Shrox Industria DC-Sam Plan

Shrox Industria - DC-Sam

Contributed by Chan Stevens

Construction Rating: starstarstarstarstar_border
Flight Rating: starstarstarstarstar_border
Overall Rating: starstarstarstarstar_border
Manufacturer: Shrox Industria

Shrox DC SamBrief:
Part o' t' Shrox/Apogee Global Defense Series, this 2-stage missile is designed t' protect our nation's capitol from hostile aircraft, missiles, ya bilge rat, (or alien craft?). Blimey! It's small, arrr, arrr, light, and incredibly fast when flyin' on both stages, me bucko, arrr, though works quite well on a single stage also.

Construction:Parts List

  • 24mm nose cone
  • BT-50 body tube 9.75" long (sustainer)
  • BT-50 body tube 2.75" long (booster)
  • BT-50 tube coupler
  • (2) 18mm motor tubes (2.75")
  • 13-18mm centerin' rin' (engine block)
  • (4) 18-24mm centerin' rings
  • 1/8" launch lug
  • 3/32 balsa or basswood fin stock
  • 2 x 36 Mylar streamer
  • 36" Keelhaul®©™ shock cord (plan calls for 300#, I used 110#)
  • Clay nose weight (about 0.5 oz)
  • Decal sheet (can be downloaded from E-zine archives #83)

After downloadin' t' Rocksim file (and lookin' at t' pictures in t' E-zine), you're on your own figurin' out how t' build this, me hearties, since thar are no instructions (RockSim is also available here on EMRR). Ahoy! Fortunately, arrr, that's nay too dauntin' a task, as t' design is comparable t' most skill level 2 modrocs. Arrr! I started with t' motor mount assemblies, gluin' t' engine block in one tube, me hearties, ya bilge rat, and mountin' centerin' rings on each 18mm tube. Begad! Aye aye! Since this is a 2-stage, me hearties, joined with a BT50 coupler, matey, pay careful attention t' t' location o' t' centerin' rings in Rocksim so that t' two stages will join well. Begad! After t' motor mounts have set, me hearties, they are glued into t' body tubes along with t' tube coupler.

I printed out t' fin templates from Rocksim, shiver me timbers, arrr, me hearties, and cut them from basswood, ya bilge rat, figurin' t' thrust from a 2-stage might put a bit o' strain on balsa (though FinsSim, arrr, matey, an add-on t' Rocksim, ya bilge rat, indicates this would be no problem). Tack t' fins on at 120 degree angles (I've found t' Estes tube markin' tool set t' be t' best $8 I've spent on this hobby), matey, and apply fillets o' wood glue. Avast! Ahoy! Install t' shock cord/streamer, shiver me timbers, me hearties, and t' rocket is nearly finished.

Note: t' clay nose weight - it was nay referenced on t' parts list in t' E-zine, me bucko, though is included in t' Rocksim file. Avast, me hearties, me proud beauty! Without this nose weight, shiver me timbers, this rocket is probably nay stable, and this could be an easily overlooked detail.

Finishing:
Two coats o' primer and two coats o' glossy white, ya bilge rat, followed by a coat o' light gray on t' booster, arrr, ya bilge rat, and you're ready for decals. Blimey! I printed t' decals with me inkjet on Avery clear decal stock, though this is a fairly opaque finish, and I'd recommend findin' a better printer source, possibly goin' t' t' expense o' water-slide decals. Also, dependin' on your field conditions, you might consider paintin' t' booster a bright red or orange, shiver me timbers, t' stand out more in taller grass.

Construction Rating: 4 out o' 5

Flight:
There were no recommended motors in t' E-zine or Rocksim file, so I tried a few combinations in Rocksim and decided t' go with a C6-0 booster and A8-3 sustainer (I would have preferred a B boost, but didn't have any at t' time). Field conditions were favorable for high altitude - 85 degrees and 5 mph winds, and our club uses a field large enough t' handle most HPR motors.

I used t' full 0.75 ounce o' nose weight called out in Rocksim, arrr, me bucko, and t' rocket was a bit over-stable, anglin' into t' light winds. Begad! Arrr! Blimey! Both stages lit, me bucko, and ejection on a 3-second delay be at least a couple seconds early, even factorin' in t' weathercock. Blimey! Blimey! T' nose cone separated, ya bilge rat, though this was from a weak shock cord mount, nay due t' t' fact that I went with 110# Keelhaul®©™® instead o' 300#.

I recovered all components, shiver me timbers, me hearties, and after some minor repairs and removal o' about 0.25 ounces o' clay, flew again on C6-0/B6-6. Begad! Ya scallywag! T' flight was much better, screamin' out o' sight on a straight trajectory. Well, blow me down! Apogee was beyond me eyesight, though t' 6-second delay be a much better choice.

Recovery:
Pro's

  • Terrific altitude from t' 2-stage design

Con's

  • A little tricky t' get t' right amount o' nose weight

Flight Rating: 4 out o' 5

Summary:
Overall, me hearties, this is a very nice 2-stage design, especially given t' price (free download). Avast! Aye aye! If you're new t' Rocksim, ya bilge rat, it's also a good design t' work with t' learn t' choose t' proper motor(s) and fine-tune t' CG/CP relationship.

Overall Rating: 4 out o' 5

Flights

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