12000lb Tallboy Bomb

Tallboy Bomb

Development of the TallBoy bomb was completed by March 1944, these bombs were designed for the attack of targets such as Uboat pens, tunnels, bridges and viaducts as normal bombs were ineffective against such targets. It had also been considered to use the bombs in area attacks but it was felt that they would be less effective than the current 8,000 and 12,000lb High Capacity bombs. The bomb was designed by Barnes Wallis, designer of the Wellington bomb and the 'bouncing bomb', Mr Wallis had been pushing for very large bombs for years and he felt that a large bomb which could penetrate deep into the ground could damage or destroy large structures.

The Tallboy bomb was expected to penetrate up to around 60 feet deep in soil and 65 feet in clay and create a crater up to 110 feet wide and 45 feet deep. Against a 13 foot thick un-reinforced concrete roof the Tallboy was expected to go right though, it was known that reinforcement was the most important factor how how much reinforced concrete the bomb could penetrate. Penetration of around 8 feet was estimated but against a 13 foot thick reinforced roof, although complete penetration was not expected the explosion would most likely destroy a large part of the roof. Against a soft target such as a railway line it was expected that it would take at least 5 days for the resulting crater to be filled in, and if the bomb was dropped near a bridge or a tunnel the repair time could be weeks or even months.

Filling for the bomb was Torpex.

First use

The first target attacked with Tallboy bombs was the Saumur railway tunnel on the night of the 8/9th of June. The raid was carried out by 19 Lancasters of 617 Squadron and their bombs were fused for 0.025 seconds. They were assisted by a flare force of 10 other Lancasters and 3 Mosquitoes. The two aiming points were the entrances to the tunnel, these were marked by red spot flares from low level by Mosquitos, the flare carrying aircraft also carried 5-8 1,000lb General Purpose bombs which were dropped on the bridge over the river.

At the Southern end of the tunnel 18 Tallboys were dropped, due to the presence of cloud the aircraft were forced to drop from 8,400 and 10,500 feet another Tallboy was dropped on the Northern end of the tunnel. 13 of the bombs fail in close proximity to the markets, 4 has significantly greater error and another missed by 680 yards. The single bomb aimed at the Northern end fell 170 yards from the aiming point.

The average crater size was 80 feet by 25 feet, the largest had a diameter of 120 feet and a depth of 30 feet. Damage the tunnel and surrounding tracks was extensive with one bomb causing the tunnel to collapse, all bombs functioned correctly.

Tallboy bomb specifications

Bomb	12000-lb DP Mk I
Construction	Cast Steel
Usual weight	11,885lb (5402.27kg)
Charge/weight ratio	45%
Total length	252in (640.08cm)
Body length	38in (96.52cm)
Body diameter	124in (314.96cm)
Wall thickness	1.25-4.1in (3.175-10.414cm)
Tail length	128in (325.12cm)
Tail width	42in (106.68cm)
Filling	Torpex

Summery of Tallboy raids

Over 700 of the bombs were dropped on enemy territory during the war.

By Night

Date	Target	No. Dropped	Fusing (secs)	Height (feet)	Result
31/1/45	Shipping in Oslo Fjord	10	0.5	7,000-12,500	Not Known
6/3/45	Sassnitz, Naval Installations	19	0.07	3,500-12,500	Not Known
8/6/44	Saumur Tunnel	19	0.025	8,400-10,500	Craters average 84/25ft, One feel on tunnel roof 30 yards from entrance and caused roof to collapse
4/7/44	St. Leu D'esserent (underground storage depot)	11	11	16,500-19,000	No bombs located on target
14/6/44	Le Have, E-Boat Pens	22	0.5	15,500 - 19,000	One bomb caused penetration and break in the top of N. Wall
23/9/44	Ladbergen (Canal aqueduct)	6	1/2 hour	14,000	Embankments breached
3/3/45	Ladbergen (Canal aqueduct)	18	1/2 hour	8,000-14,000	Not Known
21/12/44	Politz (synthetic oil)	11	11	15,000-20,500	Not Known

