Specifications of the rear hub:    
Brand:    Shimano
Model:    Nexus Inter 7 SG-C3001-7D
Color:    Silver
Number of spoke holes:    36GTS
Type of brake:    Disc (Centerlock)
Number of gears:    7S
Type of axle:    Fixed axle 187 MM
Axle included:    Yes, without nuts
Type of bearings:    Ball bearings
Average weight (GR):    1474
Intended use:    City
    
Data for spoke length calculations using the Sapim spoke size calculator:    
Total length of the hub (MM):    135
Non-gear side (MM):    37
Gear side (MM):    42
Hub diameter non-gear side (MM):    86
Hub diameter gear side (MM):    86
    
Link to spoke calculator: www.sapim.be/spoke-calculator