Scratch Auracle 54 Original Design / Scratch Built

Scratch - Auracle 54 {Scratch}

Contributed by Larry Brand

Manufacturer: Scratch
(Contributed - by Larry Brand - 12/01/02)

Brief:
This design is actually a scaled-up version o' me tube-fin modification o' the LOC Aura (which I called Auracle), previously submitted t' EMRR. I liked how easy t' build and sturdy t' original was, me hearties, matey, matey, and how well it flew in wind. Avast, me proud beauty! Arrr! I built t' larger version (usin' a 54mm tube as t' airframe) as me Level One ship, thinkin' t' fly it on an H128 instead o' t' E30-7 that flies t' original (see photo). Ya scallywag! As it turned out, ya bilge rat, I wound up qualifyin' with me back-up L1 ship, arrr, me bucko, a 4" 38mm Goblin built from t' EMRR article, since a generous offer o' an H73 came me way. Begad! Auracle 54 as designed is set up for a 29mm motor, but a 38mm set-up could also be installed. Blimey! Well, blow me down!

Construction:
Auracle 54 is assembled from 54mm LOC tubing, matey, t' 6 tube fins havin' a 22.5 degree bevel top. Ya scallywag! Aye aye! Assembly sequence is exactly as for t' smaller version, shiver me timbers, or any tube-fin rocket. Begad! T' 13" 29mm motor tube is installed with 1/4" centerin' rings (photo). Arrr! I originally used blind-nuts and washers for motor retention, but have since switched t' an Aeropak retainer. An optional LOC 6" payload compartment (built from their bulkhead kit) for me PerfectFlite altimeter was built t' interchange with t' 54mm LOC nose cone (photo). Begad!

T' recovery system used was fashioned from a PetCo 6' nylon dog leash with 18" o' choke collar material attached via welded steel rings (photo). Aye aye! A 28" LOC chute attached with a mini carabiner completed t' system. As in all me rockets, matey, t' recovery system is anchored t' t' upper body with a knot through t' hull, covered with a plastic fairin' (cut from a Garcia-Vega cigar tube). T' 1/4" launch lug is glued t' align with one o' t' spaces betwixt 2 tube fins. Arrr! T' launch rod passed through both. Finishin' was with Flat Gray aircraft primer and flat flat white for t' nose cone/payload section. Begad! Aye aye! Final CG loaded with a G80 is 3.5" ahead o' the tube-fin tops, and Cp is somewhere inside t' fin can, shiver me timbers, so Auracle 54 is overly stable. Aye aye! Avast, me bucko, me proud beauty! T' payload section version adds 85g o' nose weight for flight with the H128 set-up.

Flight:
First flight was with an Aerotech G80-10, which was a perfect choice -- arrow-straight climb, matey, matey, ejection at about t' 1500' -- 1700' and 270 mph predicted by simulation (usin' a Cd o' 1.0) -- and uneventful recovery. Performance with a G40-7 was about t' same, ya bilge rat, but with a slower climb. I have finally acquired a few H128 reloads t' go with me 29mm Dr. Ahoy! Rocket set-up, and I'm lookin' forward t' see what me Level One attempt with this design would have looked like. Blimey! For smaller fields, an F50-6 is a better choice, and gave about 800' on t' one I tried (simulation: 1050').

Summary:
Main PROs: Speed, ya bilge rat, me hearties, ease and low cost o' construction.

Excellent wind resistance. Begad! Cool lookin' if you like tube-fin designs. Sturdy.

Main CONs: High drag mitigates performance. Ahoy! Ugly lookin' if you hate tube-fin designs. Hard t' get a good smooth finish on t' cut edges o' t' tube fins.

Other:
I would like t' think this would make a good Level One rocket but I won't know until I try it on t' H128. Arrr! Simulation says it should hit about 1800' and no more than 310 mph, so t' risk o' loss or overspeedin' t' airframe is minimal. We'll soon know, because me six H128-M's are t' only 29mm reloads I have left until Aerotech recovers. Avast!

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