Air Extractor: Better than a Plastic Jesus?

[[email protected]]

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

[Brad[_2_]]

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

[JS]

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

[waremark]

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

[[email protected]]

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

[Nick Kennedy]

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.

[[email protected]]

> 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

[Papa3[_2_]]

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.php?id=mandl-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

[Craig Funston[_2_]]

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.php?id=mandl-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

[waremark]

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.php?id=mandl-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

[SF]

I had one installed in my 27, 2 years ago. What I know for sure: The cockpit is a lot quieter without the noisy front vent (it is taped closed under the flapper). The performance of the side eyeball vent is greatly enhanced, and it blows a very nice stream of air towards my face when desired. So the cockpit is quieter and more comfortable. Most of our flights are flow fairly low in pretty humid air, so this is a big feature. The cone of silence behind you head makes sure that the air being exhausted comes from the cockpit, and not from the tail boom. It also doubles as a moose call if you land out and need to start living off the land while waiting for your retrieve crew. What I surmise: the performance gain is there, however my poor decision making would make it very hard for me actually put a number on it. It's not going to turn you into a wizard.

[JS]

Schleicher TM/TN numbers for the vent:

ASW24: 18
ASW27: 15
ASW28: 7
ASG29: 4

Jim

[27 pilot]

> If it improves performance why do Schempp and Schleicher not instal it?


I believe all new schleichers do come with it from the factory now, not sure about others but good chance they do these have really caught on the last couple years.

[Dave Nadler]

On Monday, December 16, 2013 7:06:18 PM UTC-5, waremark wrote:
> If it improves performance why do Schempp and Schleicher
> not instal it? They work very hard for improved performance.

Well, its a factory option for Antares, and excepting the
Antares located in Canada and north-west, all Antares in
North America have these vents. The exit duct improves cockpit
ventilation, and prevents air leaking out where it shouldn't
(a performance issue with nose intake and inadequate exhaust).


> On Monday, 16 December 2013 19:23:31 UTC, Craig Funston wrote:
> If Dick Butler believes in it, that's good enough for me :-)

Lange copied Dick, as did Schleicher ;-)
Some details here:
http://www.nadler.com/public/2008_Uvalde/Uvalde2008.html


See ya, Dave "YO electric"

[[email protected]]

On Monday, December 16, 2013 12:17:44 PM UTC-6, 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.php?id=mandl-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

Eric,

I'm quite aware of the DG publications on their air extractor (Mandl Absaugung or Mandl Sucker)and now read with interest that you have Nixon Extractor in your LS8. DG is claiming an incredible 2 glide point increase in performance on the LS10 with the extractor. I'm wondering if you had to adjust the polar in your glide computer to account for the better performance? My interest in this modification was raised after seeing nearly all '27 and '29s at New Castle this year with Nixon Extractors.
For those questioning why Schleicher seems slow in putting these into new gliders: re-certifying even such a small change with the Luftfahrtbundesamt and the EASA takes a lot of time. Looks like DG puts these into all of the few LS gliders they are building these days - but not into the DG 808.
Maybe I should get the Nixon Extractor AND the Plastic Jesus!

Herb

[[email protected]]

I have two different fuselage air extractors on my LS8-18. The reason I did this is because I knew my cockpit was being pressurised because the canopy vent would pop open at 100kts and no air was entering the cockpit thru that now open vent.

The first one I installed was the then "holy grail" of extractors, the Mandle. This was installed as instructed by DG on the lower fuselage just aft of the gear doors. This was a hastle mainly because I had to enroll in the DG maintenance program to be able to buy the installation kit. Bottom line...NO CHANGE IN NOISE LEVELS IN THE COCKPIT AND NO CHANGE IN CANOPY AIR VENT POPPING OPEN AT 100KTS.

I then had Rex install the locally sourced airvent that is placed on the top of the fuselage just behind the canopy. Immediately quieter cockpit. Now I could feel air moving past my face when the forward vent was opened. The canopy airvent stays closed right up to redline.

Did it improve my L/D by 10 points? Can't tell you.

[BruceGreeff]

Indeed the external shape of the JS1 fuselage is a direct (and
apparently authorised) copy of the ASW26. The brothers started modifying
one that needed two new wings.
Internally it is somewhat different.

The "mould" is still gracing our skies and was for sale last I saw...

