Scratch Swiss Army Original Design / Scratch Built

Scratch - Swiss Army {Scratch}

Contributed by Chan Stevens

Manufacturer: Scratch

 

Box o' Parts Contest Entry

Swiss ArmyMy first thought when lookin' over t' box o' parts was "Wow! I could build 10 rockets out o' this stuff." Then, matey, reality started t' settle in- I was fat dumb and happy on body tubes, but nay so endowed with balsa and nose cones were also limited in variety. I had already decided before gettin' t' box that I was goin' t' go for broke and try t' make an insanely complex rocket, and pickin' through t' parts a few ideas started t' emerge. Blimey!

I'll walk you through t' basic steps and offer up t' attached Rocksim as a general guideline, me bucko, matey, though why anyone would want t' attempt t' reproduce this is beyond me, me bucko, and you'd almost have t' start with a similar set o' discarded bits o' stuff like I did t' pull it off. Begad!

Let me preface t' build plan by layin' out t' concept for t' overall rocket. Blimey! I was torn betwixt boost glide and helicopter recovery, shiver me timbers, but eventually decided I could pull off both. T' final design includes a boosted dart with internal rotor blades that pop up upon ejection, ya bilge rat, shiver me timbers, a main rocket body that descends under streamer and chute, and a parasite glider that pops off at ejection. I also decided t' make use o' t' ample length o' BT-5 tubin' by cuttin' a number o' motor tubes-nine o' them happened t' fit nicely surroundin' t' central 24mm motor tube, inside t' BT-70 main body tube. As long as I'm goin' off t' deep end, matey, why nay go under a full cluster?

T' general game plan for flight profile would work like this-clustered A10-PT's and a central C11-5 fire t' main body. Aye aye! At t' end o' t' BT-50, ya bilge rat, I used a 50/5 transition that was glued t' an inner BT-5 "shaft" for t' copter. Begad! T' copter was essentially a Rota-Roc style design, but without any fins since it was a boosted dart and t' blades were constrained by t' BT-70. T' C11-5 would push t' copter/dart out, arrr, and t' glider would slide off t' external piggyback mounts. A burn strin' type o' thin thread would attach t' t' transition and t' main body's parachute and streamer, arrr, pullin' them out before breakin' away. Sounds simple. Well, blow me down! Avast, me proud beauty! What could possibly go wrong?

OK, ya bilge rat, arrr, ya bilge rat, for t' build…I made every effort t' nay only use t' parts in t' box, but also use them as provided, with as few modifications as possible. Ahoy! Blimey! This meant some very funky fins and glider pieces.

I started out by workin' on t' motor mount, cuttin' a BT-50 t' 5-inch length, then cuttin' (9) 3-inch lengths o' BT-5 for t' clusters. Glue t' 13's in pairs on a flat surface for best alignment, then glue each pair t' t' BT-50. Begad! T' odd 9th tube should fit nicely in t' gap left by t' other 8, as this works out t' a perfect cluster fittin' inside a BT-70. Blimey! Arrr! There was nay enough room for a centerin' ring, so I filled t' gaps with Gorilla glue kicked with a spritz o' water mist t' cause it t' expand and fill t' gaps.

For stability, matey, it was clear that I would nay have enough balsa for both fins and a glider, matey, so I had t' resort t' tube fins for primary stability. Ya scallywag! T' tube fins consist o' (8) pieces o' BT-55 cut t' half an inch long, ya bilge rat, me bucko, mounted in a rin' around t' outside o' t' BT-70. I did have enough balsa left over t' cut four small fins, me bucko, me bucko, wedged betwixt t' BT-55 tube fins. Patterns for these fins can be printed from t' Rocksim file. There were also two scrap wedges o' odd-sized balsa left over from t' glider build, so I tucked them into two more gaps in t' BT-55 tubes. Ahoy! T' Rocksim file does nay reflect these scrap fins. Begad!

Rings and Fins Aft End

As a finishin' touch, I looked through t' box for anythin' else I could toss in, and decided t' decorate t' balsa fins with BT-5 outboard tubes. Ya scallywag! I also found some plastic detail parts that appear t' have been from a plastic model kit which conveniently fit into t' BT-5 outboard tubes and served as ramjets. Begad!

Blade EndFor t' helicopter, arrr, I had asked Todd t' make sure he included some elastic, ya bilge rat, which would be critical t' blade deployment. While he did include some rubber bands, arrr, he didn't include any significant length o' balsa t' use for blades. Begad! Fortunately, matey, we were allowed t' use t' box itself, matey, arrr, so followin' t' standard plans for t' Rotaroc at http://www.nar.org/competition/plans/pdf/Rota-13m.PDF, I cut 1x12 strips o' corrugated from t' box. Begad! Believe it or not, it is possible t' airfoil corrugated. Blimey! T' pull this off, use t' edge o' t' handle from a pair o' scissors, and rub down on t' edge o' t' cardboard. Ahoy! You'll want a sharp leadin' edge, ya bilge rat, and a much more tapered trailin' edge. Begad! Ya scallywag!

