• What is PropCad?
• Who should use PropCad?
• What propellers can I draw with PropCad?
• Will PropCad work with other propeller types?
• Will PropCad help me with my existing designs?
• What about developing "signature" or "custom" designs in PropCad?
• How can I transfer my PropCad design into CAD/CAM, FEA or CFD software?

PropCad is software for the geometric modeling of marine propellers. It provides all of the tools for the preparation of 2D design drawings, 3D views, construction data, and CAD/CAM file export. 

 
Manufacturers, researchers and designers of marine propellers are the principal users of PropCad. Companies large and small from every continent rely on PropCad for their propeller modeling needs.

 
Designs of virtually any type of marine propeller can be prepared with PropCad's comprehensive geometry definition. (PropCad will even help prepare drawings for other rotating machinery elements, such and turbine blades and aviation propellers). The easiest way to create a propeller drawing is with PropCad's design wizard - the Builder.

 
PropCad geometry data may be completely edited by the user to represent practically any propeller. The Builder can also simplify the creation of a new model from an exiting drawing. PropCad files can then be saved as starting "templates" for variants of the basic design.

 
The organization of PropCad is based on contemporary propeller design practices, so re-creating your designs in PropCad is an easy process. You can also look to PropCad's optional Scan Converter utility for those times when you do not have existing design data. Scan Converter lets you take blade scans (as found with a propeller scanning device) and develop a PropCad design file.

 
This has always been possible, but a new feature was developed in 2006 to expressly handle this.

In PropCad's Builder, there is indeed a library of standard geometries (e.g., Gawn, B-series, Kaplan), and we are always extending this internal library to non-standard sections (e.g., SK, Thruster, Modified wedge). The original design approach in PropCad was to first build a design using a library propeller that was close to what you wanted, then manually tweak the section offsets and radial parameters (e.g., the outline). This was quite reasonable, but did require some manual manipulation. Once you had modified a design, however, you could use this as a "parent" or "template" for future designs.

We recently added a feature to allow the user to develop custom data files and use these right from within the Builder - so no additional data manipulation is necessary. We call these "distribution files", as they are text files that define the distribution of a particular parameter, such as for skew, rake, pitch, outline (chord length), and also for section shapes. These distribution files provide the shape of the parameter and are then fit into your design objectives. For example, you could prepare a section distribution file for a wedge-type surface-piercing propeller, and the defined offsets would then be scaled to fit into each section's design chord length and thickness. The same is true for the radial distribution files, such as for the outline. If you wanted your design to some custom cleaver-style outline with a particular shape, then the outline distribution file provides the shape, which is scaled to match the design expanded area ratio in the Builder. This approach allows a user to add their own proprietary data to the Builder libraries.

So how do you create the distribution files? There are two paths you might take - manual entry or the use of PropCad's "Scan Converter" utility. The manual entry approach is simply to take your existing design data and to enter it into the distribution file format. However, what if you have a propeller but not the design data? Then you could use the Scan Converter utility to take scan measurements of the propeller and recreate a PropCad design, from which you can export distribution files for that propeller.

 
There are two 3D file formats that can be exported directly from PropCad - DXF and VRML. However, these can be limited in their usefulness as the surfaces are represented as a collection "faceted panels", not as a uniform smooth surface. For some purposes, such as FEA or CFD, these two file formats may be adequate, but they are inadequate for construction purposes, such as milling or rapid prototyping (i.e., stereo-lithography, 3D printing).

Unfortunately, the data transfer of full 3D surfaces using conventional file formats, such as IGES, STEP or SAT, is not always well-behaved. (For example, one 3D CAD modeler needs some 40+ different variants of IGES to insure that the data is transferred properly to other programs.) The approach we have adopted for PropCad is to transfer information about the surface in as simple a form as possible, and then to let the CAD/CAM software rebuild the surfaces using their own internal surface mathematics. This has proven to be a very reliable way to insure that the surfaces are true to their original design intent.

So, data export to software such as SurfCAM, Mastercam, SolidWorks or Rhino (to name a few), are built around simple ASCII files. These files are either "data files" of just the 3D XYZ points on the propeller surfaces, or "macro files" with added instructions to automatically rebuild the principal blade and hub surfaces when the file is imported.

For more about data transfer and how PropCad fits in the propeller design process, please review Report 131 - Practical Propeller Modeling: From Concept to 3D CAD Model from the Knowledge Library.