Destroyer hooks

[Schultz]

I recently saw the movie "Below", and that a german warship being out of depth charges used hooks.Now comes the question did american or british ships had hooks?

[Dread Knot]

The Japanese did experiment with such a device..

At least two types of anti-submarine explosive weapons designed for underwater tow by small surface vessels are known to have been developed and used by the Japanese, particularly early in the war. The first of these was called the "Yokosuka depth charge," and was set to explode upon contact with a submerged object. The charge was cylindrical in shape, about 1 foot in diameter by 5 feet in length, and contained 55 pounds of Type 88 explosive filler.

The second weapon was designated by the Japanese as the Mark 2 Explosive Hook and, although developed primarily for minesweeping, was occasionally used for anti-submarine work. This device was a cast iron cylinder, 8 inches in diameter and ten inches long with four grapnel-like arms projecting from the main body, each 71/2 inches long. The body contained a charge varying form 8 to 19 pounds of Type 88 explosive. Firing was accomplished after the hook secured on a submerged target; the Mod. 0 either electrically by an observer on the towing ship or automatically when an additional tension of 550 pounds was put on the towing line, and the Mod. 1 by electrical control from the towing ship. Although several reports were received from U.S. submarines of small Japanese vessels apparently using these two weapons, no large-scale employment was made and there is no information to indicated that damage was ever inflicted.

From hyperwar
http://ibiblio.org/hyperwar/USN/rep/...8/WDR58-3.html

As far as I know, the Germans and Americans never did.

[Sailor Steve]

Submerged Type VIIc uboat displaces almost 1000 tons. British 'J' class destroyer displaces 1690 tons. Destroyer hooks uboat while it's diving:

1) Hook snags outer hull of uboat and rips a hole that really won't affect the boat other than slowing it down a bit due to the jagged edges.

2) Hook snags something solid and destroyer suddenly finds itself attached to 1000 rapidly sinking tons. Kind of like deep-sea fishing and snagging a whale.

[Schultz]

Thats what happend in "Below" a hook snatched the coning tower until the periscope tubes bended and cracked so they had to clear the coning tower beacause of the water.
Here are 2 ss of the hooks.

[Sailor Steve]

My point was that they wouldn't do it because there's a perfectly good chance that the sub might drag your destroyer down with it.

[Schultz]

The point is that in the movie the sub was already at the bottom so the hooks were long enough to reach the sub. Maybe they should put this on sh5 .

[FIREWALL]

Originally Posted by Sailor Steve

My point was that they wouldn't do it because there's a perfectly good chance that the sub might drag your destroyer down with it.

Your saying it was never tried in RL back then ?

[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.

[Platapus]

Originally Posted by Sailor Steve

2) Hook snags something solid and destroyer suddenly finds itself attached to 1000 rapidly sinking tons. Kind of like deep-sea fishing and snagging a whale.

" Brody: You're gonna need a bigger boat."

[Sailor Steve]

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]

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.

[Dread Knot]

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.

[SteamWake]

Originally Posted by Sailor Steve

My point was that they wouldn't do it because there's a perfectly good chance that the sub might drag your destroyer down with it.

Surely they would have some sort of emergency release, what if the hook snagged a reef then you would be stuck

[Letum]

A net might be a better idea than a hook.

Trawl a large steel or rope net between two ships.
When you catch a sub, release the net along with an anchor attached to it.

[Subnuts]

Hey guys,
It's a movie.

Maybe they should include a Russian submarine captain with a Scottish accent, a dog that pisses all over the boat, destroyers that explode deck-first in enormous fireballs, a first officer that disagrees with everything you do, and a token black guy into SH5, too.