Air Extractor: Better than a Plastic Jesus?

Noticing all the openings behind the cockpits of mainly Schleicher gliders such as -27 and 29's I'm asking myself if this is a real drag reducer or a placebo. For those unfamiliar: people have been cutting 4x2 openings into the fuselage about 8" behind the canopy cutout and put air vents - some with funnel-like contraptions on the inside of the turtle deck into their gliders. The funnel seems to suggest to the air molecules "this way out", some pilots may put arrow stickers on the inside so the air knows which way to flow. The whole thing is meant to avoid pressurizing the cockpit from the front air vent. Air leaking from the canopy seal would trip outside air flow to become turbulent.

Are there any serious comparison flights that were done following a scientific protocol to show the effect of such devices? Is this really better than putting a Tibetan prayer flag on the tail or a plastic Jesus on the glare shield? The latter can serve double purpose since I know where I would stick my transponder or PFlarm antenna...
Seriously, I'd be interested if anyone has found this thing useful beyond the statement that it must be good since all these hotshot pilots (insert call signs here) have one.

I'm waiting with jigsaw in hand for your responses, the LS8 rests uneasily in the basement!
Herb, J7

I added one to my Tetra-15 when I built it. it was really my only solution to vent cockpit air since the tailboom is sealed off aft of the wing T.E.

no arrows to direct the outgoing air, but I can hear it rushing out the vent, so it must work. no hard data for the numbers guys, that being said the guys I fly with in their german glass seem to think the Tetra does just fine, even with a hole in the fuselage.

Brad

Isn't it a bit cold to be discussing air vents?

Believe Guy has one in his LS8/18.
Uncle Hank might know something about this.
Perhaps ask Dick Butler or the Jonker brothers.
If you have paid "LS tax", try DG.
They really suck. The extractor, of course.
Jim

The JS1 fuselage looks to me identical to the ASH 26 but with extractor vents added. There might be a problem with having the vents - it would make me feel guilty about putting the stuff I like to take with me on the luggage deck. Look forward to hearing whether anyone knows whether they really make a difference.


On Sunday, 15 December 2013 18:15:23 UTC, JS wrote:
Isn't it a bit cold to be discussing air vents?



Believe Guy has one in his LS8/18.

Uncle Hank might know something about this.

Perhaps ask Dick Butler or the Jonker brothers.

If you have paid "LS tax", try DG.

They really suck. The extractor, of course.

Jim

On Sunday, December 15, 2013 1:01:20 PM UTC-5, wrote:
Noticing all the openings behind the cockpits of mainly Schleicher gliders such as -27 and 29's I'm asking myself if this is a real drag reducer or a placebo. For those unfamiliar: people have been cutting 4x2 openings into the fuselage about 8" behind the canopy cutout and put air vents - some with funnel-like contraptions on the inside of the turtle deck into their gliders. The funnel seems to suggest to the air molecules "this way out", some pilots may put arrow stickers on the inside so the air knows which way to flow. The whole thing is meant to avoid pressurizing the cockpit from the front air vent. Air leaking from the canopy seal would trip outside air flow to become turbulent. Are there any serious comparison flights that were done following a scientific protocol to show the effect of such devices? Is this really better than putting a Tibetan prayer flag on the tail or a plastic Jesus on the glare shield? The latter can serve double purpose since I know where I would stick my transponder or PFlarm antenna... Seriously, I'd be interested if anyone has found this thing useful beyond the statement that it must be good since all these hotshot pilots (insert call signs here) have one. I'm waiting with jigsaw in hand for your responses, the LS8 rests uneasily in the basement! Herb, J7

Ask Erik Mann his opinion. He has one in his LS-8.
UH

My Mom gave me a Plastic Virgin Mary that I have faithfully carried my my various gliders for 12 years now. Works great. Low maintenance and she has found me plenty of thermals during near land outs; rope breaks, near mid-airs, power failures, Cu Nims, cross wind landings, missed turnpoints, frozen PDA's are all covered. Seriously.

Ask Erik Mann his opinion. He has one in his LS-8.

UH

I'm going for the vent installation this winter - already have the PJ ... kk

Not quite the direct answer you're looking for, but you do know that DG seems to think that venting cockpit air matters, right?

http://www.dg-flugzeugbau.de/index.p...dl-absaugung-e

On the theory that the Nixon Air Extractor had a better chance of working than the Plastic Jesus, I installed one two winters ago. Obvious improvement in cockpit airflow and decrease in canopy noise at high speed suggest it's doing "something". I built a little foam block with a string attached and plan to do some testing on cockpit pressure at speed with/without the exit orifice available. Expect to be able to show increased cockpit pressure with my handy-dandy NK Kestrel Wx meter and also see if there is measurable outflow by locating the Kestrel in the exit area. All that proves is a first-order measurement (i.e. something is happening due to the vent). In terms of performance measurement, maybe faith (along with the Plastic Jesus) is justification enough?

