Variation in blade parameters between tools

When moving propeller design data between tools – such as importing a PropCad design into PropElements – you can see differing figures for the blade parameters. Why?

This has to do with the different pitch plane definitions in the two programs. For many of the library propeller types in PropCad, the pitch plane is defined by a "traditional" baseline definition. PropElements conforms to a more contemporary and "scientific" nose-tail line definition for pitch, and converts imported baseline-oriented section data to its nose-tail format. It is important to note that the final 3D propeller geometry is unchanged – it is just that the sections are positioned against different pitch plane references.

The B Series, Kaplan, and AU-MAU propellers are good examples where differences will occur. In the root area for these types (and sometimes at radii closer to the tip), the leading edge nose point is higher than the trailing edge tail (see the example image below for an AU propeller). Thus, the PropElements nose-tail pitch of these sections would be higher than the PropCad baseline pitch, and the corresponding integrated effective mean pitch would be slightly higher. Correcting imported sections to a nose-tail orientation would also affect EAR and some of the other "whole blade" parameters due to cosine effects of the slightly longer nose-tail chord (versus the projected baseline chord length) and their position on the pitch helix.

ADDITIONAL NOTE: The "new project" utility in PropElements includes some of these "baseline-oriented" types in its library, which are corrected to its nose-tail format. For example, a constant pitch B Series propeller would see non-constant higher pitch values into the root.