Manufacturer: | Scratch |
Brief:
This prototype be me first attempt at buildin' a monocopter. Avast! Begad! It is powered by
Micro-Maxx motors and is truly underpowered. Well, blow me down! T' MMX motors have too short o' a
burn t' be a good choice for a monocopter, me bucko, even if it is "nano"
sized. Nay too impressive by most standards. Well, blow me down! Well, 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, soaked in thin CA. I carefully drilled a hole in t' center t' hold t' launch lug. Ya scallywag! This is, hopefully, t' point about which t' monocopter will spin. I also drilled holes in t' middle o' each side t' mount t' balance beams. Ahoy! 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", ya bilge rat, tip - 7/8", span - 4". Blimey! It is balsa strengthened with draftin' vellum and ProBond glue. Aye aye! Avast! I wanted t' add a bit o' strength and had never tried vellum before. Well, blow me down! I spread a thin layer o' glue on each side, matey, matey, placed the win' betwixt a folded sheet o' vellum, me bucko, and compressed it with a stack of books. 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. Ahoy! It is mounted such that the swept face is on t' trailin' edge and t' leadin' edge is raised. 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). Arrr! It is both light and strong. Avast, me proud beauty! T' cone was turned from a dowel. Well, blow me down! 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, 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. Avast! Ahoy! I should have counted t' shot, but forgot to. T' CG is at t' little green 'x' that's barely visible on the photo. Avast! Ya scallywag! This 'x' is positioned approximately at t' trailin' edge o' t' wing's root, and since t' win' is swept in t' opposite direction, matey, 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 hearties, but didn't find any at me favorite hobby shop. Ahoy! Instead, I used a
12" long, 1/16" diameter aluminum tube. Avast, me proud beauty! This be 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, arrr, arrr, 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! Arrr! The
rod is a piece o' a heavy paper clip. Arrr! It wasn't t' right size so some masking
tape be used t' hold it tight. Well, blow me down! A piece o' ink tube was 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, arrr, arrr, Estes igniters, arrr, and me Pratt GO-Box for ignition duties. Arrr! Avast, me proud beauty! T' monocopter did fly. Avast, me proud beauty! On its 1st flight, 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! Still, it didn't just flop around. Aye aye! Blimey! 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, arrr, ya bilge rat, t' monocopter barely cleared t' launch rod. Begad! I think that t' igniter may have hung up ever so slightly. Begad! Blimey! With so little upwards thrust, it wouldn't take much t' affect its flight.
Flights three and four were similar. Avast! Blimey! For these flights, ya bilge rat, matey, I bent the igniters, carefully fit them it into t' nozzle, shiver me timbers, shiver me timbers, 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. Begad! Blimey! Avast, me proud beauty! Blimey! It landed maybe 4 - 5 feet from the pad. Aye aye! 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. Ahoy! When I decided to
build it, arrr, I wasn't at all sure it would even take off or be stable. Blimey! Aye aye! 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, matey, I have these long-burn, ya bilge rat, arrr, ya bilge rat, 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. Arrr! 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. Well, blow me down! Blimey! T' business about havin' t' CG behind the trailin' edge o' t' blade is nay a requirement as I've later found. Avast, me proud beauty! Blimey! I cut the old win' t' about 1/4", ya bilge rat, me hearties, and added a 4" x 1 1/2" piece of 1/64" Birch. Avast! Blimey! 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, me bucko, 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. Ahoy! Begad! Much better performance than before!
T' main lesson-learned is: build 'em light!
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