ASG-29/ASW-27 wing refinish

Here is my hypothesis.
The SH lays up there spar cap into the wing skin, versus the
AS factory, which built there spar complete and separate from
the wing structure.
This requires a different joining technique and application
of epoxy slurry. In the later case the spar is set into the lower wing
skin in a controlled fashion, hence using less epoxy.
Before the top skin is set into place,
dams out of beaded foam are built, they are a bid higher then the
insight
of the skin when joint. The spar cap with the dams in place is now
filled
with an epoxy mixture. The shape of the mixture has a little inverted
V shape like a roof but shallower. This allows for the epoxy to make
contact in the centre first and pushes it out ward. At the same time
the foam dam gets pushed out of the way to allow for a bead to be form.
Due to the tolerances between the height of the spar cap and
the inner wing skin, there is more epoxy used then at the bottom joint,

hence more shrinking of the top skin occurs.

That does not explain the fact I did not have shrinkage on my
ASW24 wing in 16 years, unless, I venture to say, after 1999 a lot of
experience workers retired. I must assume that the tolerance were
also better before that time and better epoxies were used.
There is always a drive to keep the cost down.
I always like the idea of building the spar separate.
They got it right once they should get it right again.
Udo

Stewart Kissel wrote:
At 20:31 05 November 2006, Doug Haluza wrote:
I was at the Schleicher factory last week, and asked
about this. They did purchase new higher temperature
curing ovens to try to solve this problem, but it has
not helped much. It seems that it just has to run its
course over time. They did say that the shrinkage seems
to be a one-time thing, and it is complete after about
4 years.

Hmmm, I take it they have examined the construction
of this wing vs other wings that don't shrink and get
spar bumps. Far be it for me to question Teutonic
marketing rationale...but spending $100k+ on a glider
that is going to have its performance suffer as the
wing shrinks, then get to spend another $20k+ on reprofile
and refinish....am I missing something here?

Udo:

The DG website has a diagram of 4 different spar construction methods:

http://www.dg-flugzeugbau.de/holm-aufbau-e.html

Do I understand you to say that SH uses #3, and AS uses #1? DG says
that they use #4, so that would mean that each of the major
manufacturers uses a different method.



Udo wrote:
Here is my hypothesis.
The SH lays up there spar cap into the wing skin, versus the
AS factory, which built there spar complete and separate from
the wing structure.
This requires a different joining technique and application
of epoxy slurry. In the later case the spar is set into the lower wing
skin in a controlled fashion, hence using less epoxy.
Before the top skin is set into place,
dams out of beaded foam are built, they are a bid higher then the
insight
of the skin when joint. The spar cap with the dams in place is now
filled
with an epoxy mixture. The shape of the mixture has a little inverted
V shape like a roof but shallower. This allows for the epoxy to make
contact in the centre first and pushes it out ward. At the same time
the foam dam gets pushed out of the way to allow for a bead to be form.
Due to the tolerances between the height of the spar cap and
the inner wing skin, there is more epoxy used then at the bottom joint,

hence more shrinking of the top skin occurs.

Greg ,
# 3 is a simplified version of the SH approach. The web has a pocket
along the spar
in which the web slides upon closure.The total amount of epoxy is
reduced,
and the shrinking acts in a different direction, hence less shrinking
in the vertical.
In any case that is my take on it.
http://www.alexander-schleicher.de/englisch/e_main.htm
Udo

Greg Arnold wrote:
Udo:

The DG website has a diagram of 4 different spar construction methods:

http://www.dg-flugzeugbau.de/holm-aufbau-e.html

Do I understand you to say that SH uses #3, and AS uses #1? DG says
that they use #4, so that would mean that each of the major
manufacturers uses a different method.



Udo wrote:
Here is my hypothesis.
The SH lays up there spar cap into the wing skin, versus the
AS factory, which built there spar complete and separate from
the wing structure.
This requires a different joining technique and application
of epoxy slurry. In the later case the spar is set into the lower wing
skin in a controlled fashion, hence using less epoxy.
Before the top skin is set into place,
dams out of beaded foam are built, they are a bid higher then the
insight
of the skin when joint. The spar cap with the dams in place is now
filled
with an epoxy mixture. The shape of the mixture has a little inverted
V shape like a roof but shallower. This allows for the epoxy to make
contact in the centre first and pushes it out ward. At the same time
the foam dam gets pushed out of the way to allow for a bead to be form.
Due to the tolerances between the height of the spar cap and
the inner wing skin, there is more epoxy used then at the bottom joint,

hence more shrinking of the top skin occurs.

I sure am impressed with DG as a company! Many safety products, GREAT
web site, newsletters...etc. No, I do not own a DG glider, nor do I
have one on order. However, as soon as they make a competive glider
that I fit into (i.e., LS 10 with new cockpit I will buy it!). I just
wish the other manufacturers would make NOAH's, something to keep
spoilers from opening, and stall warning like DG does.

On Nov 5, 6:43 pm, Greg Arnold wrote:
Udo:

The DG website has a diagram of 4 different spar construction methods:

http://www.dg-flugzeugbau.de/holm-aufbau-e.html

Do I understand you to say that SH uses #3, and AS uses #1? DG says
that they use #4, so that would mean that each of the major
manufacturers uses a different method.

