default group permissions over network

[imbrokn]

I search for this on the message board but couldn't seem to find anything even though it seems like something that would be a common problem. I have a computer that multiple people connect to, its basicallly a server to write files but it isn't running os x. All users are a part of the group staff, however when new files are written to network computer, the Group permissions are set to read only. So no one else will have access to files except for the owner. How do i set it up so that files written across the network give the group permissions to read and write? Does anyone know? Thanks.