Cambered propellers in PropCad

November, 2003

What exists and what is planned for 2004.


HOW PROPCAD HANDLES CAMBER NOW

As you know, camber is a property of an individual section (i.e., its r/R cylindrical section shape). Currently, PropCad defines section geometry as a collection of X-Y points for the face and back. Splines are fit through these points to develop the chord-wise and thickness-wise shape of the section. To add camber to a section in the current versions of PropCad, you have to manually add a vertical (Y) shift to all of the Y values for the back and face.

CAMBER DEVELOPMENT

Our objectives are to provide a variety of camber options in both the Builder and for manual data entry. This will require an extensive update to the PropCad data file format. New data definitions need to be developed for the camber shape on each section, as well as a radial distribution of maximum camber (via a camber-to-chord ratio, or "f/Chord"). We have already begun development of these features following the development phases described below.

PHASE 1

Task: Simple "Arc" camber applied in the Builder
Schedule: Completed; for HydroComp use and testing

Summary:
This provides a way to add a simple arc-shaped camber (convex C-shape) to a propeller developed in the Builder. You describe the f/Chord ratio (e.g., 0.03) and the chord-wise position of the maximum camber (e.g., 0.70, meaning the peak camber is 70% back from the leading edge). The face and back Y-values are then shifted appropriately.

PHASE 2

Task: Simple "Arc" and "Cosine" camber with basic radial distributions applied in Builder
Schedule: To be released December 2003; this will be available for all 2003 MSU subscriptions

Summary:
In addition to an arc-shaped camber, Phase 2 adds a cosine-based camber shape (S-shape) to the Builder. It also allows for the selection of either a constant radial f/Chord ratio or a distribution where the f/Chord ratio goes to zero at the tip and also at the lowest defined root section.

PHASE 3

Task: Comprehensive camber shapes with arbitrary radial distributions
Schedule: Second quarter 2004; this will be available for all 2004 MSU subscriptions

Summary:
This phase will be a significant development effort, resulting in the ability to define arbitrary user-defined camber shapes and radial distributions. Camber will be defined as a separate X-Y shape. (In other words, you can define a section shape of constant geometry, and then apply any camber without changing the face and back X-Y shape values. This will make it easier for those users who are used to a more academic "thickness-camber" definition of section shape.)

Different camber shapes will also be added to the Builder, including those which correspond to NACA foil definitions. Examples of this will be the NACA 6 and 6A series of camber shapes, such as the "A=0.8 meanline". (NOTE: The magnitude of a NACA-derived camber will require the user to define the maximum camber - the f/Chord ratio. Many propeller designs base the amplitude of the camber on a "design lift coefficient", which will not be part of PropCad.) Along with the development of NACA camber lines, we expect to also include suitable NACA section shapes, such as the 6 and 16 series.

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