3D Print Flying Model Rockets

             3D printing              offers new creativity in the world of model rocket design and fabrication. 
Above is a computer model of some printed flying model rocket.  

In these instructions I will take you thru steps needed to make really cool flying rockets.

 

Things that you need.

• A 3D computer design program.
• A source for 3D printing.
• Model rocket simulation software.

Some things to remember.

• Model rockets must be lightweight.
• Model rockets must be stable when they fly.
• Model rockets must be safely returned to earth.

There is a great wealth of information available on the internet about model rocketry.  In general commercially available model rocket engines are available at hobby stores and thru the internet.  These engines come in a variety of sizes and powers. 
http://www2.estesrockets.com/pdf/Estes_Model_Rocket_Engines.pdf

In this case I am working with a standard size 18mm x 70mm engine, but don't let that limit you.

If you are new to model rockets, please download: 
http://www2.estesrockets.com/pdf/1948MRST.pdf  for a teaching document.

 In generally a rocket has a nose cone, a body, and a tail fin section. 
The nose cone usually ejects with the recovery system, commonly a parachute.

Here I show the development of the printable rocket starting with a very basic concept.

In version one of the rocket, I added a combustion chamber, nozzle, and payload section with a rounded nose. 
In version 2, I wanted the combustion chamber to stand out more so I changed the fins, and added the fuel chamber and pipes.  Raising the fins relative to the motor lowered the center of gravity (CG). 
This made the rocket marginally stable.  To raise the CG (increased stability) I thinned and lengthen the rocket arriving at the final version 3.  

Remember the CG must be above the center of pressure (CP)  in order for the rocket to be stable.

 

Here is a link to a free design tool:  http://openrocket.sourceforge.net 
This tool helps you simulate your rocket design.  There are many design packages available.

In this simulation you can see that the fin area has been simplified.  Design is a back and forth process to optimize.  In the simulation I have used 1.14mm thick PVC plastic.  The mass of the fin sections comes from the CAD package I use.  Notice the CG Blue and the CP Red.  The CG must always be above the CP. 

I have attached the OpenRocket source data file used here.
 

The rocket still needs a parachute, shock cord, launch lug, and motor retainer. 
I sectioning up the rocket into units that could be printed, added some payload detailing, and added the integral launch lug into one fin section.  Now we have a model rocket. 
The parts were mostly thinned out to 1.15mm thickness.  
As thin as most printers can print reliably.. Light weight is key to performance.

Back to the simulation software for a final stability verification, and motor-performance estimates.
The first drawing shows the simplified shape used for the simulation.
The other drawings show mass and CG's for the various parts.

The simulation software shows:
B6-4 engine will fly 63 meters 200 ft.
C6-5 engine will fly 176 meters 570 ft.

This step will likely be different for every printer, but this should be close.
Three fins sets of type A are needed (one shown) and one of type B launch lug.

I have included a zip file that has a 3d model (step) of this rocket.
I also have include the STL files for the parts shown.

Fabricate the motor clip wire.
Use a giant paper clip for the wire source.
Use a ruler to help size things.
Trim the end off, and sand it smooth if sharp.

Begin by gluing the fin halves together to make 4 fins.  At least one should be a launch lug type.
Use rubber bands, books as weights, etc to hold the fins while drying.
You can fit and glue together the fuel chamber, 2 body tubes, and upper transition.
Also fit and glue the nose cone adapter into the nose cone.
Do not glue the shock cord mount into the transition until you have attached the shock cord.
It's possible to do this later but harder.
When all the components are dry, insert a dummy motor or used motor into the combustion chamber and fuel chamber.
This will help keep things aligned while you glue the fins on. 
This is the most difficult step.
Take your time and get things squared up.

