Explained: NACA 4-Digit Airfoil [Airplanes]

[@LightAndSportyGuy]

What I find amazing is that the guys at NACA were able to come up with these equations to fit what were considered good airfoils at the time using pencil, paper, and (I assume) tables of logarithms. (Too many significant digits for slide rules.)

[@JoshTheEngineer]

There are definitely some things that engineers of older generations were able to figure out that are super impressive when you look at what they had available at the time.

[@jimrummy1300]

Hi Josh, This is a wonderful explanation. Thank you for going to the effort to produce this. It is truly appreciated! Cheers, James.

[@JoshTheEngineer]

Thanks for the nice comment!

[@pedromeirelles]

Amazing. It helped me a lot! You explain very well, and in a simple way. I am a Brazilian current studying Aerodynamics in USA. I have a project where I have to code the velocity field of an Airfoil, and the cl x alpha graph based on NACA numbers. The professor does not explain too well, to say so, and the book contains several code issues/typos. This class and your MATLAB classes were extremely hepful. Thank you! Congratulations! Best.

[@JoshTheEngineer]

I'm glad my videos could help you! Good luck on your project.

[@alwyalsaggaf8260]

This helped me a lot. We have to build/design excel software to do the airfoil calculations and I had no clue at first. This is helping me do that. THANK YOU SO MUCH!!

[@JoshTheEngineer]

You're welcome, and good luck!

[@tephthompson3926]

I asked how to rank Air Foils, but this video is very informative. Thank you.

[@JoshTheEngineer]

You're welcome!

[@savalakanekar95574]

Mean chamber line.

[@Aerospaceman]

Very understandable ...very good video. It kind of looks almost like a parabolic on the upper camber. Thanks Josh!

[@JoshTheEngineer]

Thanks, I appreciate it! Yea the contours have a definite low-coefficient parabolic look to them for sure.

[@apoorvaparvathgari]

Thank you so much for such detailed video and explanation. I understood thoroughly. 😊

[@ganeshnatarajans8129]

Thank you for the kind of efforts you put into your videos Josh, its exceptionally informative and easily understandable. Thank for being who you are man!

[@spindash64]

It seems to me that for a symmetrical airfoil, you can get a surprisingly decent approximation with a half ellipse ending at 30% chord, then a tangent circle arc to hit the trailing edge at the centerline (not perfect, but close enough if you just need to draw a visual aid rather than plotting the airfoi). I wonder if the equations simply to something similar, or if it's pure coincidence

[@joemonster55]

Great video. I've always wondered how the 4-Digit NACA airfoil series related to the airfoil geometry. I got here by watching all of your GUI tutorials, and this work you've done will really help with designing airfoils for model building and senior design class. Thanks!

[@JoshTheEngineer]

joemonster55 You're welcome! It's always nice to hear positive feedback on my videos. Back a few years ago, I was designing and building model airplanes for my senior design class as well as the AIAA Design-Build-Fly competition, so I know how fun and rewarding that can be. Good luck!

[@davooddavoodi2682]

hey josh about 2 days I was busy with this problem , your explnaition was amazing and now I'm undrestand this problem but also I have a question : you imagine the mean camber line EQ as shown in video , why? and I'll be greatful if give me another example for mean camber line equation thanks and wish the health for you,

[@JoshTheEngineer]

Hi Davood, I'm not sure I completely understand your question. The mean camber line equation stated here is defined for the 4-digit airfoils, and is given such that you can use the first two digits of the designation to define the camber line entirely. These equations can, for example, be seen in equation 6.4 on page 114 in Theory of Wing Sections by Abbott and Von Doenhoff.

[@ShivaKumar-je8kd]

Sir could you please tell what about chord length of 240mm How to calculate coordinates

[@patricklew3041]

Hi Josh, excellent video and I have learned a lot. I have a question where if the default location of the thickness is not 30% of chord but at 23% of chord, what is the thickness distribution equation? Thank you.

[@Nathouuuutheone]

If the name includes the parameters, why do sites like Airfoil Tools have huge lists of foils instead of just the means to input their parameters?

