Go to a Lowes Home Improvement Center and buy a $42.00 stack of polystyrene foam sheets (shown below). It's 4ft x 50ft x 0.25 inches thick and it's fan-folded into a stack of 2ft x 4ft sheets. One 2ft X 4ft sheet weighs just 6 ounces.
Go to Staples and purchase a roll of Staples clear 2-inch wide packaging tape (item 609139). Also purchase a package of 3 poster board sheets 14in x 22in (item 846923). This is a thinner type of poster board ideal for making a motor-mount tube. Also purchase one 22in x 28in poster board for making a payload ejection piston. Purchase Elmer's Glue-All (white all-purpose glue).
Purchase a small spool of 18-gauge steel wire from a hardware store.
Purchase G40-4W motors and First Fire Junior Igniters from www.hobbylinc.com .
Using a utility knife or box cutter, cut off a 2ft x 2ft foam sheet. Use a sharp blade and the foam will cut very easily. Make 90 degree square cuts, not beveled cuts. Use a wooden yardstick as a guide for the blade to make nice straight edges.
Roll the 2ft x 2ft foam sheet into a tube. The tube will have a length of 2ft, a circumference of 2ft and a diameter of 7.5 inches. Roll the foam sheet so that the plastic-coated side is on the outside. The foam sheet is too stiff to roll directly; it needs to be pre-shaped on a curved surface such as a 3-inch diameter pipe. The pole of an outdoor basketball net makes a good surface to pre-shape the foam. Press the foam firmly against the pole with both hands and wrap it 180 degrees around the pole, one section at a time. Take care to curve the foam uniformly; try not to make any kinks or creases. Work your way from one edge of the foam to the other until it is uniformly curved and roughly holds the shape of the letter-C.
Using the floor, 2 knees and 2 hands, carefully force the foam sheet into the shape of a tube. Try not to kink or crease the foam. Butt the 2 opposing edges of the foam together; do not overlap them. Bend the 2 opposing edges of the foam inward to form a heart-shape as shown on the figure below, then apply a 2in x 2in piece of clear tape across the mating edges near the middle of the tube. Press the tape firmly onto the foam as you release your grip on the tube and it goes from a heart-shape to a round shape. It is important that the tape pull the 2 opposing edges of foam as tightly together as possible in order to obtain a smooth round tube. Don't get discouraged if the tube is not perfectly round with the first piece of tape. Repeat the heart-shape and taping procedure with additional 2-inch pieces of tape until the entire 2-foot length of tube is fully taped.
If the tube has kinks and is not round, work the tube with your hands until it is round. If the taped seam is not smooth and round, the tape did not pull the foam together tight enough. Forming perfectly round tubes is difficult and may take some practice. If making a 2-foot section of tube seems too difficult, make two 1-foot sections of tube or four 6-inch sections of tube. It is easier to make shorter tubes. Tape the shorter tubes together to form a 2-foot long tube.
Either now or later, make 3 more 2-foot sections of body tube as described above.
Cut off a 4.5-inch by 12-inch strip of the thinner poster board purchased in step-1 above. Wrap it once around a G40-4W motor, apply Elmer's Glue uniformly across the remainder of the poster board and wrap it around the motor to form a tube. Tape it, if necessary, to prevent it from unraveling. Leave the tube on the motor over night to dry and harden.
Using a utility knife, cut two round 7.25-inch diameter foam disks. Verify that these disks fit snugly inside the main body tube. Cut a 1.1-inch diameter round hole at the center of each disk. Verify that the motor mount tube fits snugly inside these holes.
Using a utility knife, cut three 6-inch by 4-inch foam rectangles for fins. Cut notches into the fins as shown in the figure below. (These notches will be inserted into slots cut into the main body tube to hold the fins in place. These notches will also block the 7-inch disks and motor from sliding up the main body tube.) Cut 1.5-inch by 0.1-inch slots into the bottom of the main body tube to support the fins by the notches. The fins should be arranged uniformly 120 degrees apart and should be located at the very bottom of the main body tube so that they help hold the rocket upright when it is standing on a level surface. Verify that the fins fit snuggly into the slots and then remove the fins untill the motor mount is installed. The size of the slots can be adjusted by scraping with the blade of a screwdriver.
Cut a 4-inch x 28-inch strip from the heavier poster board. Form it and tape it into a 7-inch diameter cylinder. Verify that it fits loosely inside the main body tube. Cut a 7-inch diameter disk from the heavier poster board and tape it to one end of the cylinder. Verify that the piston fits loosely inside the main body tube.
Cut three 6-inch x 2-inch strips of foam to support the piston inside the main body tube. Tape these strips 6 or 8 inches down from the top of the main body tube as shown in the photo below.
