Designing and building a flying wing RC model from scratch XFLR5

This is my attempt to design and build my own flying wing.
I wanted to build a small, portable size wing that would be easy and fun to fly. I used XFLR5 analysis tool to verify my vision (I'm not an expert user).
The wing came out very light and also very wobbly. I used packing tape and 3x1mm carbon fiber spars to stiffen it, but it fluttered like crazy at certain AoA.
Apart from flutter, the wing flew pretty well. It glided well and it was stable. I could hover it at 50% power. Just what I was trying to achieve.
Part two, with improved wing: • Flying wing version 2 ...
Dimensions:
Span: 1200mm
Root chord: 150mm
Tip chord: 100mm
Winglets: 80mm high
Sweep angle: 30º
Electronics:
Cobra 1960kv
5030 x three blade prop
800mAh 3S battery
12A Blue series ESC
2x 4.3g HD-1440a servos
XFLR5
www.xflr5.com/x...
"Odyssey" Kevin MacLeod (incompetech.com)
Licensed under Creative Commons: By Attribution 3.0
creativecommons...

[@rock3tcatU233]

Wow, I had no idea that this program was so capable. Thanks a lot!

[@arthurarmour6134]

Just stumbled upon this. Interesting bit of design study and build. A few points from my (limited) experience with flying wings, your flutter is probably being caused by your winglets. Not in some weird aerodynamic way, but simply by their mass, their specific CofG, and the wing elasticity at the tips. Reality is, you don't need winglets on a flying wing (see the Hortens) and you very rarely, if ever, get adverse yaw with flying wings. The control inputs used in typical flying with elevons inherently applies differential movement, invariably creating pro-yaw.

[@mexicothesenor]

aaaaa i love the background music

[@abhinavaggarwal5488]

You highlighted some fundamental steps that i had missed, thanks!

[@user-ql6pg4wc5y]

It is wonderful. Depron planes are often wobbly; not easy to stiffen it. Id say don't worry about it.

[@cnmanoj4156]

Thanks a lot for your suggestion.I will try solving it and get back to you.

[@forsas11]

Amazing work and video. I noticed that you din't improve design too much and you got a max L/D of 19, even if the wing aspect ratio is so great. Maybe you needed to do a type 2 analysis because it’s more of a glider than an airplane? However your plane flies perfectly. For me your video is a great inspiration along with sites like aerodesign de (use google translator). I have a comfortable big flying field near my home on a very large and shallow slope. The problem is that I can't fooly microsloping on that shallow slope with the current electric glider volantex ASW 28 unless a steady 10+ m/s wind is blowing because that glider doesn't have good enough L/D 12:1 at best and has excessive wing loading 45g/dm2. So I decided that I needed a super efficient rc glider with wing loading and L/D something like F5J gliders but 10-20 times cheaper :) I am now designing in XFLR5 my custom flying wing RC glider few verssion at once actualy 2-2.2m, 60-70dm2, mass 0.8-2.5kg depends on setup and/or ballast, aspect ratio including wingtips 9.5 only! I also created my own custom airfoil because all 2D airfoil that have high L/D just don't work in the 3D wing and even in simulation. The only thing that worked is the reduction in resistance, which is incompatible with a large camber airfoil. Using type 2 anlysis I got L/D 23-27 depend on wing loading when the optimal gliding speed is as low as 7-8m/s up to 11m/s, wing loading 15-36g/dm2. My custom airfoil is 8.5% (thinner or thicker has higher resistance and poorer L/D) has a relatively small camber, 1.34%, cm = ~ 0 at cl0, max cl 1.05 at Re 160k. I use some wing twist 2 degree. My airfoil a bit similar to the MH 64 but has more reflex and cleaner bottom. What I did was just a little decrease in Cd and a little increase in max Cl + some reflex compared to MH 64. I got those results after trillions of modifications :) I will build my flying wing in the spring or summer. If the design and airfoil will work well in the real world I will post the airfoil dat file and will make some video. Sorry for my english I use much help from google translater.

[@AnttiVainik]

Sounds like you are really into this stuff, that is cool. I wish I had time to do RC planes and experiment with different designs. When you get your wing flying, send me a link to the video. It is always an inspiration to watch DIY planes fly.

[@jgardner12345]

Great job. That is really cool.

