Manufacturer: | Scratch |
Brief:
This prototype be me first attempt at buildin' a monocopter. It is powered by
Micro-Maxx motors and is truly underpowered. 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. Avast, me proud beauty! Well, me bucko, 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, arrr, soaked in thin CA. Ya scallywag! I carefully drilled a hole in t' center t' hold t' launch lug. Blimey! This is, hopefully, ya bilge rat, t' point about which t' monocopter will spin. Begad! Arrr! I also drilled holes in t' middle o' each side t' mount t' balance beams. Well, blow me down! 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", tip - 7/8", matey, span - 4". Begad! It is balsa strengthened with draftin' vellum and ProBond glue. I wanted t' add a bit o' strength and had never tried vellum before. Begad! 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. T' win' seems strong enough, me hearties, ya bilge rat, but t' surface is nay as uniform as I would have liked. Aye aye! I attached t' win' at an angle o' about 10 degrees from the monocopter's X-Y plane usin' black Bob Smith CA. Blimey! 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). Ya scallywag! Well, blow me down! It is both light and strong. Arrr! Avast! T' cone be 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, me hearties, I chose t' start with an angle o' 30 degrees (in t' opposite direction from t' wing). T' get t' CP behind t' trailin' edge o' t' fin, shiver me timbers, me hearties, I added several #7.5 lead shot t' its nose. Well, shiver me timbers, blow me down! I should have counted t' shot, ya bilge rat, but forgot to. Well, me bucko, blow me down! T' CG is at t' little green 'x' that's barely visible on the photo. Aye aye! Arrr! 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, ya bilge rat, me bucko, but didn't find any at me favorite hobby shop. Instead, I used a
12" long, ya bilge rat, 1/16" diameter aluminum tube. Avast, me proud beauty! Avast! Blimey! This was cut in half and
CA'ed into t' ink tubin' that be previously mounted in t' hub. I didn't add
much ballast at t' ends o' these beams, ya bilge rat, 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'. Arrr! Blimey! Avast, me proud beauty! Blimey! The
rod is a piece o' a heavy paper clip. It wasn't t' right size so some masking
tape was used t' hold it tight. Well, blow me down! Blimey! Arrr! Blimey! 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! Blimey!
I used MMX-II motors, Estes igniters, arrr, me bucko, ya bilge rat, and me Pratt GO-Box for ignition duties. Aye aye! Begad! T' monocopter did fly. On its 1st flight, it rose t' a whoppin' two feet, at an angle o' about 30 degrees from t' vertical, matey, before t' motor ejected and stopped t' spin abruptly. I should have removed t' ejection charge! Still, ya bilge rat, it didn't just flop around. I never expected much performance so I think it was a good first try!
On its second flight, all conditions were t' same except I removed the ejection charge from t' Micro-Maxx motor. Blimey! This time, ya bilge rat, t' monocopter barely cleared t' launch rod. Begad! I think that t' igniter may have hung up ever so slightly. Well, blow me down! Aye aye! With so little upwards thrust, arrr, it wouldn't take much t' affect its flight.
Flights three and four were similar. For these flights, me bucko, me hearties, I bent the igniters, arrr, carefully fit them it into t' nozzle, and arranged t' clips so they held it in place without any tape. Avast! Well, blow me down! Both times t' monocopter rose t' about a foot and went off sideways at a steep angle. Ahoy! It landed maybe 4 - 5 feet from the pad. Avast, me proud beauty! This seemed lower than t' first flight but definitely higher than the second did!
Summary:
In summary, arrr, arrr, I consider this experiment a complete success. T' performance was
poor, shiver me timbers, but I didn't have any expectations in this regard. Avast, me proud beauty! When I decided to
build it, me hearties, I wasn't at all sure it would even take off or be stable. Begad! T' Amazing
Under-performin' Mono-Nano-Copter met both o' these criteria. Begad! My next try may
be a lighter
MMX-powered
monocopter, but then, I have these long-burn, 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. 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. T' business about havin' t' CG behind the trailin' edge o' t' blade is nay a requirement as I've later found. I cut the old win' t' about 1/4", and added a 4" x 1 1/2" piece of 1/64" Birch. Arrr! 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, me bucko, respectively. Well, blow me down! On t' third flight, arrr, it headed off at a 45-degree angle, smacked t' side o' me SUV, and still rose t' about 7 feet. Ahoy! Much better performance than before!
T' main lesson-learned is: build 'em light!
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