Bruce


On 2013/12/15 11:28 PM, waremark wrote:
> 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
>

--
Bruce Greeff
T59D #1771

[Tom K (TK)]

http://www.ebay.com/itm/like/150944329699?lpid=82

The plastic Jesus might be cheaper, and it might help with a prayer for a divine thermal!

[kirk.stant]

On Tuesday, December 17, 2013 8:56:35 AM UTC-6, wrote:
>
> I then had Rex install the locally sourced airvent that is placed on the top of the fuselage just behind the canopy. Immediately quieter cockpit. Now I could feel air moving past my face when the forward vent was opened. The canopy airvent stays closed right up to redline.
>
>
>
> Did it improve my L/D by 10 points? Can't tell you.

I'm seriously considering installing one on my LS6b this winter - where did you get yours from?

Kirk
66

[[email protected]]

On Tuesday, December 17, 2013 9:55:32 AM UTC-5, wrote:
> On Monday, December 16, 2013 12:17:44 PM UTC-6, 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.php?id=mandl-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 Eric, I'm quite aware of the DG publications on their air extractor (Mandl Absaugung or Mandl Sucker)and now read with interest that you have Nixon Extractor in your LS8. DG is claiming an incredible 2 glide point increase in performance on the LS10 with the extractor. I'm wondering if you had to adjust the polar in your glide computer to account for the better performance? My interest in this modification was raised after seeing nearly all '27 and '29s at New Castle this year with Nixon Extractors. For those questioning why Schleicher seems slow in putting these into new gliders: re-certifying even such a small change with the Luftfahrtbundesamt and the EASA takes a lot of time. Looks like DG puts these into all of the few LS gliders they are building these days - but not into the DG 808. Maybe I should get the Nixon Extractor AND the Plastic Jesus! Herb

Approval of the ES Vent in Schleicher 24,27,28,29 took about 5 months which is pretty darned quick. Subsequently Schleicher has built mold inserts to allow implementation as part of new construction.
Variations have been installed in ASW-20, ASW-19, LS-8, Lak 17,Discus B, and Ventus B. Most are available from Eastern sailplane.
The vent insrt is common, however the collector that we consider important to the functionality of the system is unique to each type.
The FAA has determined that it agrees with Schleicher that this is a minor modification.
FWIW
UH

[Tom Kelley #711]

On Tuesday, December 17, 2013 8:45:29 AM UTC-7, kirk.stant wrote:
> On Tuesday, December 17, 2013 8:56:35 AM UTC-6, wrote:
>
> >
>
> > I then had Rex install the locally sourced airvent that is placed on the top of the fuselage just behind the canopy. Immediately quieter cockpit. Now I could feel air moving past my face when the forward vent was opened.. The canopy airvent stays closed right up to redline.
>
> >
>
> >
>
> >
>
> > Did it improve my L/D by 10 points? Can't tell you.
>
>
>
> I'm seriously considering installing one on my LS6b this winter - where did you get yours from?
>
>
>
> Kirk
>
> 66

This was discussed many, many years ago. As if you feel that with your cockpit vent open and your final glide is so critical, what Holighaus simply recommended was to "Close" your cockpit vent and stop doing final critictal glides! Whats needed is the cockpit air to "vent" and whats required to vent "all" that air. What one needs to also understand is that the fuselage is a main part of the structure strength for the prevention of flutter. It is highly suggested before cutting holes to discuss this with the manufacture.

On that DG vent, at the Worlds, it was used as a mental advantage ploy. As when statements were made that it "speeds up the exiting air" meant major discovery of a perpetual motion" had been discovered. Later, it was found as such and no performance increase was found. A sales ploy, well, maybe just another needed vent as getting "ALL" the air to exit takes more vents than gliders use. Also, exhausting air thru the wings has always been difficult to totally seal. This might help with that if used correctly.

A definition is needed on this:" Perpetual motion describes motion that continues indefinitely without any external source of energy.[2] This is impossible in practice because of friction and other sources of energy loss.[3][4][5] Furthermore, the term is often used in a stronger sense to describe a perpetual motion machine of the first kind, a "hypothetical machine which, once activated, would continue to function and produce work"[6] indefinitely with no input of energy. There is a scientific consensus that perpetual motion is impossible, as it would violate the first or second law of thermodynamics.[4][5]

Yes, JS did use a ASH 26 fuselage and agreements were then reached with AS on the continued use(my sources are very reliable on this). I have also used a very expensive manometer that reads down to a .0001 pressure difference.. I will say I wish I had my money back on that test. But my exhaust air has "more" than one way out as it escapes the aft area. If you load up your "behind head area" with all sorts of stuff, you are restricting the airflow out.