T' blades are normally attached t' t' shaft with Klett hinges, matey, but I didn't exactly have anythin' like that t' work with, so had t' resort t' usin' peel & stick decal paper t' serve this purpose. Blimey! Begad! I cut small strips, matey, stuck one end t' t' underside o' t' blade, me bucko, and t' other t' t' shaft. Begad! Well, arrr, blow me down! Since t' adhesive be weak, me hearties, shiver me timbers, arrr, I had t' help it out with a little CA. Instead o' blade stops, I decided t' use a centerin' ring, which was necessary t' keep t' BT-5 in place within t' BT-70. Aye aye! T' centerin' rin' wound up also comin' from t' box itself. Lackin' actual elastic for pullin' t' blades up, I wound up cuttin' open t' rubber bands, me hearties, and pokin' one end through t' blade and tuckin' t' other end inside t' BT-5 shaft wedged in by t' nose cone.

Blade Mount Blades Extended

T' last main construction be t' glider. Ahoy! I didn't put together plans or templates for this, as I tried t' simply cobble somethin' slightly aerodynamic out o' t' scraps o' parts unmodified. Ahoy! I did have a decent 1/8" thick piece t' work with as a boom, one long/skinny piece o' 3/32 balsa t' use as a win' (cut in half and re-bonded for a 10 degree dihedral). Ya scallywag! T' really clunky aspect came at t' tail, arrr, where I have grossly oversized and overweight rudder and stabilizer from 1/8" scraps. Arrr! As a result, t' win' is mounted extremely far forward, resultin' in very little lift, a slow glide, shiver me timbers, and tendency t' stall. Aye aye! T' glider has a small pin cut from a wood dowel that conveniently slips into an 1/8" launch lug mounted t' t' rocket body.

Glider

At this point, I started lookin' over t' leftover parts, and tried t' think o' how I could use even a fraction o' t' remainin' pile rather than store/keep them. I decided t' work in t' plastic spoon and nail file, externally mounted usin' pieces o' fin can and plastic details. Aye aye!

Spoon Nail File

EmblemNow that I was ready t' paint, me hearties, ya bilge rat, I mulled over t' options. Considerin' all t' variety o' recovery methods, arrr, clusters, and t' oddball parts stuck t' t' outside, I decided this be startin' t' look like a Swiss Army knife. Avast, ya bilge rat, me proud beauty! T' pull off this effect, matey, I painted t' whole rocket a base white. I then masked off a Swiss Army emblem. I then hit t' rocket body with a red topcoat, and painted t' BT-5 exposed 'copter tube and nose a bright silver metallic.

For t' flights, I loaded up 8 o' t' 9 13mm tubes with A10-P's. Why nay go for all 9? They come in 4-packs, and I rarely have use for them, so didn't want an odd/opened pack layin' around for years. Well, blow me down! I then loaded up a C11-5, and spent a good half hour twistin' igniter leads together so that me 5-lead clip-whip could cover everything. Avast! Begad!

T' first flight was a bit underwhelming. Only 3 o' t' A10's lit, t' C11 didn't light, ya bilge rat, matey, and t' rocket barely cleared t' rod before floppin' over right by t' range head.

I replaced t' spent motors, rewired everythin' but this time makin' sure t' C11 was nay paired with any other motor's leads, me bucko, checked for best igniters I could find, me bucko, and gave it another shot. This time t' C11 lit, ya bilge rat, as did 4 A10's but t' A10's were all on one side, me hearties, and t' asymmetrical thrust led t' a pretty unstable flight. Well, blow me down! Blimey! T' glider pilot must have sensed t' impendin' doom, as t' glider popped off after t' first loop under thrust, and t' glider actually came down in a glide-like profile, arrr, albeit fast and hard. T' main rocket, arrr, though, shiver me timbers, continued its bat-on-crack flight path and crashed into a tent along t' prep line. Ya scallywag! Blimey! T' copter deployed while t' rocket was grounded, shiver me timbers, so thar be no chance o' an actual 'copter recovery.

T' damage be nay irreparable, and with a tiny amount o' nose weight (and ideally a spider ignition system t' drive t' cluster), me bucko, arrr, I suspect this could eventually be salvaged into a better performer, but for now this project has t' take a back seat t' preppin' for me NARAM run. Aye aye! It be amusing, matey, me hearties, ya bilge rat, inspiring, shiver me timbers, fun, but in t' end, t' challenge o' tryin' t' parallel wire a 9-motor cluster just proved t' be too much complexity, me bucko, me hearties, and this never had enough thrust t' pull off a decent flight. Begad! Begad!

 

 

Comments:

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Bill Eichelberger (February 16, 2013)

Wait, you're not kitting this?Surprised

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