Vertical axis turbine foils

An externally convex FDD, not interposing between the fluid flow and the blades and attached to a turbine, comprising:

• a. an intermediate partial outline foil shape, wherein the foil is adjacent to the turbine blades by a distance of less than 10% of the foil's outer diameter.
• b. a substantially vertical flange at the end of the foil shape on one side.

A vertical axis turbine, comprising:

• a) proportional parameters of Db 1.96 meters, and Hb 1.5-3 meters within a 10% margin of their values.
• b) at least one functionally adjacent externally convex FDD, not interposing between the fluid flow and the blades and attached to said turbine, in a vertical orientation.

A vertical axis turbine, comprising:

• an inferior or superior externally convex FDD, not interposing between the fluid flow and the blades and attached to said turbine, with the proportion of a Din of 1.0-1.8 meters or greater in relation to a chord length of .4 to .9 meters, with an angle of attack of 5 degrees or greater.

A vertical axis turbine with an inferior or superior externally convex FDD, not interposing between the fluid flow and the blades and attached to said turbine, comprising:

• the proportion of Din/Dout of 1.0-1.8 meters to 2.30-2.60 meters.

A vertical axis turbine, comprising an FDD, wherein fluid vortices as determined by fluid dynamic analysis and/or testing are not present from passage of fluid without blades in the internal diameter of the FDD from the bottom to the top of the FDD.

A method of apposing an FDD to the blades of a vertical axis turbine, wherein the internal area of the FDD produces only non-vortical flow.