Modular Rocket system
This project is rocket science!

Rocket motors
The rocket is designed to use Estes motors which are either 18mm or 24mm in diameter (B, C, D series motors). You can buy the rocket motors on the internet or at good model shops. Information about the motors including safety instructions are available at the Estes website. Download the latest Estes Catalogue which includes a chart of the different rocket motor specifications.

Print your rocket
Select a Fin_18 or Fin_24 depending on the size of the rocket motor you will use.

Also included are twist fin-cans if you want to spin your rocket for added stability.

The fin-cans are stackable so that you can optionally have booster lower stages (suggested booster engines C5-0, C11-0, D12-0).

You can print the fin can in LPA but the motor retaining clips are less likely to snap off if you use PETG or ABS.

Print a top stage with a guide loop. Optionally you can print as many intermediate stages as you wish in which case it is better to have one intermediate stage with a guide loop and print the top stage without a loop.

Print the nose cone. Choose a nosecone. A simple hemispherical nose cone is fine for a single engine stage and one or two intermediate stages. The heavier solid nosecone is provided for larger rockets. Hollow nosecones are provided to carry an instrument or camera payload. These must not be flown empty otherwise the rocket will be unsttable in flight.

Print the ejection wad. This is needed to protect an optional (recommend) parachute or streamer and to push it out of the rocket at the top of the climb.

Assembly
Tie a length of flame resistant cord to the loop inside the top of the fin-can. If you are using booster fin-cans then tie the cord to the top one only in order to allow the booster stages to fall away once they are burned.

Thread the cord through the inside of any (optional) intermediate stages and the top stage.

Assemble the (optional) intermediate stages and the top stage to the fin-can. You may need to trim the stages with a knife to get them to fit if the bottom layer has printed thickly. The stages should be a fairly tight push fit. You do not want them to separate when the motor fires to eject the parachute else it may not deploy. If in doubt apply glue to the joints.

Thread the cord through the hole in the wad and drop the wad down into the rocket stages. The flat surface of the wad should face upwards with the curved surface over the motor.
Tie the cord to the underside of the nose cone leaving at least 1 foot (30cm) of loose cord.

Make a lightweight parachute or streamer. Insert it upside down into the rocket with the strings on top. Tie the strings to the underside of the nose cone.

Place the nose-cone on top of the rocket. It should be a fairly loose fit so that the parachute can deploy easily.

Stackable Rocket Booster set
If you have a large area to fly your rocket then I provide stackable booster stages. Designed for use with Estes rocket motors which are either 18mm or 24mm in diameter.

If you have a single engine stage on your rocket then use B-6, C-6 or D-6 motors.
If you have one or more booster stages then use booster stage motors (B-0, C-0 or D-0). Use upper stage motors B-7, C-7 or D-7 in the top rocket fin can.

• Fin_18_booster_18 takes five 18mm diameter motors
• Fin_24_booster_18 takes one 24mm diameter motor and four 18mm diameter motors
• Fin_24_booster_24 takes five 24mm diameter motors

These booster stages should be a loose fit into upper stages in order to fall away once burned. I do not have a large enough safe area to test the booster stages so if you build this project then please post a video on Youtube and message a link to me.

You should always check that the centre of gravity of your rocket (where it balances longitudinally on your finger) is nearer to the nose of your rocket than the centre of pressure (the point where the rocket would not weather-cock one way or the other in a side wind);

Finally I include a heavier nose-cone than the one included with my basic rocket kit. You can increase weight of the nose-cone by adjusting the infill percentage for improved stability if this is required.

Launch your rocket

The Launch Pad is best printed with the 10 inch (250mm) leg for better stability on rough ground however the 6 3/4 inch (175mm) leg is provided in case the longer legs will not fit diagonally on your printer bed.

Print 1 x launch pad, 3 x leg and 3 x screw.

The launch pad and the screws should be printed with a 0.2mm layer height in order to ensure that the screw threads are well defined.

Print the 3 screws together as one job without any other components to ensure good adhesion of the layers.
The legs may be printed in draft mode with layer height of 0.25mm or more.

The optional blast deflector plate might be printed in a higher melting point plastic such as ABS so that it will last longer however I have tested it printed in PLA and there does not seem to be any melting. Alternatively use a metal lid from a tin, punch a hole in the center so that you can fix it onto the launch pad with a small screw.

Assemble the launch pad and fit a wire rod at least 2 feet (600mm) long. There are 4 holes provided which will accept a 2mm, 2.5mm, 3mm or 3.5mm diameter rod (a wire coat-hanger straightened out is ideal).

You will require a launch controller to launch your rocket. You can buy one or make tour own. It consists of 2 crocodile clips to attach to the rocket motor igniter, approximately 10 metres of good quality cable (2 core lamp cable is suitable), a battery supplying between 6 and 12 volts, a push button and an optional safety switch.

Please check the Estes safety instructions. Take precautions as for fireworks. Children should be supervised by a responsible adult.

Pre-launch check the integrity of your rocket. Check the weight is not too heavy for your chosen motors. Check the balance. For stable flight the weight (centre of balance) must be nearer to the nose than the centre of pressure (the centre of the silhouette of the rocket as seen from the side around which it would weathercock in a wind).

Pick a day when there is little or no wind and a large safe area to launch from. I had underestimated the height to which my first rocket would travel and I have no idea where it landed!

When ready to launch, push a rocket motor into the fin-can. The engine housing prints with a raft so you will need to cut this in 4 places around the base with scissors in order to insert the engine.

Cut an igniter from the Estes strip and insert it into the engine so that it touches the gunpowder. Secure it in place with a plug. Bend the wires of the igniter to the side of the rocket and put a half bend in them (see image).

Erect the launch pad and guide rod as level as possible. You can adjust the angle of the legs for uneven ground.

Check that the switch on the controller is turned off or that the battery is disconnected.  Then clip the launch controller crocodile clips to the half bends in the igniter wires. Better still, just assume that the controller is live and never stand over the rocket nor have the motor pointing at your face when attaching the wires.

Carefully slide the rocket guide loops down the wire on the launch pad. Have a final check that the rocket is level and everything of okay.

Retreat to a safe distance, check that the safe area is clear of people, animals and anything that could get damaged and press the button!