The sloop is an interesting rig. It has only 1 mast and is usually 60-70 feet long. As you can see in the photo here, the sloop can have a square rig. Other times it will have a fore and aft rig on its one mast. A sloop's sail plan in square rig is typically as follows: Mainsail, Main topsail, flying jib, outer jib, inner jib, fore topmast staysail. A fore and aft rig sail plan is: mainsail, gaff topsail, inner jib, outer jib. It was often used by pirates in the 1720's. I have been lucky to see 1 sloop: the Friends Good Will of Michigan before, it was a beauty.