[@michaellaren1]

I designed my wing in XFLR5 and it gives me a Cl max of 1,4. After I added the fuselage and the tail, the Cl only has a range of -3 degrees and +11 degrees so i can't see the maximum Cl. This is of course important to calculate the stall speed. Do you have any idea how to increase the range of the Cl so I can see where it decreases.

[@gtalckmin]

Hello, did you used a hotwire cnc to cut the wing profiles? If so, which tool did you used to genetate the G Code? Congratz for the video. Count me in if you would like to expand this for a bigger series

[@AnttiVainik]

+gtalckmin Sorry, no CNC used here, just plain old hot wire guided by 2 pair of hands.

[@cnmanoj4156]

Hey, I am designing a tilt rotor aircraft.I did static stability calculations and found the appropriate location of cg.I added mass accordingly to get the cg at the calculated position.I am using (ch10sm) airfoil for wings and (NACA0009 for tail).When i simulate(body not included) it on xflr5 it says ,"negative lift found- could not be interpolated-errors encountered". Can I get any help please?

[@GonzZz_]

What is the airfoil you have used?

[@ahmad97ist]

I didnt get any of the graphs for the airfoil analysis, although it showed that it was calculating. what could be the reason?

[@AnttiVainik]

+CN MANOJ Hi, you get "negative lift found- could not be interpolated-errors encountered" error when plane is tail heavy, (CG is too close to NP) just move the CG forward.

[@jenonfung7992]

hey, could you share the airfoils that you used? they're a bit too blurry for to read in the video

[@TheRoc35]

That's just going to change the slope of the curve, not shift it. So the problem is still there.

[@ypsonar]

Sir can you please suggest me some good article or web so I can understand more some about comparative ratios of angles and tip cord, wingspan, size of rudder etc. So i can choose proper ratios with weight of plane and speed requirement of plane etc. Please . . . !

[@AnttiVainik]

Hi, I can recommend Model Aircraft Aerodynamics, book by Martin Simons. This book talks about ratios, stability and many other things in an understandable manner. If you read and understand this book you will be able to design your own model. It was several years ago, but I remember I found a pdf online.

[@osamaissa2264]

NASA

[@mike20h]

i'm building a flying, the S-16 rebel from crash test hobby, and analyzing it for longitudinal static stability using this same software. My wing span is 3.250 ft, wing area is 1.719 ft^2, Plane mass is 1.606 lb, Root chord is 0.708 ft, MAC is 0.549 ft, AR is 6.144, with a root-tip sweep of 27.071 degree. For some reason the software is indicating i have negative lift, and fails to generate is stability analysis. Any thoughts as to why? Any help would be appreciated

[@AnttiVainik]

Weird, I tried to do the analysis with v6.37 and I'm getting errors too. Something must have changed in this version.

[@christoph8630]

Even if i follow all your steps with the exact same values, there are no opPoints in the stability analysis stored...

[@grefimuda1042]

can you help me with the installation proses? i have some problem with that. "the code execution cannot proceed because MSCP140.dll was not found. Reinstalling the program may fix this problem"

[@felipec.k.2234]

Antii Vainkid, thanks for the tutorial! Could you tell me how good were the results?

[@dlanm2u]

how heavy did it end up?

[@noneNone-mw1px]

Can buy this software in market? How much 8s that?

[@kristianazor5469]

Hello, Can I have any advice? When you do the analysis of the wing... I miss the panel on the left where you click analysis... although I can make the analysis by double-click on enter I cannot set the angles of attack... Does anyone know where I can find the panel?

[@kristianazor5469]

sorry miss the panel on the right, but on the left also... I have the same version of xflr5

[@muhammedomar424]

How you know. The lenght and the width of the wing

[@AnttiVainik]

@@muhammedomar424 you pick length and width yourself. Look up "aspect ratio". Long and narrow wing like in sailplanes will produce a lot of lift but will be slow on roll axis. Short and wide wing will be fast on roll axis but won't produce much lift and will need more speed to stay in the air, like sport plane.

[@rohan9526]

hey, I am facing a problem that no one is able to help me with... you have done the viscous analysis in your model for stability analysis, but when I am trying to do the same with my model, it gives the - "could not be interpolated" output alongside the other parameters....resulting in a failed stability analysis, plz help. tnks.

