So the sunboat might represent the solar year. Or it might be the sun in his capacity to measure the earth, to define what is a year. The ship of pharao was made of planks sewn together, similar to the ships (pahi) of the Polensians:

"It is interesting to note…that the bottom planking and backing timbers of the Cheops ship consists of twelve timbers... In antiquity the Egyptians were notorious for doing things differently from other peoples. This was certainly true for the techniques they used in shipbuilding. While many cultures built 'sewn' or 'lashed' ships with their planks held together with ligatures, only the Egyptians used transverse lashings that did not penetrate the hull. Furthermore, while the shipwrights of other nations were careful to create straight planking seams, the ancient Egyptian shipwrights intentionally 'joggled' their planking edges into jigsawlike patterns that prevented longitudinal sliding." (Wachsmann)

12 timbers = 12 months of co(u)rse = 12 henua, sewn together. But that is done in the dark, not visible = not in the sun. In Sweden we have '20-dag Knut' = '20-day Knot', meaning 20 days after Christmas ('Knut' also being a name given to male babies).  20 days after Christmas we draw a mark in the calendar: End of Christmas. 360 / 20 = 18, but better: 180 / 20 = 9 (a number pointing towards the dark underworld) = 9 knots (in the dark) for half a year. Knots are opposite to straight (sun).