Wright Design Abstract-principal11

Development and Application of a RCglider For IITShaastra 2009 Wright Design

Pranav N Raichur Sanketh Adiga.R Shubhadeep Chowdhury Sumanth Aramadi HR 

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Outline Presentation About the event Introduction Problem Statement Approach Design Innovation

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Introduction "A soul in tension that’s learning to fly Condition grounded but determined to try Can’t keep my eyes from the circling skies Tongue-tied and twisted just an earth-bound misfit. " We at Team AUK firmly believe in letting our imagination take wings, quite literally too. The intricacy of flight, the rush of wind, from gentle zephyrs to howling headwinds, the challenges of aero modelling fueled our quest to take up this project. And what better place to showcase our flyer than at Shaastra 2009.Competing against the best will help us evaluate our position and gain invaluable experience in developing our glider. A lot of work that went into the glider taught us so much, right from mundane and arcane things like how quickly Feviquick glues your hand, to the techincal aspects like the principles that govern flight. It has been an exciting journey so far, and even more exciting is the fact that we are just starting out on our journey.

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Problem statement Design an RC electric glider with the following constraints that could have maximum time of flight after 30 sconds of powered flight carrying a payload of 100grams. Hand launch of the glider is allowed. The whole glider should completely fit inside a box of dimensions 110cm x 110cm x 35cm It should carry a payload of 100grams,which will be provided by us during the event It should have its static thrust to weight ratio (including the payload) less than 3:4. In case the ratio is higher than specified, then additional payload will be added by us until it meets the above mentioned ratio. Details on the simple experimental setup, which will be used to test your glider during the event, will be put up on web soon During the run, it should have powered flight duration of 30 seconds after which the motor has to be stopped. The non-powered time of flight, measured after that, is the winning criterion.

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Approach

  The glider configuration chosen for this project is a polyhedral wing with a traditional tapering fuselage configuration. This configuration was based on the configuration of common sailplanes. The design was created using several assumptions to provide a reference base if the design and configuration were to be altered. An initial model was constructed and substantial flight testing was performed to determine the most efficient configuration for the glider regarding wing location, incidence angles, and added weight. As this configuration was chosen, a second model is being constructed in balsa wood, exactly replicating the prototype made of coroplast. On the basis of the Problem Statement provided above we have come up with The Auk-1 a RC glider with wingspan of 48”.

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The picture below illustrates the *prototype of the glider made of coroplast

The Glider when placed along the body diagonal of the given dimensions of 110cm x 110cm x 35cm 6

DESIGN “The devil isn’t in the details , it’s the details that make the design” The design parameters of the glider can be broadly classified and studied under the head as follows : Fuselage Wing Maneuverability Electronics

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Fuselage

The fuselage is the main body of the RC glider. It serves as a housing of the internal components and holds together the outer parts.The side view and top view of the fuselage is depicted in the following design as follows:

The fuselage specifications are as follows: The fuselage has a length of 38” inches made of balsa wood with the widest part at the wing platform being 2.5”inches supported underneath with formers to hold the wings on the platform. The tail platform is supported by a former of 1.5”inches to take the weight of the tail and rudder combine which has been fixed through the slit mechanism to avoid any relative motion between the two and the fuselage to avoid any bending during the flight and hence to make it stable The Engine bearer houses the brushless motor with the propeller for the Thrust and powered flight for duration of 30 seconds 8

Wing Lift is one of the four primary forces acting upon an airplane/glider .The others are weight, thrust, and drag. Weight is the force that offsets lift, because it acts in the opposite direction. The weight of the airplane must be overcome by the lift produced by the wings. If an airplane weighs X units then the lift produced by its wings must be greater than X units in order for the airplane to leave the ground. Designing a wing that is powerful enough to lift an airplane off the ground, and yet efficient enough to fly over extremely long distances, was the challenge and we have tried to achieve the same using a 48” inch wing span with a polyhedral wing configuration.

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The aerofoil (cross-section of the wing) used in the wing is of NACA flat bottom type .The choice of this aerofoil was made due to its inherent stability. The flat bottom design is stable on the longitudinal axis and self-correcting tendency.The highest point on the aerofoil is 0.75 inches.

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The Dihedral is added to the wings for roll stability; a wing with some dihedral will naturally return to its original position if it encounters a slight roll displacement.

