SEA > TYPE VII
Tores mailbox IX C and IX C/40 operational and technical details
Rokket:
A new, extra Tore's Mailbox for IX C and IX C/40 operational and technical details
tore:
I hope we shall have an interesting discussion around the difference between the two types VIIC and IXC, and welcome Dons input.
Allthough the IX type was developed simuntaneously with the VII type both having roots back to the WW1 submarines, they were designed for different purposes, type IXC being the long distant counterpart to the medium range VIIC and the command boat for the wolfpackleader. In addition some of the IXs was in the latter part of WW2 converted as supply boats,"Milchkuhes" for the VIICs.
The IXCs had one more torpedotube than the VIICs but I guess the VIICs was a better attack boat as the divingtime was considerably quicker than the larger IXCs which took its toll when the allied airsuperiority became a problem.
Below is an image of a IXC moored together with a RN T class (two midship aft torpeotubes) and the RN A class originally designed for the Pacific.
Tore
Don Prince:
Hello Mr. Tore,
I am reviewing the trim system on the IXC and everything looks very familiar except for item a3 which is a change-over cock but no central passage way? I marked the item on the attached drawing. Now back to the basics:
a3 - is the change-over cock
e - is the main control valve
m - is a spring loaded pressure valve
When the pump man turns the main control valve (e) to pressurize the trim tank he can monitor the air pressure in the line when viewing the pressure gauge.
1. Is the main control valve (e) used to adjust the amount of air pressure in the line?
2. If the air pressure in the line exceeds the limit set by the pressure valve (m), then will the excess air pressure be vented into the pressure hull?
Regards,
Don_
tore:
Don.
The plan you are referring to is the LP system,practical identical to the IIVC system. As you know there are two ways of adjusting the trimsystem, normally by the trimpump or by LP air. Using the trimpump implies operating a closed system eg. the air and water volume is constant. When you pump the water to the aft tank the equivalent volume of air is replenishing the watervolume in the forward tank via the LP blow/vent pipe. In that case the LP air pipe is used as an "airshifting" pipe and the enclosed air is free flowing through a central bore of the aircock whereas the LP air connection is shut, you add nothing to the system.
If the trimming is carried out by LP air, you add air to the system as you turn the trim cock to put the required trimtank under pressure and simultaneously the other tank has to get rid of the excessive air to accommodate the receiving water and is vented via the cock and funnel to the bilge. The water is controlled by the trim valve and the water meter as normal. As you normally don`t want to change the amount of water used for trimming, you check the air cock for possible water in the funnel indicating when the receiving tank is full.
As you see, the central bore for the air cock is not drawn neither on the plan for the VIICs or IXCs, on the trimlineplan for the VIICs however you see the bore clearly marked, I assume you`ll find same on the trimline plan for the IXCs.
Tore
Don Prince:
Hello Mr. Tore,
I believe the Germans copied an error and promulgated it in their drawings... On the type VII drawings the TRIMMDRUCKLUFTSCHALTER item (g1) on the Lenz -und Trimmanl drawing looks to be the exact same device TRIMMDRUCKLUFTSCHALTER item (d2) on the Nd luftanlage drawing, but they are not drawn the same??? Both should be a change-over cock with a central passage.
Item (g1) looks to be drawn correctly... Perhaps, it was added to the Type VII drawings and missed on the Type IX drawings. I have attached the Type IX Trim drawing which does NOT have an air line going to the trim tanks...
Regards,
Don_
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