JS-1 Exhaust Vent

Gotta hand it to Johan Bosman on this one... look at pg 5 of this pdf:
http://www.streckenflug.at/news/js_c...on_2010_07.pdf
Personally I think his take on the exhaust vent is simply ingenious.
The opening on that thing is immense and has got to allow much air to
pass, but flow is organized by that little louver/wing. Pure genius.

I may just be preoccupied on the subject right now since I'm in the
middle of making vented ASW-20 hatches (Mandl and Butler styles) for
the upcoming 20 gathering at Tehachapi. Pics to follow...

-Paul

Paul,
I am greatly looking forward to seeing your work at the upcoming 20
get together. I was talking to a few pilots I respect at the Region 9
Logan contest last week and mentioned your proposed vent and they said
that there will be a problem with the hatch being off to one side and
not centered. What do you think? Still count me in for trying one
out.

Bruno - B4

On Jul 25, 4:33*pm, sisu1a wrote:
Gotta hand it to Johan Bosman on this one... look at pg 5 of this pdf:http://www.streckenflug.at/news/js_c...on_2010_07.pdf
Personally I think his take on the exhaust vent is simply ingenious.
The opening on that thing is immense and has got to allow much air to
pass, but flow is organized by that little louver/wing. Pure genius.

I may just be preoccupied on the subject right now since I'm in the
middle of making vented ASW-20 hatches (Mandl and Butler styles) for
the upcoming 20 gathering at Tehachapi. Pics to follow...

-Paul

On Jul 25, 8:52*pm, Bruno wrote:
... there will be a problem with the hatch being off to one side and
not centered...

You mean, like the DG exit vents ?

On Jul 25, 5:52*pm, Bruno wrote:
Paul,
I am greatly looking forward to seeing your work at the upcoming 20
get together. *I was talking to a few pilots I respect at the Region 9
Logan contest last week and mentioned your proposed vent and they said
that there will be a problem with the hatch being off to one side and
not centered. *What do you think? *Still count me in for trying one
out. *

Bruno - B4

On Jul 25, 4:33*pm, sisu1a wrote:

Gotta hand it to Johan Bosman on this one... look at pg 5 of this pdf:http://www.streckenflug.at/news/js_c...on_2010_07.pdf
Personally I think his take on the exhaust vent is simply ingenious.
The opening on that thing is immense and has got to allow much air to
pass, but flow is organized by that little louver/wing. Pure genius.

I may just be preoccupied on the subject right now since I'm in the
middle of making vented ASW-20 hatches (Mandl and Butler styles) for
the upcoming 20 gathering at Tehachapi. Pics to follow...

-Paul



Maybe equally impressive to the engineering of the JS1 exhaust vent is
the psychological-gamesmanship of emphasizing the performance
enhancement effects of this just prior to the 18m Worlds. Love it.

Darryl

On Jul 25, 4:33*pm, sisu1a wrote:
Gotta hand it to Johan Bosman on this one... look at pg 5 of this pdf:http://www.streckenflug.at/news/js_c...on_2010_07.pdf
Personally I think his take on the exhaust vent is simply ingenious.
The opening on that thing is immense and has got to allow much air to
pass, but flow is organized by that little louver/wing. Pure genius.

I may just be preoccupied on the subject right now since I'm in the
middle of making vented ASW-20 hatches (Mandl and Butler styles) for
the upcoming 20 gathering at Tehachapi. Pics to follow...

-Paul

I still think a reversed NACA duct will work better than the Butler
and much better than the Mandl. The Mandl throws the low speed air
out into the faster air stream. The JS design accelerates half the
air over the airfoil but what happens to the air under the airfoil?

On Jul 25, 6:11*pm, Darryl Ramm wrote:
On Jul 25, 5:52*pm, Bruno wrote:





Paul,
I am greatly looking forward to seeing your work at the upcoming 20
get together. *I was talking to a few pilots I respect at the Region 9
Logan contest last week and mentioned your proposed vent and they said
that there will be a problem with the hatch being off to one side and
not centered. *What do you think? *Still count me in for trying one
out. *

Bruno - B4

On Jul 25, 4:33*pm, sisu1a wrote:

Gotta hand it to Johan Bosman on this one... look at pg 5 of this pdf:http://www.streckenflug.at/news/js_c...on_2010_07.pdf
Personally I think his take on the exhaust vent is simply ingenious.
The opening on that thing is immense and has got to allow much air to
pass, but flow is organized by that little louver/wing. Pure genius.

