One of the Gemini owners (Maryanne Webb) made an excel spreadsheet for the 105mc that has literally everything you (well, we) need.
It is an excellent example - if you would like to see it you can go to
http://groups.yahoo.com/group/Gemini_Cats/
and join the group (free and automatic - quick response).
Then look in the files section for Gemini105McMaintSchedule.xls
While it's not a log per se, it does automatically tell you when to do something, what you will need to do that, and when the last time it was done etc..
It's a damn fine template for your's in any case and well worth the effort.
PM me an email address and I will email you a copy if you would like.