bombing lorient pens

Hi,
Can anyone tell me why the allies left bombing the Lorient submarine pens so late,why not do it when they were still under construction?,
Peter

 

They did , but nothing seemed to work. There was a permanent race between both camps and the technology which could destroy structures in 1942 could not do so in 1944. Not to mention that the area was defended .
Raf victims can be found in surounding cemeteries like Guidel, or smaller places like Quiberon etc... Lorient city was bombed to the ground but the pens resisted.
The Germans used local granite stone unti they found out that Norwegian granite was even more resistant and they started importing some al the way to Lorient (as long as they could afford it). This is an example of how hard they tried to find natural defences to resist bombings.

 

Bonjour Skipper, A very interesting subject to me. Granite is enormously strong in compression but it is still cut blocks. How was it tied together ? Or was it used as a binder in concrete. It could make great vertical walls but for the roof concrete seems to be used . The photos showing penetrations show rebar hanging out . A granite shield or layer could be put on the roof to disperse some of the explosion, then repaired. An outer skin so to speak. I guess eventually Tall Boys penetrated the best efforts but they were hard to hit and flying lower means running a gaunlet. The pens present a classic escalation of offense-defense-offense.

An interesting topic as they were so close to the UK yet so strong and well defended. A plum in a briar patch. Lorient really took a beating as did the bombers plus the often forgotten French civilians.


Gaines

 

Hi,
Thanks for replying guys.Why i was asking was i watched a program the other night which featured the pens.They said during the second and third stage the Germans were suprised they wern't bombed,it was only when construction was completed that they were.This is inspite of having a very brave French man on the inside relaying information to the allies.Given how serious a threat submarines were at that time and how relatively near a target it was i can't understand why it was not attempted earlier.Also the target area must have been pretty big and surely would have been extremely vulnerable at those stages,
Peter

 

Wasn't Lorient built between 1941-1942 ? The RAF wasn't in a position to mount heavy night raids at that time, and a daylight attempt would have been suicidal.

 

Don't forget that Bomber Command is operating with a limited amount of resources...and for much of 1941, the Scharnhorst and Gneisenau are at Brest, and would be joined there by Prinz Eugen on June 1, 1941. These two, and later three ships, likely diverted all British attention away from the goings on in other French ports. British bomber attacks against these ships are reported to have dropped some 3,413 tons of bombs and cost 127 aircraft.
http://www.scharnhorst-class.dk/scharnhorst/history/scharnbrest.html

This would be roughly 10% of the British bomb tonnage dropped in 1941, and account for over 10% of bomber losses for the same year
http://ww2.batcave.net/stats.html#year

 

Also, asked over at uboat.net.
http://uboat.net/forums/read.php?3,88693,88693#msg-88693

 

Prolly missed something... but, how much more impervious could another type of granit be, and would it be worth the effort ultimately...hey that rhymes.
The rapping skeleton.

 

How are yo going to cut, let alone move a granite slab that large?

 

Exactly. I feel you.

 

Hi Takao,
Many thanks for that address,subject fully covered there,
Peter

 

Yes it was and it was constantly reinforced ; so the RAF could not destroy it. I visited the place a fe wyears ago. The pens are still intact, they will probably still be around in centuries.

 

So - in 1941-42 Hampdens, Wellingtons and the like would have been fairly ineffectual and would have been cut to ribbons by flak in daylight. Precision targeting by night would have been impossible. It was only the defeat of the Luftwaffe and the advent of 617 Squadron, the SABS bombsight and the 'tallboys' in 1944 which provided a viable attack method.

 

I started answering this above but did not go far enough. Granite, an igneous rock is extremely strong in compression as long as it is supported, think of a wall of stacked granite, it will carry a great load. But a granite slab wide enough for a sub pen would have a hard time carrying it's own weight as it is not supported. Now the two things that occur to me is that granite was crushed and added to the concrete mix, I live 5 miles from a quarry that does just that or two, the roof of the pen was reinforced concrete many meters thick then it might, maybe, be advantageous to add a layer of granite slabs on the concrete to initiate the explosive sequence of even a Tallboy before it reached the concrete roof......Not unlike a Sherman crew added logs, concrete, sandbags, extra plate to beef up their armor.

Than granite was used in construction is quite likely , that it was a slab roof on it's own....no way . The pens are mainly concrete and concrete can be made with crushed granite. Gunpowder ended vertical granite wall forts, Look at the earth slopes in front of stone walls at Gravelands, Neiden, or Lucca..

A Lancaster can only carry on bunker buster so hitting the pens was the difficult aspect. When they did it was pretty impressive. but the pens were compartmented by support walls so one section could be penetrated and not greatly affect the others. And as Skipper points out the penetration could be repaired. Destroying them was not for lack of trying by good and brave men..

 

I hope so......

 

I think it was Lorient the took some direct hits...but they had what was like a ''double'' roof<>no damage to inside....the engineering of the pens was very phenomenal!

 

Shower thought:
Wonder, seeing how reactive armour works, if inserting a layer of explosive on/in the roof would help dissipate bunker buster bombs. The resulting explosion might look like the target was destroyed and therefore left alone afterwards. Hmmm.

 

Basic ERA does not really protect against a KE(kinetic energy) penetrator, which is what the British "Tall Boy", "Grand Slam", and "Disney" bombs essentially were. Basic ERA was meant to defeat the shaped charge(HEAT or HESH) warheads. Newer ERA that helps to protect against KE penetrators uses thicker plates, which upon detonation of the ERA charge spins the plates in opposite directions to exert enough torque to snap the KE penetrator.

Can't say that I can see the Germans "inventing" such ERA so late in the war, when they are already hard up for near about everything.

 

Hmm. Never heard of "Disney" bomb. Gonna have to look that up...Also, fascinating about the spinning plates. Gonna have to look up as well.
Wish there were vids of these tests posted into my "Weapons Test" thread. (flutters eyelashes)

 

Geeze, the "Disney" was a pretty big thing. Thanks for the tip MrT.
...Checked out the bunker busters from the Iraq war. They were made out of naval gun barrels if recalling correctly. But the lines were there from the Disney, compared to the Tall Boy. Also now wonder if our current bunker busters are still rocket assisted. If dropped from a speeding B2, would assist be necessary.