The following webpages contain material related to U-86:
The plans for U-63 were found on this webpage. The page also contains a wealth of information relating to naval technology of WW1.
The naval archive in the Bibliothek für Zeitgeschichte in der Württembergischen Landesbibliothek holds an extensive collection of photographs of U-boats from both World Wars.
U-boat net is probably the most extensive web archive of everything and anything related to U-boats.
This webpage has extensive information on the sinking of the Llandovery Castle.
Information on the guns on U-86 was extracted from these two webpages.