rudder design - old sailing vessels

I'm curious - I have a home-built rudder on my sailboat that uses a foil shape.
When did boats begin using "proper" shapes on rudders?

Jerry W
Warrenton, VA

 

One thing that had to happen first was separating the rudder, or the rudder and skeg, from the back of the keel. But I don't know when they started in with proper foils.

 

Manfred Curry (in Yacht Racing, The Aerodynamics Of Sails) reports experimenting with streamlined rudders & centerboards, possibly as early as 1922.

 

Viking ships, Polynesian proas and Chinese junks had separated rudders.

After a quick search I found this picture of the original(?) rudder of the Oserberg Ship, constructed around 800AD. It seems to show some foil like shape but the picture does not give a definite answer.

The rudder and stern of the Oseberg ship https://digitalcollections.nypl.org/items/510d47d9-ab9a-a3d9-e040-e00a18064a99

Oseberg Ship - Wikipedia https://en.wikipedia.org/wiki/Oseberg_Ship

It's an interesting topic, tomorrow I'll try to find some more examples from early rudders.

Edit I'm not completely sure the rudder in this picture is original. Most of the wood in the hull is but the rudder doe

 

World oldest surviving ship is the Khufu Ship from 2500BC. It has rudders but for now I can't find any clear pictures or information on them.

Khufu ship - Wikipedia https://en.wikipedia.org/wiki/Khufu_ship