Richard,

A bit on UB 81's officers that survived the sinking from the Rangliste der Kaiserlich Deutsche Marine corrected to February 14, 1918. Both Freudendahl and Denker were reserve officers:

Leutnant zur See der Reserve Hermann Freudendahl. Entered naval service on April 1, 1914, commissioned as a LzSdR on July 13, 1916 with priority of "Ee". Landwehrbezirk: Hamburg. Decorations: Iron Cross 1st class and Hamburg Hanseatic Cross.

Marine Ingenieur der Reserve Hans Denker. Entered naval service on October 1, 1911, commissioned as MIdR on September 17, 1917 with priority of "A". Landwehrbezirk: Bremen. Decorations: none

The Ehrenrangliste may contain additional details of their service and should also give their birth dates.

Some rank corrections: The rank is spelled steuermann, and it would translate as a navigating warrant officer.

A maschinistenmaat is an engineering branch petty officer. (Any rank with "maat" at the end is a petty officer.) Paul Redlin and Heinrich Borries were both maschinistenmaats. A Maschinist meanwhile is an engineering warrant officer.

Note that UB 81 had a high number of commissioned and warrant officers on board for a UBIII — three line officers (Saltzwedel, Freudendahl, plus Lt.z.S. Oskar Staabs), a steuermann, and on the negineering side Decker as LI plus a machinist (Friedrich Schleh).

Best wishes,
Michael