The Hedgehog Anti Submarine Weapon 1943

[The Sailor]

The Hedgehog was an anti-submarine weapon developed by the Royal Navy during World War II, that was deployed on convoy escort warships such as destroyers to supplement the depth charge. The weapon worked by firing a number of small spigot mortar bombs from spiked fittings. Rather than working on a time or depth fuse like depth charges, the bombs exploded on contact and achieved a higher sinking rate against submarines than depth charges did.

The major deficiency of the combined ASDIC / depth charge attack was the so-called blind time, which was the time it took the depth charges to reach the set depth at which they were to explode. This time increased with the presumed depth of the contact, and could often result in the submarine evading the attacks.

Further, it was related to the method of attack used by single destroyers. They would acquire a target, with ASDIC, then head toward the contact at speed. However, at a certain distance, the target would be too close to be spotted on ASDIC, which the submarine, again coupled with the problem of the slow-sinking depth charges, could use to avoid the attacker, since the attacker would need to speed up to minimize the time between loss of contact and attack which the submarine could hear if it had not yet picked up the destroyer.
The Hedgehog could fill this gap.

Hedgehog was a 24-spigot mortar of crude build, usually firing to 300 yds or around 250 meters ahead of the attacking ship, shortly after blind time began. It fired a circle-formed salvo in the general area of the submarine, each spigot containing 35lbs of Torpex. The spigots were contact fused, thus only creating the disturbing noise of depth charge attacks when actually hitting a submarine, which was as good as a kill though surfacing damage was possible too. It is not known that any submarine survived a hedgehog hit because no one lived to tell about it.

During 1943, it came as a shock to a U Boat crew to hear the acoustic approach of a destroyer and suddenly find themselves blown up and sinking before the ship even reached them.

The beginning of the end in the Battle of the Atlantic.

The Hedgehog fired twenty four 14.5 kg charges whereas a later development called the "Squid" fired more. A further development called "Limbo" was used into the 1960s, and this used 1 ton charges.

[TheDigger]

Interesting weapon the Hedgehog I wonder what the firing rate of this weapon was. Was this equipped in a bank of more than one, does anyone have any pictures of ships fitted with this device.

[TheDigger]

Well I could not wait and did a little research

The first Hedgehog installation was put onboard the frigate (DE) HMS Bayntun on March 12, 1943.


I found a pic of a dual setup so this got over some of the relaoding issues

[John Brown]

The 'SQUID' which replaced the hedgehog was a three barrelled mortar system which fired depth charges ahead of the ship in a triangular pattern. (On the face of it, the return to depth charges seems a bit of a retro step other than the fact that they are fired ahead of the ship). As with the hedgehog two squids could be mounted to give a salvo of 6 charges. The first squid was rushed into service in May 1943 on HMS Ambuscade with the first production unit being fitted on HMS Hadleigh Castle. HMS Salisbury was the last ship to fire a Squid in Royal Navy Service in 1977.

[Stan.J]

H.M.S.Magpie was one of the early ships to be fitted with Hedgehog. accounting for the destruction of U238 on 9/2/1944. Looking at this picture the weather was often the worst enemy on Arctic conveys.

[tomsam]

Hi John.
I am sorry to correct you but you are thinking of a Mk 10 "Limbo" Mortar.
But they were developed from the Squid.Some Squid were fitted forrard and some aft, but all Limbo's were fitted aft in echelon .
Hope this helps.
Tomsam

[John Brown]

Hi Tomsam

In the interests of accuracy I am always ready to be corrected. On this occassion however, I am not sure what you mean. Yes, the Limbo was a further development of the Squid but as far as I am aware my post gave info on the Squid itself. If you know differently please could you explain further?

Regards...John

[Batstiger]

Yes John that is correct you only mentioned the Squid in comparison with the Hedgehog.
The Squid was a far more advanced weapon as opposed to the Hedgehog. With the latter contact with bomb and submarine had to be made before it was successful, the other bombs would explode in sympathy otherwise the whole lot was wasted.
With the Squid a depth setting was being applied all the time up to the moment of firing by electronics from the Asdics. these came from a "Q" transponder and the "147" depth recorder.
When fired all charges would explode on reaching the Submarines last known depth.
As regards the Limbo, this did not come in to use until after the war.
The first ship I came across that was fitted with a single triple mounting was the Weapon class destroyer HMS Scorpion.

Bob.

[tomsam]

Hi John, Sorry if what I said was unclear. I was referring to HMS Salisbury being the last ship to fire Squid in service in 1977. When I wrote the first reply I had a momentary lapse of reason and forgot that the Salisbury class were never fitted with the limbo as the expense was too great for Air Direction Frigates (Not being ASW Frigates ) Again sorry for the confusion as all what you posted was pertinent and my brain needs "paying off".:o
Regards
Tomsam

[John Brown]

No problem Tomsam. Just glad it's cleared up now.