The parachute shock cord is a piece of .25" wide elastic 30 to 40 inches long.
Attach one end to the shock cord to the bar on the shock cord mount.
I like to stitch mine on but a double knot will do.
Glue the mount into the transition and the pay load tube together.
The cord comes out of the tube.
Make (or buy) a parachute.   https://www.instructables.com/id/Make-a-model-rocket-parachute/
Tie the parachute onto the nose cone along with the shock cord.
Install the motor retention wire.

This part is fun, and will help make your rocket the very best!
Here is a link to make simple decals.https://www.instructables.com/id/Rocket-tape-laser-decals/

Remember to be safe when flying your rockets.

For this rocket at 104grams, the software suggests that a B6-4, 63m height, or a C6-5,  175m height, are good engines.

You may have noticed that the cover picture shows other rockets.

The next 2 rockets make use of some conventional model rocket components, and some 3D printed components.

The goal is to reduce the weight for better performance, but keep the cool looks.

In this drawing you can see that the printed fins are replaced with balsa.
The body tube and payload  tubes are replace with purchased cardboard tubes.
The tubes can be found at http://www.semroc.com/Store/Products/BodyTubes.asp
BT55 for payload section, and  Series 7 for the body tube.
Balsa at your local hobby store or on line.
The attached PDF file is a  template to help you make your fins out of 1/8" thick balsa sheet.

According to the OpenRocket simulation (source data is in the rocket4.zip file) :

With a B6-4 engine the rocket peeks at 103 meters or 337 feet.
With a C6-5 or C6-7 engine the rocket peeks at 226 meters or 741 feet.

A considerable performance gain!

Here is a layout of all the parts that need to be printed on your 3D printer.

I have attached a zip file that has all of the model components needed for this version.

Cut your tubes.
Glue the nose con adapter into the nose cone.
Attach the shock cord to the shock cord mount.
Glue the shock cord mount into the upper transition.
Glue the fuel tubes together.  You should end up with 4 of them.
Cut out your balsa fins. Align the grain as shown on the template.
Using an old motor or dummy motor and align the combustion chamber and fuel chamber, so the motor clip fits into the notch.
There are 4 locating bosses on the combustion chamber for the fuel tubes.
Glue the 4 tubes to the fuel chamber and combustion chamber.
Be sure that your fins will insert, but do not glue at this time.
When the glue is dry you can install the body tube into the fuel chamber.
Now you can glue in the fins.  They glue to the body tube and the fuel chamber.
The rest is similar to how we finished the first rocket.

So going along with the theme of cool looking flying rockets, here is the evolution of one I am calling Tri-Pod.

I started with a basic three fin rocket and added some simple nacelles. 

I refined this basic design.
I personally like nozzles on rockets, so I added a few and some more curves.
At this point the model is still 100% solid.

I then refine the model and create an assembly of purchased and printed parts.
This is simulated for verification of stability.

This is the implemented flying version.

Here are the components needed for Tri-pod.
The nose cone is purchased from here  https://www.discountrocketry.com/nose-cones---transistions/vaughn-nose-cone-bt55-tubes-p-2271.html 
If you want you can also print one.
You may have to add mass to the upper of the rocket for stability.
Modeling clay pressed into the nose cone works well. 
You may have to drill a hole on the inside end to add clay.

Here you can see the tabbed fin construction.
We need strong fins to hod the nacelle pods.
The fins are cut from 1/8" balsa.  A template file is attached.
Also a drawing of Tri-pod so you can figure your cut lengths.

Tri-pod uses only a few printed components to achieve the look.

I have included all the files you should need in the attached zip.

Please make sure your nacelles are parallel to the body tube!
Please verify your launch CG is high enough.  See drawing in zip file.

The OpenRocket simulation data: (in zip file)
Suggested motors are B6-4, 129 meters 423 feet, and C6-5 253 meters 830 feet.

I hope you have enjoyed this instructable, and  have fun building and designing your own rockets.

Please leave questions or comments, I will answer as I have time available.

Happy flying.

http://www.nar.org/

More information.
http://www.spacemodeling.org/jimz/manuals/cendm-1_designersmanual/dm-1a.pdf