Documentation

Model Airplane Designer

MAD is a model airplane rapid design system.  The user inputs what they want at a high level using a form based interface.  The MAD system then builds an exact 3d model of the design, 2d full size build plans, individual part templates and layouts for laser cut sheets.

 How is MAD different from other tools?

  • MAD is not a CAD tool.  CAD tools are often very expensive and can take years to learn well enough to use effectively.  MAD is quick and easy to learn yet still produces high quality professional grade output.
  • MAD automatically generates laser cutter layout sheets that can be directly cut by your favorite laser cutter.  This allows you to create more complex and ambitious designs that are still as simple and as straightforward to build as a trainer.
  • MAD can do quite a lot, but it cannot do everything.  If you need everything you may be a good candidate for purchasing and learning an advance 3d solid modeler.
  • MAD knows how to cut built up ailerons and flaps into your fancy curved or tapered wings, and generates all the parts for you.
  • MAD makes changing your design fast and easy.  You can switch airfoils, move a stringer, add lightening holes, add sheeting, move ribs, change span or chord, add twist or sweep — all in a matter of a few seconds.  You don’t have to redraw all your parts and structures yourself, MAD does this for you automatically, exactly, and perfectly every time.

Overview and Work Flow

If you have a good idea of what you want, you can create a new wing in MAD in a few minutes.  This includes outputting an exact 3d model so you can take a close look at what you have asked for, what MAD has produced, and see exactly how your design will look when it is built.  It also includes laying out all your parts on sheets ready to send to your favorite laser cutter.

  1. Start a new design
  2. Input the basic design information on the “Overview” page and select the units you wish to use for your design.
  3. Add a Wing.  (This creates a new tab next to the Overview tab.)
  4. Fill in the basic information for your wing such as span, chord, airfoil, etc.
  5. Add any features you wish including spars, stringers, leading & trailing edges, sheeting, lightening holes, and build tabs.
  6. Save your design and build it.
  7. View your results in 3d and make sure everything looks like you have intended it, or make refinements and rebuild your design.
  8. When you are happy with the build, look in the same folder as your design file and you will find your plans, laser cut sheets, and part templates.  These are all in .svg format.  Many software packages can load and edit svg files, but if you don’t have a favorite, I recommend “Inkscape” from inkscape.org.

Interesting/Advanced Features

MAD has a number of interesting features that you might not notice at a quick glance.  Here are a few things to keep in mind as you design your next project:

  • MAD includes a database of 1500+ airfoils.  If you can find it on the internet or if it’s been used on a real model or real aircraft, it is probably in the MAD database.
  • When adding a leading edge, MAD will do a “best fit” cutout of your airfoil rib.  This means that your post assembly sanding work to get back to the exact airfoil leading edge shape will be mathematically minimized.
  • Trailing edge stick is places using a best fit algorithm as well.  Airfoils come in all shapes and trailing edge stock will rarely match the original shape exactly.  MAD matches the exact trailing edge tip to the airfoil tip and then rotates the leading edge for a best fit to your airfoil.  Even so the thickness of your trailing edge stock may not be an exact match with the airfoil at that point.  MAD will carefully shave or thicken the airfoil so it matches the trailing edge stock exactly.  This is so subtle you may not ever notice or think about it unless I point it out.
  • Quickly add features (stringers, holes, etc.) and specify the starting and ending stations.  Even though MAD allows you to quickly design structures, it still allows the designer to make all the engineering decisions.
  • When wing twist is asked for, MAD builds it right into the design for you (with optional build tabs and spar cutout alignments) so everything locks in and builds exactly the way you intended.
  • Supports tapered wings by specifying a root chord and a tip chord.
  • Want to get extra creative?  MAD allows you to enter a spline curve that defines the wing chord along the span.  Sound hard?  It’s not at all, and it allows you to take your design to the next level of creativity.
  • MAD will let you enter a sweep angle for swept wings, but doesn’t stop there.  If you want to get extra crazy, MAD lets you enter a spline curve that defines the amount of sweep along your wing span.  Why would you want to do this?  I don’t know, but it’s there as an option.
  • Many real world designs use different root and tip airfoils and blend between them.  If you’d like to do this in your design, it’s no problem in MAD.  Just define a tip airfoil and you are done.   MAD automatically blends your airfoil ribs for you.
  • As I write this, control surfaces are a work in progress, but when the gui is ironed out, you’ll be able to cut in control surfaces (flaps and ailerons), specify the starting and ending stations, hinge line location, and MAD will generate all the parts for built up ailerons.
  • Changes are easy.  The structure of MAD means you can add and remove features, change sizes, locations, even make radical changes like picking a new airfoil, and everything is rebuilt automatically and consistently.  You aren’t stuck redrawing every part like you might have to do in a typical 3d modeling tool.

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