Red Max Mini Flying Model Rocket

UPDATED:  This is still a work in progress.  While I am confident that the model is usable and safe, I will make changes as the design improves

3/31/2024:  This was test-flown with all printed parts.  It did not fair well.  The fincan coupler melted a bit (PLA+) from the deployment charge, the body tube got melty, and the nosecone exploded upon impact with the asphalt.  I will test again with a BT50 cardboard tube.  Also, I think a small cardboard liner inside the fincan coupler and the body tube is warranted.  It still looks really good and it flew fine, there just have to be some additions.  I'll also test with PETG.

3/15/2024: After consultations with my fellows at The Rocketry Forum, I decided that the body tube was too thin.  It will most likely (read: most definitely) will melt from the ejection gases.  I have included an updated Body Tube v2.stl that thickens the center portion of the body tube to make it more resilient to the motor heat.  The body tube is now form-fitting so the launch lug is closest to the aft end.

In addition, I have some recommendations:

• If you are not comfortable with a printed body tube, you can use a 75mm section of BT-50 body tubing available at Estes or many hobby stores.  I tested the nosecone/fincan with Estes tubing and the fit is fine.  YMMV.
   
• I have also included a launch lug to go with the body tube.  It's not pretty with chamfers and such but only you will know. 
   
• An alternate recommendation was to cut a piece of cardboard from a cereal box and line the interior of the body tube to protect it from melting.  I have left the original body tube in the files list in case someone would like to try it.

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Introduction:

This is the Red Max Mini rocket kit I designed using Fusion360.  It is based on the popular Der Red Max rocket kit.  I built it because I am hard on rockets, and my Estes kit didn't pass the “Frogglicker Durability Test.”

It is a park-flyer model that is easy to print and assemble and can achieve altitudes of 500' on an Estes B4 motor.  The assembly instructions are simple.

• Slice the parts or slice them all at once.
• Print in your favorite filament (PETG or PLA+ recommended)
• Use supports for the aft section of the fins, launch lugs, and retainer cap (if you print it right-side up)
• If you plan to paint, use 0.16mm resolution or higher (smaller) for your layer height, otherwise 0.2mm will do

Needed for Assembly:

• CA Glue 
• Optional: 3D Gloop
• Thin Kevlar cord for the shock cord (~1mm thick)
• ~10gm of modeling clay for nose weight
• Streamer material - Recomm. 50mm wide by 762mm (2-in x 30-ins)
• BT20 Body Tube from Estes or others (motor mount sleeve)
• Estes 18mm Rocket motors:  A or B-class motors are recommended.  C-level motors are estimated to go over 1000ft.
• Misc. launch gear
• The usual hobby tools (X-acto knife, sandpaper, popsicle sticks, etc,)

Assembly (read first and understand all steps before proceeding with assembly):

1. Clean up the excess flashing from the model.  Sand and fill if you plan to paint
2. Measure out ~3-4 body lengths of Kevlar cord
3. Pass the cord from the top of the fincan and through the aft end
4. Locate the track for the shock cord inside the fincan and CA Glue it in place with a tail of cord hanging out the back.
5. Insert the BT20 tube into the aft end and push it forward until it stops.  
   1. You should secure the tube at the top with a little CA.  Don't get CA inside the tube
6. Slide the retaining ring onto the motor mount tube and secure it to the aft end of the rocket and motor mount tube with a few drops of CA
7. Carefully trim the end of the motor mount tube with an X0acto knife
8. Once the glue is dried, screw the Retainer cap onto the ring
9. Find and fit the body tube onto the fincan.  Orientation shouldn't matter but the forward launch lug usually sits closer to the fins.
   
   NOTE:  You can substitute a BT-50 cardboard body tube for the printed one.  You will need to print the optional launch lug stl file.
    
10. Pass the shock cord up through the body tube
11. When the launch lugs for the body tube and fincan are lined up, secure them with CA or 3D Gloop.
12. Tie the end of the shock cord to the nosecone and put a drop of CA glue on the knot to keep if from slipping
13. Attach a streamer.  Roll up tight.  It should have enough room with wadding and the shock cord
14. Add one wrap of a thin strip(1-3mm wide) of masking tape to the nose cone to keep it from coming off but it has to be able to eject during deployment.  If its too tight, remove a portion of the strip of tape
15. Add ~ 10gm of modeling clay to the inside of the nose cone
16. Install the motor and screw on the retainer.  
17. Do your normal launch stuff and let 'er rip!

Final Notes:

• I have included the .3mf from OrcaSlicer.  It should load up in any slicer, though
   
• I have also included the OpenRocket Simulator file so you can do simulations of your rocket with aircraft configurations.
   
• This is my gift to the 3D Printing and Rocket community.  It took a considerable amount of time to create and it was a labor of love.  Please feel free to download and freely share the link.  If you love it too, please like and post a Make.
   
• Please don't steal this for profit.  I sell upgraded kits with the accessories to make this flyable and I will even assemble, ready to fly.  Contact me if you would like either.  I will link my Etsy storefront when it's ready.  If you want to sell it, reach out and we can make an arrangement.
   
• Model Rocketry is a safe and enjoyable hobby for kids and adults when the NAR Safety Code is observed.  If you plan to fly this, please have some experience or do some homework on flying low-power rockets.  This is the way.
   
• I provide this model without warranty or guarantee of safety.  I have tried very hard to make this a workable builder's kit for you to enjoy but sometimes, I don't get everything right. Print, display, and launch at your own risk.  
   
• If you print this and put it on your desk at work, you're gonna be the coolest cat in your cube farm.  Enjoy the fame! 
   
• Message me if you have any questions.  I love talking about rockets and 3D printing!