At least with the "new Vent" it stops you from doing this and this may be whats needed as a enlightenment for many folks and a few folks make a few more bucks!

Best, FWIW, #711.

[Tom Kelley #711]

On Tuesday, December 17, 2013 9:48:44 AM UTC-7, Tom Kelley #711 wrote:
> On Tuesday, December 17, 2013 8:45:29 AM UTC-7, kirk.stant wrote:
>
> > On Tuesday, December 17, 2013 8:56:35 AM UTC-6, wrote:
>
> >
>
> > >
>
> >
>
> > > I then had Rex install the locally sourced airvent that is placed on the top of the fuselage just behind the canopy. Immediately quieter cockpit. Now I could feel air moving past my face when the forward vent was opened. The canopy airvent stays closed right up to redline.
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > > Did it improve my L/D by 10 points? Can't tell you.
>
> >
>
> >
>
> >
>
> > I'm seriously considering installing one on my LS6b this winter - where did you get yours from?
>
> >
>
> >
>
> >
>
> > Kirk
>
> >
>
> > 66
>
>
>
> This was discussed many, many years ago. As if you feel that with your cockpit vent open and your final glide is so critical, what Holighaus simply recommended was to "Close" your cockpit vent and stop doing final critictal glides! Whats needed is the cockpit air to "vent" and whats required to vent "all" that air. What one needs to also understand is that the fuselage is a main part of the structure strength for the prevention of flutter. It is highly suggested before cutting holes to discuss this with the manufacture.
>
>
>
> On that DG vent, at the Worlds, it was used as a mental advantage ploy. As when statements were made that it "speeds up the exiting air" meant major discovery of a perpetual motion" had been discovered. Later, it was found as such and no performance increase was found. A sales ploy, well, maybe just another needed vent as getting "ALL" the air to exit takes more vents than gliders use. Also, exhausting air thru the wings has always been difficult to totally seal. This might help with that if used correctly.
>
>
>
> A definition is needed on this:" Perpetual motion describes motion that continues indefinitely without any external source of energy.[2] This is impossible in practice because of friction and other sources of energy loss.[3][4][5] Furthermore, the term is often used in a stronger sense to describe a perpetual motion machine of the first kind, a "hypothetical machine which, once activated, would continue to function and produce work"[6] indefinitely with no input of energy. There is a scientific consensus that perpetual motion is impossible, as it would violate the first or second law of thermodynamics.[4][5]
>
>
>
> Yes, JS did use a ASH 26 fuselage and agreements were then reached with AS on the continued use(my sources are very reliable on this). I have also used a very expensive manometer that reads down to a .0001 pressure difference. I will say I wish I had my money back on that test. But my exhaust air has "more" than one way out as it escapes the aft area. If you load up your "behind head area" with all sorts of stuff, you are restricting the airflow out.
>
>
>
> At least with the "new Vent" it stops you from doing this and this may be whats needed as a enlightenment for many folks and a few folks make a few more bucks!
>
>
>
> Best, FWIW, #711.

As I just couldn't help myself on this, BUT, we have spent a lot of time, money and learning ways in sealing gear doors over the years to prevent air exhausting thru that area.

Does this now mean when you now fly inverted with the new vent, it has to be sealed to prevent a performance loss?..........Now about that plastic Jesus..................

Best for the holidays..........#711.

[Morgan[_2_]]

There is a fair bit of discussion on this topic on the ASW20Owners yahoo group, with some references to performance improvements that I believe were calculated for the JS1.

I have one installed on my ASW-20 and the difference in cockpit comfort in hot conditions is tremendous. Whistles around the canopy rails or other mystery channels go away and the glider is noticeably quieter.

The 20 is an easy solution because you can replace the control hatch cover. It's a positive enough improvement in cockpit comfort that I have considered adding a vent to my Duo. It was suggested that it was a "minor modification" that wouldn't require a 337.

I figured out the performance improvement on the 20, assuming the same .3N drag reduction claimed for the JS1. Works out to a whopping 120 extra feet of glide distance on a 1000ft loss assuming 40:1 glide.

I therefore love it for the cockpit comfort. I figure that the performance increase of being comfortable is more substantial than the slight possible reduction in drag or even an increase in drag.




