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, reality started t' settle in- I be fat dumb and happy on body tubes, but nay so endowed with balsa and nose cones were also limited in variety. Begad! I had already decided before gettin' t' box that I be goin' t' go for broke and try t' make an insanely complex rocket, me bucko, matey, shiver me timbers, and pickin' through t' parts a few ideas started t' emerge. Ya scallywag!

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, matey, and you'd almost have t' start with a similar set o' discarded bits o' stuff like I did t' pull it off.

Let me preface t' build plan by layin' out t' concept for t' overall rocket. Aye aye! I be torn betwixt boost glide and helicopter recovery, but eventually decided I could pull off both. Begad! Ahoy! T' final design includes a boosted dart with internal rotor blades that pop up upon ejection, arrr, a main rocket body that descends under streamer and chute, me hearties, and a parasite glider that pops off at ejection. Ahoy! 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. Arrr! As long as I'm goin' off t' deep end, arrr, 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. Well, blow me down! Blimey! At t' end o' t' BT-50, arrr, I used a 50/5 transition that be glued t' an inner BT-5 "shaft" for t' copter. Avast! T' copter be essentially a Rota-Roc style design, arrr, but without any fins since it was a boosted dart and t' blades were constrained by t' BT-70. Arrr! T' C11-5 would push t' copter/dart out, and t' glider would slide off t' external piggyback mounts. Blimey! 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. Arrr! Aye aye! Sounds simple. What could possibly go wrong?

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

I started out by workin' on t' motor mount, me hearties, me hearties, cuttin' a BT-50 t' 5-inch length, then cuttin' (9) 3-inch lengths o' BT-5 for t' clusters. Ahoy! Blimey! Glue t' 13's in pairs on a flat surface for best alignment, then glue each pair t' t' BT-50. 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! Blimey! Begad! Blimey! 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. Blimey! Blimey!

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

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. 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. Ahoy! Well, blow me down!

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

T' blades are normally attached t' t' shaft with Klett hinges, shiver me timbers, matey, but I didn't exactly have anythin' like that t' work with, ya bilge rat, me hearties, so had t' resort t' usin' peel & stick decal paper t' serve this purpose. Blimey! I cut small strips, shiver me timbers, stuck one end t' t' underside o' t' blade, and t' other t' t' shaft. Since t' adhesive was weak, matey, arrr, I had t' help it out with a little CA. Begad! Instead o' blade stops, arrr, me bucko, I decided t' use a centerin' ring, matey, which was necessary t' keep t' BT-5 in place within t' BT-70. Ahoy! Avast, me proud beauty! T' centerin' rin' wound up also comin' from t' box itself. Aye aye! 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. 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. Avast, me proud beauty! 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). Well, blow me down! Aye aye! T' really clunky aspect came at t' tail, where I have grossly oversized and overweight rudder and stabilizer from 1/8" scraps. As a result, arrr, t' win' is mounted extremely far forward, resultin' in very little lift, arrr, a slow glide, and tendency t' stall. Ya scallywag! 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. Ya scallywag! Blimey! I decided t' work in t' plastic spoon and nail file, me hearties, externally mounted usin' pieces o' fin can and plastic details. Begad!

Spoon Nail File

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

For t' flights, me hearties, 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, ya bilge rat, ya bilge rat, so didn't want an odd/opened pack layin' around for years. Avast, me proud beauty! Avast! Blimey! I then loaded up a C11-5, me bucko, shiver me timbers, and spent a good half hour twistin' igniter leads together so that me 5-lead clip-whip could cover everything. Arrr! Blimey!

T' first flight be a bit underwhelming. Only 3 o' t' A10's lit, me bucko, me bucko, t' C11 didn't light, 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 be nay paired with any other motor's leads, me hearties, checked for best igniters I could find, and gave it another shot. This time t' C11 lit, as did 4 A10's but t' A10's were all on one side, arrr, and t' asymmetrical thrust led t' a pretty unstable flight. Blimey! T' glider pilot must have sensed t' impendin' doom, me bucko, ya bilge rat, matey, as t' glider popped off after t' first loop under thrust, and t' glider actually came down in a glide-like profile, shiver me timbers, arrr, albeit fast and hard. Aye aye! T' main rocket, though, shiver me timbers, continued its bat-on-crack flight path and crashed into a tent along t' prep line. T' copter deployed while t' rocket was grounded, so thar be no chance o' an actual 'copter recovery.

T' damage be nay irreparable, me bucko, 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, ya bilge rat, arrr, but for now this project has t' take a back seat t' preppin' for me NARAM run. Arrr! It was amusing, inspiring, arrr, fun, but in t' end, me bucko, 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. Avast!

 

 

Comments:

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Bill Eichelberger (February 16, 2013)

Wait, you're not kitting this?Surprised

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