Udo wrote:
Here is my hypothesis.
The SH lays up there spar cap into the wing skin, versus the
AS factory, which built there spar complete and separate from
the wing structure.
This requires a different joining technique and application
of epoxy slurry. In the later case the spar is set into the lower wing
skin in a controlled fashion, hence using less epoxy.
Before the top skin is set into place,
dams out of beaded foam are built, they are a bid higher then the
insight
of the skin when joint. The spar cap with the dams in place is now
filled
with an epoxy mixture. The shape of the mixture has a little inverted
V shape like a roof but shallower. This allows for the epoxy to make
contact in the centre first and pushes it out ward. At the same time
the foam dam gets pushed out of the way to allow for a bead to be form.
Due to the tolerances between the height of the spar cap and
the inner wing skin, there is more epoxy used then at the bottom joint,

hence more shrinking of the top skin occurs.

Roger wrote:
I sure am impressed with DG as a company! Many safety products, GREAT
web site, newsletters...etc. No, I do not own a DG glider, nor do I
have one on order. However, as soon as they make a competive glider
that I fit into (i.e., LS 10 with new cockpit I will buy it!). I just
wish the other manufacturers would make NOAH's, something to keep
spoilers from opening, and stall warning like DG does.

Schleicher does some nice things, too:

Starting with the ASW 27, the caps on unlocked spoilers tip up in back,
preventing the airflow from sucking open the spoilers.

They lead the way to safer cockpit construction, and still have a more
crash resistant cockpit than the DG models. For me, that is more
important than the better visibility the lower sidewalls of the DG
provide, and the availability of the NOAH system. My belief is I will be
more likely to crash into the ground than have a mid-air collision where
G loads pin me inside the glider, or to avoid the collision because of
the better visibility.

Ever since the ASW 20, their flapped gliders have had a landing flap
position that puts the flaps at 40 degrees positive, while raisig the
ailerons to a slight negative angle. This gives a high drag, high lift
configuration with no tendency to stall the tips, allowing a steeper,
slower approach and landing than gliders where the landing flap is more
like 20 degrees.

I do like the idea of DG's stall warning, and hope owners with it will
report on it's usefulness. Their web site is very good, and I visit it
more often than Schleicher's.

--
Eric Greenwell - Washington State, USA
Change "netto" to "net" to email me directly

"Transponders in Sailplanes" on the Soaring Safety Foundation website
www.soaringsafety.org/prevention/articles.html

"A Guide to Self-launching Sailplane Operation" at www.motorglider.org

At 03:54 08 November 2006, Eric Greenwell wrote:
Roger wrote:
I sure am impressed with DG as a company! Many safety
products, GREAT
web site, newsletters...etc. No, I do not own a DG
glider, nor do I
have one on order. However, as soon as they make
a competive glider
that I fit into (i.e., LS 10 with new cockpit I will
buy it!). I just
wish the other manufacturers would make NOAH's, something
to keep
spoilers from opening, and stall warning like DG does.

Schleicher does some nice things, too:

Starting with the ASW 27, the caps on unlocked spoilers
tip up in back,
preventing the airflow from sucking open the spoilers.

They lead the way to safer cockpit construction, and
still have a more
crash resistant cockpit than the DG models. For me,
that is more
important than the better visibility the lower sidewalls
of the DG
provide, and the availability of the NOAH system. My
belief is I will be
more likely to crash into the ground than have a mid-air
collision where
G loads pin me inside the glider, or to avoid the collision
because of
the better visibility.

Ever since the ASW 20, their flapped gliders have had
a landing flap
position that puts the flaps at 40 degrees positive,
while raisig the
ailerons to a slight negative angle. This gives a high
drag, high lift
configuration with no tendency to stall the tips, allowing
a steeper,
slower approach and landing than gliders where the
landing flap is more
like 20 degrees.

I do like the idea of DG's stall warning, and hope
owners with it will
report on it's usefulness. Their web site is very good,
and I visit it
more often than Schleicher's.

--
Eric Greenwell - Washington State, USA
Change 'netto' to 'net' to email me directly

'Transponders in Sailplanes' on the Soaring Safety
Foundation website
www.soaringsafety.org/prevention/articles.html

'A Guide to Self-launching Sailplane Operation' at
www.motorglider.org


In your many trips to our DG web site you may have
missed this section that deals with their extensive
work on a better safety cockpit.
http://www.dg-flugzeugbau.de/index-e.html
While other manufactures have been content with building
what looks strong enough DG has actually participated
in crash testing. As a result of this testing they
offer the consummate safety cockpit as an option on
the 800 series and as standard on the 1000.

If you counting on higher frame rails for protection
you may also want to read this.
http://www.dg-flugzeugbau.de/index-e.html

At 13:42 08 November 2006, Gary Evans wrote:
At 03:54 08 November 2006, Eric Greenwell wrote:
Roger wrote:
I sure am impressed with DG as a company! Many safety
products, GREAT
web site, newsletters...etc. No, I do not own a DG
glider, nor do I
have one on order. However, as soon as they make
a competive glider
that I fit into (i.e., LS 10 with new cockpit I will
buy it!). I just
wish the other manufacturers would make NOAH's, something
to keep
spoilers from opening, and stall warning like DG does.