On Tuesday, December 17, 2013 9:31:13 AM UTC-8, Tom Kelley #711 wrote:
> On Tuesday, December 17, 2013 9:48:44 AM UTC-7, Tom Kelley #711 wrote:
>
> > On Tuesday, December 17, 2013 8:45:29 AM UTC-7, kirk.stant wrote:
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> > > On Tuesday, December 17, 2013 8:56:35 AM UTC-6, wrote:
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> > > > I then had Rex install the locally sourced airvent that is placed on the top of the fuselage just behind the canopy. Immediately quieter cockpit. Now I could feel air moving past my face when the forward vent was opened. The canopy airvent stays closed right up to redline.
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> > > > Did it improve my L/D by 10 points? Can't tell you.
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> > > I'm seriously considering installing one on my LS6b this winter - where did you get yours from?
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> > > Kirk
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> > > 66
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> > This was discussed many, many years ago. As if you feel that with your cockpit vent open and your final glide is so critical, what Holighaus simply recommended was to "Close" your cockpit vent and stop doing final critictal glides! Whats needed is the cockpit air to "vent" and whats required to vent "all" that air. What one needs to also understand is that the fuselage is a main part of the structure strength for the prevention of flutter. It is highly suggested before cutting holes to discuss this with the manufacture.
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> > On that DG vent, at the Worlds, it was used as a mental advantage ploy. As when statements were made that it "speeds up the exiting air" meant major discovery of a perpetual motion" had been discovered. Later, it was found as such and no performance increase was found. A sales ploy, well, maybe just another needed vent as getting "ALL" the air to exit takes more vents than gliders use. Also, exhausting air thru the wings has always been difficult to totally seal. This might help with that if used correctly.
>
> >
>
> >
>
> >
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> > A definition is needed on this:" Perpetual motion describes motion that continues indefinitely without any external source of energy.[2] This is impossible in practice because of friction and other sources of energy loss.[3][4][5] Furthermore, the term is often used in a stronger sense to describe a perpetual motion machine of the first kind, a "hypothetical machine which, once activated, would continue to function and produce work"[6] indefinitely with no input of energy. There is a scientific consensus that perpetual motion is impossible, as it would violate the first or second law of thermodynamics.[4][5]
>
> >
>
> >
>
> >
>
> > Yes, JS did use a ASH 26 fuselage and agreements were then reached with AS on the continued use(my sources are very reliable on this). I have also used a very expensive manometer that reads down to a .0001 pressure difference. I will say I wish I had my money back on that test. But my exhaust air has "more" than one way out as it escapes the aft area. If you load up your "behind head area" with all sorts of stuff, you are restricting the airflow out.
>
> >
>
> >
>
> >
>
> > At least with the "new Vent" it stops you from doing this and this may be whats needed as a enlightenment for many folks and a few folks make a few more bucks!
>
> >
>
> >
>
> >
>
> > Best, FWIW, #711.
>
>
>
> As I just couldn't help myself on this, BUT, we have spent a lot of time, money and learning ways in sealing gear doors over the years to prevent air exhausting thru that area.
>
>
>
> Does this now mean when you now fly inverted with the new vent, it has to be sealed to prevent a performance loss?..........Now about that plastic Jesus..................
>
>
>
> Best for the holidays..........#711.

[Alexander Georgas[_2_]]

The powers in the know seem to indicate that just cutting a hole in the
back may not be the solution, it is important to figure out the way in
which the air re-enters the airflow.

The theoretical advantage of not having air spilling around the canopy
edge is easy to understand. How to quantify this advantage and how many
seconds of flying with the wrong flap setting this may buy you is
another question.

However, after having flown the JS1 most recently, let me add the
following observations:

The cockpit is very quiet and the ventilation is excellent, with the
adjustable air nozzle providing all the comfort you would need in a hot
day. There is a marked advantage compared to the already good (and in
other ways identical) Schleicher setup.

In fact, the ventilation is so good that there is no need to ever have
the side vent open on the Mecaplex sliding panel. To my initial surprise
JS have now discontinued the Mecaplex vent altogether. This provided no
discomfort, even on takeoff on a hot African day. Whatever the
performance gain of the air extractor, not having to open the side vent
offers an additional advantage.

I reckon the "shark gill" must have about 30pts of value on a comp day
based on psych factor alone. Just be sure to polish it thoroughly while
on the grid.


Alexander Georgas



On 15/12/2013 20:01, 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
>