Introductory Lecture

Aeromodelling club An Introductory lecture

What do we deal with ? • • • • •

Balsa gliders Boomerang Water Rocket Rc Aeromodell So, get ready for lots of fun!!

Terminology 1.Wing 2.Fuselage 3.Vertical Tail 4. Horizantal tail

Basic Aircraft Terminology Airfoil: Cross sectional shape of a wing

Leading Edge: Front edge of wing Trailing Edge: Back edge of wing

Chord Line: Line connecting LE to TE Camber: Center line between top and bottom of wing High camber found on slow flying high lift aircraft

Wing Layout Planform: Vertical projection of wing area Elliptical: good for high speed Straight: root stalls, but cheap to make Tapered: good stall characteristics Delta: used for supersonic flight

Sweep: Angle between the lateral axis and the wing (high speed aircraft) Taper: Chord decreases as you move to the wing tip Incidence: Angle between the longitudinal axis and the wing chord Angle of Attack: Angle between the wing and the relative wind

Twist: Bending of wing about lateral axis (helps prevent tip stall by changing angle of attack) Anhedral: Downward bend in wing (helps with stability) Dihedral: Upward bend in wing Aspect ratio (AR)= Span^2/Wing Area More efficient for slow aircraft Typical Values: Glider: 20-30 Trainer: 7-9 Loadstar: 18.5

How wings generate lift? • A cross section of a typical airplane wing will show the top surface to be more curved than the bottom surface. This shaped profile is called an 'airfoil' (or 'aerofoil').

How Lift is Generated: The Too Simple Version 1) As the fluid elements approach the wing, they split at the leading edge and meets again at the trailing edge 2) As a result, the air must go faster over the top of wing since this distance traveled is larger 3) Bernoulli’s equation implies that pressure will be lower on the upper surface 4) This net pressure difference causes lift

How Airplanes Fly? • The basic principles of why and how airplanes fly apply to all airplanes, from the Wright Brothers' first machine to a modern Stealth Bomber. • Essentially there are 4 aerodynamic forces that act on an airplane in flight; these are lift, drag, thrust and gravity (or weight).

Angle of attack A crucial factor of lift generation is the Angle of Attack - this is the angle at which the wing sits in relation to the horizontal airflow over it. As the angle of attack increases, so more lift is generated - but only up to a point until the smooth airflow over the wing is broken up and so the generation of lift cannot be sustained. When this happens, the sudden loss of lift will result in the airplane entering into a stall, where the weight of the airplane cannot be supported any longer.

However, a direct reaction to lift is drag and this too increases with airspeed. So airfoils need to be designed in a way that maximizes lift but minimizes drag, in order to be efficient.

Aerodynamic Controls • Elevators control pitch angle

• Ailerons control roll angle • Rudder controls yaw angle

• Flaps increase lift and drag • Leading edge slats increase lift • Drag brakes increase drag • Spoilers reduce lift and increase drag

Control Surfaces: Aileron, elevator, Rudder, Flaps

Elevators control pitch angle

Ailerons control roll angle

Rudder controls yaw angle

Vertical and Horizontal Stablizer • The stabilizer is a fixed wing section whose job is to provide stability for the aircraft, to keep it flying straight. • Horizontal Stablizer: The horizontal stabilizer prevents up-and-down, or pitching, motion of the aircraft nose. • Vertical Stablizer:The vertical stabilizer prevents side-to-side, or yawing, motion of the aircraft nose.

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; a wing with some dihedral will naturally return to its original position if it encounters a slight roll displacement.

Supersonic bullet flying

Gliders • In its simplest form, a glider is an unpowered aircraft, an airplane without a motor. • If you look at a glider next to a conventional powered plane, you'll notice a significant difference in the wings. While the wings of both are similar in general shape and function, those on gliders are longer and narrower than those on conventional aircraft.

Aspect Ratio 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.

Balsa Glider • Equipments Required: 1.Balsa wood 2.Cutter 3.Scale 4.Sand Paper 5.Adhesive 6.Pencil

Dimensioning • • • • •

Aspect Ratio =9-10 Wing span = 50-60 cm. Angle of attack = 3-4 deg. Horizontal Stablizer = 20-25% of wing area Vertical Stablizer = 40% to 50% Horizontal Stablizer area. • Dihedral = 2-3 deg. • Length of fuselage = 65%-75% of span.

Weight Balance 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 .

Lift

Weight

Design tips • Add dihedral to the wing tips by making the outer portions of the wing angle upwards. • Round the leading edges of all surfaces and “point” the trailing edges. and many more… search yourself!!!

Some Interesting facts  Air Conditioning OR Roll down windows (while travelling on highway speeds)

 Luggage on the top your Car or parcel it through train.( streamline cargo carrier) 

• Formula one car • F1 car running upside down….. • Bees fly violating the law of aerodynamics. •

Fluid/Aero-dynamics of Nature

Vortex rings in Nature

Bats  Birds  Insects 

 Fish & aquatic animals  Flying Seeds  Trees  Crops Atmosphere Wind Flow pattern Ocean flow pattern Tornadoes  Blood flow  Respiratory flow

"Once upon a time some scientists and engineers or college professors (different versions have different names and specialties) were at a dinner party. The subject of bee flight came up and the aerodynamic engineer that just happened to be present decided to do a quick calculation on bee aerodynamics. He used a conventional stiff airfoil-shaped wing, with steady state, or partially steady state, air flow analysis techniques, and lo and behold, the calculations did not work for the bee. Someone jokingly said, "I guess that proves bees can't fly", and they all had a good laugh. But, of course, they all knew it just proved that bee flight is too complicated to analyze with conventional airplane aerodynamic methods."

Here is the basis of the problem: Conventional aerodynamic calculations are relatively simple, being based on large fixed wings and steady state or quasi-steady state flow. Insect wings are small, flat, rough surfaced, and flexible. During flight they flex and twist in all kinds of horribly complicated ways. Also they are so small that important dimensional fluid analysis numbers like the Reynold's Number are very different, resulting in significantly different fluid characteristics when compared to the bigger wings of birds and airplanes (even a sparrow wing is huge compared to most insect wings). In addition, the small size and high speed of most insect wings makes it very difficult to study insect flight (imagine trying to attach a pressure sensor to an insect wing). Finally, the pressures and flow characteristics of the air around the wings are very unsteady, constantly changing as the wind flaps, bends, and twists, unlike aircraft wings which are stiff with relatively simple constant flow patterns and pressures. Conventional aerodynamic analysis methods simply don't apply to insect wings.

Typical Applications

A Stealth Aircraft: Designed by nature

Vanessa atalanta

A Case Study

The insect thorax is shielded by cuticles of thinwalled chitinous shells, joined with an elastic material, resilin. The wings and the thorax shell form a distributed vibration system.

The sequence of insect flight: Cruising Mode (Sir J. Lighthill)

Recent Attempts (UC, Berkeley)

Flapping Wings using a fourbar mechanism: piezoelectric actuators driving a mechanical amplifying thorax structure

In some insects the wing movements are produced by wing muscles directly inserted into the base of the wing.

In others, these are produced by muscles that pull on the thorax shell, while the shell movement moves the wings.

For further info: feel free to contact us at 1. Atul Nipane nipane@ 2. Abhineet Gupta abhiji@ 3. Mitul Kumar Sonker mitul@ or visit our site: http://students.iitk.ac.in/aeromodelling/