The Exploration of Airfoil Sections to Determine the Optimal Airfoil for Remote Controlled Pylon Racing

Michael DeRosaMaster of Engineering Final ProjectExploration of Airfoil Sections to Determine the Optimal Airfoil for Remote Controlled Pylon Racing

What is Remote Control Pylon Racing?3 Recognized Classes:424 class: 120 mph Quickie 500426 class: 150 mph Quickie 500Focus of Project422 class: 190-200 mphSize of 426 Class airplanes determined by Academy of Model Aeronautics rulesMinimum weight of 3.75 lbs.500 square inches of wing area50-52 inches of win spanAspect ratio of 5Wing thickness to chord ratio is 0.11875Powered by methanol fueled Jett 0.40 cubic inch engine displacement engineGoal is to fly around a 2 mile course in shortest amount of timeCourse is marked by 3 pylons: 2 are 100 ft. apart and 1 is 475 ft. from the centerline of the twin pylons4 planes race at a time10 lapsPenalties for turning inside of pylons

Typical Q-500 pylon racer Viper 500 by Great Planes Q-500 pylon race

Optimal Airfoil For Pylon Racing Not ExploredNo official studies on pylon racing airfoils completed to dateEntering into a 50 ft. radius turn at 150 mi/hr creates 30 Gs of force acting on the planeWing must pitch up to increase lift coefficient at expense of increased dragIncreased drag can slow down a plane by 15-20 mi/hr in turnsEven a 5 mph speed gain in turns is significant.Widely used airfoil for pylon racing is NACA 66-012 symmetrical laminar flow airfoilDrag penalties in turning flight translates to significant loss of speeds in turnsConversely, 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 airfoilTrade off is lower maximum speed in straight ways due to higher form dragModern airfoils created by Martin Hepperle, Selig, and Eppler are useful for drag minimization in pylon racingWings with 2 different airfoil types have not been considered and/or assessedNACA 66-012 Laminar Airfoil Typically Used for Pylon RacingHigh Lift Clark Y Airfoil Not Typically Used for Pylon Racing

Project Utilized XFOIL Airfoil Development ProgramDeveloped by Dr. Mark Drela of MITUses solutions of viscous and invisicid differential equations to solve airfoil shape for:Lift coefficient for given angles of attackDrag polars to determine drag coefficient for a given lift coefficientMoment coefficient for given angles of attackVelocity ratio with free stream velocity over any given point over airfoilPressure distribution over airfoil

http://web.mit.edu/drela/Public/web/xfoilMethodology for Determining Optimal AirfoilUtilized XFOIL and published airfoil data to obtain necessary lift and drag coefficients for the following airfoils:NACA 66-012 baselineClark Y as high lift optionMartin HepperleSeligEpplerAirfoils with flapsBlended airfoil wingsEach airfoil trial have wings and planes with following properties:500 square inches50 inches chord lengthMinimum thickness to chord ratio of 0.118753.75 lb. airplane1.8 HP engineDerive equations for acceleration/deceleration in MapleKeys to winning pylon racer performance:Maximum speed during straight and level flight and:Minimal loss of speed in turnsRace SimulationWhole plane drag coefficient calculated from airfoil drag from straight and level flight and turnsMaximum straight and level flight speed and maximum loss of speed in turns determine for all 32 airfoil candidatesTop 12 performing airfoils run through race simulation in MapleEach simulation consists of a typical race consisting of each piece shown belowSea level air properties assumed, e.g. density, temperature, absolute viscosityAirfoil section is the only variable for each plane in this simulationProvides good relative comparison of airfoil performanceTypical pylon race course layout set by Academy of Model Aeronautics rulesPylon race course will incorporate:10 lapsAssume 1 lap consisting of:2x 475.5 ft. straight ways2x 50 ft. radius semi circles12,65.16 ft. per lapTotal distance covered in race simulation is 2.40 miles

High Level Results

Martin Hepperle MH-17 airfoil with 5 degree 15% span flaps during turnsWINNER!!Commonly used NACA 66-012 airfoil is one of the worst performers!!Can improve airfoil by use of flaps during turns, orBlending it with higher performing airfoilClark Y is the slowest airfoil, as expectedAirfoil Drag Polar from XFOIL

Drag polar for 12 airfoilsStraight and level flight lift coefficient of 0.18776 is marked by left dashed lineTurning flight lift coefficient of 0.563277 is marked by right dashed lineClark Y has highest drag at level flightNACA 66-012 has highest drag during turnsMH-17 has lowest drag at level flightHighest top speed of any airfoilRelatively low drag in turns makes it a winning combination

Drag Polars are drag coefficient listed for each lift coefficientFlaps Increase Turning Performance of Airfoils

NACA 66-012 airfoil with 5 degree 15% span flaps during turns

Lift Coefficient in TurnsLaminar BucketNACA 66-012 is a symmetrical airfoilFlaps increase airfoil camberLaminar buckets shifts to the right with flapsLift coefficient range where drag coefficient is smallAirfoil drag is reduced at higher lift coefficient in turnsFlapped airfoils require less angle of attack to create same amount of lift, hence less airfoil dragNACA 66-012 airfoil with 10 degree 15% span flaps is in laminar bucket during turns, hence lower dragNACA 66-012 Airfoil Can Be Blended with Other Airfoils To Improve Performance

Wing Dimensions:10 inch chord length50 inch span length500 square inches area

NACA 66-012MH-18BMD-5MD-5 airfoil is blend of NACA 66-012 and MH-18B airfoilsProperties are approximately between these 2 airfoilsEntire wing can also be comprised of MD-5 airfoil

MD-5