[@AnttiVainik]

+D Rohan Hi, I've seen this error, if I remember correctly it occurs when foil analysis is too "rough". Try analyzing foils with smaller Re-number steps, say: from 20 000 - 1 500 000, step 20 000. It will take a bit longer, but should solve your problem. Let me know how it turns out.

[@Viachev]

great

[@SidGUDayton]

Did you experience any adverse yaw in your flight?

[@AnttiVainik]

+Sidaard Gunasekaran I didn't notice any adverse yaw, but I was flying line-of-sight. With FPV gear you could tell better, how much there is. There are a few things that counter ay on this model. It has differential elevons (up-moving elevon moves more than down-going), some anhedral angle, as well as high sweep angle of 30 degrees.

[@RabbitStew247]

what aerofoil did you use on the main wing? phoenix?

[@AnttiVainik]

+Joel Haas Yes, it is Phoenix, but that was a bad idea. Phoenix has negative Cm at low AoA, that combined with swept wing resulted in pitch down moment. To counter that I had to trim elevons up quite a lot -> inefficient flight. Check out part two of this video, I made second wing with Phoenix at root and nearly symmetrical airfoil (modified Phoenix) at tip, which seemed to reduce nose down pitching moment.

[@user-ol1qm9ey7g]

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[@krylatich]

On what have you based your Ranold's numbers?

[@AnttiVainik]

Many years have passed, but.. My goal was to make a slow flying wing, so the Reynolds number was based on speed 30-50km/h and chord length of about 20cm.

[@krylatich]

@@AnttiVainik thnx

[@pascalmueller9712]

Hey in my case it always says some points are outside the flight envelope Can someone pls help me thx

[@nhorsreymou2052]

Wing

[@shodanxx]

Is it possible to import my aircraft model from my CAD program into XFLR5 ?

[@AnttiVainik]

+shodanxx There is no direct way that I know, sorry. The whole idea behind XFLR5 is airfoil analysis. You could slice your model longitudinally into airfoil sections, create dat coordinate files, import them in XFLR5 and do the analysis. That would require some woodoo and black magic in your CAD software. Even then the end result is not guaranteed. The easiest way would be to recreate geometry in XFLR5, with appropriate airfoils. This way you will get a rough idea how your model behaves.

[@shodanxx]

Thanks, it's mostly that I just know how to draw in sketchup but I'll have to re-learn to use xflr5 and making changes will also be harder. Oh well, guess I won't get around learning xflr5 !

[@enesyilmaz626]

ı cant find phoenix.dat can you help me?

[@AnttiVainik]

You can find the coordinates on the last page of this document, just copy and paste them in notepad and save as phoenix.dat www.google.com/url?sa=t&source=web&rct=j&url=www.diva-portal.org/smash/get/diva2:450812/fulltext01.pdf&ved=2ahUKEwiR9OXR0K_iAhWdxMQBHVSwBl4QFjABegQIAhAB&usg=AOvVaw3poprORGj-Qkw0At9nHbxP&cshid=1558545037960

[@Tomvandorland]

what is the wing airfoil?

[@AnttiVainik]

In this model I used Phoenix airfoil. For a flying wing you need reflexed airfoil, such as MH45, PW75, HS522 or other similar.

[@scottrharris]

You don't need a reflexed airfoil. You can trim with sweep and twist.

[@AnttiVainik]

Phoenix. If you use make sure you compensate for negative Cm. This model has pitch down tendency. www.glide.net.au/flyingwing/coords/PHOENIX.COR

[@AnttiVainik]

Putting washout behind the c.g. with sweep? I see what you mean. Isn't that what reflex does?

[@marccretten]

Going way to fast in this vid. Can you do a tutorial at all? I have no idea what half the perimeters you have entered.

[@AnttiVainik]

Marc Cretten Hi Marc! In this video I was going around 20-30km/h (12-18mph) not that fast really. The wing is only 1.2cm (0.5in) thick at its chord, so it bends easily. I didn't really intend this video to be a tutorial on XFLR5, more like a documentation on my approach. About the parameters, I know only half what I entered ;) the rest are good guesstimations. It took me days...weeks to learn XFLR5. I don't want to tell people this is this is the way, because I'm not sure myself. I've been doing RC only for 1 year.

[@marccretten]

Antti Vainik haha no worries, i will fiddle with the software and hope i get somewhere. I never usually work with software, a piece of paper and pen always did the job for me:-)