Aerofoil Selection - RC Groups
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Dec 11, 2011, 06:01 AM
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Aerofoil Selection

Hi all,

1) What aerofoils have people used on their builds?

2) Which aerofoils are used extensively in RC-aircraft and Why?

3) If you'd be kind enough in stating the reference as to why certain aerofoils are used on RC-aircraft so that I can read up on it more

4) Would you be kind enough in provided me a link to a webpage/reference to a book on where i can get lift and drag coefficient data for aerofoils please? As I'm building an RC-aircraft with a 107g motor and a 0.8m wing span limit I am kind of confined to the specification.

*Important: Ideally I need CL and CD data for aerofoils used on RC-aeroplanes*

Thank you for your efforts and i will be eagerly waiting for your feedback my friends

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Dec 11, 2011, 06:26 AM
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flat KF on top
Dec 11, 2011, 06:59 AM
Registered User
Hi space 1

Is that a flat KF on top with a flat bottom i.e. KFM2 or is it the KFM1?

If you don't mind me asking why?

Thank you
Dec 11, 2011, 07:51 AM
Registered User
timatworksg's Avatar
Hi charlie01,

Can't help you with questions 2,3 & 4 as I'm no expert, but I mostly scratchbuild foamies and enjoy building, flying and!

I mostly use a KFm4 airfoil at 50% of Wing cord wherever I can! I mostly build slowflyers and if I can't squeeze in a KFM4 I at least put a KFM1. I do so mostly for adding that extra stiffness and strength in the wing. I like the KF airfoils as it gives me the best of both worlds in stiffness, strength and a workable airfoil. Since I build with simplicity it's so much easier to do a KF airfoil then it is a conventional airfoil with spars, or heat bend foam....takes too much time for!

Personally I like the KFm4. With a laminate both above and below the flat foam wing, you get that stiffness, speed with the top laminate and the drag needed from the bottom KF piece. Also it holds up to crashes very very well!! I crash alot anyway! However it will add weight...and effect a slow flying I try to keep things in the WS of 20 to 24" as I like the size for where I fly mostly.

I am building a Spad like design with a KFm4 26" wing...and added a CF rod near the Ailerons for added stiffness due to the size. Hoping that will give the build what has helped my other builds so much. So far I have a KFm4 on a Simple Delta, Mini Heart and both fly smoothly and stable. Thats what I have seen from my end that is.

Others may have their thoughts....but just sharing my experience with a KF. Hope that helps....though I'm still learning the whole aerodynamics in foamies thing!

Best of luck in your adventure!
Dec 11, 2011, 08:46 AM
Build straight - Fly twisty
Whiskers's Avatar
Charlie, as we tried to explain to you in your other thread on this subject, most of us here do not use airfoil data figures in our builds.
Most here build other people's designs, so such calculations do not come into the mix.
Those who design their own planes either use an established section or create a profile on the TLAR (that looks about right) principle.
Many planes employ a flat plate, If you want to see how perfectly such a plane can fly take a look at:
The KFm series is extremely popular and successful here because they have been proved to work. There is little meaningful data on their performance values, just a body of experience.
Three of my planes have very different TLAR airfoils. One has a KFm4, another has a thick rounded nose symmetrical and the third has a thin sharp nosed symmetrical airfoil. All are excellent sports aerobatic performers and all have similar stalling characteristics, so there is a lot of lee way in this area.
The PBF built with a KFm wing is your best chance of making a plane that will fly well.
Just invent CL and CD data. How will they know?
Dec 11, 2011, 12:28 PM
Registered User
Need i say more
Dec 11, 2011, 12:40 PM
Grumpy old git.. Who me?
JetPlaneFlyer's Avatar
There are thousands of different airfoils used on RC aircraft. What is best for your model depends on whet you want the model to do?

I guess the most common 'proper' airfoil (for which you can get Cl and Cd data) used on Rc models would be the Clark-Y. The good old Clark-y is a good all round airfoil with good lift, quite low drag, and a gentle stall, but it's not ideal for every application.

To perform well any airfoil must be made accurately, so a great deal of what will work best depends on your build method.

This is a good site for airfoil data:

Dec 11, 2011, 12:56 PM
An itch?. Scratch build.
eflightray's Avatar
Here's where the guys hang out who know everything about airfoils, - it's the Modeling Science forum. If you ask technical questions there, you will get the sort of answers you may be looking for.

Model aircraft airfoils are usually designed, (or just made up), to suit a specific model and the way the builder wants it to fly, or just simply for ease of making.

There are so many different types of models, and many different airfoils for each of those model types, it would be near impossible to list them all.

Also if you scroll down this page to the 'Similar Thread' list you will see other threads about airfoils. A search on Airfoil, should find many many more.

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