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Getting Started

To get started on this project, you need to make sure you have OpenSCAD installed. The project website has installers for all major platforms (Windows, Mac, and Linux). For an overview of using this program, see the Math-Magik project documentation. I highly recommend that you print out a copy of the OpenSCAD “cheat sheet” available at https://openscad.org/cheatsheet

Limited Pennyplane Rules

We cannot get much design work done without a clear understanding of the class rules. These are published in the AMA Rulebook under “Event 208”.

Basically, we need to respect a few model dimensions and weights in order to compete in this class. All of these are specified in a single OpenSCAD data file placed at the top of the model design directory:

math-magic-lpp/scad/constraints.scad

//####################################
// Math-Magik LPP - Design Constraints
// (c) 2021 by Roie R. Black
//====================================

// AMA Rules for event 208
//------------------------------------

max_overall_length = 20;
max_projected_wing_span = 18;
max_bearing_to_rear_hook = 10;
max_wing_chord = 5;
max_stab_span = 12;
max_stab_chord = 4;
max_prop_diameter = 12;

Note that in this design, all dimensions are in inches. OpenSCAD supports doing simple math when defining constants, so I am using things like 1/16 to indicate a standard modeling dimension, rather than using the actual decimal value.

Also note that I name data files with a .data extension. OpenSCAD will handle these files just fine. All files with an .scad extension will define actual model parts or assemblies.

Parts and Assemblies

In this design, a part is a single component constructed out of some building material. When we analyze the properties of a part, we will need to specify the density of the material. In order to simplify the design, and set up useful components that might be useful in other designs, some part code files will be placed in a library folder. The library parts generally use parameters that need to be set to construct an actual physical part. We will see this concept in action soon in our design work.

An assembly is a collection of parts combined to form a higher level component of the model. Assemblies can join simple parts, or other assemblies as needed to complete the model.

OpenSCAD is generally used by folks building things using 3d printers. In those applications, it is common to “fuse” parts together so generating files needed by a 3D printer can be constructed. in our design work, we will not be doing that. Instead, we need to carefully align parts so they end up placed in exactly the right spot. Fortunately, you can do simple calculations in OpenSCAD code to simplify this process.

Design Process

In the pages that follow, we will work on model parts in no particular order. We will initially focus on building a few parts, then set up assemblies that use those parts. The last thing we will be doing is assembling the complete model. This process is much the same as the one you would use to build any model using real parts. There is not one “correct” way to do this, although some things get pretty obvious.

In the next section, we will start off by building the wing.