Airfoil Basics: Understanding Shape, Terminology, and NACA Naming

hello in today's video we're going to talk a little bit about airfoil basics so the basics

that you need to know about airfoils so an airfoil is simply just the cross-sectional shape

of a wing a blade of a propeller rotor or a turbine is simply the cross-sectional area it's not the entire

wing it's just if you took an airplane wing or a propeller wing

and you just sliced it in half and you looked at the cross-sectional area that is what a airfoil is

and this is how the shape of an airfoil determines a lot about how that how that airplane or

the rotor creates lift moves material produces lift has you know induced creates drag

a lot of it has to do with the shape of the airfoil so let's learn some basic terminology

when it comes to an airfoil so the front here so if the air the wind is coming this way

the first part it hits is the leading edge so kind of distinct characteristic of airfoil is this

rounded leading edge it's that it's very rounded and all airfoils you see will have a rounded

leading edge now some like higher performance aircraft that will get thinner and thinner

but for most it's very rounded compared to the trailing edge which is almost always a

kind of a point a sharper point so the trailing edge is the back of the airfoil now there's a couple things

that you then you can break the airfoil down farther so if you draw a straight line like i

did here from the leading edge to the trailing edge this is called

the cord c so that is simply just a straight line between the leading edge and

the trailing edge and then if you want to calculate your angle of attack

which is designated by an alpha that is the angle so let's say we draw an airfoil kind of

at a angle here so it's very steep angle but this is our airfoil

and so our cord line would look something like that and if our wind or air is coming in like

this this angle right here is our angle of attack this is very

large compared to actually as most planes airfoils fly from zero to 15 degrees this is obviously

more than that but just so you could see that this right here is designated as the angle of

attack so i try to draw this one as a symmetric airfoil so the

what symmetric airflow means is that the difference in the size so the the shape is it's a

symmetrical shape it's a symmetric airfoil so there's no camber so the camber line

runs exactly on the cord line now for airfoil like this

which has a weird shape here so this is the top and this is the bottom kind of poorly drawn but as you can see

the chord line which is this first one c h o r d that runs from leading edge to the trailing edge the

chord line is simply the the the middle line it's called like the mean

camber line it's if you took the distance between the top and the bottom so the mine's a little

off because it's very bulbous on the bottom here but if you just took the the different

the area the distance between this the bottom and the top the middle right there is the camber line so this

is how so there's a difference between the cord line and the camber line

for asymmetrical airfoils so this curvature is what gives most airfoils lift

at a zero angle of attack so it can create lift at a zero angle of attack

if it's symmetrical airfoil at zero angle of attack it's not creating any lift because the

pressure differences between the top and the bottom are exactly the same now if you had a

switch gear foil then how did that angle attack it will then create lift so there's a naming

convention for basic airfoils it's called the naca naming convention you'll see a lot of

like a naca let's say 2 4 1 2 or naca 0 0

12. so these are four digit designations for kind of the shape of an airfoil

now what do these mean so the first letter that describes the maximum camber

as a function of the the cord length so just the distance

so the maximum camber as a percentage of the cord length and then the camber is this is the mean

camber line but the camber is the distance between the cord and then the mean

camber line so let's say the if let's say this number was a you know

a four the first digit was a four that means that the camber the large the maximum

camber on that aircraft is where that airflow is four percent of what the cord line is so if the cord was

a meter that the the maximum camber would be uh one four or 100 so four percent so it

would be about four centimeters okay then the second letter or second number

not letter describes distance

that maximum camber is located or where the maximum distance camber is located

so if it's a four and then this is four so if it's like a four that means so this the first letter

is a so if it was a four it'd be a four percent if the second letter is a four that's

forty percent so if a two supposed to be two percent max camber

located at forty percent from the leading edge along the core line

so if it was if against the cord was one meter long core length was one meter

the maximum camber so the maximum distance between the mean camber line and the cord

would be at 40 centimeters from the leading edge so it would be like right here would be for the max

camber is if it was a naca two four one two and then the last two digits

describe the maximum thickness

of the airfoil so no matter where the camber is where the cord

where the cord line is this is and then as a percent so if it's

so if it's a 12 that means the maximum thickness of that wing is 12 percent

of where 12 of the cord so again if our cord is one meter long

the maximum thickness of that air foil is 12 centimeters or 12 percent

over one so the neck is zero zero one two the zeros means well the first zero says

there's no camber so there can't be a location of that camber along the wing so it's

just zero zero and one two it still says the maximum thickness

is a 12 percent of the airflow the cord line it doesn't really tell you the location is located

but it just says the maximum thickness of that airfoil is 12 of the chord line so those are just the

basics of airfoil naming convention characteristics of an airfoil

thanks for watching