This is a replica of the Sentinel model rocket sold by Estes from 1988 through 1994. It is one of my favorite rockets. The photo shows the original Sentinel on the left, and the 3D printed version on the right. The original is 27" tall, the printed one is 21.5"

I scaled it down by .8 so the fin section would fit within the 6" diameter build plate of my Orion Delta printer. The body wall is 1 mm thick, allowing for two extrusions of .5mm.

If your printer's build plate is 8" diameter or greater, you can scale the rocket up by 1.25 in your slicer and use an extrusion width of .625 to print it at full original size.

I have not flown this rocket, so proceed at your own risk if you decide to do so. At the .8 scale, It should be possible to use BT-55 centering rings to make a motor mount that would be held in place between the bayonet fitting on the mid section and the retainer ring built into the bottom of the fin section. You would need to file/cut 4 notches in the rings to get them past the bayonet bumps in the fin section. Don't make the notches too large - you don't want the ejection gasses to escape out the rear of the rocket before they can eject the parachute! If printed with 1.25 scale multiplier, BT-60 centering rings should work. Always check your CG/CP locations !

Parts connect with bayonet fittings. Line up channels with bumps, insert and twist 90 degrees clockwise until you feel it snap in place.

The "fore" section has an internal lug that can be used to attach a shock cord. You will need to use a piece of stiff wire to thread a cord though the lug.

Update 5/3/2018: Updated some parts to orient them correctly for printing. It is no longer necessary to rotate them after importing them into your slicer. Also enlarged the launch lugs to make sure a 1/8 inch rod will fit even when rocket is not scaled up.

Update 5/7/2018: Added Fin2 alternate fin section. This should be printed with zero infill and either 1 perimeter for lightweight, or 2 perimeters for strength. Use 5 solid bottom layers so the built-in rafts on the three boosters will provide adequate support. Use 0 top solid layers to prevent Slic3r from trying to cap off the booster nozzles. Remove the rafts after print is done.