Bob...thanks for your input too.

Regards...John

[Batstiger]

Your welcome John, I used to be a Ping bosun many years ago.

[astraltrader]

I thought this classic picture of a Hedgehog anti-sub mortar might prove to be of some interest?

[Scurs]

Were we (SURPRISE) the last ship to be in commission with Hedgehog fitted? In 1963, someone (probably the skipper) got the bright idea to fire it...............er.............not an all together unqualified success! The Hedgehog was mounted in 'A' Gun position.
The 24 bombs ("lights" of course - no warhead) performed something like:-

6 didn't go anywhere, stayed on the mounting
10 fired and bounced off the foc'sle
3 lodged by the breakwater
5 went as designed

We also had an twin 4" gun, and two army style, hand powered, Bofors..........nobody was brave enough to attempt to fire those.
The Hedgehog experiment was not repeated, and may have been the last time one was fired in the RN, but any submarine would have been perfectly safe! :rolleyes:

[astraltrader]

It was proven to be far more accurate than depth charges once the initial teething troubles were resolved.

Apparently a copy of Hedgehog was produced in Russia known as the MBU-200 which developed in 1956 into the MBU-600 with an enhanced range of 600 metres or so....

[tim lewin]

Posted before but no harm in repeating in this context; all from the 55'56 commission of Corunna and taken in the Med; probably Ron can add detail.
tim

Squid, not h/hog or limbo

[tim lewin]

Should have posted those in reverse order! someone was asking about p/vane stowage (vertical on q/deck) if you close-up on the stern view you can see it triced up to the bulkhead.
tim

[tone]

The fact that hedgehogs only exploded on contact was a virtue, not a fault. Along with (of course) the ahead-firing aspect of these weapons, the idea was to exchange the few large area weapons that were depth charges with many smaller weapons that only fired when a hit was obtained. This meant that the escort team wasn't deafened and the waters roiled for minutes on end by explosions which may not accomplish any damage anyhow.

The hedgehog/mousetrap only caused a smaller loss of sonar utility in the event of it actually achieving something. Moreover, the explosion (or lack thereof) was itself of foreensic value.

I'm sure the squid was a good weapon, as well, but its charges' larger radius of destruction were obtained with a cost. I'm curious how the approaches compared in net results.

tone

[qprdave]

I posted this link in the pingers thread it gives you the kill rate v attacks of all the A/S Weapons

http://www.navweaps.com/Weapons/WAMBR_ASW.htm

[starshell]

Just a bit of clarification on the early development of Hedgehog.....

Early trials with the Hedgehog mounting were taking place by August 1941 on the old W Class destroyer Westcott and by September 1941 full sea trials were taking place using Westcott and Enchantress. Westcott apparently scored one of the first kills using Hedeghog on 2nd Feb 1942, sinking U-581 (Note that every source I have read on this sinking has a different account - some say just depth charges were used, one says ramming and two say hedgehog! ). By the end of 1942 over 100 ships carried Hedgehog. On smaller escorts like the Flowers and Sloops the Hedgehog was split into two units firing 12 spigots each. RN crews were quite wary of Hedgehog due to initial mistakes in installation, a general lack of maintenance information and no manuals, but when used properly in a deliberate attack they could be quite efficient and achieved a 35% successful attack rate by late 44 (based on 37attacks and 13 successes).

On 20th September 1943 HMS Escapade was unlucky enough to be the only RN ship heavily damaged by its own Hedgehog unit. Escapade had stopped to assist the frigate Lagan which had just had its stern blown off by a homing torpedo. On locating the U-boat responsible and firing her Hedgehog the bridge crew of Escapade witnessed a massive explosion above the bows. One of the bombs had exploded permaturely when leaving its spigot. This practically blew off the bow of the ship and there were 16 dead plus nine injured. Amazingly she still managed to tow the battered Lagan back to Northern Ireland and Escapade was then repaired at Portsmouth later that month. Lagan and Escapade must have been a grim and bizarre sight as they pulled into port together!

The USN used Hedgehog more widely and had more success with it. In May 44USS England famously sank 6 Japanese submarines with 12 salvoes in 11 days.

Mark

[Forester]

I have a collection of first hand reminiscences by crew members of HMS Forester (H74) and they describe in some detail a split hedgehog system installed in their ship. There was a 12 spigot mortar on each side of the forward superstructure and the crew's action station was in the shelter below the 'B' gun's blast shield and aft of the 'A' gun, which remained installed on the fo'csle. The two mortars were fired simultaneously with 12 of the 24 round salvo going from each side to make a complete pattern. The mortar bombs came up from the magazine in boxed sets and the boxes had to be stowed on deck after use, to be returned empty when they returned to port. I've never seen any pictures of such an installation, but the two crew members who tended and fired this set up gave such detailed descriptions that you can't really doubt them.

