Airfoil and Formfactor selection for small indoor Nurflügler - RC Groups
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Feb 22, 2013, 08:00 AM
Registered User

Airfoil and Formfactor selection for small indoor Nurflügler


first off, i'm not sure if i'm in the right section of rcgroups, as i don't quite understand the difference between a flying wing and a nurflügeler (beeing german i know this is the simple translation for "flying wing"). Please move topic and enlighten me ;-).

Anyways, i've recently cut my first flying wing with a hot wire from "el cheapo" EPS foam, and it worked so well that i now want to make an old dream come into life: a super small flying wing, fit to cruise our livingroom ;-). I still have to get a little better at hotwire cutting and fine-adjust cuttingspeed, and temperature so thinner parts work out well, but well ... i need to work on two problems at once: designing the wing, and providing technique for actually manufacturing it

As this project would be a bit off the tracks i guess i can't just use standard airfoils and building plans. So what i wanted to do is dive a little into flying wing design, get to know the basics, and then try my luck . So far i've read many articles from and on the original Horten-Gliders. Other good literature tips are still welcome .

Anyways, from what i have understood i should probably prefer more lift and less drag over self-stabilization for this project. A small crash or twitch in the livingroom ain't as bad as with 3m gliders out on the field. Also, you probably have to ride the sticks all the time anyways, so getting more lift and less drag combined with a smooth stall characteristics would be benificial as the selection if lightweight components would become a little less critical, right? So from what i have understood that means not-quite-as-much reflex, much much camber, and the camber moved far to the front, right? The stall characteristics would then be (over-simplified!) a tradeoff between drag and nice stall, by upsweeping the end of the airfoil a bit. Once again, i'm sorry to oversimply that badly here. I'm studying computer science, not aeronautical engineering, so i can only try my best to understand those vastly complex set of physical equations (that i'm not used to).

That is also why i seek your help. I'd really like to try and make my start into designing micro wings, but i'm a little lost at my current point of learning: Most resources are too simple, aerodesign was just right, and actual scientific papers or airfoil design tools such as xflr5 are too advanced for me. So i can either go the "trial and error" route now, or hopefully get some input from you what else to do, where to go, what to try, what to read, ... -- or just ideas on how to get started with actual designing...

Well, so far. Thanks in advance
- ShellFish
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Feb 22, 2013, 08:12 AM
HerkS's Avatar
I suggest that you take a look at this ---
Feb 22, 2013, 09:18 AM
internet gadfly
nmasters's Avatar
A German computer science major... There's a program called "Nurflügel" that you may find easier to use than XFLR5. There are also several spreadsheets that do the balancing of pitching moments needed for tailless flight. There are several links in this article. The walk along gliders are a good place to start for indoor flight but I suspect that you want RC. You may find some useful information about elevon shape and size in this thread.

walkalong glider pylon racing (0 min 56 sec)

Feb 22, 2013, 10:16 AM
Wolfking44's Avatar
This site has great info on walk along gliding
Feb 23, 2013, 08:29 AM
Registered User

thanks for the tips. I've already built a few walkalong gliders just for toying around, but what i want to build here would be a electrified small livingroom nurflügler. I have measured around a bit yesterday and found that i probably could use a old servos motor together with its controlboard as a main motor for such a small plane. I've replaced the potentiometer from the servo with a smd resistor, so this becomes a ultimately light(?probably not ultimately?) brushed esc + motor. While i don't have a proper propeller for this here i've tested with 5040 nylon props (oh wow, way to large/heavy ;P) and my genius cp tail props. The 5040 gave what felt like okay~ish thrust and reasonable RPM without warming the motor tooo much. At least i would've guessed (without measuring yet) that it should be plenty for such a small project.

Sadly on the airfoil front there isn't much news. I've read alot, i've understood little, and am still reading and trying to grasp the basics of aeronautical engeneering topics .
Feb 24, 2013, 01:10 PM
Scratch builder
Take a look at this thread and click the link at post #6. Perhaps you can scale this to what you want. A living room flyer is quite the challenge! I would guess that full thickness airfoil construction may be too eleborate and heavy. You may just need a bent sheet of foam with some trial and error.

Maybe the indoor sub forum here would have some insight as to power systems and nano radio set ups.
Feb 28, 2013, 09:42 PM
derk's Avatar
Depending on the size of your living room, your going to need lighter radio gear than converted servo boards. Deltang makes some very good Dsm2 receivers that use actuators which will give you the lowest weight. Small motors and small batteries are another must, typically 30mah or less is a good match to 4mm pager motors. If you need some inexpensive micro parts, has a good selection from motors, props, actuators and other stuff you'll need.

Just keep in mind LIGHT WEIGHT and low wing loading.
My latest room flier has a 16 inch span, 5 inch chord and weighs about 5 grams rtf
Mar 01, 2013, 12:09 AM
Registered User
slebetman's Avatar
If you're building strictly indoor then nothing beats the low weight of IR receivers. I used to scrounge some of the Silverlit/Airhogs ones but I can't find them anymore locally. Derk has a post about some fairly inexpensive IR systems from Korea:

As for airfoil and planform, I've seen everything from fly if it's light enough and has enough thrust. At micro sizes I rarely see people bothering with things like proper twist and accurate airfoil - just trim in a bit of reflex and it should fly.

Here's a nice video of a micro indoor "fake" Horten:

All wing take off 2 (3 min 1 sec)

I say "fake" because unlike what people in this forum consider "real" Hortens this had flat plate airfoil. Look carefully and you'll notice that he bent the center "tail" upwards for a bit of built in reflex. So it's possibly a reverse Horten with wash-in instead of wash-out.

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