NACA2412 vs CLARK-Y - Trainer
#1
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Hello to everyone and thanks in advance for your supoort! I am planning to build a new balsa trainer based on the Great Planes Perfect Trainer 40. The idea is to create a versatile Trainer. I he heard that Clark-Y (Default airfoil with the trainer) is easy to build but missing some features of more advanced airfoild like NACA2412. I do not have any probles for building with another profile but I would like to know your comments or suggestion to changing the airfoil. Am I losing or wining something with either of them? AoA will be the recommended one in the original design +2-+3 dregrees.
The idea is to provide more felxibility to that trainer.
All your comments and suggestions will be welcomed.
Thanks!
Dino
The idea is to provide more felxibility to that trainer.
All your comments and suggestions will be welcomed.
Thanks!
Dino
#2
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Depends on what your end goal is. With the semi symmetrical airfoil you will gain some speed. With the incidence you mention you will still maintain a fair amount of positive stability meaning the airplane will pitch trim at a narrow speed range. If that is what you want then great. If not, set the wing to zero as it will still generate enough lift to support the models weight but be more “ trim constant “ which would get even better with a CG at 30% to 33% and a couple degrees of down thrust.
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#4
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Many, many years ago I learned on a Telamaster. It used a Clark Y for the wing and a lifting tail with a flat bottom. When I designed my own, I used the same plan form but reduced the dihedral to 1.5 inches each wing tip. With the high wing and a little dihedral it was perfect self righting and pitch recovery. I reduced the incidence to half and the tail plane was zero and the speed range opened up quite a bit. If I flew it 3/4 throttle straight and trimmed it level, I found it perfect for my flying. It would easily do most beginner to intermediate aerobatics in a very scale like shape. I really liked the sheeted wing from the leading edge to the spar top and bottom as it added lots of strength. I scaled it up to 100 inch span and increased the rudder to twice the size, and it made a great glider tug. I promptly increased the rudder in the smaller one and I could carry up to 2 meter sailplanes on a cradle on the top wing. I even have an old Telecaster 66 that I converted to electric, and it has unlimited vertical because I used a motor I had lying around and didn't think it would be that overpowered.
Later I switched to a Lazy Ace, which if you really look at it, you might just see what could be a Telemaster as a biplane. It, too, has both Clark Y's for the main wings and a lifting tail. It's even more fun than the Telemaster and there are quite a few members in my club who's introductory flight was on that Lazy Ace.
Later I switched to a Lazy Ace, which if you really look at it, you might just see what could be a Telemaster as a biplane. It, too, has both Clark Y's for the main wings and a lifting tail. It's even more fun than the Telemaster and there are quite a few members in my club who's introductory flight was on that Lazy Ace.
#8
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Stall characteristics and lift to drag are two separate things. I’ve flown airplanes with Clark Y airfoils that had quite nasty stalls and airplanes with symmetrical airfoils that stalls were/are quite forgiving. My F3A design has to be forced to stall and has symmetrical airfoils with aggressive taper.
#9
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NACA 2412 versus Clark Y is in practice not that different. As long as it really is the Clark Y and not some flat bottom profile with the upper curve from the side of some shoe.
Note that the Great Plane PT-40 trainer airfoil is something different than Clark Y profile.
NACA 2412 is 12% thick with 2% camber and the highest point on the camber line 40% from the leading edge. Clark Y is 11.7% thick with 3.5% camber and the highest point on the camber line more forward at 30% from the leading edge.
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NACA 2412 is 12% thick with 2% camber and the highest point on the camber line 40% from the leading edge. Clark Y is 11.7% thick with 3.5% camber and the highest point on the camber line more forward at 30% from the leading edge.
#11
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It is perhaps worth mentioning that physical size plays a part on how a wing section behaves. In general the smaller the plane the less significant the wing section becomes as other factors like the viscosity of air play a bigger part. This explains why models are unable to achieve anything like the lift to drag ratio of a full size plane let alone at the same airspeed.
