4M Flying Wing Can't Turn - What Went Wrong?

This 4M flying wing is a custom build and it looks awesome, but it's having trouble turning. Can you spot what's wrong?

Splash

Huge Flying Wing Needs Help

This 4M flying wing is a custom build and it looks awesome, but it's having trouble turning. Can you spot what's wrong? In the video, you can see it flying and trying to make a left hand turn with full left up aileron, but the plane doesn't roll and turn. Maybe you can help the builder out with a solution.

Are the control surfaces too small? Too much wing flex? Something else? Let us know what you think is going wrong with this design and what it would take to make it better.

4 metre wing issue (1 min 27 sec)

Thread Tools
Mar 18, 2021, 09:20 AM
Registered User
Douwe's Avatar
Way too much flex and slop in the control surface/linkages. At the 57 second mark, when he is carrying the unit you can see just how much the control surface on the right wing is flapping. If there were appropriate differential with that much up aileron on the left the right should be down even more, IMO.
Mar 18, 2021, 09:27 AM
Registered User
chip.greely's Avatar
Hmmmm,

The video is showing Full Up aileron on the Left side, but where is the Full Down aileron on the right side?

Also interesting to see aileron and flap control surface, while most conventional wings have full span elevons.

Good luck
Mar 18, 2021, 11:17 AM
Registered User
Adverse yaw. The down elevon on the right wing is causing drag which is preventing the wing from turning left. The sweep angle contributes to dihedral effect so the roll input is cancelled out. Drag rudders or Frise ailerons will fix it. Notice when the wing has pitch up command applied it rolls/yaws into the right wing even though left input is made. Higher AOA accentuates the adverse yaw and then the dihedral effect causes the wing to roll right.

Edit: More washout at the tips, or a few degrees of anhedral may help too.
Mar 18, 2021, 11:32 AM
DS Junkie
Screamin' Eagle's Avatar
Looks to me like the flap on the left wing is deflected downward as well, making the plane want to roll right.
Mar 18, 2021, 12:39 PM
I'd rather be Flying
davecee's Avatar
Left aileron is full up. Right aileron appears to be essentially neutral, eg; in the same position as at launch. Actually a decent idea to prevent adverse yaw on a long wing. I do it on my sailplanes when flying slowly, via the use of flight modes. The flaps appear to remain in the launch position.
However, the wing lacks torsional rigidity. As the left aileron goes up, it acts as a trimtab, twisting the outer section of the left wing into a higher AOA. This results in no net force to lower the left wingtip, thus no way to turn left using the typical bank and yank technique often used on a flying wing.
You can see the difference in the AOA of the two wingtips in these included snippets.

Also watch the video from 51 to 60 seconds where he picks up the airplane. The wing is very flexible, fluttering a bit in the wind and flexing with his movements.
Last edited by davecee; Mar 18, 2021 at 12:53 PM.
Mar 18, 2021, 01:11 PM
dylancoffin's Avatar
You could try combining the flaps with the ailerons to get a bit more authority.
Mar 18, 2021, 03:12 PM
the occasional flyer
rothlisburger's Avatar
Agree completely with davecee. That wing needs stiffening in torsion.
Mar 18, 2021, 03:37 PM
Pro Hoarder
turbonut's Avatar
Agree too much aeroelasticity..with out stiffing up the wing so it wont twist he will need drag rudders to make it turn.
Latest blog entry: In flight
Mar 18, 2021, 05:37 PM
Walk like a camel
gizzo's Avatar
Hey that's my local!
Mar 18, 2021, 05:50 PM
Registered User
I am the owner of this wing and the one seen in the video carrying it. I've had excellent feedback on FB and in YouTube regarding what's wrong and the consensus seems to be that the wing tip rotates (just as davecee said) and that it needs more weight to fly faster. This is by far the biggest scratch-build I've ever done, so issues were not unexpected.

Addressing some of the comments above:
- I had asymmetric ailerons set up in the radio, so the outer aileron wouldn't move much at all.
- The flaps were linked to the elevator, but not the ailerons.
- There is slop in the linkage, but some of that was caused by the crash. Mind you, the whole thing is pretty floppy where the wings meet the center section.

Since this video I have covered top topside with fibreglass tape (the bottom was already covered), hoping that will increase the torsional stiffness. Haven't flow since; this was literally last night.

Your feedback and comments are excellent! Keep 'em coming, cause I need 'em!
Mar 18, 2021, 07:11 PM
Is it DS'able?
wr_mizzard's Avatar
Fin's not square.

-James
Mar 18, 2021, 08:09 PM
Walk like a camel
gizzo's Avatar
Quote:
Originally Posted by wr_mizzard
Fin's not square.

-James
*Brick
Mar 18, 2021, 09:28 PM
I'd rather be Flying
davecee's Avatar
Quote:
Originally Posted by jhbe
I am the owner of this wing and the one seen in the video carrying it. I've had excellent feedback on FB and in YouTube regarding what's wrong and the consensus seems to be that the wing tip rotates (just as davecee said) and that it needs more weight to fly faster. This is by far the biggest scratch-build I've ever done, so issues were not unexpected.

Addressing some of the comments above:
- I had asymmetric ailerons set up in the radio, so the outer aileron wouldn't move much at all.
- The flaps were linked to the elevator, but not the ailerons.
- There is slop in the linkage, but some of that was caused by the crash. Mind you, the whole thing is pretty floppy where the wings meet the center section.

Since this video I have covered top topside with fibreglass tape (the bottom was already covered), hoping that will increase the torsional stiffness. Haven't flow since; this was literally last night.

Your feedback and comments are excellent! Keep 'em coming, cause I need 'em!
Use some strips of Fiberglass reinforced tape , top and bottom, in an open diagonal criss cross fashion , kind of like this DLG uses carbon fiber over the foam wing. That should help considerably with torsional rigidity. Good luck.
Mar 18, 2021, 09:30 PM
Registered User
Douwe's Avatar
Quote:
Originally Posted by jhbe
I am the owner of this wing and the one seen in the video carrying it. I've had excellent feedback on FB and in YouTube regarding what's wrong and the consensus seems to be that the wing tip rotates (just as davecee said) and that it needs more weight to fly faster. This is by far the biggest scratch-build I've ever done, so issues were not unexpected.

Addressing some of the comments above:
- I had asymmetric ailerons set up in the radio, so the outer aileron wouldn't move much at all.
- The flaps were linked to the elevator, but not the ailerons.
- There is slop in the linkage, but some of that was caused by the crash. Mind you, the whole thing is pretty floppy where the wings meet the center section.

Since this video I have covered top topside with fibreglass tape (the bottom was already covered), hoping that will increase the torsional stiffness. Haven't flow since; this was literally last night.

Your feedback and comments are excellent! Keep 'em coming, cause I need 'em!
Looks like you are having a lot of fun with it. It really took to the air fine (popped right on up). A little bit of tuning and it will be even more fun.


Quick Reply
Message:

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Soft Wing - What went wrong? plove891 Composites Fabrication 43 Jun 25, 2019 06:33 PM
Discussion Please help - crash footage - what went wrong? lacoa1 Multirotor Drone Talk 0 Feb 24, 2016 07:58 AM
Discussion O.M.G what went wrong with my QR X350 Pro stupeo Beginner Multirotor Drones 13 Jan 18, 2016 03:57 PM
Discussion What went wrong zooom101 Multirotor Drone Talk 14 Nov 24, 2015 04:29 PM
Discussion El Faro, what went wrong? Libelle201B Life, The Universe, and Politics 23 Oct 10, 2015 09:44 PM