[CentOS] Set default file/dir permissions?

Greetings all-

I have a system running CentOS 5.5 x86_64. It's serving NFS for several 'frontend' boxes in a web application setup. All data is stored in specific dir but written by different users. When the webapp attempts to read this information, it may or may not have permissions to this data. What I'd like to do is set 'default permissions' on the data storage directory (lets call this /var/appdata) so that any file or directory created under this is assigned a default set of permissions, and if possible, ownership.

I've looked at and tested umask but it only seems to allow/disallow specific permissions, not force permissions. Am I missing something? How can I force all files/dirs created under a specific directory to have the permissions (and ownership if possible) that I specify?

Thanks!

Tim Nelson
Systems/Network Support
Rockbochs Inc.
(218)727-4332 x105