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Grob Twin Astir



 
 
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  #1  
Old October 1st 16, 12:25 AM posted to rec.aviation.soaring
Martin Gregorie[_5_]
external usenet poster
 
Posts: 1,224
Default Grob Twin Astir

On Fri, 30 Sep 2016 13:26:10 +0000, Michael Opitz wrote:

IME the elevator is reasonably functional on a G103 Twin 2 Acro but it
could certainly use a better rudder.


Does it have the Z tape installed in front of the control surfaces as
per the Grob/Lindner optional service letter SL-12? If not, you might
find the effectiveness will be enhanced if you do install it. It works
wonders for the Twin Astir rudder... It is certainly easy and cheap
enough to try, and it is factory approved as well.....

I don't recall seeing any zigzag strip in front of the rudder hinge. I'll
look next time I'm at the club and mention this where it may do some good
if it is not turbulated.

Thanks for the tip.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |
  #2  
Old October 1st 16, 01:40 AM posted to rec.aviation.soaring
Michael Opitz
external usenet poster
 
Posts: 318
Default Grob Twin Astir

At 23:25 30 September 2016, Martin Gregorie wrote:
On Fri, 30 Sep 2016 13:26:10 +0000, Michael Opitz wrote:

IME the elevator is reasonably functional on a G103 Twin 2

Acro but it
could certainly use a better rudder.


Does it have the Z tape installed in front of the control surfaces

as
per the Grob/Lindner optional service letter SL-12? If not, you

might
find the effectiveness will be enhanced if you do install it. It

works
wonders for the Twin Astir rudder... It is certainly easy and

cheap
enough to try, and it is factory approved as well.....

I don't recall seeing any zigzag strip in front of the rudder hinge.

I'll
look next time I'm at the club and mention this where it may do

some good
if it is not turbulated.

Thanks for the tip.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |



Martin,

You are welcome. If your Acro doesn't already have the Z tape
installed, I would be interested to hear your opinion as to if
the efficacy of the rudder is noticeably improved (or not) after the
installation. If the fin airfoil profiles of the Twin Astir and the Acro
are close, I suspect that you will notice a favorable improvement.

Good luck...

RO

  #3  
Old October 10th 16, 11:46 PM posted to rec.aviation.soaring
Martin Gregorie[_5_]
external usenet poster
 
Posts: 1,224
Default Grob Twin Astir

On Sat, 01 Oct 2016 00:40:43 +0000, Michael Opitz wrote:

You are welcome. If your Acro doesn't already have the Z tape
installed, I would be interested to hear your opinion as to if the
efficacy of the rudder is noticeably improved (or not) after the
installation. If the fin airfoil profiles of the Twin Astir and the
Acro are close, I suspect that you will notice a favorable improvement.

I finally checked our Acro II last Sunday: as I thought there's no fin
turbulation on it, so I've passed your reference to the Lindner TN to the
relevent club committee member.

It turns out that our Acro now has a fairly low cockpit weight capacity.
On Sunday we were using it for trial flights but we had to temporarily
take one of our ASK-21s off scheduled training duties to fly a reasonably
heavy trial flighter. Some of our members would like to use it for mutual
XC flying since its a better XC glider than an ASK-21 and has a decent
SDI flight computer fitted. That said, our ASK-21s do routinely go XC on
good days with students who are close to soloing - an 80km o/r to HusBos
is favourite with our paid instructors.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |
  #4  
Old October 11th 16, 03:45 AM posted to rec.aviation.soaring
Michael Opitz
external usenet poster
 
Posts: 318
Default Grob Twin Astir

At 22:46 10 October 2016, Martin Gregorie wrote:
On Sat, 01 Oct 2016 00:40:43 +0000, Michael Opitz wrote:

You are welcome. If your Acro doesn't already have the Z tape
installed, I would be interested to hear your opinion as to if the
efficacy of the rudder is noticeably improved (or not) after the
installation. If the fin airfoil profiles of the Twin Astir and the
Acro are close, I suspect that you will notice a favorable

improvement.

I finally checked our Acro II last Sunday: as I thought there's no

fin
turbulation on it, so I've passed your reference to the Lindner TN

to the
relevent club committee member.

