Well, I guess that you need to join the Association to get the Class Rules.... BUMMER! however, it is still better to get the Class Rules from the MARINER Class if that is what you have, the Mariner and Rhodes 19 are the same hull, but very different Classes.
Mariner Class Association (MCA) dues are only $15/year and its a break even proposition if one is a BoatUS member because MCA members get a $15 discount on BoatUS memberships. Association has a very active forum, about 400 active members, and racing and cruising events. Well worth the cost of membership.
In the spirit of full disclosure I am a member and on the Association's Board. www.usmariner.org
The Mariner class dues are much lower than the Day Sailer Class (I actually knew that, and did not intend my reaction to the need to join that group to be as negative as it ended up sounding <GRIN!>) DSA dues are $37.00 I think, and unlike the MARINER Class, in the DSA if you don't race you are not really welcome.