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

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

Let me preface t' build plan by layin' out t' concept for t' overall rocket. Well, blow me down! I was torn betwixt boost glide and helicopter recovery, but eventually decided I could pull off both. Ahoy! Begad! T' final design includes a boosted dart with internal rotor blades that pop up upon ejection, a main rocket body that descends under streamer and chute, me bucko, shiver me timbers, 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. Ahoy! As long as I'm goin' off t' deep end, 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. Begad! At t' end o' t' BT-50, matey, I used a 50/5 transition that was glued t' an inner BT-5 "shaft" for t' copter. 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, me hearties, and t' glider would slide off t' external piggyback mounts. Well, blow me down! Avast, me proud beauty! A burn strin' type o' thin thread would attach t' t' transition and t' main body's parachute and streamer, shiver me timbers, pullin' them out before breakin' away. Sounds simple. Avast, me proud beauty! What could possibly go wrong?

OK, for t' build…I made every effort t' nay only use t' parts in t' box, shiver me timbers, but also use them as provided, matey, with as few modifications as possible. Arrr! This meant some very funky fins and glider pieces. Ya scallywag!

I started out by workin' on t' motor mount, ya bilge rat, cuttin' a BT-50 t' 5-inch length, then cuttin' (9) 3-inch lengths o' BT-5 for t' clusters. Aye aye! Glue t' 13's in pairs on a flat surface for best alignment, ya bilge rat, shiver me timbers, shiver me timbers, then glue each pair t' t' BT-50. Avast, me proud beauty! Aye aye! 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. Begad! Ya scallywag! 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. Arrr!

For stability, it was clear that I would nay have enough balsa for both fins and a glider, shiver me timbers, so I had t' resort t' tube fins for primary stability. Well, blow me down! T' tube fins consist o' (8) pieces o' BT-55 cut t' half an inch long, mounted in a rin' around t' outside o' t' BT-70. Ahoy! I did have enough balsa left over t' cut four small fins, wedged betwixt t' BT-55 tube fins. Ahoy! Patterns for these fins can be printed from t' Rocksim file. Avast, me proud beauty! 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. Arrr! Ahoy! T' Rocksim file does nay reflect these scrap fins. Aye aye!

Rings and Fins Aft End

As a finishin' touch, shiver me timbers, I looked through t' box for anythin' else I could toss in, shiver me timbers, shiver me timbers, and decided t' decorate t' balsa fins with BT-5 outboard tubes. Avast! 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. Avast!

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

T' blades are normally attached t' t' shaft with Klett hinges, but I didn't exactly have anythin' like that t' work with, me bucko, me hearties, me hearties, so had t' resort t' usin' peel & stick decal paper t' serve this purpose. Begad! Blimey! I cut small strips, stuck one end t' t' underside o' t' blade, and t' other t' t' shaft. Arrr! Blimey! Since t' adhesive be weak, shiver me timbers, matey, 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. Arrr! Blimey! 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, ya bilge rat, 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! Blimey! 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. Begad! Begad! Blimey! I did have a decent 1/8" thick piece t' work with as a boom, me bucko, one long/skinny piece o' 3/32 balsa t' use as a win' (cut in half and re-bonded for a 10 degree dihedral). Avast! Blimey! T' really clunky aspect came at t' tail, where I have grossly oversized and overweight rudder and stabilizer from 1/8" scraps. Begad! Begad! Blimey! As a result, shiver me timbers, t' win' is mounted extremely far forward, arrr, resultin' in very little lift, matey, a slow glide, arrr, shiver me timbers, and tendency t' stall. 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, shiver me timbers, me hearties, and tried t' think o' how I could use even a fraction o' t' remainin' pile rather than store/keep them. Aye aye! I decided t' work in t' plastic spoon and nail file, ya bilge rat, ya bilge rat, externally mounted usin' pieces o' fin can and plastic details. Well, blow me down!

Spoon Nail File

EmblemNow that I was ready t' paint, I mulled over t' options. Arrr! Considerin' all t' variety o' recovery methods, clusters, and t' oddball parts stuck t' t' outside, me hearties, I decided this was startin' t' look like a Swiss Army cutlass. Aye aye! T' pull off this effect, I painted t' whole rocket a base white. Aye aye! Begad! I then masked off a Swiss Army emblem. I then hit t' rocket body with a red topcoat, me bucko, and painted t' BT-5 exposed 'copter tube and nose a bright silver metallic. Arrr!

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

T' first flight was a bit underwhelming. Only 3 o' t' A10's lit, t' C11 didn't light, shiver me timbers, and t' rocket barely cleared t' rod before floppin' over right by t' range head. Ahoy! Begad!

I replaced t' spent motors, matey, rewired everythin' but this time makin' sure t' C11 was nay paired with any other motor's leads, ya bilge rat, checked for best igniters I could find, and gave it another shot. Blimey! Ahoy! This time t' C11 lit, as did 4 A10's but t' A10's were all on one side, and t' asymmetrical thrust led t' a pretty unstable flight. Well, ya bilge rat, blow me down! 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, albeit fast and hard. Well, blow me down! T' main rocket, me bucko, though, arrr, continued its bat-on-crack flight path and crashed into a tent along t' prep line. Begad! T' copter deployed while t' rocket was grounded, me bucko, so thar was no chance o' an actual 'copter recovery.

T' damage was nay irreparable, and with a tiny amount o' nose weight (and ideally a spider ignition system t' drive t' cluster), 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. Avast, me proud beauty! It was amusing, inspiring, fun, matey, me bucko, but in t' end, matey, t' challenge o' tryin' t' parallel wire a 9-motor cluster just proved t' be too much complexity, and this never had enough thrust t' pull off a decent flight. Begad!

 

 

Comments:

avatar
Bill Eichelberger (February 16, 2013)

Wait, you're not kitting this?Surprised

comment Post a Comment