Roll over phenomenon - RC Groups
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Apr 13, 2017, 01:21 PM
vincent123's Avatar

Roll over phenomenon

Hi guys, I m opening a new thread, so I can reach potentially more people to get feedback from.

I m in the process of building the wings of my latest design.
The wing has anhedal for a quarter of the span, and it has drooping wing tip end plates (to act as landing skids).

Both items, the anhedral and drooped wing end plates, generate anhedral which can produce a wing roll over (to inverted flight) effect at high speed (low angle of attack minimizing the dihedral effect of the swept back wing): bottom of page 115, Tailess aircraft in T and P.

Do I have to worry, any comments would be appreciated!

Last edited by vincent123; Apr 13, 2017 at 01:30 PM.
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Apr 13, 2017, 06:21 PM
Pro Hoarder
turbonut's Avatar
I would say no problem. but depends on how much sweep you have. many aircraft with large sweep angles use anhedral to help with dihedral effect of the sweep back.
Apr 14, 2017, 02:35 AM
vincent123's Avatar
It has 33 degree of LE sweep.

No idea if this is large enough to balance the 4degree of wing anhedral..

I can still change the overall anhedral of the wing.

I mean the angle by which the wing sticks into the fuselage, in such a way that the wing starts with dihedral and ends with anhedral,
If you catch my drift..
Last edited by vincent123; Apr 14, 2017 at 02:44 AM.
Apr 14, 2017, 08:20 AM
You know nothing....
Stuart A's Avatar
If you don't catch the drift it may lead to a roll over....
Apr 14, 2017, 02:03 PM
vincent123's Avatar
Originally Posted by Stuart A
If you don't catch the drift it may lead to a roll over....

You got it
Apr 14, 2017, 02:57 PM
Pro Hoarder
turbonut's Avatar
I would think you are fine with it as is..your sweep is not huge but it is a good amount
Apr 14, 2017, 03:32 PM
vincent123's Avatar
Thanks for the feedback Turbo.

I was thinking how to calculate the dihedral back to the overall wing dihedral.
The tip has a anhedral of about 4°.
The root part has no dihedral.

The anhedral of the tip has a larger impact on the overall wing dihedral, as the center of that wing surface is further away from the COG.

So, I did this;
Wing area 1 x Distance1 to COG x dihedral 1
Wing area 2 x Distance2 to COG x dihedral 2
Overall wing area x Distance to COG x overall wing dihedral

When I do this for my wing, I get an overall wing anhedral of 2.7°.

So, when I want an overall wing dihedral of 0°, then I have to tilt the wing with 2.7°

Makes sense, does it?
Apr 15, 2017, 04:00 AM
B for Bruce
BMatthews's Avatar
I think it will be so close to acting like a flat wing that you won't be able to tell the difference.
Apr 15, 2017, 07:01 AM
vincent123's Avatar
Thanks for the feedback, I'll just tilt the wing a bit in the sadle over only 1° softening the anhedral of the wing tip. Overall anhedral is then -1.7 instead of the -2.7°.

Should be ok, as you guys suggested it would be already ok from the start.

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