Flying Wing Design?

[Wingman04]

I am new in R/C and have been wanting to build my own flying wing design for a while. I have been doing research and some sources say that the wingtip can be angled up or down to help with lift or the trailing edge can be angled up. Is any of this needed? I want to use the same techniques that FliteTest uses because they seem to get awesome results! Any help would be awsome.

 

[Hai-Lee]

Wing tip angle up or down, (spanwise), can provide roll stability or enhanced maneuverability.

The angling upwards of the trailing edge is used to supply a level of reflex which is used for pitch stability or balance.

I build many FB Flying wing designs, (mostly straight wing retro type designs), and so can inform you that the wing cord, reflex, weight, and balance are the things you should concentrate on!

Balance point is critical unless the wing cord is sufficiently long. The greater the cord the more gentle the control will be.

Love my wings!

Have fun!

 

[Wingman04]

I know all of these things help, as you said, but does FliteTest use any of these? I'm just looking for my first, simple design. Do I need any of these features to make it fly? Bending the wingtips sounds like it would take a little bit of work when using foam board. Also, if I were to mess with the trailing edge, how much angle should I put in? Thanks.

 

[TEAJR66]

You don't need to bend the wings. The reflex, on these folded foam wings, comes from UP on the elevons. For example, the Versa wing, I believe has 6 degrees of up when the control surfaces are neutral.

Use one of the CG calculators. Here are two that have worked for me. http://fwcg.3dzone.dk/. http://wingcgcalc.bruder.com.br/en_US/?
if you nose in on the launch, and your CG is correct, you need more up reflex.

Once CG and reflex is figured out, yaw stability will be the next tweak. That will be a longer discussion.

 

[Wingman04]

Thanks a lot! That really help me.

 

[Try-n-glide]

Im working on INAV control of mine now, but did a wing design last year. Perhaps my notes on early failure will be helpful. My 2nd design flies well.

http://forum.flitetest.com/showthread.php?36156-Rocket-plank

The Kfm airfoil (google the rcgroups.com thread) turned out to be a good choice for me. Easy to build and reasonably strong. The long nose helps with orientation and CG, but is an Achilles heel on the durability front. Had to be reinforced.

Watch the flying wing aerodynamic vids by rcmodelreviews at YouTube.

Find a good FW CG calculator online. It will take some experiments to find a wing sweep and taper that make CG target easier to hit. Easy to make a wing tail heavy and BAM.

I found you can effectively create washout and more stability with the combination of sweep, taper, and reflex. If reflex of elevons is carried to the wing tip, and you have a narrower wing tip than root, then the effective AOA of the tip is less than the root (imagine a line from the back of the elevon to leading edge - if the drop is equal a shorter distance has a steeper angle). Tip stalls suck!

 

[Wingman04]

Thanks so much for recommending the rcmodelreviews channel.

 

[Wingman04]

I see some planes where the wingtip thickness is less than the wing root thickness. Is there a reason for this?

 

[Wingman04]

Im working on INAV control of mine now, but did a wing design last year. Perhaps my notes on early failure will be helpful. My 2nd design flies well.

http://forum.flitetest.com/showthread.php?36156-Rocket-plank

The Kfm airfoil (google the rcgroups.com thread) turned out to be a good choice for me. Easy to build and reasonably strong. The long nose helps with orientation and CG, but is an Achilles heel on the durability front. Had to be reinforced.

Watch the flying wing aerodynamic vids by rcmodelreviews at YouTube.

Find a good FW CG calculator online. It will take some experiments to find a wing sweep and taper that make CG target easier to hit. Easy to make a wing tail heavy and BAM.

I found you can effectively create washout and more stability with the combination of sweep, taper, and reflex. If reflex of elevons is carried to the wing tip, and you have a narrower wing tip than root, then the effective AOA of the tip is less than the root (imagine a line from the back of the elevon to leading edge - if the drop is equal a shorter distance has a steeper angle). Tip stalls suck!

Could you please re-describe the last paragraph. I'm new to the hobby and don't know all of the terms yet.

I understand how washout helps with stalls (because the whole wing doesn't stall at once), but I didn't quite understand what you meant with the line between the elevons and leading edge. Thanks

 

[rockyboy]

I see some planes where the wingtip thickness is less than the wing root thickness. Is there a reason for this?

Often more strength is needed at the root as the forces of gravity & intertia in aerobatics between the wing and fuselage are greater close to the fuselage due to greater leverage of lift forces out at the wing tip.

There are also lots of wing designs that change the airfoil shape between the root and tip as well, to give different stall characteristics under certain conditions.

I find wikipedia to be a great resource for getting a better understanding of aerodynamic design principles that might help you too

https://en.wikipedia.org/wiki/Category:Aircraft_wing_design
https://en.wikipedia.org/wiki/Airfoil

 

[Fly_electric]

May depend on the amount of L.E. sweep.
After learning to fly with Real Flight and making several custom content models for a few years, friends encouraged me to get into RW flying, so I started with the Tower Hobbies CrazE during the winter two years ago (found it easy to fly from the first launch).
Then got the bug to make my own design to fly that next summer.

Started with the flying wing CG calculator V2, default setting shown

http://fwcg.3dzone.dk/ (used the extended version)

Made the FBW from one sheet of DTFB, picked a balance of about 15%, as was still a low time RW pilot.
No washout added.

Designed it with Real Flight. As the various final weights became known, added those to the physics, then adjusted the balance in RF for what worked the best, and balanced the real world model to match.

Flew great for all of its summer life. Eventually, my newbie design of the weak spot at the front corner between the motor mount and the FB gave in its first hard-er landing. But, it served its learning experience task, for may enjoyable flights.
Added one thickness of foam board for reflex.
Never needed any extra trim.

So, it may depend on the design?
Wings with some sweep offset the need for washout??
Not sure, but it doesn't seem like the CrazE has any washout either..

 

[mrjdstewart]

my delta is a bit big but was purposely built to teach people how to fly and build. it's a $1.50 of foam, 2-9gram servos, a red bottom emax RS2205-2300kv ($9 ), 20A esc, and 3s-850. it will fly slow, fast, inverted, and crash more times than you can count, and still be put back together and fly.

if interested....LINKY

laters,

me