[r.morrison]

The idea was succesful by all accounts then, the Russian Navy still use a similar system to this day. (Photo shows UDAV system on KUTZNETOV on the lower left........)

Were there are accounts of the British system having been mounted on bren carriers during WW2 for use against ground targets ?

I did read this somewhere:)

[chris westwood]

Yes John that is correct you only mentioned the Squid in comparison with the Hedgehog.
The Squid was a far more advanced weapon as opposed to the Hedgehog. With the latter contact with bomb and submarine had to be made before it was successful, the other bombs would explode in sympathy otherwise the whole lot was wasted.
With the Squid a depth setting was being applied all the time up to the moment of firing by electronics from the Asdics. these came from a "Q" transponder and the "147" depth recorder.
When fired all charges would explode on reaching the Submarines last known depth.
As regards the Limbo, this did not come in to use until after the war.
The first ship I came across that was fitted with a single triple mounting was the Weapon class destroyer HMS Scorpion.

Bob.
I was under the impression that the fact that the hedgehog bombs didn't explode unless a contact had been made was considered an advantage, because it confirmed that a contact had been hit, altough I appreciate that a near miss from an exploding depth charge coiuld damage a submarine badly.
Thanks for the description of how a squid worked, really interesting.

[John Brown]

Were there are accounts of the British system having been mounted on bren carriers during WW2 for use against ground targets ?

I did read this somewhere:)


I'm not sure about being mounted on Bren Carriers but certainly a variant, the Hedgerow, was carried in some landing craft and used to explode mines on the beaches during the Normandy landings.

Regards...John

[Forester]

I was under the impression that the fact that the hedgehog bombs didn't explode unless a contact had been made was considered an advantage, because it confirmed that a contact had been hitWhen Forester and Vidette were dispatching U413 in the Channel Forester's salvo produced two explosions but the ASDIC continued to track the submarine and Vidette hit it again with the reuslt that the one survivor burst to the surface in a huge bubble of air. It seems that in the shallow water close to the coast two of Forester's hedgehog bombs exploded on contact with the seabed.

Re: hedgehog on land, some Matilda Mk II tanks were equipped with a seven round hedgehog mortar.

[chris westwood]

When Forester and Vidette were dispatching U413 in the Channel Forester's salvo produced two explosions but the ASDIC continued to track the submarine and Vidette hit it again with the reuslt that the one survivor burst to the surface in a huge bubble of air. It seems that in the shallow water close to the coast two of Forester's hedgehog bombs exploded on contact with the seabed.

Re: hedgehog on land, some Matilda Mk II tanks were equipped with a seven round hedgehog mortar.

thanks mate

[barnsey]

Posted before but no harm in repeating in this context; all from the 55'56 commission of Corunna and taken in the Med; probably Ron can add detail.
tim

Squid, not h/hog or limbo

This is a great thread and these photos Tim are very interesting as well as being detailed....

thanks everyone

[Alandc]

With regard to Starshell's post (#19) and whether the first "kill" using a hedgehog was by HMS Westcott, my father served as a signalman on HMS Westcott from 31st Oct '41 to 23 Dec '42 and he was in no doubt that U581 was rammed. He didn't speak much about his wartime experiences but that is one I do remember. It also tallies with the account in Tom Chapman's book of HMS Wescott (Water, Water, Every Where). My father also kept a newpaper cutting from the time that refers to the ramming and which I've attached - plus some photos that I believe are the survivors being picked up.

Alan

[alan reeves]

[QUOTE=The Sailor;5333]ThAlane Hedgehog was an anti-submarine weapon developed by the Royal Navy


Am i right in believing the hedgehog bombs had a impeller on the nose and as the bomb went through the air the primer was screwed into the charge.We had the weapon on the St AustellBay and when ammunitioning ship, one of the stokers was playing with it making it fly round. Alan.

[jainso31]

Alan- none of the photographs in this thread, show an impeller on the nose ,as you put it; it had a contact fused warhead and was fired in batches.

jainso31

[qprdave]

no impeller/propeller. As Jim said it was a contact weapon. But.... They were fired so that if one went off the others detonated as well

Dave

[Scratcher]

Hedgehog Bombs with what look like impellers to me?.

[qprdave]

The impeller shown had nothing to do with depth finding, it was used as a screw type mechanism to fuse the projectile down to prime it. If it hit a target before it completed the fusing, the only bang you would have heard is it hitting the submarine and there would be very relieved submariners.

Dave

[alan reeves]

Thanks QPRDave. Does this mean if the fuse was manually screwed home and the bomb dropped on deck it would explode?

