July 18, 2024
Description
Introduction:
UPDATE 5/27/2024: I have added a printable body tube. This has not been tested but it should work with PETG, ASA, or ABS. The recess for the nose cone is shallower than the fincan (38.5mm vs 40.5mm), so don't get the orientation mixed. One tip I received from a fellow modeler is to add a strip of thin cardboard at the base of the tube above the recess to prevent warping from the ejection charge. I haven't tested this yet, but I will let you know the results.
The Extreme Series of Builders Kits were designed to be easy to print, assemble, and fly. These rockets can be flown on lower-powered motors in a park, or with higher-powered 24/29mm motors. Typically, an Estes E15 can loft these rockets to nearly 1000 ft, thus the name Extreme.
The construction is simple. The fin can is solid plastic with cut-outs for the fins to be joined using epoxy. I have included a one-piece fincan with the fins attached. The inside diameter of the fin can was designed to be lined with a 29mm motor tube. Between this tube and the fin can is a small channel for a piece of kevlar kite string (~1mm thick). This should also be epoxied in.
The motor retention ring will slip onto the end of the motor tube and glued with epoxy. The nose cone can be flown in two configurations, with the electronics sled or with the plug. Both are identical except the plug does not incorporate the sled. They will accept a ¼-20 eye-bolt. Both also include two holes for venting for altimeters and the use of e-matches for electronic deployment.
Also included is a detailed OpenRocket simulation file with potential motors that should work.
If you print and enjoy this model, please consider clicking the LIKE (Heart) button and posting a Make. It really helps me and I would love to see other models made from this.
Models Included:
Materials Needed:
Building Guide:
Starting with the fin can, your motor tube (MMT) should be as long as the fin can plus the retaining ring. I suggest using a longer tube and after the MMT and ring are glued, trimming the excess off at the ring. Dry fit your MMT into the fin can. If you encounter moderate resistance, either sand the inside of the fin can or sand/peel the top layer of the motor tube until you can slide the tube in without kinking it. If you kink the tube, the motor will not insert easily and can become jammed after flight.
Once the dry fit is complete, run one end of your shock cord down from the forward end until about 25mm (1 in) is sticking out the back. Apply a thin coat of epoxy to the aft end of the MMT and slide it in from the forward end until about 15mm sticks out the aft section. You must align the shock cord in the internal channel that was modeled to accommodate it. Take your retention ring and slide it onto the end of the tube and push it up until the ring is seated on the aft end of the fin can, pinching the shock cord. Make sure everything is aligned and seated then set aside to dry. Clean off any excess epoxy from the fin can, retention ring, or inside of the MMT with Rubbing Alcohol.
Next, you will need ~ 9-in (228mm) of Estes BT60 body tubing. Use the included body tube cutter to trim off the desired length. You can cut the tube back to the desired length after assembly (mine was about 6 inches). Apply a film of epoxy to the inside aft end of the tube and slip it over the fin can. Give the tube a little twist to make sure there's good coverage. Make sure to feed the shock cord through.
Safety Police Disclaimer:
Rocketry is a safe and rewarding hobby. With knowledge and experience, you can experience the excitement of yeeting a rocket thousands of feet into the sky. There is nothing else like it.
Having said that, you are responsible for the rockets you fly. If you build and fly one of these rockets, you should understand the NAR Safety Code and the potential risks involved with launching any rocket, especially these. They were not designed to be toys. They are real rockets that can potentially go very high and carry significant energy. This rocket is intended to be built and flown by experienced rocketeers who understand the risks and can mitigate potential issues through experience. By printing and flying this model, you do so at your own risk. You are solely liable for any unexpected results and you agree to hold me and any manufacturer harmless of any liability. I recommend you join NAR or Tripoli, join a club, and ask lots of questions. Launching a rocket as a NAR/TRA member at a sanctioned event provides you with insurance you don't get at the park. </end of Safety Rant>
License:
Creative Commons — Attribution — Noncommercial
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David Frey
