Como construir una helica

Diagram showing variations in angle at various distances from the center of the blade as well as cross sectional airfoil design

PLAN OF BLADE
LAY-OUT OF AN AIRSCREW
A Propeller is an Airscrew...       The British still occasionally refer to the propeller as the "airscrew", a term that accurately reflects the basic design and function of the propeller, which dates back as far as 1493,when Leonardo daVinci proposed the concept of a "helical screw" to power a machine vertically into the air.  While it was not implemented until the 19th century, the propeller uses that principle toprovide propulsion through the air, much like a threaded screw advances through a solid medium, but with some notable exceptions, primarily related to the loss of forward movement because the medium isnot solid.  Nonetheless, the propeller is similar to a screw in some common features.
       First, the pitch of a propeller is the theoretical distance the propeller would move forward in onerevolution (similar to a screw) and conceptually is the same as the pitch of a screw, namely the distance between threads if the propeller were a continuous helix.  For this reason, propellers will frequentlybe stamped with a designation such as "D 2550/P2610" (example.)  This means that the diameter (in this case length of propeller or thickness of a screw)  is 2.550 meters, and the pitch is 2.610meters, so that in a mathematical sense, one revolution of this propeller would move it forward a distance of 2.610 meters.  (Technically, the propeller is more of a double helix, in order to combine thetwo blades into one, but the principle is still that of a screw.) 
      The second feature that relates to its screw design is that the angle of the blade changes along the radius, so that close tothe hub, the angle is very steep and at the tip of the blade it is much more shallow (see diagram).  From a practical standpoint, this means that unless the pitch for a given propeller is known, it...