Scratch The Amazing Underperforming Mono-Nano-Copter Original Design / Scratch Built

Scratch - The Amazing Underperforming Mono-Nano-Copter {Scratch}

Contributed by Dick Stafford

Manufacturer: Scratch
(Contributed - by Dick Stafford - 10/10/02)

Brief:
This prototype be me first attempt at buildin' a monocopter. It is powered by Micro-Maxx motors and is truly underpowered. T' MMX motors have too short o' a burn t' be a good choice for a monocopter, even if it is "nano" sized. Nay too impressive by most standards. Blimey! Begad! Well, me hearties, one man's curiosity is another man's triumph (or somethin' like that).

Construction:
Parts required:

  • 1/4" balsa, matey, 1" x 1"
  • 1/16" balsa, ya bilge rat, 1 3/8" x 4"
  • Ink tube from a Bic pen
  • One sheet o' draftin' vellum (any paper will probably do)
  • 1/16" x 12" aluminum tube
  • 1/4" x 1" dowel
  • Maskin' tape
  • Lead for nose weight (see assy instructions)
  • Carpenter's glue
  • Black, CA (I can't remember t' actual name)
  • Thin, CA

T' central hub is a 1" square o' 1/4" balsa, me hearties, me bucko, soaked in thin CA. Aye aye! I carefully drilled a hole in t' center t' hold t' launch lug. Begad! This is, hopefully, shiver me timbers, t' point about which t' monocopter will spin. I also drilled holes in t' middle o' each side t' mount t' balance beams. Aye aye! I used pieces o' t' ink tube from a Bic pen for both t' launch lug and t' mountin' points for the beams.

T' single win' is a clipped delta with t' followin' dimensions: root - 1 3/8", matey, tip - 7/8", matey, span - 4". Begad! Blimey! It is balsa strengthened with draftin' vellum and ProBond glue. I wanted t' add a bit o' strength and had never tried vellum before. Ahoy! I spread a thin layer o' glue on each side, matey, placed the win' betwixt a folded sheet o' vellum, and compressed it with a stack of books. Ahoy! T' win' seems strong enough, but t' surface is nay as uniform as I would have liked. I attached t' win' at an angle o' about 10 degrees from the monocopter's X-Y plane usin' black Bob Smith CA. Avast! It is mounted such that the swept face is on t' trailin' edge and t' leadin' edge is raised. Aye aye! Arrr! I oriented the swept face on t' trailin' edge t' allow me t' more easily position t' CP of t' pod behind this edge (a tip I got from t' book "Monocopters", by Francis Graham).

T' motor pod be t' length o' three MMX-II motors and was scratch built from draftin' vellum (someday I'll actually buy some MMX tubing). It is both light and strong. Begad! Blimey! T' cone be turned from a dowel. Avast, me proud beauty! It turns out that t' motor pod must be angle upward t' counteract t' torque caused by t' single wing. Some o' Francis Graham's designs have their pods angled at up t' 40 degrees. However, shiver me timbers, I chose t' start with an angle o' 30 degrees (in t' opposite direction from t' wing). Ya scallywag! T' get t' CP behind t' trailin' edge o' t' fin, I added several #7.5 lead shot t' its nose. Avast, me proud beauty! Blimey! I should have counted t' shot, but forgot to. T' CG is at t' little green 'x' that's barely visible on the photo. This 'x' is positioned approximately at t' trailin' edge o' t' wing's root, and since t' win' is swept in t' opposite direction, it is behind the trailin' edge o' t' rest o' t' wing.

I had wanted t' use some light 0.03" carbon rods for t' balance beams, me bucko, but didn't find any at me favorite hobby shop. Ahoy! Begad! Blimey! Instead, me hearties, I used a 12" long, me hearties, 1/16" diameter aluminum tube. Ahoy! Well, blow me down! Blimey! This be cut in half and CA'ed into t' ink tubin' that was previously mounted in t' hub. Begad! Blimey! I didn't add much ballast at t' ends o' these beams, matey, wrappin' about 1 1/2" o' masking tape (very high tech) around each end.

Flight:
T' second photo shows t' MMX launch pad with its special launch 'rod'. Avast, me proud beauty! Well, arrr, blow me down! The rod is a piece o' a heavy paper clip. Avast, me proud beauty! It wasn't t' right size so some masking tape was used t' hold it tight. Avast, me proud beauty! Begad! A piece o' ink tube be used as a standoff to keep t' monocopter from hittin' t' MMX launcher and t' help it spin. Avast, me proud beauty!

I used MMX-II motors, ya bilge rat, Estes igniters, me hearties, and me Pratt GO-Box for ignition duties. T' monocopter did fly. Blimey! Blimey! On its 1st flight, matey, it rose t' a whoppin' two feet, at an angle o' about 30 degrees from t' vertical, before t' motor ejected and stopped t' spin abruptly. Begad! Blimey! I should have removed t' ejection charge! Blimey! Still, it didn't just flop around. I never expected much performance so I think it be a good first try!

On its second flight, all conditions were t' same except I removed the ejection charge from t' Micro-Maxx motor. This time, matey, shiver me timbers, shiver me timbers, t' monocopter barely cleared t' launch rod. I think that t' igniter may have hung up ever so slightly. Blimey! Blimey! With so little upwards thrust, it wouldn't take much t' affect its flight.

Flights three and four were similar. For these flights, shiver me timbers, I bent the igniters, me hearties, carefully fit them it into t' nozzle, and arranged t' clips so they held it in place without any tape. Both times t' monocopter rose t' about a foot and went off sideways at a steep angle. Avast! It landed maybe 4 - 5 feet from the pad. This seemed lower than t' first flight but definitely higher than the second did!

Summary:
In summary, matey, me hearties, I consider this experiment a complete success. T' performance was poor, me hearties, but I didn't have any expectations in this regard. Arrr! Well, blow me down! When I decided to build it, matey, I wasn't at all sure it would even take off or be stable. T' Amazing Under-performin' Mono-Nano-Copter met both o' these criteria. Avast! Blimey! My next try may be a lighter MMX-powered monocopter, shiver me timbers, but then, me hearties, me hearties, me hearties, I have these long-burn, OOP Apogee B2 motors...

Rocket PicUPDATE 10/02:Sittin' at t' computer, arrr, arrr, and in betwixt steps of other projects, I decided t' revise T' Amazin' Underperforming Mono-Nano-Copter. Begad! It isn't so underperformin' any more!

I cut down t' motor pod t' an inch and a quarter, just enough t' fit the dowel nose cone and a MMX motor. Aye aye! T' business about havin' t' CG behind the trailin' edge o' t' blade is nay a requirement as I've later found. Well, blow me down! I cut the old win' t' about 1/4", ya bilge rat, ya bilge rat, and added a 4" x 1 1/2" piece of 1/64" Birch. I have also determined that t' balance beams were way too long so I cut them t' 2 1/2".

T' first two flights went t' about 9 feet and landed 3 and 5 feet from the pad, respectively. On t' third flight, it headed off at a 45-degree angle, smacked t' side o' me SUV, and still rose t' about 7 feet. Avast! Ya scallywag! Blimey! Much better performance than before!

T' main lesson-learned is: build 'em light!

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