P3

On Sunday, December 15, 2013 6:51:45 PM UTC-5, wrote:
On Sunday, December 15, 2013 1:01:20 PM UTC-5, wrote:

Noticing all the openings behind the cockpits of mainly Schleicher gliders such as -27 and 29's I'm asking myself if this is a real drag reducer or a placebo. For those unfamiliar: people have been cutting 4x2 openings into the fuselage about 8" behind the canopy cutout and put air vents - some with funnel-like contraptions on the inside of the turtle deck into their gliders. The funnel seems to suggest to the air molecules "this way out", some pilots may put arrow stickers on the inside so the air knows which way to flow. The whole thing is meant to avoid pressurizing the cockpit from the front air vent. Air leaking from the canopy seal would trip outside air flow to become turbulent. Are there any serious comparison flights that were done following a scientific protocol to show the effect of such devices? Is this really better than putting a Tibetan prayer flag on the tail or a plastic Jesus on the glare shield? The latter can serve double purpose since I know where I would stick my transponder or PFlarm antenna... Seriously, I'd be interested if anyone has found this thing useful beyond the statement that it must be good since all these hotshot pilots (insert call signs here) have one. I'm waiting with jigsaw in hand for your responses, the LS8 rests uneasily in the basement! Herb, J7



Ask Erik Mann his opinion. He has one in his LS-8.

UH

On Monday, December 16, 2013 10:17:44 AM UTC-8, Papa3 wrote:
Not quite the direct answer you're looking for, but you do know that DG seems to think that venting cockpit air matters, right?



http://www.dg-flugzeugbau.de/index.p...dl-absaugung-e



On the theory that the Nixon Air Extractor had a better chance of working than the Plastic Jesus, I installed one two winters ago. Obvious improvement in cockpit airflow and decrease in canopy noise at high speed suggest it's doing "something". I built a little foam block with a string attached and plan to do some testing on cockpit pressure at speed with/without the exit orifice available. Expect to be able to show increased cockpit pressure with my handy-dandy NK Kestrel Wx meter and also see if there is measurable outflow by locating the Kestrel in the exit area. All that proves is a first-order measurement (i.e. something is happening due to the vent). In terms of performance measurement, maybe faith (along with the Plastic Jesus) is justification enough?



P3



On Sunday, December 15, 2013 6:51:45 PM UTC-5, wrote:

On Sunday, December 15, 2013 1:01:20 PM UTC-5, wrote:



Noticing all the openings behind the cockpits of mainly Schleicher gliders such as -27 and 29's I'm asking myself if this is a real drag reducer or a placebo. For those unfamiliar: people have been cutting 4x2 openings into the fuselage about 8" behind the canopy cutout and put air vents - some with funnel-like contraptions on the inside of the turtle deck into their gliders. The funnel seems to suggest to the air molecules "this way out", some pilots may put arrow stickers on the inside so the air knows which way to flow. The whole thing is meant to avoid pressurizing the cockpit from the front air vent. Air leaking from the canopy seal would trip outside air flow to become turbulent. Are there any serious comparison flights that were done following a scientific protocol to show the effect of such devices? Is this really better than putting a Tibetan prayer flag on the tail or a plastic Jesus on the glare shield? The latter can serve double purpose since I know where I would stick my transponder or PFlarm antenna... Seriously, I'd be interested if anyone has found this thing useful beyond the statement that it must be good since all these hotshot pilots (insert call signs here) have one. I'm waiting with jigsaw in hand for your responses, the LS8 rests uneasily in the basement! Herb, J7







Ask Erik Mann his opinion. He has one in his LS-8.



UH

If Dick Butler believes in it, that's good enough for me :-)
Craig

If it improves performance why do Schempp and Schleicher not instal it? They work very hard for improved performance.

On Monday, 16 December 2013 19:23:31 UTC, Craig Funston wrote:
On Monday, December 16, 2013 10:17:44 AM UTC-8, Papa3 wrote:

Not quite the direct answer you're looking for, but you do know that DG seems to think that venting cockpit air matters, right?







http://www.dg-flugzeugbau.de/index.p...dl-absaugung-e







On the theory that the Nixon Air Extractor had a better chance of working than the Plastic Jesus, I installed one two winters ago. Obvious improvement in cockpit airflow and decrease in canopy noise at high speed suggest it's doing "something". I built a little foam block with a string attached and plan to do some testing on cockpit pressure at speed with/without the exit orifice available. Expect to be able to show increased cockpit pressure with my handy-dandy NK Kestrel Wx meter and also see if there is measurable outflow by locating the Kestrel in the exit area. All that proves is a first-order measurement (i.e. something is happening due to the vent).. In terms of performance measurement, maybe faith (along with the Plastic Jesus) is justification enough?







P3







On Sunday, December 15, 2013 6:51:45 PM UTC-5, wrote:



On Sunday, December 15, 2013 1:01:20 PM UTC-5, wrote:







Noticing all the openings behind the cockpits of mainly Schleicher gliders such as -27 and 29's I'm asking myself if this is a real drag reducer or a placebo. For those unfamiliar: people have been cutting 4x2 openings into the fuselage about 8" behind the canopy cutout and put air vents - some with funnel-like contraptions on the inside of the turtle deck into their gliders. The funnel seems to suggest to the air molecules "this way out", some pilots may put arrow stickers on the inside so the air knows which way to flow. The whole thing is meant to avoid pressurizing the cockpit from the front air vent. Air leaking from the canopy seal would trip outside air flow to become turbulent. Are there any serious comparison flights that were done following a scientific protocol to show the effect of such devices? Is this really better than putting a Tibetan prayer flag on the tail or a plastic Jesus on the glare shield? The latter can serve double purpose since I know where I would stick my transponder or PFlarm antenna... Seriously, I'd be interested if anyone has found this thing useful beyond the statement that it must be good since all these hotshot pilots (insert call signs here) have one. I'm waiting with jigsaw in hand for your responses, the LS8 rests uneasily in the basement! Herb, J7















Ask Erik Mann his opinion. He has one in his LS-8.







UH



If Dick Butler believes in it, that's good enough for me :-)

Craig