GLIDER DESIGN PROJECT

The TaskTo design, build and test a scale-model gliderDesigns will be judged on four criteria:Distance travelled, DTime of flight, TThe product DTThe quantity DTM where M is the glider mass

Design RequirementsThe glider must:Have a wing span of no more than 60 cmBe no more than 50 cm long

MaterialsThick foam board 2 sheets ~338 cmThin foam board 2 sheets ~3119.5 cmA4 paper 4 sheetsDrinking straws 8Tissue paper 1 sheetMasking tapeAdhesive

EquipmentScissors Stanley knifeSteel rulerSand paperRadius aidsBluetack (for centre of gravity adjustment)

ObjectivesTo give a taste of what Engineering is all about:Problem solvingBeing creative an Engineer is by definition an ingenious personTeam workRewardingFun

Project TimetableIntroduction to Design Task10 minutesIntroduction to Glider Design20 minutesDesign Session15 minutesConstruction/Test Session60 minutesFinal Test Session15 minutes

An Introduction to Glider DesignGeoff Parks

Glider Parts

Glider Control Surfaces

Forces on a Glider

WeightThe weight of a glider is simply its mass multiplied by g, the acceleration due to gravityW = Mg

Lift IThe Coanda Effect: a fluid has a natural tendency to follow the shape of a body as it flows past itIf the body is correctly shaped (airfoil shaped), this can be used to generate lift

Lift IIFluid is deflected downwards by airfoil Force acts downwards on fluid Force acts upwards on airfoil (by Newtons 3rd Law)

Lift IIIThe amount of lift depends on:Wing size larger area more liftSpeed higher speed more liftAirfoil shape more flow turning more liftAirfoil angle of attack larger angle of attack more lift

StallIf the airfoil angle of attack (a) becomes too large and/or the flow speed becomes too largeThe Coanda effect can break down, leading to flow separationThis separation, known as stall, reduces liftAttachedSeparated

Drag IThere are two forms of drag: Form DragInduced DragForm Drag depends on:The size of the object larger projected area more dragSpeed higher speed more drag

Drag IIInduced Drag, ID, depends on:The amount of lift, LWing aspect ratio, ARID L2 AR

Typical Glider Profile

Lines of ActionTo maximise flight distance, the lines of action of the lift and weight must coincide

Design Tips ITape pieces of thin board onto the glider to act as ailerons, elevator and rudder; you can then slightly bend these to help trim your glider and direct it in flight.Add dihedral to the wing tips by making the outer portions of the wing angle upwards.

Design Tips IIMake the wings moveable so you can slide them fore and aft along the fuselage to find their optimal position.Round the leading edges of all surfaces and point the trailing edges.