CAD Software Computer-Aided-Design (CAD) software is used to draw, model, visualize and document a design.  CAD programs are not required for this; many excellent aircraft have been designed with nothing more than pencil, paper, and calculator.  But drafting boards have given way to computer screens.  After creating preliminary sketches, drawings and artwork by hand, most designers will want to document their design with a computer. A wide variety of CAD programs are available today.  There are two general categories: Two-dimensional (2D) drafting programs and three-dimensional (3D) solid modeling programs.  Within those two categories are entry level, mid-range, and high-end products.  Cost varies from less than $100 to $10,000 or more depending on features and capabilities.  Complexity and ease-of-use also vary greatly.  Here’s a description of what they do: 2D DRAFTING PROGRAMS This class of product creates 2D drawings with lines, polylines, circles, arcs, splines, fillets, cross-hatching, etc.  The drawings can be annotated with notes, dimensions and title blocks.  Some 3D commands may be available, but they lack the power and flexibility of a true 3D modeler.  2D CAD programs can be used to create detailed top, front and side views of your aircraft.  They are generally less complex to use than 3D solid modelers. 3D SOLID MODELERS These programs create 3D “solids” that represent a part’s features in 3 dimensions.  Solids are constructed from parametric sketches that are easy to modify.  Individual parts can be inserted into assemblies or sub-assemblies.  Most 3D CAD programs include functions for lofting and surfacing that can develop an aircraft’s exterior surfaces.  With these tools, the designer can create a 3D digital mockup of the entire aircraft to any level of detail.  Modeling in 3D is more complex, more difficult to learn and takes longer, but it provides the following benefits in return: 1. Designers can rotate parts and assemblies in 3 dimensions and see rendered views from any direction. 2. The form, fit and function of 3D parts can be checked and interferences are more easily identified. 3. Control systems can be checked at their extreme limits of travel. 4. 2D drawing views and isometric views are created almost automatically from the 3D model. 5. Parts can be assigned material properties to determine an assembly’s CG for weight and balance reports. 6. Machined parts and lofted surfaces can be exported to CNC tools to machine the parts or to create molds. 7. Parts and assemblies can be exported to Finite Element Modelers or Computational Fluid Dynamics programs. With all the advantages listed above, one can see why 3D modeling has become the standard practice at most aircraft companies.  Professional grade 3D modelers like CATIA used to cost more than $50,000 per license, but now amateur designers can have similar capability for a couple thousand dollars.  Before we examine popular CAD systems in use today, here’s some advice I’ve developed over the years: ADVICE FOR CAD BUYERS Do you really need 3D models?  3D programs are more expensive and take more time/effort to master. 3D modelers require more computer resources than a 2D drafting program.  Some 3D modelers may slow down or even crash on low-end computers or laptops. Whether 2D or 3D, get as big a monitor as you can afford.  CAD programs need a lot of screen space. CAD proficiency has no shortcuts.  Take the time to learn it and you will be rewarded. Most vendors offer a free 30 day trial version.  Try it before you buy it! Some vendors offer student versions or personal-use editions that are heavily discounted but include some restrictions.  The discount can approach 90% so be sure to check this out. Review the program’s support for importing and exporting different CAD formats.  It’s fairly common to import files from another CAD system, so the more file formats it can read and export, the better. Some of the higher end products charge hefty annual support fees in exchange for automatic upgrades.  This can be a bargain if you want upgrades every year, but may be an unnecessary expense for non-professionals.  You could invest hundreds (or more) hours of your time creating CAD models.  Make sure you pick a product and file format that will be around in 5 years.  And make sure you have an upgrade path in case the company discontinues your CAD product or goes out of business. CAD programs are tools-of-the-trade.  They do not design airplanes, the designer does!  No program can substitute for actual engineering knowledge.  Learning to use a CAD program will not make you an engineer any more than learning to use a wrench makes you a mechanic. Click on the following link for a description of popular CAD programs used today:  List of Popular CAD Programs Site Map Email the Designer Copyright © 2012 Apollo Canard