TDC

[snakedocpl]

Originally Posted by TorpX

Yes, I see your point. I kind of forgot about that aspect of the operation.

Please note, that US TDC made possible to launch torpedoes without using periscope. If the target course parameters for the Position Keeper were correct and target moved on steady course, the Commander did not have to look through the periscope to aim the torpedoes. In reality, just before launch, the Commander looked through the scope to make sure, that target is there, where it should be.

Originally Posted by BigWalleye

Cap'n Scurvy has a periscope photo of the stabilized azimuth line and a description of how it was used in Post #26 of this thread.

The stabilized line in space was also present in the German periscopes manufacted by Zeiss. They called it "Feste Linie im Raum". As far as I know, the WWII U-Boats were not fitted with periscopes with this feature.

Originally Posted by ColonelSandersLite

From the instructions on the thing, I get the impression that it is a pretty fat line too. If it was as thin as the regular lines on the optics, using one side of the line as reference would probably be a non issue in practicality I think.

I'm also pretty sure it wasn't holographic from the description. It was probably literally a plain black metal bar that would move across the periscopes eyepiece at a rate determined by the gyrocompass, periscope bearing, and submarine speed.

Well, looking at the drawing at the end of the manual (http://www.maritime.org/doc/pdf/peri...type2-1940.pdf), it seems, that it is quite fat line. I have attached the drawing with essential elements marked:


I think, that in the view field, this line looked as on images below:




On the first image, the line was positioned at the bow of the (stationary) ship. On the second image, the periscope was moved to the left.

Originally Posted by CapnScurvy

Hi BigWalleye, that photo you mentioned is not looking through a periscope. It's looking through one of the eye pieces of a TBT (that's the Nautilus conning tower in the background).

I forget which side it was, but the stationary lines within the one lens is what you're looking at.

Looking at this manual (http://www.maritime.org/doc/pdf/tbt.pdf), it seems, that TBT was not fitted in "stabilized line in space".

Originally Posted by ColonelSandersLite

I'm also pretty sure it wasn't holographic from the description. It was probably literally a plain black metal bar that would move across the periscopes eyepiece at a rate determined by the gyrocompass, periscope bearing, and submarine speed.

The stabilized line compensated only change of periscope bearing and change of submarine course. It could do nothing with the speed. To make the target speed most accurate, the speed of own submarine should be relatively small.

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Regards
Maciek