A three-stage design for high-altitude payload flights


1. Mark the two (2) booster tubes and the sustainer tube for three (2) fins. Mark the sustainer for the two launch lugs. Draw lines through these marks on the boosters for the full length of the tubes. Draw lines through these lines on the sustainer for a distance of 5" from the rear of the tube for the fins, and for the full length of the tube for the lugs. Mark the lug line at 5" from each end of the tube, and draw lines completely around the tube at these marks.

2. Cut out the three fin sets and the launch lug standoffs from BFS-40 sheet stock. Flat-sand the surfaces to remove any raised grain. Do not round any of the edges at this time, but carefully square up the root edges.

3. Assemble two standard 24mm motor mounts, and one long 24mm motor mount. Insert the standard mounts into the two boosters, aligning the rear of the motor tubes with the rear of the booster tubes. The engine hooks should stand proud of the body tubes. Glue in place using slightly thinned glue, applied with a brush or a glue applicator, at the joint between the centering rings and the body tubes. Set these aside to dry. Insert the long motor mount into the rear of the sustainer tube, aligning the rear of the motor tube with the rear of the body tube. Glue in place in the same manner as with the boosters above, and set aside to dry.

4. Mark the two couplers 3/4" from one end, and draw a line completely around the coupler at this point. Apply glue into the inside-front ends of the two boosters, and insert the couplers into the tubes until the 3/4" line is just hidden (there should be 3/4" of the coupler exposed at the front of the tube). Allow to dry.

5. Thread the screw eye into the base of the transition, remove carefully, and force glue into the hole. Reinsert the screw eye and set aside to dry. Assemble two 18" parachutes, attaching the shrouds to swivels.

6. Attach the fins to their respective body tubes using Stine's double-glue method. Use the profile view of the model to determine the correct fin for each tube, and the correct orientation of the fin. Hold the fins in place with clamps, weights, and jigs as required until the glue dries.

7. Attach the launch lugs to the standoffs, allow to dry, and attach these to the sustainer tube. The lower lug is mounted on the front side of the lower 5" line. The upper lug is mounted on the front side of the upper 5" line. Allow to dry completely.

8. Attach the shock chord to the inside-front of the sustainer tube using a folded-paper mount. The mount should be at least 2" down from the edge. When dry, attach the other end of the chord to a swivel. Attach one parachute to the shock chord by their swivels. Attach the other parachute to the screw eye. Slip the transition into one end of the clear payload tube, and the nose cone into the other end.

9. Round the leading and tip edges of the sustainer fins, the tip edges of the second booster fins, and the tip and trailing edges of the first booster fins. Do not round the remaining edges.

10. Prime, sand, and finish paint the model in a color scheme of your choice. When the paint has dried completely, spray a clear gloss coat over the model and allow this to dry. If you wish to apply decals, do so at this time and allow to dry. Spray a final gloss coat to seal and protect the decals, and allow this to dry for a couple of days.

11. GO FLY!