Sport Rocketry

unstable about the Z axis (the central ro- tation axis). Adding some counterweight in the X axis via a dowel or threaded rod makes the X axis slightly unstable. e net motion is to prefer to have instability in X, which makes it stable in Z . e moral is do not omit some sort of counterweight in the X-axis, and Francis outlines four different ways of adding this counterweight. I used a threaded rod in my design. Several vendors, including Alien Enter- prises and Art Applewhite, offered mono- copters many years ago. Alien Enterprises marketed the M-24, and Art Applewhite sold the Hornet, among others. I based this 3D printed design loosely on the Alien En- terprises M-24. Figure 2 shows the original M-24 beside my 3D printed rendition. e 3D printed version is somewhat heavier and flies to lower altitude. My first attempt at this design failed dis- mally. It had inadequate li, as it utilized a wing with a flat profile at five degrees angle of attack. As a result, the monocopter spun on the launch rod and flew apart. ese findings prompted me to explore airfoil shapes for the wing. One advantage of 3D printing is the ca- pability to create parts that would be very difficult to shape manually. For example, I designed an aerodynamic wing profile us- ing the "Rhode St. Genese 30" airfoil, and the OnShape CAD program contains a set of scripts for creating airfoils from a data- base of standard ones. is particular air- foil produces good li at subsonic speeds, and a 14-degree angle of attack delivers maximum li. Too high an angle of attack creates a stall, and too low an angle of at- tack results in lower li. I was able to 3D 16 MAY/JUNE 2024 SPORT ROCKETRY parts. e next sections of this article detail all the steps for building this rocket. Sourcing the Materials For the first step you will procure the parts and 3D print the wing and the motor block (Figure 3). You must source the parts listed in the "Bill of Materials (BOM)" table. Required tools include coarse sandpaper for surface preparation, 11/64-inch and 13/32-inch drill bits for the holes, as well as items for epoxy preparation and appli- cation: nitrile gloves, wipes, paper towels, wax paper sheets, popsicle sticks. 3D Printing the Motor Block and Wing You must 3D print the two parts or have someone print them for you. I posted the STL files from the CAD designs (Figure 4) at https://github.com/chrocket/3D- printed-rocket-part-designs.git for down- load. Several Sport Rocketry articles de- scribe the process of 3D printing rocket parts if you need to become more familiar with 3D printing. Figure 2. Alien Enterprises M-24 (le) and my 3D printed version (right). Bill of Materials (BOM) Quan. Item Notes For Assembly: 1 3D printed motor mount Monocopter Base Design 2 Strong - V21.stl 40% infill PETG, 0.2 mm layer height 1 3D printed wing Monocopter wing Design 2 Copy 1 - Part 1 V21, 40% infill PETG, 0.2 mm layer height 1 8-32 12-inch thread rod 6-32 or 10-32 will work as well 6 8-32 hex nuts 1 BT-50 thick-wall, 2.5" long 24mm motor tube 1 BT-50 24mm motor block - Good quality epoxy I like Rocketpoxy. Quantity as needed. For Flying: 1 launch rod post, 3/8" dia. It can be aluminum or wood. I like this cut to 3 inches long fiberglass rod from McMaster-Carr, part number 8543K619 1 3/8 PFTE washer Example: McMaster-Carr, part number 6389K115 print a perfect airfoil shape and design a slot in a base for perfect mate fit. My revi- sion with this airfoil flies very well. Hopefully, the monocopter can regain the popularity it deserves. To that end, this article describes a 3D printed monocopter with instructions so you can build it and add it to your fleet. Monocopters fly low and slow and are perfect for small fields and this one flies on an Estes D impulse motor to about 300 feet. is is an inter- mediate skill build as it requires experi- ence creating strong glue joints between

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