This is a model rocket of a RIM-67A missile, for launching with a C or D motor (18 mm). It is not at a perfect scale, because of the need of having much larger fins. But it looks pretty much like the real one. I have designed the fins and the rocket base (motor case, and stern fin support) to be 3D printed. To avoid ending up with a very weighty rocket, the tube and nose cone are made of cardboard a very light plastic (from Estes kits and parts). I have designed the parts with Sketchup, and then converted to STL. I have simulated the rocket with OpenRocket, and the stability estimation is 3,21 cals, which should be adequate for this model.

BOM

• 4 x Middle fins (plastic, printable)
• 4 x Stern fins (plastic, printable)
• 1 x Rocket base (plastic, printable)
• 1 x Estes BT-55 tube (cardboard)
• 1 x Estes BT-55 nose cone (plastic)

Printing

I have used a XYZPrinting Da Vinci Jr 1.0 printer, with XYZPrinting white PLA. The general printing parameters are:

• no need for support material or build plate adhesion
• standard speed
• 210-215 deg extrusor temperature

Specific parameters for the fins:

• solid printing (100% infill)
• 0.1 mm layer height

Specific parameters for the rocket base:

• 10% infill
• 0.3 mm layer height

Building

Cut a BT-55 tube to 320 mm of length. Cut out four 1x180 mm recesses in the tube, at 10 mm from the tube base, along the main axis. Insert the middle fins from inside out in the tube. Then glue them in place.

The coupler between the rocket base and the tube might need a little sanding, depending on the accuracy of the printer. Plug and glue tube into the coupler.

Insert the stern fins into the recesses of the rocket base. If they get too loose, fill with excess of glue, or print them oversized in only the thickness dimension. You might want to print a single stern fin, and depending on the final thickness, print the remaining ones.

Prepare and add a parachute, and finally insert the BT-55 nose cone, linking the tube, the parachute and the nose cone with a 70 cm elastic band. Glue a 50 mm of 3 mm diam. plastic tube for launching, at a distance of 130 mm from the bottom of the rocket.

Launching

I have only tested a full cardboard version of this model. It is quite tricky, because the fins need a good alignment. I advise trying with a C motor first (C6-7), and upon success going to a more powerful D motor (D9-7). The 18 mm rocket motor should fit neatly into the motor case. It it gets too loose, add a little of duck tape to the motor. The motor must be firm inside the case, otherwise the expulsion charge might not work properly, and the parachute not deployed. The motor case is designed so that the motor protrude some 7 mm from the rocket bottom, in order for easy removal of the motor after flight.

Simulations with OpenRocket indicate that the rocket could reach 337 m height with a single D9-7 motor.