At one time, these vessels were the principal mode of transportation around the western isles of Scotland. The terrain was too rugged with large forests. There were no roads. So the sea lochs and minches of the western isles were the equivalent of today's motorways at that time.
The Birlinn is said to have been developed from the Norse Galley by Somerled, who led the Kingdom of the Isles in the 1100s. These were clinker-built wooden boats that could be rowed or sailed, with a single mast and square sail. These small but sturdy seagoing ships were an improvement on the Norse Longship.
They were used for everything from ferrying people and cargo to going to war. The design was more manouverable than that of the Norse boats and suited to both rough seas and shallow water. The boats were light, but could be weighted with ballast to make them more stable in rougher conditions and the shallow draught made them easy to haul out of the sea.
Historically, there are very few visual references to these boats in existence. So for help I approached the Lord of the Isles Trust who own and operate Aileach, the first replica galley to built. The trust very kindly assisted me with the loan of a set of drawings and rigging plans showing the general arrangement.