Michael DeRosa Master of Engineering Final Project

1. Exploration of Airfoil Sections to Determine the Optimal Airfoil for Remote Controlled Pylon Racing Michael DeRosa Master of Engineering Final Project

2. What is Remote Control Pylon Racing? • 3 Recognized Classes: • 424 class: 120 mph Quickie 500 • 426 class: 150 mph Quickie 500 • Focus of Project • 422 class: 190-200 mph • Size of 426 Class airplanes determined by Academy of Model Aeronautics rules • Minimum weight of 3.75 lbs. • 500 square inches of wing area • 50-52 inches of win span • Aspect ratio of 5 • Wing thickness to chord ratio is 0.11875 • Powered by methanol fueled Jett 0.40 cubic inch engine displacement engine • Goal is to fly around a 2 mile course in shortest amount of time • Course is marked by 3 pylons: 2 are 100 ft. apart and 1 is 475 ft. from the centerline of the twin pylons • 4 planes race at a time • 10 laps • Penalties for turning inside of pylons Typical Q-500 pylon racer Viper 500 by Great Planes Q-500 pylon race

3. Optimal Airfoil For Pylon Racing Not Explored • No official studies on pylon racing airfoils completed to date • Entering into a 50 ft. radius turn at 150 mi/hr creates 30 G’s of force acting on the plane • Wing must pitch up to increase lift coefficient at expense of increased drag • Increased drag can slow down a plane by 15-20 mi/hr in turns • Even a 5 mph speed gain in turns is significant. • Widely used airfoil for pylon racing is NACA 66-012 symmetrical laminar flow airfoil • Drag penalties in turning flight translates to significant loss of speeds in turns • Conversely, a cambered airfoil such a Clark Y will retain more speed in turns due to higher lift coefficients at much lower drag increase; higher L/D than NACA 66-012 airfoil • Trade off is lower maximum speed in straight ways due to higher form drag • Modern airfoils created by Martin Hepperle, Selig, and Eppler are useful for drag minimization in pylon racing • Wings with 2 different airfoil types have not been considered and/or assessed NACA 66-012 Laminar Airfoil Typically Used for Pylon Racing High Lift Clark Y Airfoil Not Typically Used for Pylon Racing

4. Project Utilized XFOIL Airfoil Development Program • Developed by Dr. Mark Drela of MIT • Uses solutions of viscous and invisicid differential equations to solve airfoil shape for: • Lift coefficient for given angles of attack • Drag polars to determine drag coefficient for a given lift coefficient • Moment coefficient for given angles of attack • Velocity ratio with free stream velocity over any given point over airfoil • Pressure distribution over airfoil http://web.mit.edu/drela/Public/web/xfoil

5. Methodology for Determining Optimal Airfoil • Utilized XFOIL and published airfoil data to obtain necessary lift and drag coefficients for the following airfoils: • NACA 66-012 baseline • Clark Y as high lift option • Martin Hepperle • Selig • Eppler • Airfoils with flaps • Blended airfoil wings • Each airfoil trial have wings and planes with following properties: • 500 square inches • 50 inches chord length • Minimum thickness to chord ratio of 0.11875 • 3.75 lb. airplane • 1.8 HP engine • Derive equations for acceleration/deceleration in Maple • Keys to winning pylon racer performance: • Maximum speed during straight and level flight and: • Minimal loss of speed in turns

6. Race Simulation • Whole plane drag coefficient calculated from airfoil drag from straight and level flight and turns • Maximum straight and level flight speed and maximum loss of speed in turns determine for all 32 airfoil candidates • Top 12 performing airfoils run through race simulation in Maple • Each simulation consists of a typical race consisting of each piece shown below • Sea level air properties assumed, e.g. density, temperature, absolute viscosity • Airfoil section is the only variable for each plane in this simulation • Provides good relative comparison of airfoil performance • Pylon race course will incorporate: • 10 laps • Assume 1 lap consisting of: • 2x 475.5 ft. straight ways • 2x 50 ft. radius semi circles • 12,65.16 ft. per lap • Total distance covered in race simulation is 2.40 miles Typical pylon race course layout set by Academy of Model Aeronautics rules

7. High Level Results WINNER!! Martin Hepperle MH-17 airfoil with 5 degree 15% span flaps during turns • Commonly used NACA 66-012 airfoil is one of the worst performers!! • Can improve airfoil by use of flaps during turns, or • Blending it with higher performing airfoil • Clark Y is the slowest airfoil, as expected

8. Airfoil Drag Polar from XFOIL Drag Polars are drag coefficient listed for each lift coefficient • Straight and level flight lift coefficient of 0.18776 is marked by left dashed line • Turning flight lift coefficient of 0.563277 is marked by right dashed line • Clark Y has highest drag at level flight • NACA 66-012 has highest drag during turns • MH-17 has lowest drag at level flight • Highest top speed of any airfoil • Relatively low drag in turns makes it a winning combination Drag polar for 12 airfoils

9. Flaps Increase Turning Performance of Airfoils NACA 66-012 airfoil with 5 degree 15% span flaps during turns • NACA 66-012 is a symmetrical airfoil • Flaps increase airfoil camber • Laminar buckets shifts to the right with flaps • Lift coefficient range where drag coefficient is small • Airfoil drag is reduced at higher lift coefficient in turns • Flapped airfoils require less angle of attack to create same amount of lift, hence less airfoil drag • NACA 66-012 airfoil with 10 degree 15% span flaps is in laminar bucket during turns, hence lower drag Lift Coefficient in Turns Laminar Bucket

10. NACA 66-012 Airfoil Can Be Blended with Other Airfoils To Improve Performance NACA 66-012 MH-18B MD-5 • MD-5 airfoil is blend of NACA 66-012 and MH-18B airfoils • Properties are approximately between these 2 airfoils • Entire wing can also be comprised of MD-5 airfoil • Wing Dimensions: • 10 inch chord length • 50 inch span length • 500 square inches area MD-5