There are as many sailboats keel designs than there are boats. For a keel, the objective is to offer a lateral plan to counteract the wind pressure on the sails by presenting a form below the waterline to help prevent sailing sideways. The keel produces the hydrofoil action, influences handling and steering and offers a location for ballast. But why so many options ? If our concern is towards relatively small sailboats, we can attribute the evolution to going from work boats, to cruising boats and onto racing.
From immemorial time the keels were long and adopted to the type of boats, commercial activities, conquest
but mostly for building consideration. The possibility to be launched from the beach, deep sea fishing, and private enterprises, they all show that feature which offers directional stability, ability to hove -to, all included with the logical thinking of the time. They did not get involved, but superficially into the elements of keel action to resist the drift force.
Colin Archer's Norwegian Rescue boats, showing the underwater profile of a long keel.