[qprdave]

I should imagine it wouldn't be advisable to mess with it. And if you did. Don't drop it!!!!!

Dave

[Blaydon]

From what I have heard there was a Hydrostatic component to the fusing and although the vane would screw the pistol home the weapon was required to descend to a depth of 15 feet prior to it being fully armed.

[Forester]

I should imagine that the impeller was a modification to the early bombs. designed to prevent premature detonation in the event of a bomb failing to be thrown clear of the ship, as happened a number of times - most spectacularly to HMS Escapade.

[Don Boyer]

Very interesting thread this, as I had not heard or read much of the early development of this weapon. I do know it was a very effective piece of work, as the US Navy was all over it as soon as it was invented and it sprouted on destroyers and destroyer escorts just as fast as they could get them manufactured.

The US destroyer escort England's famous sortie against the Japanese navy in 1944 generated six submarine kills in 12 days, all the kills being made with Hedgehog. She was working a Japanese submarine scouting line revealed by code-breaking and managed to pick up an extra submarine that just happened to be passing through. (England, by the way, was not named for the well-known country, but for a gentleman by that name -- :D)

[Forester]

England, by the way, was not named for the well-known country, but for a gentleman by that name I wonder where his ancestors came from... ;)


I read in notes that Dad left me, that Forester had "Split Hedgehog" fitted. I'd never seen a photo of this set-up, but it seems from reading "British Destroyers from Earliest Days" that this installation was quite common. It allowed a ship to retain both the A and B guns for firing ahead when chasing E-boats and surfaced U-boats.

BTW, they're not on the ship post 1942 refit as shown in my signature photo. They were fitted in April 1943.

[BobM]

A book by Gerald Pawle entitled 'The Wheezers and Dodgers' gives some very interesting information about the development of this weapon.

The genesis of the project lay in the development of a spigot mortar by Major Jefferis as the basis of an anti-tank weapon, the 'Blacker Bombard' after the originator of a spigot Lt. Col Stuart Blacker. Blacker had approached the Admiralty before the war suggesting a spigot weapon might be used against submarines but was told there was "no naval requirement".

When war came Charles Goodeve who had been placed in charge of a team of original thinkers tasked with developing new weapons championed the idea. It was Goodeve's idea that instead of firing one bomb it should fire a series. Goodeve met some opposition. Apparently on approaching a senior member of the Ordnance Board he was told:
"This idea was put up by Major X in 1910, and it was turned down by the Ordnance Board then. The spigot mortar was put up by Colonel Blacker in 1930, and was turned down again. It was put up by Major Jefferis in 1939, and the Ordnance Board turned it down for the third time. If God Almighty Himself sponsored the spigot mortar, I tell you it would still be turned down by the Ordnance Board!"

The early projectiles were made by Boosey & Hawkes who are better known for making musical instruments. The name 'Hedgehog' was the winning entry in a competition to find a name with the winner receiving a bottle of sherry for his idea.

At the time work began the Hedgehog was up against several other ahead throwing weapons: the Bell-mouthed Bastard, the Fairlie mortar and a couple of others. The hedgehog eventually triumphed because the problem of the fuses was solved. How this was done is extremely interesting and will form the basis of my next post.

[BobM]

The principal challenge was posed by the Fairlie mortar and its supporters in the Admiralty. This weapon used a projectile with an iron nose which limited the quantity of explosive carried to 20 pounds with the fuse carried in the tail.

Goodeve and his team designed the hedgehog bomb with a load of 30 pounds of explosive fired by a fuse in the nose and used a tubular tail to confer stability. Experiments with a range of designs revealed that bombs with a flat nose were less likely to skid on hitting the surface of the sea. Further experiments showed that a 20 pound charge would not do enough damage to submarine plating. Goodeve was uncertain whether their 30 pound charge would be any better. One source of concern was that if the bombs hit the deck of submarine rather than the pressure hull the explosive force would be reduced. To find out how much effect this deck would have it was vital to know the height above the pressure hull of the deck. Up to date information about U boats was not immediately available but fortunately an Italian magazine ran an article on the Italian navy which included a picture of a man standing on the pressure hull to work on the deck of a German U boat. By calculating the approximate height of the worker's legs it was possible to estimate this distance.

Various types of fuses were tried to ascertain which was most effective with the best proving to be a mechanism activated by a propeller which began turning as the projectile hit the water.

The idea behind the pattern of charges was to catch a U boat in any combination of evasion manoeuvres it might attempt when it's commander knew it was under attack. This pattern was worked out using a device like a roulette wheel on which a scale model of a submarine was placed. Over many days tiny missiles were thrown at this model and the result was the discovery of the correct elevation of the spigots.

In the next post I will describe the trials and how the weapon was finally 'sold' to the Admiralty.