If follows that in models the wing section performance is less significant than its general characteristics. After all a perfectly controllable model plane can be built with a flat plate wing.
Certainly up to 2m span some of my best flying home design planes use a Clark Y type wing section and for scale planes I have no problem using a true scale wing sections right up to the complex twists in Concord's wing..
![](https://cimg1.ibsrv.net/gimg/www.rcuniverse.com-vbulletin/750x359/wingtwists_0c16d0f6dd458ab379bf5af234a669b0f076db3e.jpg)
As it flies perfectly well at just 1/10 of the take off speed of the full size it raises the question does the wing section in this case make any difference?
A still from a flight video
![](https://cimg7.ibsrv.net/gimg/www.rcuniverse.com-vbulletin/750x560/24apr14_890e1e27cef1b169d9206c6c27f280398b06d3ba.jpg)
Just saying.
.
If follows that in models the wing section performance is less significant than its general characteristics. After all a perfectly controllable model plane can be built with a flat plate wing.
Certainly up to 2m span some of my best flying home design planes use a Clark Y type wing section and for scale planes I have no problem using a true scale wing sections right up to the complex twists in Concord's wing..
![](https://cimg1.ibsrv.net/gimg/www.rcuniverse.com-vbulletin/750x359/wingtwists_0c16d0f6dd458ab379bf5af234a669b0f076db3e.jpg)
As it flies perfectly well at just 1/10 of the take off speed of the full size it raises the question does the wing section in this case make any difference?
A still from a flight video
![](https://cimg7.ibsrv.net/gimg/www.rcuniverse.com-vbulletin/750x560/24apr14_890e1e27cef1b169d9206c6c27f280398b06d3ba.jpg)
Just saying.
.
#12
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Funny that you mention lift to drag ratio. IMO on a powered model that is not a concern nor should it be except for a speed model. In fact one of my most successful models has what ai call transitional airfoils that from root to tip the drag increases. Note how the TE gets thicker at the tip. Not evident is the airfoil percentage goes up root to tip as well.
![](https://cimg3.ibsrv.net/gimg/www.rcuniverse.com-vbulletin/2000x1504/img_0998_5ff9be60bccd692211ac28afb6993f37cf588019.png)
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#13
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Wings with flat bottom airfoils are certainly easier to build with a high degree of accuracy. However many assume that a flat bottom airfoil wing is incapable of anything beyond beginning aerobatic maneuvers, and this is simply NOT true. The design of the airframe, incidence angles and tail design have WAY more to do with aerobatic capability. Many trainers are designed for a high degree of positive stability, indeed many trainers from the early days of RC were set up more like free flight aircraft than RC trainers. It’s no surprise their aerobatic capabilities are limited.
Remember that when the wing sits flat on the fuselage with the BOTTOM surface flat with tail, the wing actually has about 2 degrees of POSITIVE incidence which will cause a pitching up with speed or power increases, and will certainly affect inverted flight. Remember that the angle of incidence for the wing is measured from the CENTER of the leading edge to the center of the trailing edge and has nothing at all to do with the bottom surface of the wing.
An airplane with a REAL Clark Y airfoil, set at a TRUE 0-0 incidence with the tail, and a few degrees of down thrust, will likely surprise you with it’s aerobatic capabilities, inverted flight, and reaction to power and speed changes.
Remember that when the wing sits flat on the fuselage with the BOTTOM surface flat with tail, the wing actually has about 2 degrees of POSITIVE incidence which will cause a pitching up with speed or power increases, and will certainly affect inverted flight. Remember that the angle of incidence for the wing is measured from the CENTER of the leading edge to the center of the trailing edge and has nothing at all to do with the bottom surface of the wing.
An airplane with a REAL Clark Y airfoil, set at a TRUE 0-0 incidence with the tail, and a few degrees of down thrust, will likely surprise you with it’s aerobatic capabilities, inverted flight, and reaction to power and speed changes.
Last edited by 049flyer; Today at 11:59 AM.