recommended motors:
B6-4 B8-5 C5-3 C6-3 C6-5
D, E, F, and shorter motors are conceivable, but require larger-calibre motor/recovery pods.

3 - round 8-ounce baby bottles (I used Evenflo Classic nurser system)
1 - nipple (I used Evenflo Classic Sensitive Response)
1 - nipple retainer ring (for above bottles)
1 - sealing disc (for above bottles)
1 - 140 mm of BT-20 body tube
1 - 18mm-dia, 6mm thick nose block
1 - motor clip for 18mm motor
1 - motor block for 18mm motor
1 - 120mm x 120mm x 1.5mm thickness paper board, or game card stock, or 3/32" balsa wood
1 - 3mm (1/8") x 70cm (27.5") elastic shock cord
1 - small snap-swivel
1 - 23cm (9") of Kevlar® twine, crochet twine, or parachute shroud line
1 - 13mm x 100mm strip of kraft paper or masking tape
Some plastic cement (I used Testor's)
Some yellow or white glue.
1 - 46cm (18") octagonal plastic parachute "kit"
        This parachute kit can be put together with:
          1 - large black or orange garbage bag
          4 - 36" length of crochet twine
         16 - hole reinforcement rings for 3-ring binder paper
          1 - single-hole paper punch 

Boddomuk construction can be split into three phases: airframe construction, pod construction, and final assembly.

NOTE: For the following instructions,
"Cement" implies the use plastic cement (such as Testor's Plastic Cement) or any other adhesive that will effectively bond the flexible, non-porous plastic that the baby bottles are made of.
"Glue" implies the use of yellow glue (alphatic resin, or "carpenter's glue") or any adhesive that will effectively bond cardboard, balsa wood, and paper.

1. Airframe Construction

1.1  Cut the bottom 6 mm off of the three baby bottles. Use a band saw or a razor saw for this step. The bottles are too slippery, too tough, and too thick to do this safely with a hobby knife.

1.2  Select which bottle will be the body. Make six tube fins from the other two bottles by cutting the bottles into 37 mm lengths. Again, use a band saw or a razor saw.

1.3  Cement two tube fins together, side-by-side with the ends even. Set the assembly aside, resting on the sides of the tubes fins rather than on the ends. Wait for the cement to dry. Repeat with the two remaining pairs of tube fins.

1.4  Cement a pair of tube fins to the body bottle, extending 10 mm beyond the bottom cut edge of the body bottle. Cement another pair to the body bottle and to the mounted tube fin pair. Cement the final pair to the body bottle and to the mounted tube fin pairs. All tube fins must extend 10 mm beyond the bottom of the bottom of the body bottle. Wait until the cement is dry.

1.5  Wrap an adhesive label around the straw. Cement the label-wrapped straw to the body bottle, aligned with a triangular gap formed by two tube fins and the body bottle. This should provide enough clearance for easy insertion of a launch rod between two tube fins.

2. Pod Construction

2.1  Cut centering rings from 1.5 mm thick paper board or 3/32" balsa wood. Each centering ring must have an inner diameter of 18.7 mm and an outer diameter of 52 mm. Sand the outside edge of the rings for a tight fit inside the body bottle.

2.2  Punch or cut four 1/4" diameter holes, evenly spaced around the BT-20 tube, centered 21 mm from one end of the tube. This end of the tube is referred-to as the "top" end in following steps.

2.3  Glue the 5 mm (1/4") thick balsa block into the "top" of the BT-20 tube so that it is flush with the "top" edge of the tube. What is meant by a "nose block" is a balsa cylinder whose diameter is the inner diameter of the BT-20 tube. It can be made by turning it on a mini-lathe or by cutting an 18 mm circle out of a 1/4" thick sheet of balsa wood.

2.4  Glue a motor block 60 mm (2 1/2") up the "bottom" end of the BT-20 tube as follows:
     a)  Spread a bead of glue, 2" inside the "bottom" end of the BT-20 tube.
     b)  Insert the motor block into the "bottom" end of the BT-20 tube.
     c)  Push an expended 18mm motor casing, into the "bottom" end of the BT-20 tube until 5 mm (1/4") of the casing sticks out of the tube. Immediately withdraw the expended motor casing.

