Yep! Thanks for the link, Cat. Easy to understand.

I'm just thinking, if they got equipment to get salinity and temperature = they got the density because that's pure mathematic after we know the temp. and sal.

I'll give my quess: It was the temperature they lacked. (I think USN boats got the "temperature tool" quite late in the war. Which doesn't mean, of course, that germans didn't got that earlier...)

Well, next to the uboat.net.

Greetings,

-RC-

From the Uboat Commanders Handbook:

57.) As regards the condition of ASDIC in relation to the transmitting capacity of the water, it has been ascertained that the efficiency of the submarine-detecting gear is considerably reduced in sea areas with numerous layers of water.

a.) Formation of layes of varying density ("stratification") of the water of the sea occurs after a long spell of sunshine on a calm sea, and also in a high degree in places where there is a mingling of different types of water.............. Continual observation and measuring of water densities and temperatures are therefore important and indenspensible, for establishing the presense of "stratification" when submerging to considerable depths as a means of evading pursuit by position finding.

b.) In additon, position finding is very difficult, and almost impossible, in shallow water of varying depths (sand banks), where there are many wrecks, as well as in narrow bays (Norwegian fjords), as it is usually not an echo that is produced, but numerous echoes, which make it difficult to keep, but more especially to locate, the target.

Well...that depends on which country!! :hmm:

Hello Rosencrantz,
i think you got it all right -
You can calculate salinity if you have density and temperature, and all other combinations, but all a U-boat needs to trim the boat after all is the density - so if you have a spindle floating in a fresh probe you can read from the scale which density the surrounding water has, and thus adjust trimming directly. If a spindle with a given scale of density (which is not automatically equal to the salinity) tells you a certain value you do not need temperature and salinity - just trim the boat according to the observed density - it already incorporates the other values.

If you had the exact salinity of the surrounding water, and the temperature, you could easily calculate the density - but density could be measured directly after all.
If you were in the Caribbean sea maybe you know the salinity for the Caribbean sea is 1,022 - when you use a thermometer to measure temperature you could theoretically calculate the density using the two values, but in reality there are a lot of exceptions depending on sea state, sun etc., so even if you knew all exact values the best way would still be to measure the density directly via spindles.

I take it there were several glass tubes with spindles in it which could be flooded and emptied all the time for testing. As well imagine a metal tube flanged to the inner pressure hull with in-and outlet and a thermometer in it - you can read the temperature of the surrounding water all the time. This tube certainly had two valves to cut off any water if the boat went really deep to prevent breaking of the glass tube that would not withstand a pressure of say 200 m.
Taking temperature is not the problem, but since there was no automatic device like in the later US subs, you would have had to thoroughly control changes of temperature and density all the time if you wanted to take any advantage of different layers for hiding.
As said before i never read of U-boat commanders who intentionally looked for layers of different salinity/temperature to hide - which certainly does not mean anything. Maybe this was thought of as top secret even after the war and the new confrontation during the cold war, so no one wrote about this.

I hope this makes sense :lol:

Greetings,
Catfish

Yep Cat! You (we) are right.
Germans didn't have a tool compared BT (bathythermograph). The only way to find out the temperature was to take external water in the boat using salinometer for that. Everyone can imagine the results = water temperature quickly changed so that was far out to be an exact method.
Diving officer could note the heavy layer if the boat was in good trim, but as you wrote, there is many parts affecting to layers so they change "all the time". Also, in North Atlantic conditions layers usually lay well down in maybe 600 - 1000 fts, in the depths out of normal operating depth of the boat, especially in early war time. In Pac the situation was totally different, boats could usually easily achieve the layer. So I was reading, it was common that on approach phase USN boat often used to dive to find out were layer laid and after attack just dived to under it and dissapeared.

But, once again we can see, how the germans did loose the "technical war". BTW, BT was a rather new invention and USN did research to find it to be very useful. By early -43 many of the USN boats got the BT.

-RC-