It turns out that our Acro now has a fairly low cockpit weight

capacity.
On Sunday we were using it for trial flights but we had to

temporarily
take one of our ASK-21s off scheduled training duties to fly a

reasonably
heavy trial flighter. Some of our members would like to use it for

mutual
XC flying since its a better XC glider than an ASK-21 and has a

decent
SDI flight computer fitted. That said, our ASK-21s do routinely go

XC on
good days with students who are close to soloing - an 80km o/r to

HusBos
is favourite with our paid instructors.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |



Martin,

Low seat load was the reason we sold our Acro several years ago.
If you have a lot of 2 seaters, you can schedule around it, but the
issue becomes a pain if you only have one or two 2-seaters to work
with.

If you can put up with the ground handling issues of a tail dragger,
and a little bit stiffer flight controls, you may find (as we have) that
the original Twin Astir gives a lot for the money invested. A lot of
them had been used as advanced XC trainers, and not for basic
training, so therefore minimal damage history.. This equates to a
retention of the already very high factory seat load of 242 Lbs/seat
plus another 22 Lbs in the baggage compartment. Some even have
water ballast. For XC training, the Twin 1 has a markedly slower
stall speed (with very effective trim) than the Twin II for better
thermalling performance. Best L/D is also ~4 points better than the
Twin II, so it is also noticeably better on the glides as well. For XC
training, I would take the Twin Astir over an Acro any day....IMHO

You can crash a Twin Astir, then add 40 Lbs of repair material and
still have a higher seat load than a NDH (No Damage History)
Twin II (let alone an Acro which will be 30-40 Lbs less than a
regular Twin II). Of course, these numbers are for the rest of the
world which doesn't have the RAF and BGA Twin II increased gross
weight agreements with Grob.....

RO




  #5  
Old October 11th 16, 07:00 AM posted to rec.aviation.soaring
Frank Whiteley
external usenet poster
 
Posts: 2,099
Default Grob Twin Astir

On Monday, October 10, 2016 at 9:00:20 PM UTC-6, Michael Opitz wrote:
At 22:46 10 October 2016, Martin Gregorie wrote:
On Sat, 01 Oct 2016 00:40:43 +0000, Michael Opitz wrote:

You are welcome. If your Acro doesn't already have the Z tape
installed, I would be interested to hear your opinion as to if the
efficacy of the rudder is noticeably improved (or not) after the
installation. If the fin airfoil profiles of the Twin Astir and the
Acro are close, I suspect that you will notice a favorable

improvement.

I finally checked our Acro II last Sunday: as I thought there's no

fin
turbulation on it, so I've passed your reference to the Lindner TN

to the
relevent club committee member.

It turns out that our Acro now has a fairly low cockpit weight

capacity.
On Sunday we were using it for trial flights but we had to

temporarily
take one of our ASK-21s off scheduled training duties to fly a

reasonably
heavy trial flighter. Some of our members would like to use it for

mutual
XC flying since its a better XC glider than an ASK-21 and has a

decent
SDI flight computer fitted. That said, our ASK-21s do routinely go

XC on
good days with students who are close to soloing - an 80km o/r to

HusBos
is favourite with our paid instructors.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |



Martin,

Low seat load was the reason we sold our Acro several years ago.
If you have a lot of 2 seaters, you can schedule around it, but the
issue becomes a pain if you only have one or two 2-seaters to work
with.

If you can put up with the ground handling issues of a tail dragger,
and a little bit stiffer flight controls, you may find (as we have) that
the original Twin Astir gives a lot for the money invested. A lot of
them had been used as advanced XC trainers, and not for basic
training, so therefore minimal damage history.. This equates to a
retention of the already very high factory seat load of 242 Lbs/seat
plus another 22 Lbs in the baggage compartment. Some even have
water ballast. For XC training, the Twin 1 has a markedly slower
stall speed (with very effective trim) than the Twin II for better
thermalling performance. Best L/D is also ~4 points better than the
Twin II, so it is also noticeably better on the glides as well. For XC
training, I would take the Twin Astir over an Acro any day....IMHO

You can crash a Twin Astir, then add 40 Lbs of repair material and
still have a higher seat load than a NDH (No Damage History)
Twin II (let alone an Acro which will be 30-40 Lbs less than a
regular Twin II). Of course, these numbers are for the rest of the
world which doesn't have the RAF and BGA Twin II increased gross
weight agreements with Grob.....

RO


Competent repairs add little weight. A former BGA senior inspector who had a repair station flew a DG-300 through some wires and smashed it to pieces.. When rebuilt, it weighed within 10oz of new. That same inspector removed 37 lbs of filler from my previously repaired Kestrel 19 while re-contouring the fuselage between the wheel and tail boom. Takes a craftsman I guess..

