Description:
This is an approximate 2X scale-up replica of the Estes Nike Arrow, with coloring and dimensions approximating the model kit rather than the real rocket. The model has a 24mm engine mount, but can fly on as small an engine as a B6-4 with a removable engine adapter. The parachute comes out the top attaching to the nose cone, rather than separating at the transition like the original. This model is 34" tall, and weighs about 3.4oz. without an engine. The fin size and length are 2:1, but the diameter is slightly less than 2:1 due to unavailability of exact 2:1 diameter body tubes.

Parts:

• one 18" BT-50
• one 12" BT-50
• one 10" BT-55
• one 4" white plastic NC-50(the white one in the Estes Designer's Special is perfect)
• three 55/50 heavy duty centering rings
• one 50/20 heavy duty centering ring
• one BT-50 body tube coupler
• engine hook
• shock cord
• clay
• 3/16" launch lug
• balsa fin stock
• Fin Pattern

Assembly:
1. Glue one of the 55/50 centering rings part of the way into the top of the BT-55 tube. This will be later used as a lip for mounting the transition shroud. An optional Kevlar® shock cord could be attached to the forward centering ring, and later threaded through into the BT-50 body tube under the transition shroud between step 3 and 4.

2. Glue the 50/20 centering ring into the 12" BT-50 tube 2 1/2" from the rear. This will serve as the thrust ring. Glue the engine hook into the tube with the front of the hook 2 1/2" from the rear, and just behind the thrust ring. Glue the remaining two larger centering rings onto the 12" BT-50 engine mount tube 1" and 2 1/2" from the rear.

3. Glue the 12" engine mount tube into the 10" BT-55 tube so that the rear of the engine mount tube is flush with the BT-55 tube. Note that the front of the engine mount tube will protrude out of the front centering ring and BT-55 tube about 2".

4. Glue the BT-50 tube coupler halfway into the front of the engine mount tube. Glue the 18" BT-50 tube into the other half of the tube coupler. Check for straightness before the glue sets.

5. Choose thickness and strength of fin material as desired. I used 1/16" balsa for the upper fins and 3/32" balsa for the lower fins. Measure the dimensions on the fins of an Estes Nike Arrow, and double the dimensions, cutting out the fins with grain pattern following the leading edge of the 4 smaller front fins, and perpendicular to the root edge on the 4 rear fins. Make 2 paper transitions for a 2 1/4" long BT-55/BT-50 transition. The dimensions of the shroud should be {small radius: 6.311"; large radius: 8.568"; angle: 27.84 degrees with some extra for overlap}. (Note: These calculational results were obtained using a shroud calc. program on Rob Blaske's home page)

6. Glue first one paper transition shroud, and after it is dry, a second one. Be liberal with the carpenter's wood glue, as it is an excellent strength enhancer after it is dry. After the transition shroud hardens, the glue will shrink and ripple. Sand down any edges and ridges, then fill in the ripples with undiluted Elmer's Fill & Finish, sanding to desired shape and smoothness.

7. Make a BT-55 fin marking guide for 4 fins and a launch lug, and mark the body tube all the way to the front of the BT-55 tube. Make a 4 fin marking guide for a BT-50 tube, and mark the tube just forward of the transition with the front fins in line with the rear fins.

8. Put pin holes in the body tubes and the root edges of the fins for increased bonding strength, and glue on the fins.

9. Finish to the desired smoothness with Elmers F&F.;

10. Prime and sand. Paint the rear tube and transition shroud gloss white. For a better looking orange, all areas that will be orange should have one coat of white. Mask the section that will remain white, and paint the rear fin section as well as the front fins and the entire 18" of the BT-50 tube gloss orange. Do not remove the masking over the white section, as it will be easier to mask for the chrome layer. Mask and paint the middle section of the forward tube chrome, leaving the front 4" orange. It was just more masking work than I wanted to do to paint the transition shroud silver, so I left it white.

11. If a Kevlar® shock cord was not used, glue in a traditional paper shock cord mount with a 3 foot shock cord.

12. Put enough clay in the nose cone to keep the CG forward or in the middle of the front fins with the largest engine intended to be used. Prime and paint the nose cone if required. Add decalcomania as desired.

13. Attach shock cord to the nose cone, attach a 14" parachute, and prep for launch.

Flight:
Depending on final weight, the maiden flight should be on the smallest engine advisable, and work your way up. For my 3.4oz. model, I first used a B6-4, which flew straight and stable to about 150 ft. It then flew to about 300ft on a C6-5. I haven't tried a D engine yet, as I need a bigger field.

11/99 -
1. It flies great and straight on a D12-5 to about 1000ft. However, since I did not do through-the-wall fin mounting, and I had forgotten to do a glue fillet on one fin before doing an Elmer's Fill-N-Finish fillet, one lower fin ripped off during flight on a D. The Fill-N-Finish does not work like glue! There was enough other fins to keep the rocket stable. I recommend cutting slots for the lower fins and modifying the fins to be through-the-wall.
2. I realized after publishing that I forgot to mention launch lugs in the instructions. Use 3/16" lugs and glue them on just before finishing, one down by the engine and one just below the transition.