How fast do Depth Charges sink

[fiendlittlewing]

I sometimes time the interval between splash and boom and compare the values between attacks. This tells me the DDs are setting them shallow or deep. But I was wondering, is there any formula to estimate the depth?

[Admiral8Q]

Great question! I usually do it by ear, but a second by second count-down would help.

[Admiral8Q]

I'd guess about 10 feet per second, or 3 meters per second.

[TorpX]

10 ft./sec. was what I used to use for mental calculations for SHCE, but I don't know what it is in SH4.

I believe it's in one of the game files, and can be changed.

[Admiral8Q]

Originally Posted by TorpX

10 ft./sec. was what I used to use for mental calculations for SHCE, but I don't know what it is in SH4.

I believe it's in one of the game files, and can be changed.

It could be double that, or even triple. Those cans were heavy. I'm thinking from actual experience. In water things tend to move in slow motion.

Maybe 30 feet (10 meters) per second?

[TorpX]

30 ft./sec. seems too fast to me. That would mean about 6 sec. to reach 200 ft. It would be very hard to dodge charges at that rate.

I know different types had different fall rates. The familiar cylindrical type was suited to the racks, but wasn't stable in the water and did not have an optimum drop rate. The British had a large bomb-shaped type that was designed to reach depth quickly.

The weight of the charges isn't really the critical factor, but rather the density and shape. TNT, or TORPEX isn't all that dense, and the steel casings are thin, so they will not drop as fast as a hunk of steel, or rock would.



Edit:

Here is a little info from Wiki on a few types:

The Royal Navy Type D depth charge was designated the Mark VII by 1939.[9] Initial sinking speed was 7 ft/s (2.1 m/s) with a terminal velocity of 9.9 ft/s (3.0 m/s) at a depth of 250 ft (76 m) if rolled off the stern, or upon water contact from a depth charge thrower.[9] Cast iron weights of 150 lb (68 kg) were attached to the Mark VII at the end of 1940 to increase sinking velocity to 16.8 ft/s (5.1 m/s).[9] New hydrostatic pistols increased the maximum detonation depth to 900 ft (270 m).[9] The Mark VII's 290 lb (130 kg) Amatol charge was estimated capable of splitting a 7⁄8 in (22 mm) submarine pressure hull at a distance of 20 ft (6.1 m), and forcing the submarine to surface at twice that.[9] Change of explosive to Torpex (or Minol) at the end of 1942 was estimated to increase those distances to 26 and 52 ft (7.9 and 15.8 m).[9]
The British Mark X depth charge weighed 3,000 pounds (1,400 kg) and was launched from 21-inch (53 cm) torpedo tubes of older destroyers to achieve a sinking velocity of 21 ft/s (6.4 m/s).[9] The launching ship needed to clear the area at 11 knots to avoid damage, and the charge was seldom used.[9] Only 32 were actually fired, and it was known to be troublesome.[10]
The teardrop-shaped United States Mark 9 depth charge entered service in the spring of 1943.[11] The charge was 200 lb (91 kg) of Torpex with a sinking speed of 14.4 ft/s (4.4 m/s) and depth settings up to 600 ft (180 m).[11] Later versions increased depth to 1,000 ft (300 m) and sinking speed to 22.7 ft/s (6.9 m/s) with increased weight and improved streamlining.[11]
Although the explosions of the standard United States' 600 lb (270 kg) Mark 4 or Mark 7 depth charge used in World War II were nerve-wracking to the target, an undamaged U-boat’s pressure hull would not rupture unless the charge detonated closer than about 15 ft (4.6 m). Placing the weapon within this range was entirely a matter of chance and quite unlikely as the target maneuvered evasively during the attack. Most U-boats sunk by depth charges were destroyed by damage accumulated from a long barrage rather than by a single carefully aimed attack. Many survived hundreds of depth charges over a period of many hours; U-427 survived 678 depth charges in April 1945, though many may have detonated a considerable distance from the target.

[fiendlittlewing]

I found this

Other studies have determined the rate of depth charge descent as 200 ft takes 18 seconds, 300 ft takes 28 seconds and 400 ft takes 38 seconds.

This would imply ~ 10.5-11' / sec

[Sailor Steve]

The main Japanese depth charge, the type 95, sank at 6 f/s. The later Type 2 sank at about 10 f/s.
http://www.navweaps.com/Weapons/WAMJAP_ASW.htm

The Standard British Mk VII was also about 10 f/s. Later mods increased the sink rate dramatically.
http://www.navweaps.com/Weapons/WAMBR_ASW.htm

The Americans were about the same.
http://www.navweaps.com/Weapons/WAMUS_ASW.htm

[TorpX]

A lot of interesting stuff there.

I never saw the details of the Squid or Mousetrap before.

Neat stuff!

[razark]

Originally Posted by Sailor Steve

The main Japanese depth charge, the type 95, sank at 6 f/s. The later Type 2 sank at about 10 f/s.
http://www.navweaps.com/Weapons/WAMJAP_ASW.htm

According to the link, the Type 95 had depth settings for 98, 197, or 295 feet. How accurate would these settings have been, and was this information known at all during the war?

Has anyone modded this into the game?

[Sailor Steve]

Originally Posted by razark

According to the link, the Type 95 had depth settings for 98, 197, or 295 feet. How accurate would these settings have been, and was this information known at all during the war?

The 295-setting only came later in the war. Early on the US Navy knew about the 197-foot maximum setting, and used it to their advantage. The Japanese had no idea about what the Americans knew until the secret was inadvertantly revealed by US Congressman Andrew J. May in June 1943. The Japanese may have already been preparing the deeper setting before May's revelation, but after that they certainly knew the truth.
http://en.wikipedia.org/wiki/Andrew_J._May

Has anyone modded this into the game?

Of that I have no idea. I believe there was one, but I can't find it now.

[Armistead]

Be funny to set them in game to drop at 30ft per sec. Someone should do it with TMO and see how fun it is.

[razark]

Originally Posted by Sailor Steve

Early on the US Navy knew about the 197-foot maximum setting, and used it to their advantage.

Do you know if they actually knew it was a maximum setting or did they think the Japanese were just setting them too shallow?

Originally Posted by Sailor Steve

The Japanese had no idea about what the Americans knew until the secret was inadvertantly revealed by US Congressman Andrew J. May in June 1943.

I guess I removed that reference before I posted. I couldn't remember his name, though.

[Red Devil]

it also depends on saline density

[Sailor Steve]

Originally Posted by razark

Do you know if they actually knew it was a maximum setting or did they think the Japanese were just setting them too shallow?

Sorry I missed this the first time. No, I don't know for certain, but I suspect the latter.