GEMINI STRIKEFIGHTER

by David S. Chen

FANTASY BACKGROUND

The USAF Gemini Strikefighter was commissioned in 2039, the contract being awarded to the new Boeing- Douglas-Martin corporation. The Mercury prototype made its first flight in 2044. The first production example was delivered in 2046 and is represented by this model. The Strikefighter, designated as the F-48 Gemini was a single seat hypersonic air/space superiority fighter. Although not able to operate in true space as can the current Apollo Strikefighter, it was the first fighter capable of operating at the edge of eart h's atmosphere. Powered by two GE-Rolls Royce scramjet engines, the F-48 operated from both terrestrial bases as well as being air launched and recovered from the C-211 carrier aircraft. Early examples were equipped with lower wings that folded into a horizontal position to allow terrestrial operations. Later examples lacked this feature and operated exclusively with C-211 carrier aircraft. These versions relied on an emergency parachute tail-first recovery system should rendevous with a C-211 fail.

CONSTRUCTION

In the spirit of a true kitbash design, all of the materials necessary to build this rocket are found in the Estes Gemini DC kit with addition of a 12" length of 1/8" wooden dowel (I could not find 1/16" dm wooden dowel). The canopy was cut out of cardstock utilizing a pattern taken from the "Designers Resource Pack" published by Apogee Components Inc. (www.apogeerockets.com). Any resemblance of this design to the OOP Estes Strikefighter is purely intentional. I love the Estes Strikefighter design.

ENGINE NACELLE CONSTRUCTION : Cut the balsa fin stock as shown in the photograph such as to create eight 3" long strips of balsa approximately 3/32" square in cross section. As illustrated, cut the leftover finstock into two pieces which are glued together to create one of the two engine struts. The finished struts are 0.5" wide with a tip chord length of 2 5/8" and a root chord length of 3 1/8". As shown in the picture, cut the BT-50 tube into an 8" section and two 2 7/8" sections. Save the remaining portion of the tube (with holes and fin slots) for later. Cut exactly 1" off each of the two BT-20 tubes. Start by gluing the nosecone into the BT-20 tube (orient the tube so that the hole is towards the nosecone/tube junction (NTJ). Next, glue four of the balsa strips around the shortened BT-20 tube starting at the NTJ. Glue one of the 2 7/8" BT-50 sections over the BT-20/strut assembly, position it so that it lies 0.5" back from the NTJ. Glue the engine strut previously assembled to one side of the nacelle paralleling and adjacent to one of the four balsa strips. Make sure the trailing edge is flush with the rear of the BT-50 tube. Set aside and allow the assembly to dry thoroughly.

BODY CONSTRUCTION: Assemble the engine mount as instructed by Estes and glue into one end of the 8" BT-50 tube. Glue the engine tube even with the end of the BT-50 tube. At the other end, tie together the two shock cords and attach using the Estes paper fold method. Assemble the BT-50 nosecone. Attach either one of the 12" chutes or substitute with one 18" chute.

WING CONSTRUCTION: This is the trickiest part. Remove the "fin slot" portion of balsa from each of the four fins with a sharp razor knife. Then, utilizing graph paper or a measuring mat, cut the fin in half using a line that begins at a point that is 2 7/8" from the pointy front end of the fin (as measured along the root chord) and make sure this line is exactly PARALLEL to the trailing edge of the original fin. Sand the cut edge flat and then glue the two sections back together again as illustrated in the photograph. Make sure the posterior fin half is offset by at least 1/8" or more as illustrated to accomodate the transiton between the BT-50 and BT-20 tubing of the engine nacelles (alternately, the posterior half of the wing can be glued first to the BT-20 portion of the completed engine nacelle followed by the anterior half of the wing to the BT-50 portion later). When dry, cut the 12" 1/8" dm wooden dowel into four 3" sections an d glue one section to the tip chord of each of the four wings.

FINAL ASSEMBLY: Glue each of the two engine nacelles to the body by lining up the trailing edge of the engine strut with the back end (engine end) of the 8" BT-50 tube. Make sure the engine struts are parallel to each other and to the ground and that the engine hook is facing the ground. The double glue technique works well here as does setting the whole assembly on a flat surface and leaving it undisturbed until dry. Reinforce the strut to the body with several layers of glue fillets. As illustrated, take the remaining portion of BT-50 tube (with holes and fin slots in it) and make two cuts in it at each end of the fin slots to produce four quarter sections of body tube. Glue each of these body tube sections to the top and bottom of the engine strut straddling the two BT-50 sections. Reinforce with glue fillets. Glue two of the wing assemblies to each engine nacelle at 90 degrees to each other and along the outside half of the nacelle. Each fin root should transect the distance between two of the balsa strips. Some careful sanding of the p osterior half of the root chord may be necessary to produce a flush fit with the engine nacelle (This step can be omitted by gluing the back and forward halves of the wing separately to the completed engine nacelle). Reinforce with glue fillets. Construct the canopy and glue it to the top of the body tube. I placed my canopy such that the back end of the canopy was 1 7/8" from the back end of the body. Cut the launch lug into two pieces and glue them along the bottom of the body 2.25" apart from each other. I offset mine away from the midline so that the launch rod would clear the engine hook. I finished my model with two coats of gray primer followed by two coats of gloss white ("America's Finest" brand sold by Home Depot) paint. Extensive use of adhesive auto detailing stripe and tape was used to finish the model. A roll of ordinary vinyl electricians tape was utilized to create the non-glare black surfce in front of the canopy. The final weight (without engine) is 2.55 ounces with an 18 inch chute installed. The CG with a C6-3 Estes engine loaded is exactly at the forward end of the BT-50 section of the engine nacelles.

FLIGHT REPORT

I flew the strikefighter early in the morning with winds less than 5 mph.  The first flight was on an Estes B6-2 engine with a 18" chute. No problems, flew straight up to around 300 ft and drifted down very slowly.  The second flight was on an Estes C6-3 with a 12" chute. A very straight flight to at least 600 ft.  Unfortunately, it came down on the roadway surrounding the field breaking one wing.   The design is definitely flight stable for engines weighing as much as an Estes C6-3.