Transflex 02 Transponder Antenna

[Kibby]

Looking for a Transflex 02 transponder antenna for my Discus-2T. Don't see any at W&W or Cumulus. Does anyone in the US offer this antenna? thanks, Bob Kibby Discus-2T N722BK

[Scott Williams]

On Monday, April 16, 2018 at 7:52:39 AM UTC-5, Kibby wrote:
> Looking for a Transflex 02 transponder antenna for my Discus-2T. Don't see any at W&W or Cumulus. Does anyone in the US offer this antenna? thanks, Bob Kibby Discus-2T N722BK

I see from an online search that the transflex 03 is available from vendors in Europe. I don't know how to link a similar thread "filser flexible antenna" from 2015.
good luck,
Scott

[Scott Williams]

On Monday, April 16, 2018 at 7:33:16 PM UTC-5, Scott Williams wrote:
> On Monday, April 16, 2018 at 7:52:39 AM UTC-5, Kibby wrote:
> > Looking for a Transflex 02 transponder antenna for my Discus-2T. Don't see any at W&W or Cumulus. Does anyone in the US offer this antenna? thanks, Bob Kibby Discus-2T N722BK
>

correction, "filser transponder antenna"
> I see from an online search that the transflex 03 is available from vendors in Europe. I don't know how to link a similar thread "filser transponder antenna" from 2015.
> good luck,
> Scott

[bumper[_4_]]

Not what you are after, but less drag. Can be special ordered with a threaded hole instead of mounting studs, no additional. This allows mounting with brass threaded rod with filed notch for breakaway if on belly.

http://www.deltapopaviation.com/Ultra_Low_Drag_Transponder_Antenna.html

bumper

[AS]

On Tuesday, April 17, 2018 at 2:39:09 AM UTC-4, bumper wrote:
> Not what you are after, but less drag. Can be special ordered with a threaded hole instead of mounting studs, no additional. This allows mounting with brass threaded rod with filed notch for breakaway if on belly.
>
> http://www.deltapopaviation.com/Ultra_Low_Drag_Transponder_Antenna.html
>
> bumper


..... but less drag.
Careful here. If you install this type of antenna on the fuselage off the centerline in an area where the fuselage is necking down and you don't know the exact flow conditions in this spot, you may have it sitting slightly sideways.
Not exactly comparable to a glider but to show what I mean, take a look at his kind of antenna mounted to the belly of power planes. One side is typically black from the exhaust and oil coming from the engine due to the spiraling prop-wash airflow. The airflow is not parallel to the centerline at this spot and the paddle antenna will create a bit more drag.

Uli
'AS'

[bumper[_4_]]

On Tuesday, April 17, 2018 at 5:31:17 AM UTC-7, AS wrote:
> On Tuesday, April 17, 2018 at 2:39:09 AM UTC-4, bumper wrote:
> > Not what you are after, but less drag. Can be special ordered with a threaded hole instead of mounting studs, no additional. This allows mounting with brass threaded rod with filed notch for breakaway if on belly.
> >
> > http://www.deltapopaviation.com/Ultra_Low_Drag_Transponder_Antenna.html
> >
> > bumper
>
>
> .... but less drag.
> Careful here. If you install this type of antenna on the fuselage off the centerline in an area where the fuselage is necking down and you don't know the exact flow conditions in this spot, you may have it sitting slightly sideways.
> Not exactly comparable to a glider but to show what I mean, take a look at his kind of antenna mounted to the belly of power planes. One side is typically black from the exhaust and oil coming from the engine due to the spiraling prop-wash airflow. The airflow is not parallel to the centerline at this spot and the paddle antenna will create a bit more drag.
>
> Uli
> 'AS'

Watch this short old video comparing drag of various shapes - from a drag perspective, you can't do much worse than round except maybe a flat plate!

https://www.youtube.com/watch?v=ftq8jTQ8ANE

bumper

[AS]

On Tuesday, April 17, 2018 at 12:18:55 PM UTC-4, bumper wrote:
> On Tuesday, April 17, 2018 at 5:31:17 AM UTC-7, AS wrote:
> > On Tuesday, April 17, 2018 at 2:39:09 AM UTC-4, bumper wrote:
> > > Not what you are after, but less drag. Can be special ordered with a threaded hole instead of mounting studs, no additional. This allows mounting with brass threaded rod with filed notch for breakaway if on belly.
> > >
> > > http://www.deltapopaviation.com/Ultra_Low_Drag_Transponder_Antenna.html
> > >
> > > bumper
> >
> >
> > .... but less drag.
> > Careful here. If you install this type of antenna on the fuselage off the centerline in an area where the fuselage is necking down and you don't know the exact flow conditions in this spot, you may have it sitting slightly sideways.
> > Not exactly comparable to a glider but to show what I mean, take a look at his kind of antenna mounted to the belly of power planes. One side is typically black from the exhaust and oil coming from the engine due to the spiraling prop-wash airflow. The airflow is not parallel to the centerline at this spot and the paddle antenna will create a bit more drag.
> >
> > Uli
> > 'AS'
>
> Watch this short old video comparing drag of various shapes - from a drag perspective, you can't do much worse than round except maybe a flat plate!
>
> https://www.youtube.com/watch?v=ftq8jTQ8ANE
>
> bumper

Thanks for the link, Bumper! I even do have Asher Shapiro's book 'Shape and FLow' and am well aware of this ~10:1 ratio. All I am saying is that the advantage is reduced, if the flat antenna is not aligned properly with the flow.
I have the stick antenna installed and plan on 3D-printing a free moving, self-aligning airfoil for it. That should take care of the bad drag of the round wire.

Uli
'AS'

[Bob Kuykendall]

Aeronautic engineer and sailplane pilot Steve Smith did the exterior profile on this antenna. It's about as good as you can do on a protruding antenna.

--Bob K.