Schleicher does some nice things, too:

Starting with the ASW 27, the caps on unlocked spoilers
tip up in back,
preventing the airflow from sucking open the spoilers.

They lead the way to safer cockpit construction, and
still have a more
crash resistant cockpit than the DG models. For me,
that is more
important than the better visibility the lower sidewalls
of the DG
provide, and the availability of the NOAH system. My
belief is I will be
more likely to crash into the ground than have a mid-air
collision where
G loads pin me inside the glider, or to avoid the collision
because of
the better visibility.

Ever since the ASW 20, their flapped gliders have had
a landing flap
position that puts the flaps at 40 degrees positive,
while raisig the
ailerons to a slight negative angle. This gives a high
drag, high lift
configuration with no tendency to stall the tips, allowing
a steeper,
slower approach and landing than gliders where the
landing flap is more
like 20 degrees.

I do like the idea of DG's stall warning, and hope
owners with it will
report on it's usefulness. Their web site is very good,
and I visit it
more often than Schleicher's.

--
Eric Greenwell - Washington State, USA
Change 'netto' to 'net' to email me directly

'Transponders in Sailplanes' on the Soaring Safety
Foundation website
www.soaringsafety.org/prevention/articles.html

'A Guide to Self-launching Sailplane Operation' at
www.motorglider.org


In your many trips to our DG web site you may have
missed this section that deals with their extensive
work on a better safety cockpit.
http://www.dg-flugzeugbau.de/index-e.html
While other manufactures have been content with building
what looks strong enough DG has actually participated
in crash testing. As a result of this testing they
offer the consummate safety cockpit as an option on
the 800 series and as standard on the 1000.

If you counting on higher frame rails for protection
you may also want to read this.
http://www.dg-flugzeugbau.de/index-e.html








Hmmm, sorry for some reason my original links only
take you to the DG web site opening page. If I paste
the link it works but it doesn't from clicking in the
post. Anyone know what I'm doing wrong?
From the opening page click on DG-808 and under DG-808
General find 'The Consummate Safety Cockpit'.

Gary,



Depending on your newsreader and computer, at, for instance, the DG808
page, hover your mouse over the "The Consummate Safety Cockpit" and
right-click or option-click the link. Choose "Copy Link Location" or
some such from the options. Then you can paste that link into the
email.



Larry

"01" USA












Hmmm, sorry for some reason my original links only
take you to the DG web site opening page. If I paste
the link it works but it doesn't from clicking in the
post. Anyone know what I'm doing wrong?
From the opening page click on DG-808 and under DG-808
General find 'The Consummate Safety Cockpit'.

The Safety cockpit is now standard in the DG 808 as well. They where
amazed that not many new owners where taking the safety cockpit option.
One reason given ( apart from the cost ) was the width of the seatpan
was narrower when it was installed.They improved the design and also
made it part of the base glider price.

So same sized cockpit as before and stronger to boot.

Paul

Gary Evans wrote:

While other manufactures have been content with building
what looks strong enough DG has actually participated
in crash testing.

This is not correct. Gerhard Waibel won an OSTIV prize for his work in
cockpit safety about 20 years ago. Gerhard's ideas, and the ASW 24
cockpit (the first of the really crashworthy cockpits) was based on
extensive testing by a group at MIT, and others. In the years since
then, Schleicher continues to monitor the performance of their designs
by examining their gliders that are involved in crashes, either when
they are brought to their shop for repair, or using pictures sent to
them by the mechanics repairing the glider elsewhere. An advantage of
this approach is it shows what happens in an actual crash.

As a result of this testing they
offer the consummate safety cockpit as an option on
the 800 series and as standard on the 1000.

I have been impressed with DG's improvements in safety over the years,
but their single seaters cockpits still do not match what Schleicher has
done. This page on the DG website shows that this view is shared by
others (go to the "Safety Cockpit" row):

http://www.dgflugzeugbau.de/ash-dg-ventus-e.html

These differences are not surprising. The low sides and open nose of the
DG single seater cockpit pose a difficult engineering problem for the
designer, compared to the greater enclosure of the Schleicher cockpits.

I'm not suggesting that the DG cockpit is unsafe or inadequate, but only
that it does not match what Schleicher has done. A prospective owner
should consider the value of that protection along with the other
features of the gliders he is considering; for example, the lower sides
of the DG cockpit (particularly if the NOAH option is selected) should
make baling out easier than from a Schleicher cockpit.


If you counting on higher frame rails for protection
you may also want to read this.
http://www.dg-flugzeugbau.de/index-e.html

I was unable to find this reference, but I would like to read it.

--
Eric Greenwell - Washington State, USA
Change "netto" to "net" to email me directly

"Transponders in Sailplanes" on the Soaring Safety Foundation website
www.soaringsafety.org/prevention/articles.html

"A Guide to Self-launching Sailplane Operation" at www.motorglider.org