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