Destroyer hooks

Letum · 10-08-09, 01:11 PM

I'm not so sure Steve.

The Sub may displace 1000 tons, but it' weight in the water with tanks
flooded will be far, far less than 1000 tons. At neutral buoyancy the weight
will be zero.
I would be surprised if the basalt tanks could get more than 10 tons extra
weight, but I could certainly be wrong.

Sailor Steve · 10-08-09, 01:18 PM

Quote:

Originally Posted by Letum

I'm not so sure Steve.

The Sub may displace 1000 tons, but it' weight in the water with tanks
flooded will be far, far less than 1000 tons. At neutral buoyancy the weight
will be zero.
I would be surprised if the basalt tanks could get more than 10 tons extra
weight, but I could certainly be wrong.

As I understand it a basketball filled with air weighs more on the scale than a deflated one, but I might be misremembering.

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.

And if the boat is headed downward at the time of the snagging, you will also have the momentum added into the equation.

All I know for sure is that the Japanese experiment describes a bomb attached to the hook, and that the Allies didn't do it as a matter of course.

Letum · 10-08-09, 01:55 PM

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..

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.

Sailor Steve · 10-10-09, 12:50 PM

Quote:

Originally Posted by Letum

I think you might be confusing mass and weight.

Possibly. It wouldn't be the first time.

Quote:

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.

So if a diver came upon the submerged sub, he would be able to push it as if it wasn't there? Or if a fisherman snagged it he could just reel it in? That doesn't sound right to me. The thing still has the same mass, and any attempt to hook it is going to meet with that many tons of resistance.

Schultz · 10-10-09, 02:58 PM

I one of the hooks catches some holes of the hull of the sub it would just rip it apart, how it happend in the movie

Letum · 10-10-09, 03:02 PM

Quote:

Originally Posted by Sailor Steve

So if a diver came upon the submerged sub, he would be able to push it as if it wasn't there? Or if a fisherman snagged it he could just reel it in? That doesn't sound right to me. The thing still has the same mass, and any attempt to hook it is going to meet with that many tons of resistance.

It's not the weight that would stop him, but the momentum and drag that
would make is difficult to move the sub fast. However, the diver would
theoretically be able to get the sub moving with virtually no effort, just very
slowly at first because of the momentum/inertia and then not reach a high
top speed because of the drag.
The weight of the sub would not be an issue as it has no weight in the
water at neutral buoyancy. Inertia and drag would be the big issues.

othr · 10-10-09, 05:10 PM

Imagine the submarine as a very big paddle. VERY big paddle, now imagine the said diver try and paddle with it.

Sledgehammer427 · 10-10-09, 06:40 PM

I don't they would try to "catch" the sub.

IIRC the japanese would "Hook" a sub and let go of it, buoy attached. that way you can watch exactly where this sub is going, and there was even some oddball way to tether a pole (with buoy) to it and guess within a few feet how deep the sub was.

Hartmann · 10-11-09, 06:51 PM

I´s better use a giant net with some explosive devices attached to it

Dread Knot · 10-08-09, 01:55 PM

I think using a rather improbable movie like 'Below' as a basis for which ASW devices to include in SH5 would be a detriment to the sim. It's the only sub movie I can think of which rivals U-571 for historical inaccuracies.

10-08-09, 01:11 PM	#1
Letum Navy Seal Join Date: Feb 2005 Location: York - UK Posts: 6,079 Downloads: 43 Uploads: 0	I'm not so sure Steve. The Sub may displace 1000 tons, but it' weight in the water with tanks flooded will be far, far less than 1000 tons. At neutral buoyancy the weight will be zero. I would be surprised if the basalt tanks could get more than 10 tons extra weight, but I could certainly be wrong. __________________

10-10-09, 02:58 PM	#5
Schultz Officer Join Date: Feb 2009 Location: Bucharest - Romania Posts: 237 Downloads: 16 Uploads: 0	I one of the hooks catches some holes of the hull of the sub it would just rip it apart, how it happend in the movie __________________ Old nickname: Infernos http://www.overheat.ro/

10-10-09, 06:40 PM	#8
Sledgehammer427 Ocean Warrior Join Date: Jun 2007 Location: Drinking coffee and staring at trees in Massachusetts Posts: 2,908 Downloads: 287 Uploads: 0	I don't they would try to "catch" the sub. IIRC the japanese would "Hook" a sub and let go of it, buoy attached. that way you can watch exactly where this sub is going, and there was even some oddball way to tether a pole (with buoy) to it and guess within a few feet how deep the sub was. __________________ Cold Waters Voice Crew - Fire Control Officer Cmdr O. Myers - C/O USS Nautilus (SS-168) 114,000 tons sunk - 4 Spec Ops completed V-boat Nutcase - Need supplies? Japanese garrison on a small island in the way? Just give us a call! D4C!

10-11-09, 06:51 PM	#9
Hartmann Sea Lord Join Date: Mar 2005 Location: Grid CH 26, Spain ,Barcelona Posts: 1,857 Downloads: 204 Uploads: 0	I´s better use a giant net with some explosive devices attached to it __________________ But this ship can't sink!... She is made of iron, sir. I assure you, she can. and she will. It is a mathematical certainty. Strength and honor

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10-10-09, 05:10 PM	#7
othr Mate Join Date: Jul 2009 Posts: 54 Downloads: 83 Uploads: 0	Imagine the submarine as a very big paddle. VERY big paddle, now imagine the said diver try and paddle with it.

10-08-09, 01:55 PM	#10
Dread Knot Ace of the Deep Join Date: Mar 2007 Posts: 1,288 Downloads: 85 Uploads: 0	I think using a rather improbable movie like 'Below' as a basis for which ASW devices to include in SH5 would be a detriment to the sim. It's the only sub movie I can think of which rivals U-571 for historical inaccuracies.