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All Forums >> RC Airplanes >> Aerodynamics >> Modern Airfoil for 28% plus... Extreme Aerobats
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Modern Airfoil for 28% plus... Extreme Aerobats - 3/10/2008 3:13:16 PM   
reaaz



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From: POS, TRINIDAD AND TOBAGO
Status: offline 		In as much as the selig 8036 airfoil is considered one of the best choices for large scale warbirds for its forgiving stall & high wing load capability.....

What is considered the best choice "modern" thin airfoil for those 28 to 35% aerobats like the edge 540 , extra300 &Yak 54's that allow them to snap, do harriers & good high speed flight so easily??





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RE: Modern Airfoil for 28% plus... Extreme Aerobats - 3/10/2008 4:15:54 PM   
dick Hanson



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From: slc, UT, USA
Status: offline 		basically -it is almost all in wing loading -
as for the best responding foils - --as thin as you can make em with out bending or breaking -is the best .
This ain't theory but actual application and in some cases gradual reduction in thickness and high point changes . _I built many of these size types . a foam core 1 /16" balsa sheeted and film covered wing - -seems best practical choice
as for airfoil - 12% root and 9-12% tip is about a practical limit. a low aspect ratio also helps a lot -the lower the better .

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RE: Modern Airfoil for 28% plus... Extreme Aerobats - 3/18/2008 5:38:05 PM   
reaaz



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From: POS, TRINIDAD AND TOBAGO
Status: offline 		Well, I'm leaning towards the naca 0012 airfoil for root & tip, But I have also noticed that those TOC yaks have rather sharp LE.. (so it stalls faster??) thinking thay may be on of the eppler airfoils. possibly a eppler 168

Started 3D modelling a yak 54 in 3D & am now at the airfoil selection point. What airfoil do these carden yaks use??

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RE: Modern Airfoil for 28% plus... Extreme Aerobats - 3/19/2008 4:47:34 AM   
pimmnz


 

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RE: Modern Airfoil for 28% plus... Extreme Aerobats - 3/19/2008 4:56:00 AM   
dick Hanson



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RE: Modern Airfoil for 28% plus... Extreme Aerobats - 3/19/2008 7:52:26 AM   
BMatthews



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quote:

ORIGINAL: reaaz

Well, I'm leaning towards the naca 0012 airfoil for root & tip, But I have also noticed that those TOC yaks have rather sharp LE.. (so it stalls faster??) thinking thay may be on of the eppler airfoils. possibly a eppler 168

Started 3D modelling a yak 54 in 3D & am now at the airfoil selection point. What airfoil do these carden yaks use??


You've hit the nail right on the head. With this sort of model it's not about the best airfoil. It's about the one that let's you fly the way you want. "Best" implies the one that lifts the most and stalls the latest. But for aerobatics it's about being the one that makes the plane do what you want it to do. It's about a stall that really works for the snaps and 3D stops in mid air like it hit a wall. So it's about choosing a compromise that stalls when you want but is forgiving enough that it doesn't stall when you don't expect it. That's a fine line between airfoil and wing loading.

All of which is to say that I don't know because I'm not into big pattern/3D models but I do know that this is a "fashion" sort of deal. Copy what the other models in the same size and weight range are using. Copy the ones that consistently come out in the top ten positions.


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RE: Modern Airfoil for 28% plus... Extreme Aerobats - 3/19/2008 3:16:03 PM   
HighPlains


 

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Status: offline 		Copy another design, make minor changes, change the name and call it your own.

Design by continental drift.

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RE: Modern Airfoil for 28% plus... Extreme Aerobats - 3/19/2008 3:23:41 PM   
reaaz



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From: POS, TRINIDAD AND TOBAGO
Status: offline 		yes I do wish to use/copy a proven large scale airfoil... problem is I haven't been able to find out what the carden & somenzi yaks, or those 40% extra's are using.
Thats why i posted here, because i hope someone would be able to tell me or if they had one of those kits...... scan a wing rib or two for me. lol

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RE: Modern Airfoil for 28% plus... Extreme Aerobats - 3/19/2008 3:36:33 PM   
Tall Paul



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< Message edited by Tall Paul -- 3/19/2008 3:49:35 PM >

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RE: Modern Airfoil for 28% plus... Extreme Aerobats - 3/19/2008 3:58:20 PM   
dick Hanson



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Status: offline 		The airfoils used on the BEST performance 3D/IMAC/aerobatic stuff follow a very simple rule: Make the airfoil as strong as possible yet as light as possible
This boils down to : make it as thin as practical .
If you exceed this - it will break.
The strongest is still a foam core with a well bonded balsa skin.
Some carbon wings are close but still not as good as weight in the skin is higher.
also they need some internal bracing -always.
Again - about a 12% root section is minimum
--but up to 15% at the root makes little if any performance difference
thetips tho ---a different matter - down to 8-9% is good

Also the thicker the root - the thinner the tip can be - a simple mater of strength and how it distributes
If you think you can make the wing thinner or lighter with built up methods - go ahead - You may find tho that ANY stress riser ( weak spots) will show up --unexpectedly
as for the best shape (airfoil)
not worth worrying about . just make it smooth and within the parameters seen in the avove drawings. Tho you may doubt it --- the big problem is in keeping it all rigid and flutter free as it gets lighter .
be it a model or the real thing
Full scale Sukhoi's had some structural problems
also some of the latest Sukhoi models - same problem --the designers relied on glue joints at critical root attchment points and when these loosened up- the wings literally exploded.
Spend your time learning structures- this far more important than some imagined perfect airfoil
If you get really good at light structures -you will then be able to make the betst aerobatic airfoils - thin -light and absolutely twist resistant.

You simply can NOT make the airfoil too thin -or too light - it is a practical impossibility


< Message edited by dick Hanson -- 3/19/2008 4:04:37 PM >

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RE: Modern Airfoil for 28% plus... Extreme Aerobats - 3/19/2008 4:55:54 PM   
reaaz



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Status: offline 		Thanks for the info D. Hanson, Paul & bmatt, thus sofar i am thinking of using the Eppler 168 (12.45% thk) for the root & about a 10% version of the eppler for the tip (don't see any 10% version of the e168 series on the UIUC airfoil cordinate site) so i may have to scale it. And yes you have convinced me to go with a foam cored/balsa sheeted & glassed wing.

Any advice on how not to end up designing a wing/plane that lands as notoriously as a CAP

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RE: Modern Airfoil for 28% plus... Extreme Aerobats - 3/19/2008 6:08:02 PM   
dick Hanson



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quote:

ORIGINAL: reaaz

Thanks for the info D. Hanson, Paul & bmatt, thus sofar i am thinking of using the Eppler 168 (12.45% thk) for the root & about a 10% version of the eppler for the tip (don't see any 10% version of the e168 series on the UIUC airfoil cordinate site) so i may have to scale it. And yes you have convinced me to go with a foam cored/balsa sheeted & glassed wing.

Any advice on how not to end up designing a wing/plane that lands as notoriously as a CAP

Sure -build it light - i have a number of scale Caps -here's one and they land eas easily as pie

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RE: Modern Airfoil for 28% plus... Extreme Aerobats - 3/19/2008 6:44:58 PM   
BMatthews



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Status: offline 		Yep.... Lighter is always righter. Print that in big letters and staple it to your shop wall.


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RE: Modern Airfoil for 28% plus... Extreme Aerobats - 3/19/2008 7:26:22 PM   
Red B.