I have a loose end I've been meaning to tie since 2012--a large R/C rocket glider.

Loose End is a family of aircraft. I use OpenSCAD to define parametric models that can scale from parkflier to giant scale. A goal of this project is to automate as much of the process as possible to allow for faster iteration of the design. I use a Makefile to generate individual STLs from the master design, and g-code from the STLs. Some parts (fins and wing joiner tabs) are in 1.6mm fiberglass (G10); the Makefile generates DXFs for them.

Initial versions use off-the-shelf wings from a HobbyKing RadJet800. This version has a 24mm motor mount. This version has flown on E9, E15, E6, E20 and F12 motors. In January 2023, I am designing printable wings.

Fuselage prints upright, in sections. Most pieces use a single perimeter and 2% infill. Spar carrythrough (green in the image below) uses 15% infill. This part allows me to cut wing spar in two and the motor to pass through the wing, similar to mid-wing jet fighters like MiG-21 or F-16.

I print these models on a Prusa MK3S+ using Prusament PLA. I use PrusaSlicer in batch mode: slicer-config directory holds the INI files I use. Key settings are:

• Most parts are single wall:
  • Perimeters: 1
  • Horizontal Shells: top: 3, bottom: 1 (max shell thickness bottom: 0 to force single layer)
  • Infill Density: 2%
  • Infill Pattern: Grid
  • Max Length of Infill Anchor: 0 (with some infill patterns, other values create arbitrarily long anchors; 3mm would be ideal)
  • Filament Extra Length on Retract: 0.1mm (helps avoid gaps between infill and perimeters)
  • Brim: outer, 3mm
• Spar carrythrough:
  • Perimeters: 2
  • Infill Density: 15%
  • Infill Pattern: Grid
  • Brim: outer, 3mm
• MMT plug:
  • Fill Pattern: concentric
  • Top Fill Pattern: concentric
  • Bottom Fill Pattern: concentric
  • Brim width: 0mm (the model has its own shoulder)

I make a new tag (release) when I print a new flying aircraft. Release notes summarize changes from previous version and actual experience with them.

• January 2024: 29mm version using wings and fins from 80mm Freewing F-86
• October 2022: PLA fuselage, RJ wings, G10 fins
• April 2022: first flights, PLA fulseage, RJ wings and fins