By Day

15/9/44	Tirpitz	15	-	11,350-17,500	Smoke Screen, No serious damage
29/10/44	Tirpitz	32	-	12,000-16,000	Smoke Screen, No serious damage
12/11/44	Tirpitz	29	0.07	12,500-16,500	Ship capsized and sunk by 3 direct hits and 2-3 very near misses
19/6/44	Watten (V-Site)	17	11	15,500-18,000	No damage
24/6/44	Wizernes(V-Site)	16	11	16,500-17,500	Landslide of quarry face, railway track blocked
25/6/44	Siracourt(V-Site)	16	11	16,000-19,000	Section of overhanging roof 100'x15' broken off
6/7/44	Mimoyecques(V-Site)	14	11	16,000-19,000	Corner of concrete construction destroyed - 63'x35'. Crater 35'x100'
17/7/44	Wizernes(V-Site)	16	11	16,000-18,600	Part of chalk cliff collapsed, the four tunnel entrances blocked
25/7/44	Watten(V-Site)	16	1/2 hour	17,000-18,500	Direct hit, caused severe damage to structure
31/7/44	Rill La Montage	12	1/2 hour	16,700-17,000	Not Known
15/6/44	Boulogne(U-Pen)	11	0.5	7,500-18,500	Pens not hit
5/8/44	Brest(U-Pen)	14	11	16,500-18,500	6 craters on roof of pens, one penetration
6/8/44	Lorient(U-Pen)	11	11	16,000-18,000	3 craters on roof, no penetrations
9/8/44	La Pallice(U-Pen)	12	0.5	16,500-18,000	6 direct hits, large parts of concrete dislodged, large area of roof torn up
12/8/44	Brest(U-Pen)	8	0.5	16,000-18,000	Three hits on roof, one probable penetration
13/8/44	Brest(U-Pen)	5	0.5	16,000-18,000	One hit on roof, no penetration
18/8/44	La Pallice(U-Pen)	6	0.5	16,000-18,000	No appreciable damage
24/8/44	Ijmuiden(U-Pen)	8	11	16,000-18,000	Two direct hits, one penetration, other caused roof to breakaway
15/12/44	Ljmuiden(U-Pen)	13	11	9,000-10,000	140'x33x section of roof collapsed as a result or one or two hits.
29/12/44	Rotterdam(U-Pen)	16	11	16,000-18,000	Section of roof over entrance 158'x20' destroyed
12/1/45	Bergen(U-Pen)	24	0.5(6),11(18)	14,500-18,000	Three or four direct hits
3/2/45	Poortershaven(U-Pen)	18	0.5	13,000-14,000	Severe damage or virtual destruction of all buildings
3/2/45	Ijmuiden(U-Pen)	17	1/2 hour	14,000-17,000	No damage
8/2/45	Ijmuiden(U-Pen)	15	1/2 hour	14,000-17,000	One direct hit destroying uncompleted portion of roof over 3 pens
27/3/45	Farge(U-Pen)	4	1 hour	14,000-19,000	2 Penetrations of roof but possible due to 22,000lb MC
22/2/45	Bierfield	18	11	12,500-14,500	Two piers of one viaduct destroyed
22/2/45	Altenbeken	16	11	12,000-14,000	One span destroyed
13/3/45	Arnsberg	1	11	12,500	No damage
14/3/45	Bielefeld	13	11	12,000-16,000	Seven spans of each viaduct destroyed
14/3/45	Arnsberg	15	11	12,000-14,000	Direct hit at tunnel entrance, blocked lines
15/3/45	Arnsberg	6	11	13,000-14,000	Not Known
19/3/45	Arnsberg	12	11	11,000-13,000	2 spans collapsed and embankment undermined
19/3/45	Vlotho	15	11	11,000-13,000	Bridge damaged by near miss
21/3/45	Arbergen	17	11	13,000-14,000	Viaduct breached for 180 feet. One Span destroyed, adjoining section thrown off piers
22/3/45	Nienburge	12	25(5) 1 hour(7)	9,000-10,000	All 3 spans broken or torn off piers
22/3/45	Bremen	14	25(7), 1 hour(7)	15,000-20,000	No damage
23/3/45	Bremen	11	25(7), 1 hour(7)	16,000-18,000	One span collapsed by year miss
23/3/45	Bad Oeynhausen	10	11(5), 25(5)	12,800-13,900	Both parallel halves of bridge collapsed by near miss
7/10/44	Rembs(Dam)	11	0.025-1/2 hour	600 and 6,000-8,500	One span of bridge destroyed by direct hit
15/10/44	Sorptz(Dam)	16	11(12),1/2 hour (6)	13,000,15,000	2 direct hits, dam not breached
8/12/44	Urft(Dam)	3	11	6,500-12,000	Dam not hit
11/12/44	Urft(Dam)	35	11	4,500-10,000	Dam not hit
27/3/45	Farge(Oil)	15	1/2 hour	15,000-17,000	Not known

Sources - AVIA 46 285, AVIA 46 163