problems designing a shift pattern

Hi all,
I'm new to this, so please bear with me.
I've been tasked at work to come up with a shift pattern for a local fire station!!
the parameters are:-

4 watches- green, blue, white, red

4 watch manager (wm)
8 crew managers (cm)
28 firefighters (ff)
each watch consists of 1 wm 2 cm 7 ff
2 fire engines
1st fire engine is crewed by 1 watch manager and 4 firefighters for a 24h period-then is crewed by another watch for the same period.
2nd fire engine is crewed by a crew manager and 4 firefighters for a 12h period from 7am-7pm
with an average working time of 42hours a week over a 6 month period.

all of the crews will be required to work on both fire engines over that 6 month period and it is to be evenly and fairly distributed.

over the course of a 12 month period each wm/cm/ff is entitled to 41 days leave/holiday.

i'm really looking for a calender or spreadsheet on how i can work this all out fair and square.

i would reall appreciate any help

thanks

Lee