Define penetration.

Hi

I was recently challenged to define Penetration.
We failed to find a suitable definition - although I have my own opinions.

Views presented on the subject include:
Glider penetration is represented by the polar curve.
Penetration is proportional to wing loading.
Penetration is the "real world L/D" taking into account the energy
reserves over drag to overcome upsets caused by turbulence etc.
Penetration is related to weight only. (variant ratio of- weight and
frontal area * Coefficient of Drag)

I know we must be missing the point so -
Any takers from our learned aerodynamicist types?

What exactly is "penetration" as applied to gliders and how does it
differ from the polar curve.

Bruce Greeff wrote:

What exactly is 'penetration' as applied to gliders
and how does it differ from the polar curve.

I don't think I have heard anyone refer to penetration
as a glider performance concept since the seventies!
It referred to the performance in the medium to high
speed part of the polar curve.

John Galloway

Bruce Greeff wrote:
Hi

I was recently challenged to define Penetration.
We failed to find a suitable definition - although I have my own opinions.

Views presented on the subject include:
Glider penetration is represented by the polar curve.
Penetration is proportional to wing loading.
Penetration is the "real world L/D" taking into account the energy
reserves over drag to overcome upsets caused by turbulence etc.
Penetration is related to weight only. (variant ratio of- weight and
frontal area * Coefficient of Drag)

I know we must be missing the point so -
Any takers from our learned aerodynamicist types?

What exactly is "penetration" as applied to gliders and how does it
differ from the polar curve.

In the glider sense at least:
Being able to go fast and still keep it up.
Hope this helps.

Cheers,
Shawn

K8's, PW5's and Libelles don't 'penetrate' well because flying fast just
brings 'em down faster. Going cross country in anything but a gentle breeze
becomes seriously hard work.

ASW27's full of H2O penetrate like darts. You can get round the task with
20kt breezes on the nose all day.

I suppose it relates to how flat the polar curve is above 100 kph.


Ian


"Shawn Curry" wrote in message
link.net...
Bruce Greeff wrote:
Hi

I was recently challenged to define Penetration.
We failed to find a suitable definition - although I have my own
opinions.

Views presented on the subject include:
Glider penetration is represented by the polar curve.
Penetration is proportional to wing loading.
Penetration is the "real world L/D" taking into account the energy
reserves over drag to overcome upsets caused by turbulence etc.
Penetration is related to weight only. (variant ratio of- weight and
frontal area * Coefficient of Drag)

I know we must be missing the point so -
Any takers from our learned aerodynamicist types?

What exactly is "penetration" as applied to gliders and how does it
differ from the polar curve.

In the glider sense at least:
Being able to go fast and still keep it up.
Hope this helps.

Cheers,
Shawn

SNIP

I suppose it relates to how flat the polar curve is
above 100 kph

SNIP

Okay, I'll bite. If glider penetration describes the
ability of a ship to make progress into the wind without
falling out of the sky, is it soley a matter of looking
at the polar at the indicated airspeed? Intuition
tells me that is it, but an aeronautical engineer type
might make be look like a big dummy here.

In article ,
Stewart Kissel wrote:
SNIP

I suppose it relates to how flat the polar curve is
above 100 kph

SNIP

Okay, I'll bite. If glider penetration describes the
ability of a ship to make progress into the wind without
falling out of the sky, is it soley a matter of looking
at the polar at the indicated airspeed? Intuition
tells me that is it, but an aeronautical engineer type
might make be look like a big dummy here.




I'd say it's how flat the polar curve is past the
best L/D point. I've often used 80 knots as
a standard speed where I look at the sink rate
of a polar and I compare gliders based on that
sink rate.

For a comparison of how this works into the wind,
with a 30 knot headwind, a PIK20 or LS-4 has a
20:1 effective glide, while a SGS 2-33 has a
9:1 effective glide, when flown at the "best
glide for 30 knot headwind airspeed."

Quite a difference. Some of my past experiences
fighting 20+ knot headwinds in a glider, while
thermalling, have caused a few "moments of great
concern." Drifting downwind, not frequently enough
checking the landing spot, and having my thermal get
all blown out, has gotten my attention...

Then pushing over the nose and seeing the vario go
way down and the ASI and ground not doing much is
even worse...

If it weren't for ground effect I don't know
WHAT I'd do :PPP

Bruce Greeff wrote in message ...
Hi

I was recently challenged to define Penetration.

A measure of the ratio of forward progress to altitude lost when
flying into a head wind.

The ability to make forward progress against a headwind while engaging
is sawtooth profile thermalling flight.

What a 1-26 hasn't got.

I'm glad I didn't dump the water!

With inadequate pentration the top of current climb is no further down
course than the top of the last one. The further down course it is,
the better the penetration.


Andy

A 2-33 penetrates like mashed potatoes thrown at a screen door.

A 2-33 penetrates like mashed potatoes thrown at a screen door.

True, but for what it's designed to do, a 2-33 is as good as an ASW-27

Don't tell this to the guy who won sports class nationals last year in a
standard Libelle. He may have a differing opinion!!!

Brian

"tango4" wrote in message
...
K8's, PW5's and Libelles don't 'penetrate' well because flying fast just
brings 'em down faster. Going cross country in anything but a gentle
breeze
becomes seriously hard work.

ASW27's full of H2O penetrate like darts. You can get round the task with
20kt breezes on the nose all day.

I suppose it relates to how flat the polar curve is above 100 kph.


Ian


"Shawn Curry" wrote in message
link.net...
Bruce Greeff wrote:
Hi

I was recently challenged to define Penetration.
We failed to find a suitable definition - although I have my own
opinions.

Views presented on the subject include:
Glider penetration is represented by the polar curve.
Penetration is proportional to wing loading.
Penetration is the "real world L/D" taking into account the energy
reserves over drag to overcome upsets caused by turbulence etc.
Penetration is related to weight only. (variant ratio of- weight and
frontal area * Coefficient of Drag)

I know we must be missing the point so -
Any takers from our learned aerodynamicist types?

What exactly is "penetration" as applied to gliders and how does it
differ from the polar curve.

In the glider sense at least:
Being able to go fast and still keep it up.
Hope this helps.

Cheers,
Shawn