Feedback on 20/10/2010

The lesson on Wednesday , 20/10/2010 was interesting . The lesson about how to know the lift , the center of gravity is quite complicated . The formulae that had been taught is still not that clear . As it is so hard to be memorise .

But , the lesson on that day is fun . Hope , I get to know more how to make a glider . And understand more on the formulae clearly .

Thanks .

Wing Planform

http://www.pilotoutlook.com/glider_flying/wing_planform

Lift coefficient
Main article: Lift coefficient
If the lift coefficient for a wing at a specified angle of attack is known (or estimated using a method such as thin-airfoil theory), then the lift produced for specific flow conditions can be determined using the following equation:[46]

where
L is lift force,
ρ is air density
v is true airspeed,
A is planform area, and
CL is the lift coefficient at the desired angle of attack, Mach number, and Reynolds number[47]
This equation is basically the same as the drag equation, only the lift/drag coefficient is different.

Aspect Ratio

In aerodynamics, the aspect ratio of a wing is the length of the wing compared with the breadth (chord) of the wing. A high aspect ratio indicates long, narrow wings, whereas a low aspect ratio indicates short, stubby wings.[1]
For most wings, the length of the chord varies along the wing so the aspect ratio AR is defined as the square of the wingspan divided by the area of the wing planform.[2][3]

where
b is the wingspan, and
S is the area of the wing planform

http://en.wikipedia.org/wiki/Aspect_ratio_(wing)

Glider Wing Design

Abstract from : http://science.howstuffworks.com/transport/flight/modern/glider1.htm

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. 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.

Glider wings have very high aspect ratios -- their span is very long compared to their width. This is because drag created during the production of lift (known as induced drag) can account for a significant portion of the total drag on a glider. One way to increase the efficiency of a wing is to increase its aspect ratio. Glider wings are very long and thin, which makes them efficient. They produce less drag for the amount of lift they generate.

Abstract from : http://www.4p8.com/eric.brasseur/glider2.html

Why such wide wings?

An airplane keeps flying because its wings constantly blow air downwards. Just like an helicopter does. Yet an helicopter stays at the same place and moves its wings/propeller through the air by rotating them, while an airplane passes its wing through the air by moving itself through the air. The air that an airplane's wings blow downwards does not travel all the way towards the ground. Instead it rotates sideways and you get two slow and huge turbulences/vortexes; one generated by each wing. This is kind of an invisible trail left by the airplane. Now, according to the laws of mechanics, the more volume of air the wings make rotate every second, the slower that air will move and the less energy the airplane will have to spend. That's one reason why gliders have very long wings; in order to span over a huge volume of air. The least the air moves once a glider went through it, the better that glider's yield is.

Check out this solar powered glider : http://www.dfrc.nasa.gov/gallery/photo/Helios/HTML/ED03-0152-4.html

Glider Training on 20th Oct 2010 at 2pm

Hi Gliders,

I have to change our date of training to 20th Oct 2010 at 2pm after your school dismissal as some of you can't make it for 18th or 19th.

Anyway, for those who can make it for the training on the 20th (Wed), please come to the design lab at 2.00pm. The training will end at 4.00pm if we start at 2.00pm sharp.

Training Details:

- Flight Theory (1/2 hour)
- Theory on Glider design (1/2 hour)
- Review on 2010 glider design (1/2 hour)
- Design Calculation (1/2 hour)


Things to bring for the training:
1) Writing materials
2) Calculator