The Twin Astir and T version winch launch very nicely and are quite cross country capable. If someone designed a nice filet for the wing root, it would probably go 10% better.

I'd heard there might be an effort to increase the Twin II payload, but nothing recently.

Frank Whiteley
  #6  
Old October 11th 16, 08:27 AM posted to rec.aviation.soaring
David Salmon[_3_]
external usenet poster
 
Posts: 54
Default Grob Twin Astir

At 06:00 11 October 2016, Frank Whiteley wrote:
On Monday, October 10, 2016 at 9:00:20 PM UTC-6, Michael Opitz wrote:
At 22:46 10 October 2016, Martin Gregorie wrote:
On Sat, 01 Oct 2016 00:40:43 +0000, Michael Opitz wrote:

You are welcome. If your Acro doesn't already have the Z tape
installed, I would be interested to hear your opinion as to if the
efficacy of the rudder is noticeably improved (or not) after the
installation. If the fin airfoil profiles of the Twin Astir and the
Acro are close, I suspect that you will notice a favorable=20

improvement.

I finally checked our Acro II last Sunday: as I thought there's no=20

fin=20
turbulation on it, so I've passed your reference to the Lindner TN=20

to the=20
relevent club committee member.=20

It turns out that our Acro now has a fairly low cockpit weight=20

capacity.=20
On Sunday we were using it for trial flights but we had to=20

temporarily=20
take one of our ASK-21s off scheduled training duties to fly a=20

reasonably=20
heavy trial flighter. Some of our members would like to use it for=20

mutual=20
XC flying since its a better XC glider than an ASK-21 and has a=20

decent=20
SDI flight computer fitted. That said, our ASK-21s do routinely go=20

XC on=20
good days with students who are close to soloing - an 80km o/r to=20

HusBos=20
is favourite with our paid instructors.


--=20
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

=20
=20
Martin,
=20
Low seat load was the reason we sold our Acro several years ago.
If you have a lot of 2 seaters, you can schedule around it, but the=20
issue becomes a pain if you only have one or two 2-seaters to work=20
with.
=20
If you can put up with the ground handling issues of a tail dragger,
and a little bit stiffer flight controls, you may find (as we have)

that=
=20
the original Twin Astir gives a lot for the money invested. A lot

of=20
them had been used as advanced XC trainers, and not for basic=20
training, so therefore minimal damage history.. This equates to a=20
retention of the already very high factory seat load of 242 Lbs/seat
plus another 22 Lbs in the baggage compartment. Some even have=20
water ballast. For XC training, the Twin 1 has a markedly slower=20
stall speed (with very effective trim) than the Twin II for better=20
thermalling performance. Best L/D is also ~4 points better than the=20
Twin II, so it is also noticeably better on the glides as well. For

XC=20
training, I would take the Twin Astir over an Acro any day....IMHO
=20
You can crash a Twin Astir, then add 40 Lbs of repair material and=20
still have a higher seat load than a NDH (No Damage History)
Twin II (let alone an Acro which will be 30-40 Lbs less than a=20
regular Twin II). Of course, these numbers are for the rest of the=20
world which doesn't have the RAF and BGA Twin II increased gross=20
weight agreements with Grob.....
=20
RO


Competent repairs add little weight. A former BGA senior inspector who
had=
a repair station flew a DG-300 through some wires and smashed it to
pieces=
.. When rebuilt, it weighed within 10oz of new. That same inspector
remove=
d 37 lbs of filler from my previously repaired Kestrel 19 while
re-contouri=
ng the fuselage between the wheel and tail boom. Takes a craftsman I
guess=
..

The Twin Astir and T version winch launch very nicely and are quite cross
c=
ountry capable. If someone designed a nice filet for the wing root, it
wou=
ld probably go 10% better.

I'd heard there might be an effort to increase the Twin II payload, but
not=
hing recently.

