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Old Oct 30, 2012, 03:24 PM
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Cluj-Napoca
Joined May 2007
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Airfoil selection for a BWB flying wing

Hi,

I am looking now to design a flying wing that I will use to improve my building techniques using foam core and balsa sheeting. I have also plans to start in FPV and this plane it may become a good platform.

I have decided on the size and plan form of the wing. I am not looking for high performance so the criteria are just to respect the basic design requirements. See the link bellow for details.

http://j.mp/Svax2R
Wingspan = 1.6m
Wing area = 45 qdm
Weigth = 1300-1400 grams

I am not a specialist and I cannot decide what airfoil to use for the central section.
I would like to build the plane as a blended wing body with a 15-18% thick for the center section and a 9-11% thick for the outer wing sections.

For the outer sections I can use MH45 or similar that I already used with success in a previews design ( http://www.rcgroups.com/forums/member.php?u=156072 ).

Could you please provide me some suggestions on what airfoils will do well for this flying wing?

Thanks,
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Old Nov 01, 2012, 02:46 PM
Never trust laughing dolphins
Joined Feb 2011
2,086 Posts
There are quite a few options but I would stick with fiberglass tape and keep things as lightweight as possible. There's no true advantage to heavy use of covering except maybe giving it a color.

Some use all kinds of oracovers, monokote and strong paint cover but it all comes with a weight penalty.
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Old Nov 02, 2012, 11:05 AM
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Colorado
Joined Aug 2006
2,153 Posts
MH-45 and PW-51 are both very good thin airfoils for flying wings. You can thicken either one of those for the center section with satisfactory results. I am using NACA 8-H-15 for mine. The thick sections will all perform better with turbulator tape both top and bottom. The tape on the bottom will make the pitching moment much smoother.

--Norm
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Old Nov 08, 2012, 02:57 PM
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Cluj-Napoca
Joined May 2007
18 Posts
Hi,

Thanks for the replies,it is much appreciated. And I apologize for the late answer.

I am not able to build more then one plane per year so if there is only one it should not be a foamy. This is the reason I want it nicely build, maybe using also fiber glass. And it must be my own design.

Altough I don't have any problem with foamies. I have build few some years ago.

Norm, thanks for the tip with thickening the airfoil. As I have told I didn't know this works. This can save a lot of time when chousing the airfoil for a R/C model plane.

I have create a first 3D CAD model using MH45 airfoil that I've thickened to 16% at the root, 12% at the joint and standard 9.8% at the tips. But to me it looks quite similar to X8 FPV that way that I have been discouraged. I really hate to make copies!!

Conclusion is, I don't know if I should continue with this design....

Thanks,
Cristi
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Old Nov 09, 2012, 12:54 AM
Never trust laughing dolphins
Joined Feb 2011
2,086 Posts
I wouldn't worry about copying a design, but you should figure out why certain design choices were made. Not any random shape will make for a good plane. If you're going fpv, make sure there's enough room to put your gear in cleanly and that getting the center of gravity right is managable. That's often why the fpv planes have larger noses / canopy areas.

Building your own designed planes also involves trial and error, as you'll probably learn things that you could have done better along the way. Don't hesitate to start over if need be.
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Last edited by PHMX; Nov 09, 2012 at 01:15 AM.
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Old Nov 09, 2012, 03:14 AM
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Cluj-Napoca
Joined May 2007
18 Posts
Thanks for the advice, I am a flying wings fun and this design does not look bad.

The reason I have added the nose was as you said, to make more room for equipment and to provide some larger freedom for CG adjustments. The thicker root section is about 100mm.This provides enough space for FPV equipments.

Before I do any progress I need to decide what technique to use to cover the foam cores: balsa sheeting, fiberglass + LE carbon fiber. I really don't want to cover with oracover, monokote,...

Cristi,
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Old Nov 10, 2012, 06:54 AM
Never trust laughing dolphins
Joined Feb 2011
2,086 Posts
I see. Well I would definitely keep an eye on the total weight regardless of what you wish to go for. Thing is, you can always make a plane heavier, but it's pretty tough to make it lighter once you've got half way past covering the entire hull with whatever you go for.

So far I'm getting best results using just the fiberglass tape stuff and using a lightweight paintjob to get some good looking planes. Colored tape is an option, but in my experience the tape I've tried often doesn't bond well with foam and its a waste to cover it all up in glue.
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Old Nov 12, 2012, 09:26 AM
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Cluj-Napoca
Joined May 2007
18 Posts
@PHMX can you please indicate me what fiberglass tape are you using?

You say you use a lightweight paintjob.Do you have pictures of a wing built and paint like you suggest?

Thanks,
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Old Nov 12, 2012, 12:55 PM
Never trust laughing dolphins
Joined Feb 2011
2,086 Posts
Sure, I'll shoot some pictures soon, I'm finishing one up actually. The fiberglass tape is nothing special, but does not cover the entire plane. Weight is a concern both when it comes to the tape and paint. The larger wings can handle it though, no sweat.
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