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Astrir turbulator tapes



 
 
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  #1  
Old March 27th 20, 07:27 AM posted to rec.aviation.soaring
[email protected]
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Posts: 83
Default Astrir turbulator tapes

Hi Ruediger,

there is a drawing from Grob, specifying the turbulator location for the single-seaters as follows (distances measured on the pressure side of the wing from the trailing edge to the trailing edge of the tape):

Wing root: 360mm
Inboard end of the aileron: 300mm
Wing tip: 178mm

Twin I and II twoseaters receive the tape only at the ailerons with the following dimensions:
4300mm from the wing tip: 380mm
Inboard end of the aileron: 370mm
Wing tip: 208mm

Unfortunately, these locations are not included in the service letters from LTB Lindner.

The tapes do not significantly improve the performance - perhaps 1 or 2 points, you won't notice that. But they remove the seperation bubble from the ailerons and improve the airflow there. You will notice that the glider becomes more stable in a turn. You will also need less aileron input for corrections and the aileron in general is a bit more responsive.

Best
Christoph
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  #2  
Old March 27th 20, 06:03 PM posted to rec.aviation.soaring
Michael Opitz
external usenet poster
 
Posts: 290
Default Astrir turbulator tapes

At 07:27 27 March 2020, wrote:
Hi Ruediger,

there is a drawing from Grob, specifying the turbulator location for

the
si=
ngle-seaters as follows (distances measured on the pressure side

of the
win=
g from the trailing edge to the trailing edge of the tape):

Wing root: 360mm
Inboard end of the aileron: 300mm
Wing tip: 178mm

Twin I and II twoseaters receive the tape only at the ailerons with

the
fol=
lowing dimensions:
4300mm from the wing tip: 380mm
Inboard end of the aileron: 370mm
Wing tip: 208mm

Unfortunately, these locations are not included in the service

letters
from=
LTB Lindner.

The tapes do not significantly improve the performance - perhaps

1 or 2
poi=
nts, you won't notice that. But they remove the seperation bubble

from the
=
ailerons and improve the airflow there. You will notice that the

glider
bec=
omes more stable in a turn. You will also need less aileron input for
corre=
ctions and the aileron in general is a bit more responsive.

Best
Christoph



Christoph,

Please re-read Lindner SL-12. It plainly states that all control
surface seals including the rudder may have the Z-Tape installed
just in front of the gap seals. In the case of the rudder, IMO, it
greatly increases the effectiveness of that control surface,
especially at low speeds like on initial take-off roll, etc.. The
drawings you refer to may be for possible increased performance
due to dealing with the laminar separation bubble where the
Z-tape is extended beyond the ends of the ailerons, but it is not
the same as where the service letter basically allows all Grob
glider types to have sealed control surfaces with optional Z-Tape
included.

RO



  #3  
Old March 27th 20, 07:01 PM posted to rec.aviation.soaring
[email protected]
external usenet poster
 
Posts: 83
Default Astrir turbulator tapes

Hi Michael,

indeed, SL12 includes a reference to turbulator tape in front of the control surfaces. Especially in case of the rudder, this helps to reduce the lack of rudder authority that most Astir. Turbulators on the suction side in front of the ailerons also seem to improve aileron authority on some gliders, like the ASK21.

However, the drawing that Grob released in the 80s and which the Aerokurier article refers to, includes additional specifications for turbulator tape on the pressure side of the Eppler airfoil. These are not part of SL12. When following these instructions, the tape will not be right in front of the aileron gap as shown in SL12. It will be a few centimetres further upstream..

Regards
Christoph
  #4  
Old March 27th 20, 07:51 PM posted to rec.aviation.soaring
Michael Opitz
external usenet poster
 
Posts: 290
Default Astrir turbulator tapes

At 19:01 27 March 2020, wrote:
Hi Michael,

indeed, SL12 includes a reference to turbulator tape in front of the
contro=
l surfaces. Especially in case of the rudder, this helps to reduce the
lack=
of rudder authority that most Astir. Turbulators on the suction side

in
fr=
ont of the ailerons also seem to improve aileron authority on some
gliders,=
like the ASK21.

However, the drawing that Grob released in the 80s and which the
Aerokurier=
article refers to, includes additional specifications for turbulator

tape
=
on the pressure side of the Eppler airfoil. These are not part of

SL12.
Whe=
n following these instructions, the tape will not be right in front of

the
=
aileron gap as shown in SL12. It will be a few centimetres further
upstream=
..

Regards
Christoph

I agree that the additional turbulator tape instructions which the
article refers to may bring some not so noticeable performance
increases. We have underwing turbulators installed in those
positions on our Twin 1's also, and absent side by side glide testing,
there is not much to notice. The handling was always a complaint
with the Twin 1's. and in this case, the addition of turbulators in
front of the control surfaces does help markedly, and the difference
is plain to see and feel. The rudder is most noticeable. Aileron
response is also better. I have even had success using it on the
upper stabilizer to enable more effective high speed nose-down
trim. Operators of Twin 1's that do not have the Z-tape installed
should try it. It doesn't cost much money, and I think the pilots
will be pleasantly surprised.

RO

 




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