Fuselage Vents

On Jul 30, 12:43*pm, "
wrote:
On Jul 30, 8:46*am, "Ken Kochanski (KK)"
wrote:

The performance claims look extremely good ... is this plausible ?

http://www.dg-flugzeugbau.de/mandl-absaugung-e.html

KK

Ventusmods have used a funnel behind the wheel well for years,
typically a 2" piece or pipe would form the exit.

Improvement here is the shape of the exit.

Regards

Al

Can someone e-mail more info on Ventus mods?
Thanks,

Andy

In that case, I suppose you would have to go onto oxygen a little bit lower
down with the fuselage extraction vent fitted!

At 16:40 31 July 2008, Jim White wrote:

Now there is a thought.... Open the air vent if you are close to
airspace
to make the logger think you are lower, and fit an extraction vent if
you
want that height record.

jim

So assuming this is worthwhile ... what about putting extractors on
the back of the gear doors ... the door area is probably already
messing up the laminar flow ... and there are no structural issues ...
and yes, you would have to then allow fuse air to pass into the gear
well - I think most of the newer ships have this sealed up - and the
doors would have to be sealed, so you don't just pull air through the
door gaps ...

On Jul 30, 2:43*pm, "
wrote:
On Jul 30, 8:46*am, "Ken Kochanski (KK)"
wrote:

The performance claims look extremely good ... is this plausible ?

http://www.dg-flugzeugbau.de/mandl-absaugung-e.html

KK

Ventus mods have used a funnel behind the wheel well for years,
typically a 2" piece or pipe would form the exit.

Improvement here is the shape of the exit.

Regards

Al

On Aug 2, 3:25*am, Derek Copeland
wrote:
In that case, I suppose you would have to go onto oxygen a little bit lower
down with thefuselageextractionventfitted!

At 16:40 31 July 2008, Jim White wrote:





Now there is a thought.... Open the airventif you are close to
airspace
to make the logger think you are lower, and fit an extractionventif
you
want that height record.

jim- Hide quoted text -

- Show quoted text -

I made this vent to replace the access hatch for connecting my
controls
http://griderpirate.smugmug.com/gall...55235771_pv8zu
Next weekend I will fly with a manometer to compare static to cabin
pressure with the 'normal' hatch, then the 'Mandl Extractor' hatch. I
can report subjectively that I was MUCH more comfortable in the
cockpit.

On Jul 30, 10:46 am, "Ken Kochanski (KK)"
wrote:
The performance claims look extremely good ... is this plausible ?

http://www.dg-flugzeugbau.de/mandl-absaugung-e.html

KK

I posted pictures of Dick Butler's air exhaust in my Uvalde blog.
You need to accelerate the air smoothly inside the fuselage
then direct it to exit parallel the exterior flow; these photos
show how Dick did it.

www.nadler.com

See ya, Dave "YO electric"

I made this vent to replace the access hatch for connecting my
controlshttp://griderpirate.smugmug.com/gallery/3702283_9hEKD#355235771_pv8zu
Next weekend I will fly with a manometer to compare static to cabin
pressure with the 'normal' hatch, then the 'Mandl Extractor' hatch. I
can report subjectively that I was MUCH more comfortable in the
cockpit.

Awesome! My SZD-59 is going to get one of these on it's booby hatch
now too, thanks for sharing!

-Paul

On Aug 19, 6:42*pm, sisu1a wrote:
* I made this vent to replace the access hatch for connecting my

controlshttp://griderpirate.smugmug.com/gallery/3702283_9hEKD#355235771_pv8zu
Next weekend I will fly with a manometer to compare static to cabin
pressure with the 'normal' hatch, then the 'Mandl Extractor' hatch. *I
can report subjectively that I was MUCH more comfortable in the
cockpit.

Awesome! My SZD-59 is going to get one of these on it's booby hatch
now too, thanks for sharing!

-Paul

Speaking of thanks.... in characteristic style, I neglected to than
Bob Kuykendall for his advice regarding mold making, and DG for
publishing their findings in the first place. Does any other glider
manufacturer 'share' as much? This is an honest question. I've spent
quite a lot of time on the DG site, very little on any others.

