INTRODUCTORY LECTURE A NORMAL INSECT B-2 STEALTH BOMBER WHY AEROMODELLING???

• Answer is in the previous slide.

• Aeromodelling is the art of fabricating flight models of relatively smaller size than the actual flight vehicle. • A Simple Rule – “Any flight model fabricated, must fly!!!” WHAT KIND OF AEROMODELS DO WE MAKE???

• Gliders • Boomerangs • Water Rockets • Remote Controlled • R.C. • R.C Hovercrafts And many more…

FIRST STEP INTO AEROMODELLING: GLIDERS

Lilienthal’s Biwing Hang PRESENT DAY GLIDER WHAT IS A GLIDER?

• Unpowered designed to glide through air after being launched at some height, with some initial velocity.

• Can be catapult launched or driven from some other mechanism, then left to glide.

• Usually installed with basic control surfaces used for flight maneuverability.

TODAY’S LECTURE

Topics to be covered in the following sequence: • Terminologies • Aerodynamic Forces • Aircraft Controls • Significance of tail in an • Wing Design and Lift Generation • Airfoil Theory • How to make your gliders • Few other designing tips • Our team

OVERVIEW OF CONTROL SURFACES WITH THEIR AXIS AERODYNAMIC FORCES

WHY THE TAIL???

• A flight model with just a lifting wing and fuselage is not stable.

• Tail shifts the Centre of Pressure behind the Centre of Gravity to prevent undesirable nose up motion.

• Nose moving up might stall the wing.

• Tail provides with control surfaces for maneuverability.

WING PLANFORM SPECIFICATIONS

• Planform: Vertical projection of wing area

• Elliptical planform: good for high speed

• Straight planform: root stalls, but cheap to make

• Tapered planform: good stall characteristics

• Delta planform: used for supersonic flight

• Sweep : Angle between the lateral axis and the wing (high speed aircraft)

ASPECT RATIO OF A WING

• The slenderness of a wing is expressed as the aspect ratio, which is calculated by dividing the square of the span of the wing by the area of the wing.

WING DESIGNING

• Lift force acts at nearly ¼ from the leading edge of the wing. Hence , we try to position centre of mass of glider at this point . • Some weight, ballast, is usually added at the nose to bring Cg to c/4, thereby increasing speed.

This is where the concept of airfoils came from!!!

FROM FLAT PLATE TO AIRFOIL

• Cd for flat plate higher at higher angle of attacks • Not the case for airfoils. • L/D for flat plate increases at a slower rate (virtually stagnates), than that of an airfoil.

• Therefore, airfoils better than flat plate for lift generation. P SIMULATED FLOW PAST AN AIRFOIL

ANGLE OF ATTACK VARIATION OF LIFT COEFFICIENT WITH ANGLE OF ATTACK GLIDER DIMENSIONS

• Aspect Ratio =6-10 • Wing span = 60-80 cm. • Angle of attack = 0-4 deg. • Horizontal Stabilizer = 20-25% of wing area • Vertical Stabilizer = 40% to 50% Horizontal Stabilizer area. • Dihedral angle = 2-3 deg. • Length of fuselage = 65%-75% of span. VARIOUS AIRFOILS AVAILABLE TOMORROW

• NACA 0012: Symmetrical Airfoil Zero lift at 0o Camber=Chord Used for aerobatic planes

• NACA 2412: Cambered Airfoil. Lift not zero at 0 degrees AoA. Requires elevator down??? These airfoils with different chord lengths will be given to you tomorrow: 10cm; 12cm; 14cm; 16cm

HOW TO MAKE YOUR OWN GLIDERS TOMORROW???

1. Select the type of glider you want to make, i.e. select your airfoil. 2. Set the dimensions for your glider. 3. Prepare the wing. 4. Strengthening and smoothening of the wing. 5. Fabricate the fuselage. 6. Make the tail. 7. Assembly

FEW OTHER DESIGNING TIPS

DIHEDRAL ANGLE: • The angle that the wing makes with the local horizontal is called the dihedral angle. Dihedral is added to the wings for roll stability

MORE TIPS…

• Try to increase the dihedral angle gradually, in the spanwise directions. • Small winglet-type structures reduce drag. • MINIMIZE WEIGHT AS MUCH AS POSSIBLE!!! • Reduction in chord along spanwise direction (high aspect ratio) might increase Glide Ratio. • Round all leading edges in your model. • Reduction in fuselage cross section. Enjoy it fly!!!!

CONTACTS

• MRIDUL MISHRA – mridulm@ F104/5 9453094730 • PIYUSH NEGI – piyushae@ D241/2 9559753812 • TIGMANSHU GOYAL – tgoyal@ E201/9 9559753800 • Visit - http://students.iitk.ac.in/aeromodelling