Little trick to hide only the Left Quick Launch bar in SharePoint 2013.
Place a content editor Web Part to your page
paste the following code into the HTML Editor:
<style>
.ms-core-sideNavBox-removeLeftMargin{ DISPLAY: none }
#contentBox { margin-left: 20px }
</style>
http://blogs.msdn.com/b/ronalg/archive/2013/03/14/remove-the-quick-launch-in-sharepoint-2013.aspx
https://richmintzbi.wordpress.com/2013/04/18/remove-left-navigation-bar-sharepoint-2013/