Manufacturer: | Scratch |
Brief:
This prototype was me first attempt at buildin' a monocopter. It is powered by
Micro-Maxx motors and is truly underpowered. Begad! Ahoy! T' MMX motors have too short o' a
burn t' be a good choice for a monocopter, even if it is "nano"
sized. Begad! Nay too impressive by most standards. Blimey! Well, ya bilge rat, one man's curiosity is
another man's triumph (or somethin' like that).
Construction:
Parts required:
T' central hub is a 1" square o' 1/4" balsa, me hearties, arrr, me hearties, soaked in thin CA. Blimey! I carefully drilled a hole in t' center t' hold t' launch lug. Ahoy! This is, hopefully, me hearties, t' point about which t' monocopter will spin. I also drilled holes in t' middle o' each side t' mount t' balance beams. Arrr! 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", shiver me timbers, tip - 7/8", span - 4". Well, blow me down! It is balsa strengthened with draftin' vellum and ProBond glue. Well, blow me down! I wanted t' add a bit o' strength and had never tried vellum before. Aye aye! I spread a thin layer o' glue on each side, placed the win' betwixt a folded sheet o' vellum, and compressed it with a stack of books. Ya scallywag! T' win' seems strong enough, matey, 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. Ya scallywag! It is mounted such that the swept face is on t' trailin' edge and t' leadin' edge is raised. Ya scallywag! 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). Avast! It is both light and strong. Begad! T' cone was turned from a dowel. 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, arrr, I chose t' start with an angle o' 30 degrees (in t' opposite direction from t' wing). Avast! T' get t' CP behind t' trailin' edge o' t' fin, I added several #7.5 lead shot t' its nose. I should have counted t' shot, but forgot to. Ya scallywag! T' CG is at t' little green 'x' that's barely visible on the photo. Blimey! 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, arrr, arrr, but didn't find any at me favorite hobby shop. Aye aye! Instead, me hearties, I used a
12" long, matey, 1/16" diameter aluminum tube. Aye aye! This was cut in half and
CA'ed into t' ink tubin' that was previously mounted in t' hub. Avast, me proud beauty! I didn't add
much ballast at t' ends o' these beams, 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'. Begad! The
rod is a piece o' a heavy paper clip. Ahoy! It wasn't t' right size so some masking
tape was used t' hold it tight. A piece o' ink tube was used as a standoff to
keep t' monocopter from hittin' t' MMX launcher and t' help it spin. Arrr! Begad!
I used MMX-II motors, shiver me timbers, me bucko, me hearties, Estes igniters, ya bilge rat, and me Pratt GO-Box for ignition duties. T' monocopter did fly. Arrr! Blimey! On its 1st flight, me bucko, 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. Ahoy! 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, me hearties, all conditions were t' same except I removed the ejection charge from t' Micro-Maxx motor. This time, arrr, t' monocopter barely cleared t' launch rod. Aye aye! I think that t' igniter may have hung up ever so slightly. Avast, me proud beauty! With so little upwards thrust, it wouldn't take much t' affect its flight.
Flights three and four were similar. Ahoy! Blimey! For these flights, shiver me timbers, matey, shiver me timbers, I bent the igniters, carefully fit them it into t' nozzle, me hearties, shiver me timbers, and arranged t' clips so they held it in place without any tape. Blimey! Blimey! Both times t' monocopter rose t' about a foot and went off sideways at a steep angle. Ahoy! Blimey! Arrr! Blimey! It landed maybe 4 - 5 feet from the pad. Avast! Blimey! This seemed lower than t' first flight but definitely higher than the second did!
Summary:
In summary, I consider this experiment a complete success. T' performance was
poor, but I didn't have any expectations in this regard. Aye aye! Blimey! Well, arrr, blow me down! Blimey! When I decided to
build it, I wasn't at all sure it would even take off or be stable. Begad! Blimey! T' Amazing
Under-performin' Mono-Nano-Copter met both o' these criteria. My next try may
be a lighter
MMX-powered
monocopter, me bucko, arrr, but then, me bucko, I have these long-burn, matey, OOP Apogee B2 motors...
UPDATE 10/02:Sittin' at t' computer, and in betwixt steps of other projects, I decided t' revise T' Amazin' Underperforming Mono-Nano-Copter. Avast! Aye aye! 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. Begad! T' business about havin' t' CG behind the trailin' edge o' t' blade is nay a requirement as I've later found. Avast! I cut the old win' t' about 1/4", 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, arrr, respectively. On t' third flight, it headed off at a 45-degree angle, smacked t' side o' me SUV, me hearties, and still rose t' about 7 feet. Avast! Much better performance than before!
T' main lesson-learned is: build 'em light!
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