A Tallboy instead of a bouncing bomb

Non-naval discussions about the Second World War. Military leaders, campaigns, weapons, etc.
paul.mercer
Senior Member
Posts: 950
Joined: Fri Mar 26, 2010 10:25 pm

A Tallboy instead of a bouncing bomb

Post by paul.mercer » Sat Oct 31, 2020 10:59 am

Gentlemen,
We have discussed 'Earthquake' bombs and 'Bouncing' bombs in another thread, however I have often wondered what the result would have been if Barnes Wallis had developed his 'Tallboy' and 'Grand Slam' bombs earlier on an used either one or both types on the dams, would they have destroyed them if they had been dropped close enough to undermine the dam?

OpanaPointer
Senior Member
Posts: 271
Joined: Wed Jul 06, 2011 1:00 pm

Re: A Tallboy instead of a bouncing bomb

Post by OpanaPointer » Sat Oct 31, 2020 12:45 pm

CEP factor here. The whole point of the bouncing bomb was that it would roll down the upstream side of the dam and end up right at the base.

Anybody know the minimum CEP to be expected by a Tall Boy?

Steve Crandell
Senior Member
Posts: 697
Joined: Wed Feb 05, 2014 7:05 pm

Re: A Tallboy instead of a bouncing bomb

Post by Steve Crandell » Sat Oct 31, 2020 7:22 pm

When you consider the bouncing bomb was going off in contact with the dam, several hundred feet down with all that water pressure adding to the effect ... kinda hard to beat that sort of thing in destructive power.

OpanaPointer
Senior Member
Posts: 271
Joined: Wed Jul 06, 2011 1:00 pm

Re: A Tallboy instead of a bouncing bomb

Post by OpanaPointer » Sat Oct 31, 2020 8:31 pm

You could get the Good Boy* bomb to the bomb of the reservoir by using a 3 second or so delay.


*Sorry, dog lover.

User avatar
marcelo_malara
Senior Member
Posts: 1272
Joined: Sun Oct 02, 2005 11:14 pm
Location: buenos aires

Re: A Tallboy instead of a bouncing bomb

Post by marcelo_malara » Sun Nov 01, 2020 11:36 pm

OpanaPointer wrote:
Sat Oct 31, 2020 12:45 pm
CEP factor here. The whole point of the bouncing bomb was that it would roll down the upstream side of the dam and end up right at the base.

Anybody know the minimum CEP to be expected by a Tall Boy?
I don´t know, but seeing what it took the the US to impact the Thanh Hoa bridge in Vietnam you can assume the bouncing bomb was best.

OpanaPointer
Senior Member
Posts: 271
Joined: Wed Jul 06, 2011 1:00 pm

Re: A Tallboy instead of a bouncing bomb

Post by OpanaPointer » Mon Nov 02, 2020 12:12 am

Once they got the laser guided bombs up and running it was over PDQ.

Steve Crandell
Senior Member
Posts: 697
Joined: Wed Feb 05, 2014 7:05 pm

Re: A Tallboy instead of a bouncing bomb

Post by Steve Crandell » Mon Nov 02, 2020 10:15 pm

OpanaPointer wrote:
Mon Nov 02, 2020 12:12 am
Once they got the laser guided bombs up and running it was over PDQ.
Yes, but I don't think they had those in WWII. :lol:

OpanaPointer
Senior Member
Posts: 271
Joined: Wed Jul 06, 2011 1:00 pm

Re: A Tallboy instead of a bouncing bomb

Post by OpanaPointer » Tue Nov 03, 2020 12:10 am

Steve Crandell wrote:
Mon Nov 02, 2020 10:15 pm
OpanaPointer wrote:
Mon Nov 02, 2020 12:12 am
Once they got the laser guided bombs up and running it was over PDQ.
Yes, but I don't think they had those in WWII. :lol:
...what it took the the US to impact the Thanh Hoa bridge in Vietnam...

paul.mercer
Senior Member
Posts: 950
Joined: Fri Mar 26, 2010 10:25 pm

Re: A Tallboy instead of a bouncing bomb

Post by paul.mercer » Tue Nov 03, 2020 5:45 pm

Gentlemen,
As always, many thanks for your replies, As you say the 'Bouncing Bombs' used water pressure to crack the dam wall(a bit like a giant depth charge) what I was wondering is what the effect would be if a 'Tallboy' (or 'Grand Slam') did land close to the dam wall, would they undermine it and cause it to collapse?

