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SPECIFICATIONS OF CONSTRUCTION OF MODEL ROCKET
BODY TUBE
This uses light PVC plastic conduit with an 18mm inside diameter. Cut to length and file ends square and smooth.
Set out and drill the two 3mm diameter holes at the nose end of the tube through one side of the tube wall only. These holes are used to tie the rubber band shock cords to the body.
Set out and drill the one 3mm diameter hole at the motor end. Drill this hole right through the body tube. Cut a 25mm length of 3mm diameter cane and glue this in place through the body with a hot melt glue. Trim off any excess cane protruding past the outer surface of the tube. This small length of cane acts as an engine mount and prevents the movement of the rocket engine up through the body when in the thrust phase.
The rocket engine needs to be a firm fit into the bottom end of the body tube. If the engine is a little loose, you will need to wrap a layer or two of masking tape around the rocket engine just prior to launching, so that the engine remains firmly inside the body tube.
NOSE CONE
This is made from solid square section balsa wood. It can be carefully whittled to shape with a craft knife and some hand sanding, taking extra care to ensure that the reduced end is a "gentle push fit" into the top end of the body tube. Remember the rocket engine needs to eject the parachute recovery device just after apogee, so make sure the fit of the nose cone into the body tube is not too tight or too loose.
LAUNCH LUG
Cut one piece of 10mm diameter polythene tube to a length of 20mm. This will be attached to the body tube to act as a guide during the initial launch from the launch pad and launch rod.
FINS
You will need to make three fins from sheet balsa wood that is about 3mm or 4mm thick. Carefully mark out three fins with the timber's grain running along the 80mm length. Cut each fin to size using a craft knife. Carefully sand the leading edge over to a round (similar to the leading edge of an aeroplane's wing) to assist in the airflow during flight.
Using hot melt glue attach the three fins around the body tube so that they are evenly spaced around the circumference at 120 degrees apart and overhanging the rocket engine nozzle by 15mm. (see the Assembly Drawing of model rocket).
Using hot melt glue, attach the polythene Launch Lug against one fin and the body, in the position indicated on the assembly drawing.
PARACHUTE
Mark out a circle of approx. 250mm diameter onto a piece of very thin plastic (eg white plastic grocery shopping bag). Mark the position of the 8 equi-spaced holes for the shroud line connection to the parachute. Reinforce both sides of the plastic at the hole locations by folding over a piece of masking tape. Punch a small hole at each of the 8 positions. Cut 8 pieces of fine twine, each 400mm long and tie one end of each through a punched hole. Using coloured permanent marker pens, apply a colour scheme and design to the plastic parachute.
SHOCK CORD
Tie 5 rubber bands (approx. 75mm long each) end to end. Attach one end of the rubber band shock cord to the two holes drilled in the top of the body tube. Attach the other end of the shock cord to the nose cone using a small piece of twine passing through the nose cone hole and last link of the shock cord. (see Assembly drawing)
Gather the free ends of the 8 shroud lines together and attach them near the mid point of the shock cord by fastening a knot. (see Assembly drawing).
PREPARATION OF ROCKET
Sand and seal the balsa fins and nose cone.
Select a colour scheme and design for the rocket and carefully apply two coats of paint. NB ensure that the nose cone is able to come away from the body tube without too much resistance.
Insert a piece of fire-resistant wadding into the top of the body tube and push it down into body so that it rests above the cane engine mount. This wadding prevents the parachute from scorching or burning when the parachute is deployed by the rocket engine ejection charge.
Carefully fold the parachute and shroud lines and gently push them into the body tube. Finally, insert the nose cone into the end of the body tube. NB No live rocket engine is to be handled or inserted into the body tube except by the class teacher at the moment of launching.