Goals

• Have a small-field capable rocket ready to fly

• Try new things:

  • A modern, tiny altimeter

    FlightSketch Mini

  • An ejection baffle instead of recovery wadding

    https://www.apogeerockets.com/Building_Supplies/Parachutes_Recovery_Equipment/Ejection_Baffles/BT-50_24mm_Ejection_Charge_Baffle

• Practice construction techniques:

  • Tube cutting
  • Fin alignment

• Practice finishing techniques:

  • Tube spiral filling

    Filling Tube Spirals - Revisited

  • Wood grain filling (CWF 2.5:1)

    Balsa Grain Fillers and Added Weight

    Carpenter's Wood Filler Mix Ratios

  • Nose-body transition smoothing

  • Spray painting

Planning

I am going to assemble this model differently than from what is specified in the instructions

• [x] Motor mount prep
  • [x] Measure and cut slot for engine hook in motor mount tube
  • [x] Treat fore and aft ends of the motor mount tube with thin CA
  • [x] "Clip and flip" the engine hook
  • [x] Glue engine block in place
  • [x] Determine fore centering ring offset so it will be at the top of the fin slot when the bottom of the motor mount tube is flush with the aft end of the airframe, mark engine tube accordingly
  • [x] Glue fore centering ring to motor mount tube
  • [x] Notch the aft centering ring to accommodate the motor mount hook
• [x] Airframe prep
  • [x] Treat aft opening of the lower airframe and precut fin slots with thin CA
  • [x] Clean up fin slots with hobby knife and small files
  • [x] Treat fore opening of the upper airframe with thin CA
  • [x] Assemble ejection baffle
  • [x] Determine desired size of altimeter payload bay
  • [x] Fit-test lower airframe, upper airframe, ejection baffle, and recovery system to ensure there is sufficient space
  • [x] Tie shock chord to fore eye ring in the ejection baffle and apply wood glue to the knot
  • [x] Glue together lower airframe and upper airframe using the ejection baffle as a coupler
  • [x] Using a fingernail or a plastic spoon, crease the top, glassine layer of the cardboard tube along the seams (there are two, one is shallower than the other)
  • [x] Use a sharp pencil to mark the both spiral lines in the airframe
  • [x] Fill tube grooves
    • [x] Use a table knife to apply thinned wood filler in the tube grooves
    • [x] Use a plastic razor blade as a putty knife to sculpt and scrape away the excess filler on the tube grooves
    • [x] Let dry completely
    • [x] Sand airframe smooth using a 400 grit sanding block
    • [x] Clean out any residual wood filler from fin slots
• [x] Payload bay modification
  • [x] Wash the nose cone with soap and warm water to remove any residual mold release
  • [x] Trim away lower nose cone shoulder
  • [x] Cut two sections from the upper airframe for the "switch band" and the payload shroud
  • [x] Treat all cut ends of the upper airfame with thin CA and touch-up sand
  • [x] Use epoxy clay to cement the loose-fitting nose cone to the fore end of the payload shroud
    • [x] Try Rocketpoxy since the epoxy clay failed during sanding
  • [x] Smooth the transition from the nose cone to the payload shroud (this may take several applications of epoxy clay and/or wood filler)
  • [x] Assemble fore coupler bulkhead
  • [x] Glue switch band one caliber from the base of the fore coupler bulkhead assembly
  • [x] Test fit the payload shroud on the fore couple bulkhead assembly; apply thin CA and sand as necessary
  • [x] Drill pressure equalization holes in switch band and treat with thin CA
• [x] Launch lug installation
  • [x] Using a sharp pencil, mark launch lug alignment line 180° from one of the precut fin slots
  • [x] Glue launch lug to airframe assembly
  • [x] Fillet each side of the launch lug with wood glue
• [ ] Fin & motor assembly

  • [x] Stack-sand all sides of fins except the fin root (that happens later)

  • [x] Bevel fin edges proportionally to the fin width, round in front, tapered in back