2.5  Make a 3 mm (1/8") mark, 65 mm from the "bottom" end of the BT-20 tube. Cut a 5 mm (1/8") slit along this mark. Insert one end of a motor clip into this slit.

2.6  Secure the inserted end of the motor clip to the BT-20 tube by applying glue to one side of a 13 mm x 100 mm strip of kraft paper, then wrapping the strip over the inserted end of the motor clip. A weaker alternative would be to use a 13 mm x 100 mm strip of masking tape in place of the kraft paper. The main purpose of this strip is to ensure that no exhaust gases enter the parachute compartment, so masking tape should be fine.

2.7  Mount a centering ring 42 mm from the "top" end of the BT-20 tube. Secure the ring with a bead of yellow or white glue.

2.8  Mount a centering ring 28 mm from the "top" end of the BT-20 tube. Secure the ring with a bead of yellow or white glue.

2.9  Mount a centering ring 17 mm from the "bottom" end of the BT-20 tube. Secure the ring with a bead of yellow or white glue. This ring will squeeze the motor clip against the BT-20 tube. 

3. Final Assembly

3.1  Sand the centering rings of the pod for a snug fit into the body bottle of the airframe.

3.2  Assemble the parachute.

3.3  Tie the center of the 70 cm elastic shock cord to the middle of the pod's BT-20 tube, using a square (or "full") knot.

3.4  Tie one end of the shock cord to one end of a 23 cm length of twine (crochet, Kevlar®, or shroud line).

3.5  Tie the free end of the twine to one of the airframe's tube fins.

3.6  Tie the free end of the shock cord to the ring-end of the snap-swivel.

3.7  Tie the parachute to the snap-end of the snap-swivel.

3.8  Assemble the nose as follows:
     a)  Place a sealing disc on the mouth of the body bottle, with the flat side against the mouth.
     b)  Place a nipple on the sealing disc.
     c)  Place a nipple retaining ring over the nipple and sealing disc so that its threads engage the threads of the airframe's body bottle. Screw the ring firmly in place.

Flight Preparation

1.  Fold the parachute as usual, but press the folded parachute into a flattened rectangular shape.

2.  Wrap the parachute shroud lines loosely around the parachute.

3.  Press the parachute onto the pod, between the middle and bottom centering rings of the pod.

4.  Slide the pod partially into the airframe body, so that the parachute is held in place by the body.

5.  Loosely fold up the shock cord and slip it into the same compartment the contains the parachute. The twine part of the shock cord should also be slipped into this compartment so that when the pod is completely slid into the airframe body, it is held tight by the bottom centering ring of the pod.

6.  Slide the pod completely into the airframe body, so that the "top" of the pod is against the sealing disc at the mouth of the airframe body bottle.

7.  Prepare the Boddomuk for flight as you would any other rocket, ie. install the engine, slip the Boddomuk onto a launch rod, install the igniter, and connect the igniter to the launch controller. 

Session 1
Date: Saturday, August 10, 2002 Time: 3:30pm CST
Location: Lakeview Park, Saskatoon, Saskatchewan, Canada
Temperature: 27 degrees Celsius (81 degrees Fahrenheit)
Wind: near calm

Loaded with a B6-4, the Boddomuk's take-off was slow and majestic (especially for a baby bottle :). It reached apogee within easy viewing range, and showed us a beautiful pod and 'chute deployment, with no apparent tangles. Under a 40-cm 'chute, the Boddomuk's descent was moderately fast, landing on a hard-packed gravel walkway 20 metres northwest of the launch pad. For a recovery crew game that I have in mind for this design, a 45-cm 'chute would probably give an ideal descent rate. Anyhow, the Boddomuk was recovered with no damage. The body was internally coated with dust from the motor's deployment charge, but became perfectly clear again when cleaned out with a baby bottle brush and some soapy water. The topmost centering ring of the pod was stained a little where deployment exhaust gases exited the pod's tube.