Air Extractor: Better than a Plastic Jesus?

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.

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.

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:



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.

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