Hi I'm rebuilding and modifying my single seater aero setup
I'm looking for anywhere I could buy preformed aerofoil sections about 45 to 50 inches long and about 12 inch cord
I'm even looking at model aircraft type construction methods maybe
Any ideas or suggestions ?

There was a thing on Uphill Racers about using small wind turbine blades, its basically sold as an aluminium extrusion.

Found something here:

http://www.thebackshed.com/windmill/Trade/AlBladeOrders.asp

Might be of use.

Competition Car Downforce by Simon McBeath shows how to make wings.
It's been superseded by Competition Car Aerodynamics which I haven't read.

This post gave me the idea to use PVC pipe and heat it and extrude it to shape.
Once formed, you may fill with expanding foam for rigidity.
Donīt have the slightest idea about final weight or resistance...