Bouncing bombs against ships

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paul.mercer
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Bouncing bombs against ships

Post by paul.mercer » Sun Oct 18, 2020 9:52 am

Gentlemen,
I'm not sure here to put this so i placed it in this bit!
Following the success of the 'Dams' raid the RAF experimented with a smaller bouncing bomb to be dropped against ships by a Mosquito bomber.
although I believe they were not particularly well regarded as a weapon.
My question is this, if it was designed to attack a ship at anchor like Tirpitz would it have carried enough explosive to sink her bearing in mind that even the 500 pound charges dropped underneath her by the midget subs did not do so even though they caused a lot of damage?
I am of course assuming that the bombs bounced over the anti-torpedo nets

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wadinga
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Re: Bouncing bombs against ships

Post by wadinga » Sun Oct 18, 2020 2:08 pm

Hello Paul,

A nice history of the Highball Project is here
and a video on you tube called "Highball Project Background" featuring HMS Malaya and an old French battleship in Loch Striven as targets. How about those observers on deck watching the bombs coming towards them? I'm not sure whether they or the aircraft have the biggest "pair" underneath them. :D

The idea was that the backspin would keep the charge close to the target's hull when it exploded, and just as depth charges needed to be close to a u boat's hull to crack it, so these smaller bombs might be more effective even against Tirpitz.

BTW the X craft deployed 2 × 4,400 lb detachable amatol charges but the damage they caused depended on how far from the bottom of the hull the seabed where they were dropped was. The last line below confirms how the steeply the imparted energy drops off with distance.


From Wikipedia:
The killing radius of a depth charge depends on the depth of detonation, the proximity of detonation to the submarine, the payload of the depth charge and the size and strength of the submarine hull. A depth charge of approximately 100 kg of TNT (400 MJ) would normally have a killing radius (hull breach) of only 3–4 meters (10–13 ft) against a conventional 1000-ton submarine, while the disablement radius (where the submarine is not sunk but put out of commission) would be approximately 8–10 meters (26–33 ft). A larger payload increases the radius only relatively little because the effect of an underwater explosion decreases as the cube of the distance to the target.
All the best

wadinga
"There seems to be something wrong with our bloody ships today!"

paul.mercer
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Re: Bouncing bombs against ships

Post by paul.mercer » Sun Oct 18, 2020 5:35 pm

Thanks Wadinga,
I would have thought that a fairly large target like a Mosquito approaching a well armed ship like Tirpitz at the low level needed to drop the bomb would have been extremely hazardous. There is one of the practice bombs recovered from Chesill Beach in Dorset on display at the swan sanctuary there, with the dimples in the casing it look just like an oversized golf ball, I'm not sure what it weighs but I think it is actually solid metal,so probably around a ton or so, it would have certainly put a large dent in her side even if it didn't explode!
it would have been interesting to see what an actual 'Dambuster' bomb would have done to Tirpitz- probably straight through her side, but I wouldn't like to be in the Lancaster that had to drop it!

OpanaPointer
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Re: Bouncing bombs against ships

Post by OpanaPointer » Sun Oct 18, 2020 6:13 pm

Skip bombing.

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wadinga
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Re: Bouncing bombs against ships

Post by wadinga » Sun Oct 18, 2020 7:54 pm

Hi OpanaPointer,

Skip bombing with a conventional bomb as I understand it, put the weapon into the side of the ship, above the waterline, but with only aircraft velocity and against belt armour it would barely scorch the paint. Very effective against unarmoured vessels, but useless against Tirpitz.

The Upkeep mine would have worked the same as Highball as an underwater threat to Tirpitz but no four engined aircraft could survive the AA so low and close. Like Paul, I suspect survival chances would have been pretty minimal for Mosquitoes too against late war AA batteries, but with cannon-armed aircraft suppressing some defensive fire , and a mass assault from different directions maybe some would succeed.

The near spherical highball with the dimples was the original design, and like a golf ball they were supposed to minimise drag by creating a "boundary layer" of the fluid medium (air/water). For the heavy Upkeep they couldn't get a spherical casing strong enough, so it ended up cylindrical. As the video explains the test weapons were filled with concrete, not solid metal. Ideally the actual forward velocity at target is fairly low so as to not break up the casing or damage the hydrostatic fuses but allow the bomb to sink and do its deadly mining effect underwater.

All the best

wadinga
"There seems to be something wrong with our bloody ships today!"

gcogger
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Re: Bouncing bombs against ships

Post by gcogger » Mon Oct 19, 2020 9:13 am

The book "Most Secret Squadron: The First Full Story of 618 Squadron and its Special Detachment Anti-U-Boat Mosquitos" by Des Curtis is an interesting read, covering the development of the Highball weapon and 618 squadron that was to carry it. Des Curtis was part of 618 squadron, so the book is written from that perspective.

From my recollection of reading it, I'd make a couple of small points regarding the original post:
  • Highball and Upkeep were developed in parallel right from the start - Highball was not developed because of the success of Upkeep. The intention was to deploy them at the same time, for maximum surprise, but that didn't happen due to my second point
  • I'm not sure it's true to say that it was not well regarded as a weapon, as testing looked very promising. Bear in mind that, compared to torpedo bombers, the Highball attacks would be made at much higher speed (therefore for a shorter time), which would reduce the risk to the aircraft. The reason it was not used on Tirpitz was because that vessel was moved further north, almost out of range, and the RAF could not work out a way to make the attack and get the Mosquitos home safely. The squadron and its bombs was sent to the Pacific late in the war, with the intention of launching from carriers (yes, some trials were successfully carried out!). They were again not used, this time because the commanders in the Pacific did not want to dedicate a carrier to an untried weapons system with a single purpose.

OpanaPointer
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Re: Bouncing bombs against ships

Post by OpanaPointer » Mon Oct 19, 2020 11:35 am

Yeah, I would have been more verbose if they hadn't come for me right then.

pgollin
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Re: Bouncing bombs against ships

Post by pgollin » Wed Oct 21, 2020 3:26 pm

.

Highball was highly rated, after tests the RAF assessed them as twice as effective as torpedoes, and the aircraft attacked at a much higher speed.

When 618 squadron was sent to the Far East they took three hooked photo-reconnaissance which were rated for multiple arrested landings and the Highball bombers, which carried two Highballs each, but were only rated at one arrested landing (they then needed to be formally examined).

The problem in the Far East SEEMS (???) to have been a combination of not wanting to show the weapon to the Japanese (one of the main reasons for its lack of use in Europe) and the USN authorities not being willing to authorise its use (no known reason).

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