What is this called? Some sort of sealing for aileron surface

[Senna Van den Bosch]

I'm seeing this more and more but have no idea what they're called. Refer to this picture: https://cdn.jetphotos.com/full/6/53013_1459261993.jpg
This was Stefan Langer's Libelle, it's got those black plastic(?) thing at the aileron and wing. So does this Cirrus: https://cdn.airplane-pictures.net/images/uploaded-images/2017/10/14/975766.jpg

What are they called and do they help in performance? Would it be worth installing?

[Dave Walsh[_2_]]

At 10:58 08 April 2019, Senna Van den Bosch wrote:
>I'm seeing this more and more but have no idea what they're
called. Refer
>to this picture:
https://cdn.jetphotos.com/full/6/53013_1459261993.jpg
>This was Stefan Langer's Libelle, it's got those black plastic(?)
thing at
>the aileron and wing. So does this Cirrus:
>https://cdn.airplane-pictures.net/images/uploaded-
images/2017/10/14/975766.jpg
>
>What are they called and do they help in performance? Would it
be worth
>installing?
>
They are aerodynamic "fences". Standard on inboard end of
flaps/faperons on many gliders, DG800, Antares and others.
All mods make you go faster, no?

[Charlie M. (UH & 002 owner/pilot)]

Yes, they're typically called fences. They attempt to keep higher pressure air from the bottom of the wing from going past a control surface when you move a flight control.

[Senna Van den Bosch]

Op maandag 8 april 2019 13:30:06 UTC+2 schreef Dave Walsh:
> At 10:58 08 April 2019, Senna Van den Bosch wrote:
> >I'm seeing this more and more but have no idea what they're
> called. Refer
> >to this picture:
> https://cdn.jetphotos.com/full/6/53013_1459261993.jpg
> >This was Stefan Langer's Libelle, it's got those black plastic(?)
> thing at
> >the aileron and wing. So does this Cirrus:
> >https://cdn.airplane-pictures.net/images/uploaded-
> images/2017/10/14/975766.jpg
> >
> >What are they called and do they help in performance? Would it
> be worth
> >installing?
> >
> They are aerodynamic "fences". Standard on inboard end of
> flaps/faperons on many gliders, DG800, Antares and others.
> All mods make you go faster, no?

I've googled a bit and found this document testing the effect of those fences: https://tu-dresden.de/ing/maschinenwesen/ilr/ead/ressourcen/dateien/dateien/berichte/140303_TS.pdf?lang=en

Fairly neglectable, even 5 pairs of fences were teste: "...the loss in overall performance by applying for
example four additional pairs of fences on the
wings of an ASW-28 (Fig. 1). The result was a
decrease in maximum L/D of about 0.25 points
for a singe pair of fences..."

Worth the read :)

[[email protected]]

These aileron fences do not help performance. They may help with some other issues:
1) most gliders require counter-aileron while circling. The fences prevent ailerons from being sucked to the upper side when the aileron is deflected. The suction is applied by beginning airflow seperation at high angles of attack. This issue exists with some older gliders (e.g. LS1, Libelle) when getting close to stall while circling.
2) slight improvement of aileron authority
3) improve airflow on wing/fuselage intersection on flapped gliders

[Senna Van den Bosch]

Op maandag 8 april 2019 18:23:48 UTC+2 schreef :
> These aileron fences do not help performance. They may help with some other issues:
> 1) most gliders require counter-aileron while circling. The fences prevent ailerons from being sucked to the upper side when the aileron is deflected. The suction is applied by beginning airflow seperation at high angles of attack. This issue exists with some older gliders (e.g. LS1, Libelle) when getting close to stall while circling.
> 2) slight improvement of aileron authority
> 3) improve airflow on wing/fuselage intersection on flapped gliders

I'm owner of a DG-101, would it be interesting to fit them? I know a few Std Cirrus and Std Libelles which have them fitted.

[Roy B.]

Difficult to use with wing covers.
I found out the hard way on my Nimbus 3.
ROY