The polyhedral wingconfiguration was chosen as our design, allows the Glider to “hang” from their center of lift, and are therefore more stable and self correcting during normal flight conditions. A turn is initiated via use of the rudder, and once the rudder is returned to center, a properly trimmed glider will return to level flight on its own.They are also typically more drag inducing, and suitable more for slower flight envelopes than a straight wing design.  As the basic requirement of the glider is to stay air borne for a longer period of time and achieve a greater range the polyhderal wing design was chosen and applied to auk -1

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The wing span was chosen to be 48” inches long as measured tip to tip of the polyhedral wing, as to achieve the longest possible wing span on loading the wing 1/3 rd of the fuselage length located right at the centre of gravity position and placing the glider in a diagonal position of the given box as specified in the rules. The wing chord length is 6”inches and it was achieved to achieve a high aspect ratio of 8 in order to minimize the induced drag so which is a effect related to three dimension wings

With the above diagram as reference Aspect ratio (AR) is calculated as follows : Aspect ratio =s/c where “s “is the span of the wing and “c “is the chord length In our case s=48” inches and c =6”inches therefore AR=48”/6”=8 “inches

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One half of the wing is illustrated in the design explaining the polyhedral and the dihedral

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Maneuverability

To control and maneuver the glider , smaller wings are located at the tail of the plane. The tail usually has a fixed horizontal piece (called the horizontal stabilizer) and a fixed vertical piece (called the vertical stabilizer). The horizontal stabilizer prevents an up-and-down motion of the nose or pitching motion of the nose . With the tail wing span of 20”inches and wing chord length of 8.5” inches . The elevator is attached to the horizontal stabilizerin hinged manner it is used to control the position of the nose of the glider and the angle of attack of the wing. Changing the inclination of the wing to the local flight path changes the amount of lift which the wing generates. This, in turn, causes the glider to climb or dive depending on the need. The vertical stabilizers, or fins, of glider , are typically found on the end of the fuselage or body, and are intended to reduce aerodynamic side slip. The rudder is used to control the position of the nose of the glider or the yaw motion of the glider . The rudder and the fin stands 7.3” tall and the rudder is attached to the fin in a hinged reinforced configuartion for easy movement and hence better maneuverability of the glider .

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desgin illustrating the horizontal stabilizer of the glider

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Electronics

The aircraft powerplant consists of all the accessories needed by the aircraft to produce thrust,the accessories used to gain thrust during the first 30 seconds of the glider flight make use of electronics and can be described as follows :  The Electric motor is used to turn the propellers and inturn which provide thrust to the glider . We are using brushless motor is called "outrunner".These motors have the rotor "outside" as part of a rotating outer case while the stator is located inside the rotor.This arrangement gives much higher torque than the conventional brushless motors, which means that the "outrunners" are able to drivelarger and more efficient propellers without the need of gearboxes.We are using the 2212-13 outrunner brushless motor Battery combination of electrochemical cells which discharge high voltage or current is used as the power source to run the motor .We for auk -1 are using Lithium polymer rechargable battery as they achieve higher voltage and power output, with more capacity, in a lighter weight package.We are going to use 3cell 1amp Li-Polymer to form a battery with potential difference of 11.4 v(less as compared to maximum allowable 12 v )

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Electronic speed control is used to vary the speed of a brushless motor. Controlled by the throttle signal from an RC receiver, the brushless ESC provides variable power to the motor allowing proportional speed adjustments.We are using a ESC with a cell rating ranging from 2-4 as we are using 3 celled Li-Polymer battery set up with a low voltage cut-off so as this will limit how deeply the battery is allowed to discharge, and preventing it from being damaged. Radio transmitting and reciever –We are going to use a 6 channel radio setand the operations of the different channels are being listed below : The first channel is to control the ESC (electronic speed control) hence the motor and the thrust produced The second channel is used to control the elevator so as to control the nose position of the wing and the angle of attack of the wing for lift or descent The third channel is to control the rudder of the plane so as to control the yaw motion of the plane and hence maneuver it in the direction required The fourth channel is used to control the hatch movement in the fuselage so as to drop the relief package from the glider

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radio control illustration

Basic Electric powerplant components 1 20

Innovation –Slider wing extension Traditional gliders have a solid wing that’s made of a single composite material.In a radically new concept we at team auk are trying to incorporate the Slider wing extension . As the name suggests ,this mechanism will extend the wing span during the course of the flight and there by giving extra lift to the glider ,and as a consequence of the same greater flight time can be achieved . The mechanism works with the help of a bell-crank,and is activated by a servo motor.A small rotation of the servo arm is magnified by the bellcrank,which causes wing extension via the push rod, as illustrated in the diagram We are in the Testing phase of the innovation ,and the feasibility of the same is being analysed.

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Note:•*The prototype of the glider as depicted in the pictures is made of coroplast and the original glider for the event will be made of Balsa wood •All dimensions in inches “ if not mentioned

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