Beautiful airfoils !

Airfoil Investigation Database - Showing GEMINI (smoothed)

I found this GEMINI really awesome for its looks !

Is there any story about it..where has it been used ?

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http://www.ae.illinois.edu/m-selig/ads/afplots/geminism.gif

Seem to be a low Reynolds number foil...R/C sailplane..no wonder.

 

Another beauty;

Airfoil Investigation Database - Showing EPPLER 642

Eppler 642

Lotsa more L/D than in a NACA 747A315..which to me looks a bit similar..laminar ?

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Another beauty NACA 65 ( 2 ) 415 a; http://www.worldofkrauss.com/foils/1657

 

Are you looking at these for the aircraft in your avatar, and using The World of Krauss aerodynamic data? That data looks like it is all calculated at Reynolds numbers < 10^5 or lower -- probably not relevant for your design (it's closer to normal for model aircraft). Most manned aircraft operate at Re=5 x 10^5 or higher -- big difference! See links off this page for info on what aircraft use what airfoil: UIUC Airfoil Data Site

 

Yeah I am looking at the Krauss data..seemlike the Gemini performs better the higher the Reynolds number is; Airfoil Investigation Database - Showing GEMINI (smoothed)

I also have to make possibly 2 R/C models before the real one...first to see if there is fundamentally something wrong and then to study taxiing and stall + aerobatic caracteristics near the real one size..and structrures how to make it efficient and strong.

The symbolic value of a small model is also good..just seeing it 3D for real...sorta.

UIUA is one I used already to get the data.

 

Airfoil Investigation Database - Showing naca-2414 the NACA 2414 looks sorta slow to me...its dragcoefficient as an object does not please me. NACA 65 ( 2 ) 415 looks better ( only the moment seems hard ) http://www.worldofkrauss.com/foils/1657 .

http://www.worldofkrauss.com/foils/1419 GOE 679 ( if you meant this ) looks even worse in this dragcoefficient aspect point of view.

But you are right the Gemini has weird polars.

Wortmann FX 61-147 looks awesome too, but it has vanished from Krauss investigations ?

http://www.ae.illinois.edu/m-selig/ads/afplots/fx61147.gif

Plane using it flew in 1968 already ?

http://en.wikipedia.org/wiki/Akaflieg_Stuttgart_FS-25

....but the one using it in 1953 crashed; http://en.wikipedia.org/wiki/Akaflieg_Stuttgart_FS-23

is it dangerous ?

 

Yes, the GOE is much better for slow gliders, not your speedster. What cruise Cl are you planning to use?

As for the naca 65:
Airfoil Investigation Database - Showing NACA 65(2)-215
Maybe the low Re data is not showing any good laminar flow effects that would appear at higher Re. But compared head to head with the naca 2414 in this database, the 2414 has a lower minimum drag coefficient. And it has a much lower drag coefficient than the gemini.


And if I'm wrong about this database being valuable for comparing airfoils head to head, I hope someone lets me know.

 

All the investigations at that site are for model size aircraft. Not applicable to anything larger and contrary to what you posted above, using low Rn data to extrapolate to full scale application is not directly possible since relationships are rarely linear or simply scalable.

 

Here you can see where the foils have been used in; The Incomplete Guide to Airfoil Usage

 

Right and when in 65 215 why not 65 212 as well..straight to the jet age ? If I get the Jetcat 200 engines I go for that foil !!!

And if I enhance them turbines I go for this; http://www.ae.illinois.edu/m-selig/ads/afplots/naca65210.gif

I have to get the wheel retracted before that.



The cruise Cl I have ?...I have to ask my friend Karoliina about it ! DESIGN|A|PLANE: Relation of cruise Cl and wing loading

Cruise Cl seems like an important matter..it sorta defines the incident mounting angle and size of the wing.

 

But there is one aspect that makes it slightly easier to study high speed behaviour..you can actually fly a small model at well beyond mach 1 or 2...relatively speaking that is. See if I make a 1/12 scale FNXII ( avatar byrd ) leave the wheels away and install solid plywood 65(2)210 wing and use a heavy duty rubberband and a sling I can make it go 150 km/h..that is 1800 km/h ( 1125 mph ) scale speed. I won't get supersonic data out of the test, but I'll sure get lotsa data of the stability of the design at high speed.

Don't I ?

 

How about this beauty; Airfoil Investigation Database - Showing MH 24 9.01%

MH24 9% thick