[@JoshTheEngineer]

I just went to their site, and it looks like they do have a 4-digit and a 5-digit generator page if you want to use that, but like you mention, they also just have them as static pages. I'm guessing it's so that they have a complete database with static pages including all the necessary airfoil information, instead of always needing to generate that information every time a different combination is run by a user. Also, a bunch of airfoils don't use the airfoil name/number to create the shape, so those will need to always just be available as a data file. But I could be wrong.

[@naisargchauhan3590]

Can you please explain how to give thickness distribution to naca 6 series? Thanks for this awesome videos.

[@samprutha6757]

Hii, Im working mini project in this , I mean designing an airfoil by changing the coordinates like as u explained for the naca series which is already exist, soo can u please assist, what may be the advantages if we just change the coordinates of an airfoil,, hope you will assit Thank you

[@jayantpohani2179]

Great video Josh, appreciate it!

[@JoshTheEngineer]

Thank you!

[@usernamenotknown]

Super description Josh. Thank you.

[@JoshTheEngineer]

No problem!

[@darrylabapo2775]

Hey man, great work! Highly appreciate it.

[@JoshTheEngineer]

Thank you!

[@nmnm8111]

Thank u for this explanation I would aske u from where can i get coordinates for all sections ?

[@JoshTheEngineer]

The following site has a bunch of airfoils: m-selig.ae.illinois.edu/ads/coord_database.html You can also use XFoil to generate 4-digit and 5-digit NACA airfoils.

[@arjunappadurai9544]

Tell me how to calculate surface area for NACA 2412 Airfoil

[@jimjayes8672]

Thank you for the explanation. please excuse my ignorance, but are symmetrical aerofoils designed for use at different speeds?

[@JoshTheEngineer]

You're welcome! The nice thing about symmetric airfoils is that they generate no lift at zero angle of attack. This is perfect for vertical stabilizers. One thing that a thicker symmetric airfoil will let you have is more structure, so they can be made stronger if necessary.

[@nogigglingmajor]

What happens when the chord length is greater than 1? How does,the second equation change?

[@JoshTheEngineer]

The equations are for a normalized airfoil, where the chord length is 1 (and units don't matter). So if you wanted to design an airfoil with a chord length of 2 feet or meters, you would just multiply all the coordinates by 2.

[@hadleymanmusic]

I made a 6 inch 23012 flat iron lifting body twin rudder with a nickle for a weight balance . incredibly stable model. Would set up a hurricane fan pointed up and about 15 feet away toss it straight over and it would just fiercely roll and always back upright and straight on stable

[@hadleymanmusic]

Every flight at the end of its flight speed it would always just kinda flutter in the sweet spot on stall. Had a noticeable ground effect landing on hard surfaces.

[@Channel-tr1hx]

Great Explanation! Is there perhaps a way to find the y as a function of the X - projection of the point (not the x as defined in your equations) ?

[@TheHuesSciTech]

That function might end up being multivalued depending on how rotated-over the leading edge is. You can have a go at getting wolfram alpha to find a closed form solution if you like, one might not exist though. Computationally, using Newton's method or even binary search would be trivial to implement. If you don't understand what I'm saying, please clarify what you're trying to do.

[@lancelotlalla7561]

What is the difference between M and P sounds like the same thing in different places.

[@sameershaik8934]

Thank you for the explanation. It helped me a lot

[@JoshTheEngineer]

You're welcome!

[@kartikprajapati9808]

Can u make video about aerodynamics forces and moment ???

[@JoshTheEngineer]

I'll definitely add that to my list, but I can't say for sure when I'll get to it.

[@itswhoppertime]

What about 3 digit airfoils?

[@Hugomllg]

Very clear explanations, thank you !

[@JoshTheEngineer]

No problem! I think I saw that you posted a question too, but I can't seem to find that comment. Did you figure it out?

[@Hugomllg]

Yes I deleted it because I just had missed something, but it's all right now, thank you for asking ! :) I have another question though : if you wanted to model a full wing (let's say simply straight from the NACA profile, to begin), would you use a mesh ? If you could hint me that would be great !

[@AkshayAshok]

Why the maximum thickness and maximum camber are not at the same place..?

