Viking Navy ship sail view
A good view of the two main sails.
The short mast had always made me wonder about the lack of sail area. This two sail design gives three times the sail area. This larger sail area brings this design very close to modern sail size for a boat this size. It also allows the Viking Navy ships to sail upwind. Each small diamond sail can be thought of as a stunt kite attached at its' four corners. This can not be seen on this picture because these sails are just a flat mockup.
Sail, 9 inch picture