.

It might get a knot or three of extra speed on the way up because the
VIIC can have a positive buoyancy of exactly 102 tonnes when the
basalt is all blown.
Come to think of it, that much positive buoyancy could really rocket it
upwards.

ed: going to do the math...
ed:2

Wow!

This is all just calculated guess work, so don't take it too seriously...

If we assume that the motors and dive planes can only give enough
thrust in the vertical to counteract vertical drag. (they can at low
speed, but this is very optimistic as the speed rises)...
And we assume that the VIIC can blow all it's basalt and get into a
climb angle instantly (Ha!)...

Blowing basalt from 220m gets us about 14knots of vertical speed
when the boat breaks the surface.
However, the dive planes and motors, even at a 45 degree climb,
can only counteract drag up to the speed of ~4.5 knots (half the
underwater top speed at 45 degrees).

I don't have enough info to work out the drag forces, but it's a safe
bet that it will take off a lot of the speed above 4.5 knots.

A top vertical speed of 8 knots seams to be in the ball park. This is in
addition to the ~4.5 knots of horizontal velocity. that gets the VIIC
from crush depth to the surface in just under one min.

Of course, the VIIC can't blow all 102 tonnes of basalt instantly and it
can't get to a 45 degree climb angle instantly, but even with the most
conservative figures, you can expect a good knot or two of vertical
climb if all the basalt is blown.


I ran the calculations for a sinking u-boat and the effect of the ~10
tonnes of basalt that the VIIC can take on top of the neutral
buoyancy load gives it less than 1 knot of extra sink as it passes
220m.

ed3: removed some mistakes.
ed4:

As a calculated guess it would take 18-24min to sink a VIIC to 220m
without dive planes.