Steeper dive angle in the control room please

[JU_88]

I presume a submarine must gain speed in steep dive, just like an aircraft gains airspeed in this way.
Gravity is slightly reduced in water, but not by all that by much.

Is this modelled in SH3/4? I have never thought to really monitor My boats submerged speed while diving or accending.

Does the boat accellerate and still continue at a higher than normal speed after levelling off (having gained momentum), then gradually reduce speed down to whatever RPMs your electrics are driving?

IN SH3/4 I never noticed the effects of gravity or physics simulated in thii way, but then I was never looking for it.....
Then again, maybe my theroy is wrong?

Originally Posted by JU_88

I presume a submarine must gain speed in steep dive, just like an aircraft gains airspeed in this way.
Gravity is slightly reduced in water, but not by all that by much.

Is this modelled in SH3/4? I have never thought to really monitor My boats submerged speed while diving or accending.

Does the boat accellerate and still continue at a higher than normal speed after levelling off (having gained momentum), then gradually reduce speed down to whatever RPMs your electrics are driving?

IN SH3/4 I never noticed the effects of gravity or physics simulated in thii way, but then I was never looking for it.....
Then again, maybe my theroy is wrong?

not really, in a dive its a momentum (or inertia) vs resistance thing which follows the same patterns as aircraft but they are different. the effects of gravity are much less effective on submerged objects containing an air pocket because the floatation cancels out gravity to a large extent. if anything IMO the opposite is true, it would lose speed in a dive due to the increased resistance forces against it trying to push against the forces of resistance, floatation, and pressure changes.

a boat never really levels off, it has a bowl like action as it bottoms out its dive but bouyancy is all part of it too because the dive planes putting force against that bouyancy is what gives you the control or you would forever be in flux going up or down constantly

[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.

[Reece]

This is 20 Degrees Blowing Ballast:

Can change this angle to what ever, if anyone wants to see, as well as external view, but this is about max before the view starts to look a little weird, would be nice if the crew positions reacted properly as in the photo in post #1, hopefully this will be the case in SHV.

[oscar19681]

Originally Posted by Reece

This is 20 Degrees Blowing Ballast:

Can change this angle to what ever, if anyone wants to see, as well as external view, but this is about max before the view starts to look a little weird, would be nice if the crew positions reacted properly as in the photo in post #1, hopefully this will be the case in SHV.

Please show in downward angle please

[IanC]

Originally Posted by Letum

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.

Don't forget these guys were literally crash diving for their lives. So the dive angle might look crazy, but how it looks is irrelevant, whatever gets you to the bottom fastest!
Unless you meant crazy math wise, I'll admit I don't know the math behind all this, so I'll trust you (although I'm still pretty sure they can dive at 45 and pull up before crush depth, no?).
That SH3 picture from Reece at 20 degree looks alot like that photograph! Combine that and the report; "Thereafter the angle down is normally from 12-15°, though angles up to 45 have been reported, after complete submersion." My rough guess would be that about, oh, 15-25 degrees seems like the 'normal' crash dive angle.

[Letum]

Originally Posted by IanC

(although I'm still pretty sure they can dive at 45 and pull up before crush depth, no?).

Well, you can recover from 90 degrees if you want. It's just going to
take a lot of time because you will need to stop the motors and trim up
with basalt.
Whether or not you need to do this at 45 degrees depends on the
vertical turning circle. i.e. the rate at which you can change dive angle.


25 degrees looks much more feasible.

[IanC]

Originally Posted by Letum

Dig those gifs!

[IanC]

Hey I was just doing a little Das Boot reading now and came across this, looks like Buchheim has the boat crash diving at at least 30 degrees.

Page 194,
"The Chief slowly levels the boat out and orders, "Man diving stations!" The seamen who rushed forward now work their way back hand over hand up the slope. The sausages act like a scale: we're still a good thirty degrees bow heavy."

[Reece]

Please show in downward angle please

Because of the camera angle this is about the best view or you only see the valve operator: