Keel

In the British and American shipbuilding traditions, this event marks the beginning date of a ship's construction.

It has the distinction of being regarded by some scholars as the first word in the English language recorded in writing, having been recorded by Gildas in his 6th century Latin work De Excidio et Conquestu Britanniae, under the spelling cyulae (he was referring to the three ships that the Saxons first arrived in).

Still older is the mortice and tenon edge-to-edge joining of hull planks in the Mediterranean during the classical period.

Where grounding is possible, this type of keel is suitable with its massive scantlings, but there is always a problem of the increased draft with no additional cargo capacity.

Fixed hydrodynamic keels have the structural strength to support the boat's weight.

[8]In sailboats, keels serve two purposes: 1) as an underwater foil to minimize the lateral motion of the vessel under sail (leeway) and 2) as a counterweight to the lateral force of the wind on the sail(s) that causes rolling to the side (heeling).

As an underwater foil, a keel uses the forward motion of the boat to generate lift to counteract the leeward force of the wind.