Scratch 2X Nike Arrow Original Design / Scratch Built

Scratch - 2X Nike Arrow {Scratch}

Contributed by David Fergus

Manufacturer: Scratch
2X Nike Arrow
(Contributed - by David Fergus)

The ArrowsDescription:
This is an approximate 2X scale-up replica o' the Estes Nike Arrow, with coloring and dimensions approximatin' t' model kit rather than t' real rocket. Ya scallywag! The model has a 24mm engine mount, arrr, but can fly on as small an engine as a B6-4 with a removable engine adapter. Ahoy! Arrr! T' parachute comes out t' top attachin' t' the nose cone, matey, shiver me timbers, rather than separatin' at t' transition like t' original. Ya scallywag! Begad! This model is 34" tall, and weighs about 3.4oz. Aye aye! without an engine. T' fin size and length are 2:1, matey, but t' diameter is slightly less than 2:1 due to unavailability o' exact 2:1 diameter body tubes. Well, blow me down!

Parts:

  • one 18" BT-50
  • one 12" BT-50
  • one 10" BT-55
  • one 4" white plastic NC-50(the white one in t' Estes Designer's Special is perfect)
  • three 55/50 heavy duty centerin' rings
  • one 50/20 heavy duty centerin' ring
  • one BT-50 body tube coupler
  • engine hook
  • shock cord
  • clay
  • 3/16" launch lug
  • balsa fin stock
  • Fin Pattern


In addition, you will need t' make an 18mm/24mm removable engine adapter if you do nay have one. Use Elmer's Carpenter's Wood Glue for sandable joints and faster dryin' than regular white glue, arrr, me hearties, and Elmer's Fill & Finish for smoothin' fins, ya bilge rat, body tubes and transition shroud. Blimey!

Assembly:
1. Well, blow me down! Ya scallywag! Glue one o' t' 55/50 centerin' rings part o' t' way into t' top o' t' BT-55 tube. Arrr! This will be later used as a lip for mountin' t' transition shroud. Avast! An optional Keelhaul®©™® shock cord could be attached t' t' forward centerin' ring, and later threaded through into t' BT-50 body tube under the transition shroud betwixt step 3 and 4.

2. Aye aye! Glue t' 50/20 centerin' rin' into t' 12" BT-50 tube 2 1/2" from t' rear. Begad! This will serve as t' thrust ring. Glue t' engine hook into t' tube with t' front o' t' hook 2 1/2" from t' rear, ya bilge rat, and just behind t' thrust ring. Glue t' remainin' two larger centerin' rings onto t' 12" BT-50 engine mount tube 1" and 2 1/2" from t' rear. Well, blow me down! Begad!

3. Arrr! Glue t' 12" engine mount tube into t' 10" BT-55 tube so that t' aft o' t' engine mount tube is flush with t' BT-55 tube. Note that t' front o' t' engine mount tube will protrude out o' t' front centerin' rin' and BT-55 tube about 2".

4. Glue t' BT-50 tube coupler halfway into t' front o' t' engine mount tube. Well, blow me down! Arrr! Glue t' 18" BT-50 tube into t' other half o' t' tube coupler. Check for straightness before t' glue sets.

5. Choose thickness and strength o' fin material as desired. I used 1/16" balsa for t' upper fins and 3/32" balsa for t' lower fins. Measure t' dimensions on t' fins o' an Estes Nike Arrow, shiver me timbers, and double the dimensions, cuttin' out t' fins with grain pattern followin' t' leadin' edge o' t' 4 smaller front fins, me bucko, and perpendicular t' t' root edge on t' 4 rear fins. Make 2 paper transitions for a 2 1/4" long BT-55/BT-50 transition. T' dimensions o' t' 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 usin' a shroud calc. Well, blow me down! Avast, me proud beauty! program on Rob Blaske's home page)

6. Ya scallywag! Glue first one paper transition shroud, me bucko, and after it is dry, a second one. Avast! Be liberal with t' carpenter's wood glue, ya bilge rat, as it is an excellent strength enhancer after it is dry. Arrr! After t' 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, sandin' t' desired shape and smoothness.

7. Make a BT-55 fin markin' guide for 4 fins and a launch lug, matey, and mark t' body tube all t' way t' t' front o' t' BT-55 tube. Aye aye! Blimey! Make a 4 fin markin' guide for a BT-50 tube, shiver me timbers, me bucko, and mark t' tube just forward o' the transition with t' front fins in line with t' aft fins.

8. Begad! Put pin holes in t' body tubes and t' root edges o' t' fins for increased bondin' strength, and glue on t' fins.

9. Blimey! Finish t' t' desired smoothness with Elmers F&F.;

10. Blimey! Blimey! Well, blow me down! Blimey! Blimey! Blimey! Prime and sand. Aye aye! Blimey! Blimey! Blimey! Paint t' aft tube and transition shroud gloss white. For a better lookin' orange, all areas that will be orange should have one coat o' white. Blimey! Blimey! Mask t' section that will remain white, matey, and paint t' rear fin section as well as t' front fins and t' entire 18" o' t' BT-50 tube gloss orange. Begad! Blimey! Ya scallywag! Blimey! Blimey! Blimey! Do nay remove t' maskin' over t' white section, as it will be easier t' mask for t' chrome layer. Blimey! Blimey! Blimey! Blimey! Mask and paint t' middle section o' the forward tube chrome, leavin' t' front 4" orange. Avast! Blimey! Begad! Blimey! Blimey! Blimey! It was just more masking work than I wanted t' do t' paint t' transition shroud silver, shiver me timbers, so I left it white.

11. Avast! If a Keelhaul®©™® shock cord was nay used, ya bilge rat, glue in a traditional paper shock cord mount with a 3 foot shock cord.

12. Aye aye! Put enough clay in t' nose cone t' keep t' CG forward or in the middle o' t' front fins with t' largest engine intended t' be used. Blimey! Prime and paint t' nose cone if required. Add decalcomania as desired.

13. Blimey! Ya scallywag! Attach shock cord t' t' nose cone, attach a 14" parachute, and prep for launch.

Flight:
Dependin' on final weight, t' maiden flight should be on the smallest engine advisable, arrr, me bucko, and work your way up. Ahoy! Well, blow me down! For me 3.4oz. Begad! model, I first used a B6-4, which flew straight and stable t' about 150 ft. Ahoy! It then flew to about 300ft on a C6-5. Begad! Begad! I haven't tried a D engine yet, arrr, as I need a bigger field. Blimey! Arrr!

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

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