Starfighter

Modeled by: Ellison Lenz (Age 17)

This design based on a kit bash of the Estes DC Gemini. It has a single 18mm engine mount and a combination of tube and flat fins. It is build using Titebond and 5 minute epoxy. What make this design unique is the duel BT 20 tubes that make the from fusalage and twin BT 20 nose cones.

The build started by gluing the two BT 20 body tube together, side by side. Card stock was cut and used to cover the gap between the two tubes. Next the BT 50 tube was notched one inch to fit centered over the ends of the BT 20 body tubes and glued on. One of the BT 20 nose cones was cut in half lengthwise and sanded to fit into the end of the BT 20 and along the BT 50 and glued on. This completes the main body structure.

The engine tube was glued together with the engine clip, two BT50/20 centering rings and an engine thrust ring. While this was drying, the remaining two BT 20 nose cones were glued together, side by side while inserted in the front ends of the BT 20 tubes. These were then streamlined with card stock like the BT 20 had been. The engine tube was then glued into the main body tube, leaving ¼" sticking out of the rear. Glue soaked tissue was used to fill any remaining gaps between the body tubes.

The BT 50 nose cone was also cut in half lengthwise, sanded to fit the body tubes and glued to the top of the main body, end to end with the joint even with the end of the BT 20 tubes.

The tube fins were then attached to the rear of the rocket evenly spaced around the BT 50 tube (120% apart) and the balsa fins attach over then and to the main body tube. The leading edges were then reinforced with the 1/8" bamboo skewer. The main launch lug was attached to the bottom of the rear of the rocket at one of the tube fin joints and the remaining launch lug pieces were used to detail the rocket as gun mounts with two on the bottom center line just in front of the BT 50 and the larger two on both side just behind the nosecones. Pieces of the ¼" balsa was cut and sanded to streamline and support the rear of these gun mounts.

The shock cord was attached Estes style into one of the BT 20 tubes and also to one of the BT 20 nose cones and the parachute was assembled and attached to the other nose cone. Recovery wading is needed in both BT 20 tubes, one to protect the shock cord and the other to protect the parachute.

All of the joints were then buffeted using titebond glue on paper to paper and wood to paper joints and epoxy on plastic to wood and plastic to paper joints. As a final step, thin CA was applied to the card stock pieces to strengthen them.

The CP/CG stability was verified with a swing test, no nose weight was required. The model was launch at one of the MASA January launches in White Bear, Minnesota - Good Flight.

Parts

• BT 50 Body Tube 6.0"
• BT 20 Body Tubes 2 * 5.0"
• BT 20 Engine Tube 2.75"
• BT 50 Tube Fins 3 * 3.0"
• BT50/20 Centering Rings 2
• Estes Engine Clip 1
• BT20/5 Thrust Ring 1
• BT20Y Nose Cones 3 or 4 * 2.75 Ogive
• BT50 Nose Cone (Cockpit) 2 5/8 Ogive
• 100 lb Kevlar String 10"
• 1/8" Launch Lug 2 3/8" long
• 1/8" Launch Lugs (guns) 2 * 1"
• ¼" Launch Lugs (guns) 2 * 1"
• 1/8" Balsa As Required
• ¼" Balsa (gun mounts) As Required
• 1/8" Bamboo Skewer As Required
• 1/8" Elastic Shockcord 24"
• Parachute or Streamer As Desired
• ¾" Card Stock 16" As Required