[Headline: Al Clark’s Mysterion]
[Subhead: Build your own inexpensive aerobat]
[Author: Al Clark]
[Photos by the author]
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[Tablet and online bonus construction article]
Type: Electric sport model
Wingspan: 47 inches
Wing area: 400 square inches
Weight: 36.7 ounces
Wing loading: 13.2 ounces per square foot
Power system: 200 to 300-watt brushless motor; 36-amp ESC
Propeller: 10 x 6 folding
Battery: Three-cell 2,700 mAh LiPo
Radio: Four-channel; four micro servos
Construction: Balsa and plywood
The Mysterion was designed in response to a request from my brother, Rod, who has flown several of my lightweight park flyer designs. Rod has access to a large, well-manicured grass field and wanted a slightly larger model that would excel at aerobatics and be able to handle the wind.
When designing the Mysterion, I spent much time trying to come up with the best combination of weight, size, aerodynamics, and equipment. I believe the result hits the sweet spot.
I incorporated everything I’ve learned from my previous designs into the Mysterion. The motor, wing, and stabilizer are all on the thrustline as well as the vertical CG. The model balances perfectly on the spinner if stood up vertically on its nose.
The fuselage is thin, has ample side area, and the canopy is placed well forward. This provides good knife-edge flight and good tracking in maneuvers. The wing uses the marvelous Eppler 168 symmetrical airfoil section, which has a wide speed range, is well behaved at slow speeds, and refuses to tip stall while performing excellent snap rolls and spins.
The wing has no dihedral—making inside and outside maneuvers similar. The rudder area is large, providing good control in knife-edge flight and making hammerhead stalls easy.
I incorporated some other features into the design to make flying the model more convenient. The wings are attached using a carbon-fiber tube, music wire pin, and two 10-32 nylon thumbscrews. Easy wing removal makes the Mysterion convenient to transport in any small vehicle.
The propeller is a folding Aeronaut—allowing for grass landings without the worry of breaking expensive propellers. It also has the bonus of cutting the drag when the motor is off, improving the glide.
The BB Model Turbo spinner unit does a great job of introducing cooling air to the motor and battery.
The fuselage top—from the rear edge of the canopy all the way forward to the motor cowling—is removable and uses a magnetic attachment for battery and radio access.
The power system uses reliable and readily available components. The E-flite 480 Brushless 1020 Kv outrunner motor, Castle Creations Thunderbird 36-amp ESC, Thunder Power 3S 2,700 mAh Pro Lite 25C battery, and Aeronaut 10 x 6 folding propeller are a good match to the Mysterion’s airframe and provide excellent performance.
Digital servos are used throughout with JR DS290G on the ailerons and Hitec HS-5065MGs on the rudder and elevator. Short aileron pushrods and stiff carbon-fiber rudder and elevator pushrods result in precise control inputs. A Spektrum AR 6200 receiver provides a solid radio frequency link.
The finished model weighs 36.7 ounces. When using a Thunder Power 3S 2,700 mAh battery, the flight duration is approximately 8 minutes at mostly full throttle.
When it comes to aerobatics, the Mysterion performs better and more precise aerobatics than any of my previous designs. It does exactly what you tell it to do—no more and no less. It rolls as if on a string.
Outside maneuvers look as good and are as easy to perform as inside maneuvers. Snaps and spins, both inside and outside, immediately stop when the sticks are released. Vertical performance is excellent, requiring the throttle to be reduced to perform hammerhead stalls. Knife-edge flight requires only a small amount of down-elevator mix (no more than 5%).
Slow-flight performance is amazing with the Eppler E168 airfoil section. If you didn’t know better, you’d swear the model had a semisymmetrical airfoil when slowly flying. It happily flies around with complete control and refuses to tip stall.
With the power off, the Mysterion has a flat glide because it is clean. It is fun to give it a little altitude, shut off the motor, and perform dead-stick aerobatics.
The Mysterion is a great all-around model. It is relatively inexpensive to build, small enough to fit in any vehicle, large enough to be visible in the sky and handle some wind, and has excellent flight performance. In my more than 40 years of model designing, it is my best effort!
Before you head out to test-fly the aircraft, double-check the balance point, control directions, and look for any warps caused by covering. It’s easier to correct these in the shop than at the field.
The control throws shown on the plans result in a fairly responsive aircraft. If you like controls that are softer, or offer a slower response, you might want to set up dual rates and start with somewhat reduced throws.
I think you’ll find the Mysterion a pleasant model to fly. It is capable of any pattern maneuver as well as sport aerobatics, upright or inverted. Because the power-off glide is excellent, you may need to get accustomed to making your turn to final approach farther out, or lower than you are used to.
I hope you enjoy flying your Mysterion. It is compact enough to keep handy in your car and rates high on the “fun-per-buck” scale.
AMA Plans Service
(800) 435-9262, ext. 507