defining wing profile / formulas

[hpghost]

hi,

I would like to understand how to define the wing profile to obtain the proper lift for the proper surface area and plane speed.

I suppose that lift should be as much as possible close but over the weight force of plane, is it? if the plane is 12kg, lift force when flying should be over, am I right?

If I'm asking this, it is because, I afraid of having a plane that requires too much speed for having the adequate lift!

I some of you can help me on the way to choose an airfoil, it would be great!

[Sparky Paul]

hi,

I would like to understand how to define the wing profile to obtain the proper lift for the proper surface area and plane speed.

I suppose that lift should be as much as possible close but over the weight force of plane, is it? if the plane is 12kg, lift force when flying should be over, am I right?

If I'm asking this, it is because, I afraid of having a plane that requires too much speed for having the adequate lift!

I some of you can help me on the way to choose an airfoil, it would be great!
.
Your question is the very first of a never-ending :) series, which are best answered by referring to books on the subject.
Two which relate to these questions and model aviation are:
"Basics of R/C Model Aircraft Designby Andy Lennon,
"Model Aircraft Aerodynamics by Martin Simons.
Amazon carries both.
These will explain why planes look the way they do for different purposes: gliders, speed, aerobatic..
.
But firstly, to fly, lift must equal weight.
When lift is greater than the weight, the plane goes up, when the lift is less the plane goes down.
Choosing how to make this occur is a long course of instruction, either formal or by your self.

[Ollie]

Paul is said!
Part at:
http://www.rcgroups.com/forums/showthread.php?t=324935

[BMatthews]

The airfoil is only part of the equation and mostly a minor part. Far more important is the wing loading and desired flying speed. The slow speed is set by the wing loading and the wing loading is a function of the wing area and the weight of the model.

The lift from the wing is related to the speed you are flying. You can play with your wing design, model weight and flying speed with Foilsim which you can find at http://www.auf.asn.au/FoilSim/FoilSim.html . This is a great tool to see what happens. Pay particular attention to the lift (weight of your model) and flying speed. adjust the angle of attack and then vary the airspeed to return to the same lift amount. Just before it stalls that's as slow as you can fly with that size wing and weight.

A model in level flight generates exactly the same amount of lift as the model weighs. If it was more or less the model would be climbing or diving. Using different angles of attack with the wing you can generate that lift at low speed or high speed. The bigger the wing and lighter the model the lower the low speed can be without stalling.

An airfoil with more camber will generally delay the stall to a lower airspeed.