OpanaPointer
Senior Member
Posts: 271
Joined: Wed Jul 06, 2011 1:00 pm

Re: A Tallboy instead of a bouncing bomb

Post by OpanaPointer » Tue Nov 03, 2020 6:23 pm

There's nothing special about a depth charge other than the device that tells it when to explode, a hydrostatic trigger. And that's kind of the issue. If a Tallboy landed in mud, say some Polish river, it might not detonate. The bouncing bombs used a hydrostatic trigger, right?

SO, the Tallboy would have to land in the idea place, getting it right the first time (for that bomb) and then hit some 1909 Humpmobile that had been thrown off the bridge and landed in the exact spot that was needed for the Tallboy to fuse.

UNLESS the Tallboy was equipped with a hydrostatic fuse.

THEN it would only need to be aimed at and dropped within the range of the explosive shock wave (of sufficient intensity to blow the dam.)

If we remember that the war started out with the Brits hitting ~5% of their target in bombing raids I'm not confident.

User avatar
wadinga
Senior Member
Posts: 2134
Joined: Sat Mar 12, 2005 3:49 pm
Location: Tonbridge England

Re: A Tallboy instead of a bouncing bomb

Post by wadinga » Tue Nov 03, 2020 7:37 pm

Fellow Contributors,

As has been previously shown the "water hammer" effect drops off pretty rapidly with distance, so the Upkeep mine had to explode close to the concrete dam wall. With a dam like the Sorpe, which was a very deep front-to-back earth dam with a concrete core, 617 dropped the mines along the front edge but their shockwave had little effect. Later in the war, 9 squadron attacked the Sorpe with Tallboys but even two hits on the crest causing impressive craters were insufficient to cause even minor leakage. The absolutely massive construction defeated even:
or use on underground targets, the bomb was fitted with three separate inertia pistols. These triggered detonation after a pre-set delay, which gave the bomb sufficient time to penetrate the target before exploding. Depending on mission requirements, the time delay could be set to 30 seconds or 30 minutes after impact. In order to guarantee detonation, a total of three separate Type 47 long delay fuzes were fitted inside the rear of the bomb. This dramatically improved reliability of the weapon: even if two of the fuzes failed to function, the third would trigger detonation. Despite this elaborate fusing system however, at least one Tallboy failed to explode during the second attack on the Sorpe dam and was found during repairs in late 1958 when the reservoir was emptied.
The bomb disposal team in 1958 successfully defused this Tallboy. :shock:

However late in the war attacks were made with Tallboy against the "airside" of the concrete Urft dam, but it would seem even hits failed to dislodge tens of thousands of tons of concrete. There were no Upkeep-capable Lancasters available in winter 1944 and besides the approach was apparently too hazardous. I guess Highball was too small, and maybe even Mosquitos could not get in.

This enthusiast thread discusses the Urft attacks in detail: http://forum.12oclockhigh.net/showthread.php?t=17698

As it observes, Bomber Harris considered attacks on point targets a waste of resources and a worthless distraction from his self-appointed task of flattening every city in Germany.

Ground penetration was a vital feature of successful Earthquake bomb use. The ground had to be hard enough to initiate fusing but ideally not so hard that the bomb might break up on impact. The soggy bottom of the Kaiserfahrt or the Sorpe reservoir were obviously not hard enough. The hard geology of Norway, covered with just a little sediment might have been unfortunately effective for Tirpitz. Direct hits work too. :cool: Dropping from a high enough altitude so the weapon could accelerate to supersonic terminal velocity was also important, but European weather often made this impossible.

Fascinating factoid: skinny engineering apprentices were used inside the cast bomb casing during preparation to remove burrs on the surface so that points of shock to the explosive would be minimised to lessen the chance of premature detonation on first impact with the ground.

All the best

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

OpanaPointer
Senior Member
Posts: 271
Joined: Wed Jul 06, 2011 1:00 pm

Re: A Tallboy instead of a bouncing bomb

Post by OpanaPointer » Tue Nov 03, 2020 9:28 pm

The apprentices were obviously not American teenagers. We tend to get to market weight rather more quickly. :lol:

Post Reply