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U-boat VIIc bow doors and muzzle doors sequence

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In my stash of kits is a U-boat Revell 1/144 Type VIIC/41 and while looking for information and inspiration on internet, i noticed something about representations of open outer bow doors and muzzle doors on torpedo tubes.

Some models have muzzle door open against (in front) of open bow door - so outer bow doors must have opened first.

Other models have open muzzle door behind open bow door - so muzzle door must have opened first.


EG Muzzle door in front:




Or Muzzle door behind...




Anyone know which is correct sequence for opening of muzzle doors and outer bow doors?



Edited by Pak75

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Hi Pak75


heres the answer to your question; http://www.ubootwaffe.pl/en/u-boats/equipment/torpedo-tubes-of-german-u-boats


in short the muzzle and outer (shutter) doors opened simultaneously, so the first picture is the correct one.


All the best Chris

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HI Chris

Thanks yr reply.

I must confess that i was considering posing this question on ubootwaffe.pl but as they don't speak much English i thought i would try here first.

This is also a good site:




What started this was a purchase of RCSubs PE kits for this scale U-Boat. In the kit are optional doors or shutters - I asked RCSubs twice what they were for but got no answer other than if i thought parts were 'bad' to not use them. 

Incorrect text deleted

Last night i found photo U-505 (a type IXc) which clearly shows muzzle door mechanism.




Incorrect text deleted

There is this one of U-505 which appears to show edge of open muzzle door resting against open bow door but this would mean the bow door opened first... or is is just the photograph angle?



It would be a pity to have to conceal open PE muzzle doors behind open bow doors.

Another thing that occurred to me is that U-505 being a type IX may have had different mode of operation for bow doors as photo suggests they might have slid forward somehow as they opened?

However, RCSUbs (known for their historical accuracy) claim their torpedo PE set with optional shutters is suitable for all type VIIs but these shutters are not supplied in type IXc kits.


Note bars on limber holes to prevent entry objects into bow compartment.


Edited by Pak75
typo and incorrect supposition deleted

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I'd hazard to guess the outer (oblong) doors opened first, then flood the tube, then open the bow (tube) doors. This would be towards the finish of the firing sequence, and if the shot was aborted they wouldn't want water in the tube it'd have to be pumped dry to remove the torpedo for servicing which would be noisy and affect the sub's trim. As I understand it, submergence of the torpedo was kept to the absolute minimum before firing. Something to do with possible electric failures perhaps.


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My ceaseless pinging of internet and looking at countless U-boat images in trying to resolve this question was rewarded when I received an echo from Jerry Mason, the brains behind excellent www.uboatarchive.net site.

Jerry confirmed that muzzle doors and outer bow doors/shutters are operated simultaneously by same hand crank from torpedo room. Outer bow doors are connected to muzzle doors by either hinge or linkage.


Therefore whitestar12chris was correct in citing reference from http://www.ubootwaffe.pl/en/u-boats/equipment/torpedo-tubes-of-german-u-boats


As U-boat development continued during the war, this simultaneous opening mechanism for muzzle and bow doors was refined for Type IX boats and then the Type XXI. So as not to confuse matters, I will make a new topic for these craft if anyone is interested and confine this thread to Type VII.

Jerry also supplied a photo of type VIIc on a slipway showing bow doors open and muzzle doors completely hidden behind the open bow doors.




This photo is apparently typical of type VIIc boats and Jerry has never seen any other arrangement.

Therefore I have to conclude that second/bottom picture in my original post is correct.


No wonder RCSubs would not answer my question as any detail of the muzzle doors from their kit is effectively hidden by open bow doors.


The mechanism for this is detailed in a diagram in Westwood’s Anatomy of a Ship – Type VII U-boat. A hinge for the outer bow door is attached to the muzzle doors pivot hinge at one end and to a pin within a slot on the inside of outer bow door at the other. As muzzle door is cranked open, the hinge pin initially just slides in its slot in outer bow door, allowing the moving muzzle door to pass behind the still stationary outer bow door.  The hinge pin eventually reaches the end of the slot and as the muzzle door continues to open, this forces the outer bow door to begin to move inwards until the fully open position is reached.




An interesting detail that few modellers/manufacturers seem to have picked up on is that ends of torpedo tubes are angled inwards so muzzle door has to open less than 90 degrees.





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