On Aug 19, 9:15 pm, Uncle Fuzzy wrote:
On Aug 2, 3:25 am, Derek Copeland



wrote:
In that case, I suppose you would have to go onto oxygen a little bit lower
down with thefuselageextractionventfitted!

At 16:40 31 July 2008, Jim White wrote:

Now there is a thought.... Open the airventif you are close to
airspace
to make the logger think you are lower, and fit an extractionventif
you
want that height record.

jim- Hide quoted text -

- Show quoted text -

I made this vent to replace the access hatch for connecting my
controlshttp://griderpirate.smugmug.com/gallery/3702283_9hEKD#355235771_pv8zu
Next weekend I will fly with a manometer to compare static to cabin
pressure with the 'normal' hatch, then the 'Mandl Extractor' hatch. I
can report subjectively that I was MUCH more comfortable in the
cockpit.

Nice work.

Now DB is a pretty smart guy, so chances are he has this figured out.
But I sure don't. I can't see how exhausting air into the low
pressure area that's responsible for producing aerodynamic lift is a
good thing. Perhaps the mass flow is trivial and doesn't matter as
long as the flow isn't spoiled. But we sure go to a lot of effort to
eliminate air leaks in this area and sealing surely does help....

I posted pictures of Dick Butler's air exhaust in my Uvalde blog.
You need to accelerate the air smoothly inside the fuselage
then direct it to exit parallel the exterior flow; these photos
show how Dick did it.

OK, I need help to understand this from real aerodynamics geeks. I've
heard that these exits are placed in "areas of low pressure", and the
turtledeck sure looks like an obvious candidate for such an area. But
if you exhaust air there, surely you get separated or at least
disturbed airflow downstream of it. Just past "low pressure" is where
there should be "pressure recovery", and I would think venting air to
the low pressure point destroys the pressure recovery. For example,
the lowest pressure place possible would be right on the top of the
wing in the middle. But venting air there is obviously suicide. If
anything you want to suck air at that point to keep the boundary layer
attached. OK, if you've found a low pressure area where airflow is
already separated behind it, that would seem ok, which is what the
vents at the bottom of the rudder or through control horns do. But
otherwise, aren't you creating more drag than you reduce, by causing
separated flow downstream of the vent?

John Cochrane BB

On Aug 20, 4:13*am, PMSC Member wrote:
On Aug 19, 9:15 pm, Uncle Fuzzy wrote:





On Aug 2, 3:25 am, Derek Copeland

wrote:
In that case, I suppose you would have to go onto oxygen a little bit lower
down with thefuselageextractionventfitted!

At 16:40 31 July 2008, Jim White wrote:

Now there is a thought.... Open the airventif you are close to
airspace
to make the logger think you are lower, and fit an extractionventif
you
want that height record.

jim- Hide quoted text -

- Show quoted text -

I made this vent to replace the access hatch for connecting my
controlshttp://griderpirate.smugmug.com/gallery/3702283_9hEKD#355235771_pv8zu
Next weekend I will fly with a manometer to compare static to cabin
pressure with the 'normal' hatch, then the 'Mandl Extractor' hatch. *I
can report subjectively that I was MUCH more comfortable in the
cockpit.

Nice work.

Now DB is a pretty smart guy, so chances are he has this figured out.
But I sure don't. *I can't see how exhausting air into the low
pressure area that's responsible for producing aerodynamic lift is a
good thing. *Perhaps the mass flow is trivial and doesn't matter as
long as the flow isn't spoiled. *But we sure go to a lot of effort to
eliminate air leaks in this area and sealing surely does help....- Hide quoted text -

- Show quoted text -
Thanks,
There's a link in the first post of this thread to an article on the
DG website that explains why they firgured there would be a
performance gain. DG placed their extractor behind and to the side
of the gear well. Mine is above and toward the rear of the wing
strictly because there was a control hookup access panel there,
allowing me to go back to original at any time. Perhaps not an ideal
location, but the only place I could put it without cutting my glider.
My motivation for the exhaust vent was comfort, and regardless of any
aerodynamic gains or losses, it certainly helps keep more comfortable
in the 100+ degree desert heat. Without the vent, I was hot even at
17,000 feet, with just the left side of my face cold where the canopy
vent blasted a thin stream of cold air.