Dùthchas was the collective right of the clan to live in its traditionally possessed lands. Oighreachd was the concurrent concept of the inheritance of the land by the Chief as ceann-cinnidh. As the Scots crown asserted feudal authority, Kings granted charters specifying the lands of the Chief. Mismatches between the Dùthchas and the Oighreachd caused clan battles. Sometimes this was orchestrated by the crown, granting the same land to two different clans, like Trotternish on Skye to both branches of MacLeods in the 16th Century. Land was granted by the King in exchange for the military service of the clan, usually specified in size and number of boats.
The boats in question were called Galleys and Birlinns. A 1615 Privy Council Report specified a Galley as having 18-26 Oars (9-13 pairs), Length was probably 46’+, as crews were listed as 3 to an Oar, so 54-78 crew total. This would be at fighting strength, as 10 men could sail one at minimum crew complement, the rest being marine-equivalents who could row and disembark to fight on land. A Birlinn was defined as 12-18 Oars (6-9 pairs), so likely length of 25-50’. The two extant reproductions, Aileach of Clan Donald is 40’ Long, 16 oars; and Orcuan of the GallGael Foundation is 30’ long with 8 oars.
The west highland galley likely evolved from the Norse Longship Snekkja (24 Oar Tólfoeringr, 30 Oar Fimtánsessa and 40 Oar Tvitogsessa), Karfi, and Skuta class warships, and the Birlinn probably evolved from the dual-purpose byrðingr troop-carrier, fishing and cattle transport vessel.
In 1343, King David II granted Chief Torquil of Lewis Assynt’s 4 Davocs & Assynt Castle (probably about 2560 acres) for the service of a 20-oar galley, and Chief Malcolm of Harris about 2/3rds of Glenelg for the services of a 26-oar galley. A Davoc was a land measurement similar to an Ounceland (a property who’s Skat was one ounce of silver): 20 House townland + surrounding farmland of 4 ploughgates (32 oxgangs/640 acres).
In 1498, King James granted Chief Alexander Crotach of Harris, Ardmanach/Harris for the service of 26 Oar galley and two 16 Oar Birlinns. His other lands at that time were Dunvegan, Minginish, Bracadale, Duirinish, Lynedale, Glenelg, Trotternish, Sleat, N. Uist. By the 1600s, the sea-power of the chiefs was more of a threat than an asset to the crown, so in 1616 a Bond limited all Hebridean Clan Chief to one boat of 16 or 18 oars. Boats lasted about 30 years each, and seemed to cost about 20-30% of the Net annual income from associated property. In the 1600s, a Birlinn cost 200-300 Scots pounds to make. This was equivalent to a Maj/Lt Col’s monthly pay in a Scots Regiment of the time, or the market price of 300 Sheep, or 22-33 cows or horses.