Frank Whiteley


20 years ago we had an Acro with a strange history. Apparently it had spun
in and the whole front end replaced with one from another that had caught
fire in the factory. I don't remember any weiight problems. It was a lovely
glider to fly, except, with the slightest rain on the wings it reverted to
the performance of a brick. Never managed to spin it, and a 1g stall
attempt would just result in mushing flight. I have ridge soared it with
the stick on the back stop. It was a very well engineered and made glider,
and we too used it for cross country training, and I well remember once
taking a visiting king for a flight in it.
It came with a small pair of canards, to enable it to enter a spin more
easily, but because it had a new nose, the fixing holes were not there, and
we didn't need it to spin anyway as we had Puchaczs. Not the easiest to
rig, but it lived in the hangar, so not a problem. A glider I remember
with a great deal of affection.
Re the Kestrel 19, when mine was being rigged, you could hear the loose
bits left in thhe wings, rattling around.
Dave



  #7  
Old October 11th 16, 12:10 PM posted to rec.aviation.soaring
Bruce Hoult
external usenet poster
 
Posts: 961
Default Grob Twin Astir

On Tuesday, October 11, 2016 at 4:00:20 PM UTC+13, Michael Opitz wrote:
At 22:46 10 October 2016, Martin Gregorie wrote:
On Sat, 01 Oct 2016 00:40:43 +0000, Michael Opitz wrote:

You are welcome. If your Acro doesn't already have the Z tape
installed, I would be interested to hear your opinion as to if the
efficacy of the rudder is noticeably improved (or not) after the
installation. If the fin airfoil profiles of the Twin Astir and the
Acro are close, I suspect that you will notice a favorable

improvement.

I finally checked our Acro II last Sunday: as I thought there's no

fin
turbulation on it, so I've passed your reference to the Lindner TN

to the
relevent club committee member.

It turns out that our Acro now has a fairly low cockpit weight

capacity.
On Sunday we were using it for trial flights but we had to

temporarily
take one of our ASK-21s off scheduled training duties to fly a

reasonably
heavy trial flighter. Some of our members would like to use it for

mutual
XC flying since its a better XC glider than an ASK-21 and has a

decent
SDI flight computer fitted. That said, our ASK-21s do routinely go

XC on
good days with students who are close to soloing - an 80km o/r to

HusBos
is favourite with our paid instructors.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |



Martin,

Low seat load was the reason we sold our Acro several years ago.
If you have a lot of 2 seaters, you can schedule around it, but the
issue becomes a pain if you only have one or two 2-seaters to work
with.

If you can put up with the ground handling issues of a tail dragger,
and a little bit stiffer flight controls, you may find (as we have) that
the original Twin Astir gives a lot for the money invested. A lot of
them had been used as advanced XC trainers, and not for basic
training, so therefore minimal damage history.. This equates to a
retention of the already very high factory seat load of 242 Lbs/seat
plus another 22 Lbs in the baggage compartment. Some even have
water ballast. For XC training, the Twin 1 has a markedly slower
stall speed (with very effective trim) than the Twin II for better
thermalling performance. Best L/D is also ~4 points better than the
Twin II, so it is also noticeably better on the glides as well. For XC
training, I would take the Twin Astir over an Acro any day....IMHO


All you say is correct.

The only problem is the diabolical rear seat shape cause by making room for the wheel to retract.

My club flew a pair of original 1978 Twin Astirs as the basic trainers for about a dozen years (mid 90s to late 00s). They were great in almost every way and a huge step up from the Blanik's we had before them. But the DG1000 18s we've replaced the Grobs result in sooo much less money going to the instructors' chiropractors.
  #8  
Old October 11th 16, 01:54 PM posted to rec.aviation.soaring
Michael Opitz
external usenet poster
 
Posts: 318
Default Grob Twin Astir


All you say is correct.

The only problem is the diabolical rear seat shape cause by

making room
for=
the wheel to retract.

My club flew a pair of original 1978 Twin Astirs as the basic

trainers for
=
about a dozen years (mid 90s to late 00s). They were great in

almost every
=
way and a huge step up from the Blanik's we had before them.

But the
DG1000=
18s we've replaced the Grobs result in sooo much less money

going to the
i=
nstructors' chiropractors.


I wish our club could afford to buy and insure a couple of DG-
1000/18's, or Duo Discus, or even K-21's, but we don't have the
money at present. Maybe after some more years.. We own our own
airport where we have runway and hangar repair/replacement
issues to deal with also. Money has to very carefully allocated.
We were tenants for 47 years, being forced to move from one
airport to another at the whim of the owners, so having our own
permanent home now is a blessing, but it also has it's own issues.

When I instruct in the back seat of a Twin, I just use one of those
curved lumbar support cushions myself. One of our club members
has back issues, and has carved himself a foam cushion that suits
his needs for longer flights. I am 6'2" / 205 Lbs, and I am OK in
the back seat, even on flights of 3-4 hours duration. We are buying
a Trainer version with the fixed, sprung gear to use for primary
training. We are hoping that the sprung gear helps absorb the
shocks of some of the primary students "less than smooth"
landings.