  • [x] Apply thinned wood filler to fin surfaces

    • [x] Let fin surfaces dry completely and sand smooth; repeat if wood grain is still prominent

  • [x] Apply glue to the inside of the airframe just above the precut fin slots

    • [x] Install the motor mount assembly with the engine hook in line with the launch lug and with the rear centering ring NOT glued in place, floating half way into the aft end of the airframe assembly
    • [x] Verify that aft centering ring can be removed
    • [x] Let glue on fore centering ring dry completely

  • [x] Test fit fins and motor mount assembly, stack sand fin roots to make sure they are free from filler and shorten (or lengthen) the fin tabs if necessary

  • [x] With the rear centering ring dry fit halfway into the aft end of the airframe, "double glue" the fins in place using the ESTES fin alignment guide to ensure they are perpendicular to the airframe

    Glue for rockets that will dry quickly or tips to make it dry

  • [x] Let dry completely

  • [ ] Remove rear centering ring and set aside

  • [ ] Fillet fin roots on the motor mount tube with slightly-thinned Titebond molding and trim wood glue applied via cue tip or fine-tiped glue applicator

    • [ ] Suspend the rocket horizontally with one fin facing downward
    • [ ] Apply glue to the inside roots of the two topmost fins
    • [ ] Let dry before rotating the rocket so the next fin faces downward
    • [ ] Repeat until all fin roots are filleted

  • [x] Glue rear centering ring in place with wood glue

  • [ ] Fillet fin roots on the airframe tube with slightly-thinned Titebond molding and trim wood glue applied via a mixing stick

    • [ ] Suspend the rocket horizontally with one fin facing downward
    • [ ] Apply glue to the roots of the two topmost fins and smooth the bead of glue along the airframe with your finger
    • [ ] Let dry before rotating the rocket so the next fin faces downward
    • [ ] Repeat until all fin roots are filleted
• [ ] Finishing
  • [ ] Apply coat of sandable filler primer to assembled rocket
  • [ ] Use fine sandpaper to smooth over any imperfections. Pay close attention to the nose-payload shroud joint and to the fin surfaces
    • [ ] Apply another coat of primer and re-sand if necessary
  • [ ] With the rocket assembled but with slight gaps showing around the switch band
    • [ ] Clean model with a rag dipped in isopropyl alcohol
    • [ ] Apply an even, base coat of paint
    • [ ] Let cure completely, at least 24 hours
  • [ ] Accent color
    • [ ] Mask off any secondary areas, like a single fin to help indicate roll, with painter's tape; cover larger areas of the model with blank copy paper or ink-free newsprint
    • [ ] Lightly sand exposed area with 600+ grit sandpaper
    • [ ] Remove any dust with a rag dipped in isopropyl alcohol
    • [ ] Apply an even coat of paint on the accent areas
    • [ ] Remove masking tape when paint has dried to a very tacky state
    • [ ] Clean up any over-spray or gaps in the masking tape with a cue tip dipped in isopropyl alcohol
  • [ ] Apply any decals or stickers as desired
  • [ ] Clear coat the entire model

Notes & Decisions

• The payload shroud does not have to be very long as the FlightSketch Mini can be comfortably mounted inside the forward coupler.

  • Payload shroud: 1"
  • Switch band: ¼"

• An Apogee 12" nylon chute can be packed into 2" of BT-50

  Apogee Components - 12

• The Estes BT-50 cutting guide does not fit over a LOC I airframe

  Estes Tube Cutting Guides Set

  • My improvised pipe-clamp cutting guide didn't work very well

    New photo by Rocket Lab Delta

  • A Kuhn Tube Cutter would be better

    Kuhn Tube Cutter

  • You can also use a hobby knife and aluminum angle

    https://www.youtube.com/watch?v=VKpUCnRntSA

  • Or a piece of paper and a hobby knife

    https://www.youtube.com/watch?v=5vpvAgkAVPY

• FixIt Epoxy clay: