Hello Rainer ,

I'm sorry , i did not give this precision : the torpedo door that i spoke was the external torpedo door !
The inner torpedo door never change !
The external torpedo doors on the bow of the typ IXa, IXb, IXc, and majority of IXc/40 were different of the over U-boot typ !
The size of the external door is less than the hole and two rails are visible on the top and on the bottom of this hole !
The forward of the door move along the rails and the back of the door is fixed to the torpedo door tube.
When the tube is open , the tube door push the external torpedo door forward along the rails !
Some pictures show that : U-37 in dock with a close up of the doors , also U-534 !

For typ IXd2 is different !
The size of the external door is the same as the hole !
It's so impossible to move the door , well the backward of the door isn't fixed of the tube door but slips ! Exatly as typ VII , XXI and XXIII !
Well , i saw a picture in a polish book , showing the bow of U-1225 typ IXc/40 moving towed by a crane with the typ IXd2 hole !

It's seems that some typ IXc/40 were fitted with the typ IXd2 system !
So , my question is : somebody have a list of typ IXc/40 fitted with typ IXd2 external torpedo door at the bow ?

Thank you very much.

Best regards ,

Ludovic.