Air extractor for sustainer and motor gliders?

I reviewed this news group, Buttler/Nixon/Murray vent and DG's page on Mandl air extractor. Could not find a suitable reference for and extractor for a sustainer or motor glider. I did note that the open tails of DG and LS gliders apparently did not do a good job of extracting air, hence the Mandl, which according to comments on this news group does not good avery effective job either. Anyone come up with a good method of extracting air from a glider with a fuel tank in the baggage compartment?

On Sunday, August 23, 2015 at 10:47:29 PM UTC+1, wrote:
I reviewed this news group, Buttler/Nixon/Murray vent and DG's page on Mandl air extractor. Could not find a suitable reference for and extractor for a sustainer or motor glider. I did note that the open tails of DG and LS gliders apparently did not do a good job of extracting air, hence the Mandl, which according to comments on this news group does not good avery effective job either. Anyone come up with a good method of extracting air from a glider with a fuel tank in the baggage compartment?

Look at the Jonker Sailplanes website for one example

On Monday, August 24, 2015 at 12:43:49 PM UTC-7, wrote:


Look at the Jonker Sailplanes website for one example


The poster was looking for solutions that would work in gliders with fuel tank in baggage compartment. The JS-1 has a take on the Buttler/Murray/Nixon vent which would not work with a gas tank were the vent would be.

Am Montag, 24. August 2015 23:53:39 UTC+2 schrieb Jonathan St. Cloud:
On Monday, August 24, 2015 at 12:43:49 PM UTC-7, wrote:


Look at the Jonker Sailplanes website for one example


The poster was looking for solutions that would work in gliders with fuel tank in baggage compartment. The JS-1 has a take on the Buttler/Murray/Nixon vent which would not work with a gas tank were the vent would be.

I have put extractor vents into the small engine bay doors on my Ventus cM. Needed to put two 5 cm dia holes into the bulkhead separating the cockpit from the engine bay (Schempp-Hirth confirmed me that this bulkhead is not structural and that I could put any holes I'd like).

On Tuesday, August 25, 2015 at 1:41:15 AM UTC-5, Tango Whisky wrote:
Am Montag, 24. August 2015 23:53:39 UTC+2 schrieb Jonathan St. Cloud:
On Monday, August 24, 2015 at 12:43:49 PM UTC-7, wrote:


Look at the Jonker Sailplanes website for one example


The poster was looking for solutions that would work in gliders with fuel tank in baggage compartment. The JS-1 has a take on the Buttler/Murray/Nixon vent which would not work with a gas tank were the vent would be.

I have put extractor vents into the small engine bay doors on my Ventus cM. Needed to put two 5 cm dia holes into the bulkhead separating the cockpit from the engine bay (Schempp-Hirth confirmed me that this bulkhead is not structural and that I could put any holes I'd like).

Aside from the questionable Mandl report on the DG website and anecdotal evidence from those who had air extractors installed - are there measurable effects? While I believe that venting of the cockpit is improved, I doubt this is making for better performance until someone shows me data. Until then, I would call this snake oil.
Herb

I also have a "CM" and interested in doing that-Did you only drill the 2 holes or did you add a funnel as well ? can you install the upper gas tank after this operation ?
Dan

I have put extractor vents into the small engine bay doors on my Ventus cM. Needed to put two 5 cm dia holes into the bulkhead separating the cockpit from the engine bay (Schempp-Hirth confirmed me that this bulkhead is not structural and that I could put any holes I'd like).

At 13:59 25 August 2015, wrote:
On Tuesday, August 25, 2015 at 1:41:15 AM UTC-5, Tango Whisky wrote:
Am Montag, 24. August 2015 23:53:39 UTC+2 schrieb Jonathan St. Cloud:
On Monday, August 24, 2015 at 12:43:49 PM UTC-7,
wrote=
:
=20
=20
Look at the Jonker Sailplanes website for one example
=20
=20
The poster was looking for solutions that would work in gliders with
fu=
el tank in baggage compartment. The JS-1 has a take on the
Buttler/Murray/=
Nixon vent which would not work with a gas tank were the vent would be.
=20
I have put extractor vents into the small engine bay doors on my Ventus
c=
M. Needed to put two 5 cm dia holes into the bulkhead separating the
cockpi=
t from the engine bay (Schempp-Hirth confirmed me that this bulkhead is
not=
structural and that I could put any holes I'd like).

Aside from the questionable Mandl report on the DG website and anecdotal
ev=
idence from those who had air extractors installed - are there measurable
e=
ffects? While I believe that venting of the cockpit is improved, I doubt
t=
his is making for better performance until someone shows me data. Until
the=
n, I would call this snake oil.
Herb


http://www.jonkersailplanes.co.za/airextractor.htm

No raw data, but you could always ask them?

Shaun

Am Dienstag, 25. August 2015 16:04:46 UTC+2 schrieb :
I also have a "CM" and interested in doing that-Did you only drill the 2 holes or did you add a funnel as well ? can you install the upper gas tank after this operation ?
Dan

I installed a vent (inspired by Jonkers ;-) ) on each engine bay door.
Then I drilled the two holes into the bulkhead to achieve airflow from the cockpit into the engine bay (somewhere in the middle between upper border of the main tank and the top of the fuselage.
I fixed a stainless steel mesh in front of each hole so that the stuff packed onto the turtle deck stays on the turtle deck.

I don't have the option to install the upper gas tank because I have a canopy which opens by swinging up and to the back, and the hinge + gas strut sits where the gas tank would go. However, I don't see why you couldn't fit the tank after the mod - it just eats space corresponding to the thinkness of the mesh.

Does it improve venting? Yes.
Does it improve performance? I have no way to measure that.

Does it improve venting? Yes.
Does it improve performance? I have no way to measure that.

You could always tape the vents up for a "control" flight, compared against another glider of similar performance, and then un-tape them and repeat the flight. Then repeat the whole exercise 5 times in still air for statistical validity.

I'm in a cT. Any pictures you can post of your modifications?

Cheers
DH

On Sunday, August 23, 2015 at 5:47:29 PM UTC-4, wrote:
I reviewed this news group, Buttler/Nixon/Murray vent and DG's page on Mandl air extractor. Could not find a suitable reference for and extractor for a sustainer or motor glider. I did note that the open tails of DG and LS gliders apparently did not do a good job of extracting air, hence the Mandl, which according to comments on this news group does not good avery effective job either. Anyone come up with a good method of extracting air from a glider with a fuel tank in the baggage compartment?

What type of glider are you referring to?
John Murray and I have looked at the feasibility on many gliders.
Among those that have had variants of the ES vent are ASW-24,27,28,27-18, Discus B, Ventus B,Ventus 2B, LS-6, LS-8, DG400, Lak-17,Lak 17T, and Std Cirrus.
ASG-29E is on the horizon for this Fall.
Others are obviously possible, provided there is enough potential to justify the one time costs for a particular installation.
UH