1 User

 devise
 *email		:string
 *password	:password

has_many :forum_threads has_many :forum_posts

2 ForumThread

user_id  :integer
title	 :string

belongs_to :user has_many :forum_post

3 ForumPost forum_thread_id :integer user_id :integer text :string

has_many :user belongs_to :forum_thread