[@haveanicetime]

Hello Josh, thank you sir very much for your excellent steps. Could you tell me what should we do if we have a CFD code and we wanna write the values of the temperature through the time to a txt file? We need the values of the temp. at t=0 to a specific time value....Thank you!

[@karthisivaraman7452]

Thanks for the video - was very useful to understand airfoil coordinate plotting, for a non engineer like me. Are you planning on another video for a reflexed camber too? Thanks in advance.

[@300483rahul]

Thank you josh, you are Brilliant. Helped a lot.

[@JoshTheEngineer]

Thanks Rahul!

[@ing.anthony7097]

Hello plz I have a presentation to make on Wednesday about airfoils (wind turbines)... the only thing I don’t know is how to determine the rotating speed or the rpm of the rotor if I know the wind velocity is 8m/s... how does it affect a certain airfoil? If for instance I have a NACA 4418... a wind speed of 8m/s will result in how much RPM ? Plz this is top urgent

[@proshantasaha21proshanta36]

What does NACA BE50 Stand for

[@JoshTheEngineer]

Looks like it's a low speed airfoil for free flight models (see the document titled "Summary of Low-Speed Airfoil Data" by Selig, Guglielmo, Broeren and Giguere).

[@mohamd8891]

if the maximum camber was zero what is that mean?

[@JoshTheEngineer]

If there's no camber, then the mean line is just the x-axis, and it's a symmetric airfoil.

[@mmnyako]

Thanks for sharing!

[@sebastianrada4107]

Great video! Thank you!

[@JoshTheEngineer]

You're welcome!

[@ismannful]

Good Video! I still have a question: In my recent research I often got confronted with the name NACA651210 (some digits may be subscript). Can you tell me something about this notation/syntax? I hardly can find any information about it. Thank you very much

[@JoshTheEngineer]

There are two things this notation could be referring to, and I should note that I'm taking this information from Theory of Wing Sections by Abbott and von Doenhoff, which I recommend if you are interested in airfoils. The first is a NACA 4-digit that has modifications designed to change the thickness distribution. The example they give in the book is a NACA 0012-64. It seems like the notation will always look like this, with the first four digits, then a dash, then the last two modifying digits. Now in your case you mention that the values could be subscripts, so what I'm leaning towards is a NACA 6-digit airfoil, which are much more complicated than the simple 4-digit series. In the 6-digit series, you'll see numbers, commas, parentheses, and subscripts. Some of the designations might even have more or less than six digits, and some might include letters instead of numbers. I would need to read a little more about it to understand it, but this can be a starting point for you. I'll try to make a video about this in the future, but it's too much to explain each variation in a simple comment like this. I would get the book I mentioned above if you don't already have it.

[@ismannful]

Thank you very much! I'll check the book and see if I can find the exact information I'm looking for

[@alexanderreimer387]

I am using a 4409 airfoil on an 80 % SPAD 13 replica and need to know the cg limits of the airfoil in % of chord...!!! I am not an engineer but have studied structures as an A&P mechanic...!!! Airplane is done, awaiting my “ visit” from the FAA INSPECTOR. I just need to know my CG LIMITS...!!!

[@nicholasdebonis8653]

Thanks for the explanation! Helped a lot.

[@JoshTheEngineer]

You're welcome!

[@harshittewari9960]

sir , what is your graduation please guide me . may you are doing aeronautical engineering btech or masters please reply please

[@JoshTheEngineer]

I have a B.S. in Mechanical and Aerospace Engineering, an M.S. in Aerospace Engineering, and I'm working on my Ph.D. right now.

[@harshittewari9960]

Sir iam pursuing btech in mechanical engineering And I try to design and make a turbo fan jet engine so sir As the diameter of turbo fan is 280 mm Sir which NACA airfoil is best for such small blades For turbo fan . Compressor .and what for guide vanes and turbines Sir please help

[@JoshTheEngineer]

The compressor and turbine blades are most likely not going to simple NACA airfoils. Especially for the turbine blades, you'll note that they are highly cambered, so you're probably going to want a specialized airfoil for those. For a bunch of airfoils (maybe not what you need though), check out the UIUC Airfoil Data Site.