Cut a 2-foot long piece of string and tape one end to the inside of the ejection piston. Use clear tape to tape the other end of the string to the outside and top of the main body tube.
Use clear tape to tape another 2-foot section of main body tube below the tube that will hold the piston and nose cone.
Insert the two 7-inch disks and motor mount tube into the main body tube so that the disks support each end of the motor mount tube. Verify that the motor mount tube is aligned straight with the main body tube. Remove these parts from the main body tube and securely tape (with duct tape) or glue (with Elmer's glue) the disks to each end of the motor mount tube. Position the lower disk so that the motor mount tube extends about one inch below the lower disk. (The bottom 1-inch of the motor mount tube must be exposed so that the motor can later be secured by wrapping duct tape around the bottom of the motor and motor mount tube.)
Insert the motor mount assembly into the main body tube so that the lower disk is about 3 inches from the end of the main body tube. Insert the fins into the slots. Push the motor mount forward until the lower disk contacts the notches on the fins. The lower disk should now be recessed about 4 inches from the bottom of the main body tube. (Recessing the motor helps to shift the rocket's center of gravity forward for more stable flight.)
Tape or glue the upper and lower disks to the inside of the main body tube. (Duct tape sticks better to the rough foam surface on the inside of the main body tube.)
Use clear tape to tape the fins to the outside of the main body tube. (Use tape, not glue, so that the fins can be easily replaced if damaged.)
After the motor mount and fins are fully assembled onto the main body tube, tape another 2-foot section of main body tube to the 2-foot fin section using clear packaging tape.
Cut two 5-inch long wires from a spool of 18-gauge wire. Bend the wires as shown in the figure above. Verify that the loops fit loosely around a 1/2-inch diameter launching rod and verify that the 1-inch straight sections can lie flat against the side of the body tube.
Use clear packaging tape to tape one of the launching lugs to the lower part of the main body tube near the fins. Tape the other launching lug near the top of that same 4-foot section of main body tube.
Cut six long thin foam equilateral triangles 24-inches long and 4-inches wide at the base. Bevel the long edges so that the gaps will be minimized when the triangles are assembled into a cone. Bevel the edges so that the clear plasti-coated side of the foam is outward. Place the six triangles edge to edge on a flat surface with plasti-coated side upward and tape them together with clear packaging tape. Curve the triangle foam assembly into the shape of a cone and tape the final seam.
Cut a 6-inch diameter foam disk and push it into the bottom of the cone to round-out the bottom of the cone.
Cut a 4-inch x 23-inch strip of foam and tape it into the shape of a cylinder as was done to make the main body tubes.
Force this 4-inch long cylinder into the bottom of the nose cone. Tape it to the inside of the cone.
Insert the bottom of the nose cone into the top of the main body tube and verify that it fits loosely.
Cut another 4-inch x 23-inch strip of foam and tape it into the shape of a cylinder as was done to make the main body tubes.
Insert this 4-inch long cylinder 2-inches into the top of the lower main body tube and tape it into place.
The purpose of this coupler is to make it easier to line-up and connect the two 4-foot long sections of main body tube just before launch. The two 4-foot long sections should then be taped together before launch. The two 4-foot long sections can be un-taped and separated after launch.
Cut a 24-inch diameter circle from a plastic garbage bag. Wipe the plastic with a fabric softener towel to eliminate static cling. Use small pieces of duct tape to attach six 30-inch long pieces of kite string uniformly along the perimeter of the circle. Tie the ends of the six pieces of string together with a 2-foot piece of a thicker string. Use clear packaging tape to attach the end of the thicker string to the outside and top of the main body tube.
Tape a 10-foot long streamer to the base of the nose cone. The purpose of the streamer is to slow the descent of the nose cone and to make it possible to calculate the height of the flight. To calculate the height, record the nose cone by digital video as it strikes the ground. Count the number of frames that it takes the nose cone to fall 10 feet. Count the number of frames that it takes the nose cone to fall from the peak of the flight. The ratio of the two counts gives the altitude of the flight.
Slide a G40-4W rocket motor into the Motor mount tube and use a small strip of duct tape to tape it into place. Simply over-lap the tape partly around the base of the motor and partly around the base of the motor mount tube.
Tie a piece of string to the main body tube so that the foam rocket can be suspended horizontally outdoors in the presence of some wind. Verify that the rocket turns naturally by itself and points into the wind. If the rocket turns away from the wind, it needs more weight in the payload area. Purchase some 6-inch tall plastic action figures from a dollar store if weight is needed. Make a 1-foot diameter parachute for each action figure. Tennis balls with or without streamers can also be used for ballast.
