Could bouncing bombs have been used on submarine pens?

I’ve been watching the new series of Das Boot and wondered if it was ever considered using the Barnes Wallis ‘bouncing bomb’ to attack the heavily-fortified German submarine pens in France and elsewhere? I know such installations were targeted with Tallboy and Grand Slam bombs, which penetrated the concrete roofs. But could Dambuster-style bouncing bombs have been used to skip directly into the open sea entrances of the pens? Or where they too heavily guarded by anti-aircraft defences to make such a mission unfeasible?

 

Re U boat pens in Norway

http://www.dambusters.org.uk/after-the-dams/raids/bergen/

 

I believe that the 'Highball' variant had been identified as suitable for the pens, but yes it seems the creation of Tallboy etc. superseded.

 

Looks like a mine sweeper was hit by a Tallboy as it was leavng harbour according to the web site on the Jan 45 raid.

In the harbour the minesweeper M1 was steaming towards Helleneset (Away from Bergen), trying to avoid the Lancasters. One Lancaster decided to go for the minesweeper and managed to hit the boat. It is probably the only time a minesweeper was hit by a Tallboy! 20 of the crew of 34 were immediately killed.
Three Lancasters were lost on this raid.

 

Having seen the submarine pens at St Nazaire & Lorient I would say that there is insufficient 'flat' area at any of them to allow you to 'bounce' a bomb into the pens, obviously at a reservoir there is a large flat area behind the dam

TD

 

I do not think that Highball or Upkeep had sufficient explosive charge to cause material damage to the civil engineering works of the U Boat pens.Minimal damage would be caused to the pen support structure if it was possible to explode such a bomb against it.

There was also the added prerequisite to have a sufficient run in path over water to skip and deliver the weapon to the target.U Boat pens were not located open to the sea and hence an adequate run in over water was never available.In addition, relatively calm waters would be required to ensure accurate delivery if Highball was used as an anti shipping weapon

The only weapons to inflict serious damage would be the Tallboy as a penetration bomb to clear the roof and explode in the roof voids.The U Boat pen roofs were designed with multi roof voids so that if penetration did occur,the core of the pen would not be subject to damage,the design was to ensure that bombs were detonated in the higher voids.However if the bomb penetrated as far as the first void,ie over the internal roof, delayed timing of detonation would inflict damage to the roof of the pen as graphic evidence demonstrated.

 

Construction detail for Submarine pen roof | WW2Talk

St Naz Sub pens3.jpg | WW2Talk

I guess another aspect would be that the submarine pens were heavily fitted out with Anti aircraft protection and a Lancaster flying straight and level at 60 feet would make a lip smacking target for all the AA gunners

TD

 

Low level torpedo missions against Brest by Beauforts in 1941 to attack German capital ships proved to be virtual suicide missions due to the flak. So I would expect little difference with the bigger target of Lancaster/Upkeep combination. But there do not appear to have been any such plans considered. Maybe speed would help the Mosquito IV/Highball combination but the aircraft carried no guns to help supress the flak.

Reading "A Hell of A Bomb" reveals that the only major ports that were in Mosquito range from UK bases were Trondheim, Kiel and Brest. In the latter case it was considered that several pens would need to be hit and would require a large force, surprise and an acceptance of heavy losses.

Other prospective Highball targets considered were canal locks in Germany and the locks at St Nazaire and Lorient, destruction of the latter would have penned up the U-boats in the inner harbours. All were rejected. Overseas the Italian fleet and Singapore shipping (from the aircraft carriers Implacable & Indefatigable) were considered potential targets. Trials were also undertaken against land targets including a disused railway tunnel in Wales. Did the latter provide the inspiration for the film Mosquito Squadron released in 1969?

Why RAF bombed Welsh rail tunnel

As noted above, and ignoring the flak, the issue is one of sufficient space to ensure an accurate line up with the target. While Highball wouldn't have caused significant damage to the structure, I would expect that 545lb of high explosive going off in an enclosed space surrounded by heavily reinforced walls and roof, would have caused severe damage to the contents.

 

Incidentally one of the next Mosquitoes to be rebuilt in New Zealand is DZ542 which was a Highball conversion scrapped in Australia postwar. Now what are the chances ..........