[@pranav4522]

Bro how can I choose this NACA 4 or 5 digit is fix for this aerofoil is there is any possibility to find out ???

[@jackcarr45]

Hello, great video! Extremely informative and has helped me a lot with a project I am working on. Would you mind if I used some of the information you provided in this video in my presentation ? I will give you full credit !

[@JoshTheEngineer]

Glad I could help! And absolutely, feel free!

[@oussamasouadka1156]

Very Good job sir, thank u very muck. Keep it up

[@JoshTheEngineer]

Thanks for the kind words!

[@zazachin]

Thanks for the video. It was very informative. The only thing is that you speak very fast. I had to slow down the video to 0.75X to understand everything.

[@JoshTheEngineer]

Thanks for watching! Yea, I always end up speaking fast in my videos, but I figured that people could do what you did (slowing the video down in the settings) if they need it to go slower.

[@williamsworkshop1389]

Could you also explain (or link me a resource) cosine spacing, like what airfoiltools.com uses? I've been trying to figure it out but I don't know what to do. All I know is that it changes the distribution of the points towards the leading and trailing edge.

[@JoshTheEngineer]

I made this video for you to help explain it. It's easiest to visually see it. goo.gl/K5Rai9

[@williamsworkshop1389]

+JoshTheEngineer Thanks! left a comment on the video.

[@samovarmaker9673]

the EngineeringExplained guy sounds different

[@erockromulan9329]

Airfoils after dark!

[@ghazalajabeen8766]

Quiz saver!

[@Rahulvlogok]

Nice explain

[@JoshTheEngineer]

Thanks!

[@gaytuhoc8921]

hi sir. how to build camber ?

[@bakrybsata3114]

:) Thank you soo mush.

[@JoshTheEngineer]

You're welcome!

[@BANTIZ]

thanks good job!

[@JoshTheEngineer]

Thank you!

[@BANTIZ]

​@@JoshTheEngineer I was here for my university project back then, now I am here to review it for a project at work :) Josh thanks again :)

[@mukherjee5]

ex, 5 digit

[@matthewmoilanen787]

Smart dude but not camebur but camber.

[@JoshTheEngineer]

In aerodynamics it's typically pronounced CAYM-bur. In vehicle dynamics (for tires) it's typically the other pronunciation.

[@matthewmoilanen787]

@@JoshTheEngineer Um no it isn't, I was a Aircraft drafter designer and a Crew Chief in the Air Force. Neither place used the pronunciation camebur. Not trying to be difficult but it's kinda like calling a glacier a "glassier".

[@JoshTheEngineer]

@@matthewmoilanen787 I think we'll just have to agree to disagree on this one. Reasonable people can pronounce words differently, and that's okay.

[@matthewmoilanen787]

@@JoshTheEngineer Pronouncing differently, maybe, asking people to accept it as normal just because you want them to is a bit of a stretch. The reason you stated for your pronunciation is simply not right though. There is absolutely no difference in the pronunciation of camber between the two groups you described. Sir I created engineering drawings for the aviation industry and nobody used the pronunciation that you do for goodness sakes.

[@JoshTheEngineer]

@@matthewmoilanen787 I'm not quite sure where I'm asking people to accept this way of pronunciation. The pronunciations I mentioned here are what I've experienced over the years (hence why I said typically). I think it's fine that you worked in the industry, but just note that others also work in the industry, and pronounce it differently than you. Again, we can agree to disagree. This discussion reminds me of a comment on another video of mine many years ago, where the commenter was very upset that I was using a certain type of mathematical formulation for a problem, and was adamant that it was never used anymore. In fact it was in widespread use and still is to this day, but perhaps he was so adamant because he was used to using a different formulation. All of this is to say, we can have different opinions on this topic, and that's perfectly fine.

[@MuhammadIrfan-ju9kn]

haah buddy ... need An example of 10 section x and y cordinate .... tomorrow i have an exam :(

[@tinolino58]

What a terrible presentation

[@JoshTheEngineer]

Thanks! You're very kind!

[@nmnm8111]

Thank u for this explanation I would aske u from where can i get coordinates for all sections ?

[@ganeshnatarajans8129]

airfoiltools.com may be of help