To Frank's point about repair weight gains, I know... I worked for
Klaus H at S-H between college and going into the USAF a long, long
time ago. The fact (in the USA) is that virtually all Twin II's which
do come up for sale are "single seaters with a large baggage
compartment". Some have gained over 100(!!!) Lbs in repair
weight due to multiple accidents. Our answer has been to go to the
Twin I which has a much higher seat load to start with, and can
tolerate a repair weight gain much more readily...

RO

  #9  
Old October 11th 16, 05:22 PM posted to rec.aviation.soaring
[email protected]
external usenet poster
 
Posts: 2,124
Default Grob Twin Astir

On Tuesday, October 11, 2016 at 9:00:07 AM UTC-4, Michael Opitz wrote:
All you say is correct.

The only problem is the diabolical rear seat shape cause by

making room
for=
the wheel to retract.

My club flew a pair of original 1978 Twin Astirs as the basic

trainers for
=
about a dozen years (mid 90s to late 00s). They were great in

almost every
=
way and a huge step up from the Blanik's we had before them.

But the
DG1000=
18s we've replaced the Grobs result in sooo much less money

going to the
i=
nstructors' chiropractors.


I wish our club could afford to buy and insure a couple of DG-
1000/18's, or Duo Discus, or even K-21's, but we don't have the
money at present. Maybe after some more years.. We own our own
airport where we have runway and hangar repair/replacement
issues to deal with also. Money has to very carefully allocated.
We were tenants for 47 years, being forced to move from one
airport to another at the whim of the owners, so having our own
permanent home now is a blessing, but it also has it's own issues.

When I instruct in the back seat of a Twin, I just use one of those
curved lumbar support cushions myself. One of our club members
has back issues, and has carved himself a foam cushion that suits
his needs for longer flights. I am 6'2" / 205 Lbs, and I am OK in
the back seat, even on flights of 3-4 hours duration. We are buying
a Trainer version with the fixed, sprung gear to use for primary
training. We are hoping that the sprung gear helps absorb the
shocks of some of the primary students "less than smooth"
landings.

To Frank's point about repair weight gains, I know... I worked for
Klaus H at S-H between college and going into the USAF a long, long
time ago. The fact (in the USA) is that virtually all Twin II's which
do come up for sale are "single seaters with a large baggage
compartment". Some have gained over 100(!!!) Lbs in repair
weight due to multiple accidents. Our answer has been to go to the
Twin I which has a much higher seat load to start with, and can
tolerate a repair weight gain much more readily...

RO


I suspect that much of what RO calls "repair weight" is actually lazy refinishing weight. I know of a couple Grobs that got a sanding to rough up the gelcoat, a bunch of filler to bury the cracks, then finish coats.
A properly done repair doesn't add much weight, the added weight is only that of the doubling plies or internal backing added before the scarf and laminating gets done.
UH
  #10  
Old October 11th 16, 07:54 PM posted to rec.aviation.soaring
Bruce Hoult
external usenet poster
 
Posts: 961
Default Grob Twin Astir

On Wednesday, October 12, 2016 at 2:00:07 AM UTC+13, Michael Opitz wrote:
But the DG1000 18s we've replaced the Grobs result in sooo
much less money going to the instructors' chiropractors.


I wish our club could afford to buy and insure a couple of DG-
1000/18's, or Duo Discus, or even K-21's, but we don't have the
money at present. Maybe after some more years.. We own our own
airport where we have runway and hangar repair/replacement
issues to deal with also. Money has to very carefully allocated.
We were tenants for 47 years, being forced to move from one
airport to another at the whim of the owners, so having our own
permanent home now is a blessing, but it also has it's own issues.


Understand that. My club just moved six months ago from being renters on an airport for 50+ years to a single-purpose gliding site. That's meant some big upfront expenses for a new winch ($140k) and new hangar, adjusting the fleet a little (PW5 isn't very winch friendly, Pawnee won't get enough utilization to be worth keeping), and lesser ongoing expenses as we can afford them for putting in clubhouse, bunkhouse, caravan/tent park and facilities, water and electricity. Ongoing though, the expenses should be a lot lower than the airport land rental plus landing fees plus tower fees which together came to something like $40 a flight before spending a cent on the tow or glider. Plus, uncontrolled airspace to at least 9500 everywhere nearby instead of altitude restrictions of 2500, 3500, or 5500 ft everywhere within 15 km of the old field.
 




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