I may just be preoccupied on the subject right now since I'm in the
middle of making vented ASW-20 hatches (Mandl and Butler styles) for
the upcoming 20 gathering at Tehachapi. Pics to follow...

-Paul

Maybe equally impressive to the engineering of the JS1 exhaust vent is
the psychological-gamesmanship of emphasizing the performance
enhancement effects of this just prior to the 18m Worlds. Love it.

Darryl

perhaps some will file the trailing edge of their wings to a knife
like edge...............no, wait, that's been done before!

On Jul 25, 9:54*pm, Tim Taylor wrote:

I still think a reversed NACA duct will work better than the Butler
and much better than the Mandl. *The Mandl throws the low speed air
out into the faster air stream. *The JS design accelerates half the
air over the airfoil but what happens to the air under the airfoil?

All good points, but I have an even bigger question: What happens when
the cockpit air intakes are closed (say on a cold day or at high/cold
altitudes)? It seems to me that there would be an ideal extractor
position & size (or louver camber/AOA) for each particular air intake
position... You're looking for a balance in order to keep the fuselage
airflow from being unnecessarily disturbed at one end or the other,
right? I mean, with a tight canopy seal and closed intakes isn't your
fixed-size extractor going to be starved for airflow once the cockpit
pressure reaches its minimum, and that is going to in turn wind up
disturbing the airflow over the extractor itself?

--Noel

On Jul 26, 12:02*am, "noel.wade" wrote:
On Jul 25, 9:54*pm, Tim Taylor wrote:



I still think a reversed NACA duct will work better than the Butler
and much better than the Mandl. *The Mandl throws the low speed air
out into the faster air stream. *The JS design accelerates half the
air over the airfoil but what happens to the air under the airfoil?

All good points, but I have an even bigger question: What happens when
the cockpit air intakes are closed (say on a cold day or at high/cold
altitudes)? *It seems to me that there would be an ideal extractor
position & size (or louver camber/AOA) for each particular air intake
position... You're looking for a balance in order to keep the fuselage
airflow from being unnecessarily disturbed at one end or the other,
right? *I mean, with a tight canopy seal and closed intakes isn't your
fixed-size extractor going to be starved for airflow once the cockpit
pressure reaches its minimum, and that is going to in turn wind up
disturbing the airflow over the extractor itself?

--Noel

EXACTLY!! No extractor design optimized for a given airspeed and vent
opening will be optimal for all speeds and vent openings. When might
I close my vents (mostly)? Likely running near redline near cloudbase
or the PCA. (though that doesn't happen as often as I'd like!). I
made one for my Speed Astir (aka - the Grob solar sauna) right after
seeing the DG article. I have no idea how it changes the glider
performance, but it keeps ME from roasting quite so much, and that's
gotta' help!

On Jul 25, 8:54*pm, Tim Taylor wrote:

I still think a reversed NACA duct will work better than the Butler
and much better than the Mandl. *The Mandl throws the low speed air
out into the faster air stream. *The JS design accelerates half the
air over the airfoil but what happens to the air under the airfoil?

The NACA duct was designed such that the edges create vortices
which force the air into the duct. Reversing the flow through a NACA
duct is an inefficient way to exit fluid from a body.

On Jul 26, 9:05*am, nurflugel wrote:
On Jul 25, 8:54*pm, Tim Taylor wrote:

I still think a reversed NACA duct will work better than the Butler
and much better than the Mandl. *The Mandl throws the low speed air
out into the faster air stream. *The JS design accelerates half the
air over the airfoil but what happens to the air under the airfoil?

The NACA duct was designed such that the edges create vortices
which force the air into the duct. Reversing the flow through a NACA
duct is an inefficient way to exit fluid from a body.

Actually a "modified" NACA duct with an extended top cover that also
adjusts the angle of the exit stream and only allows about the last
third of the length to be open will accelerate the air back to proper
speed to match the outside air and place it gently into the air-
stream. It will have a smaller opening than the butler design and not
put the air out at about a 45 degree angle like the Mandl. It would
be very easy to modify the standard inlet design to be a very low drag
air exit. The NACA duct is designed to allow laminar flow of the air
through the duct and it will work both directions to accelerate as an
exit as well as decelerate when used as an inlet.