Deploying rails with Passenger
This is a matter of permissions in the directory, and not the deamon itself; do you have an index file in DocumentRoot /home/insane-36/Documents/Web/Rails/sampleapp/public? Who owns it? What is Apache running as?
I know that is an old question, still is top result for google search for that error.
Solution is to add Require all granted as last line inside
<Directory /home/insane-36/Documents/Web/Rails/sampleapp/public> AllowOverride all Options MultiViews Order allow,deny Allow from all Require all granted </Directory>