The Group module is a commonly used contributed module that is modern and seems to be well maintained. It is a good way to offer you site to an organization but parts of it to some smaller groups like divisions and departments. You might want to make a forum for people who RV but have special groups who use Class A versus Class B and Class C units or even who have different brands and modules where they can talk about their unique units.
There is a good overview of the Groups module for the creation of Microsites. This video will show you the great capabilities you can leverage with this module.