Twin Lark - CG release

[Mark Zivley]

We've done a few winch launches w/ our club's twin lark and when the
winch driver starts to reduce power at the release point on the launch
the cable back releases w/ a solid bang. I haven't had a chance to take
a look and see if it is possible to rotate the CG release so that the
cable has to be unloaded a bit more before it can back release. Does
anyone out there know?

Thanks,

Mark

[goneill]

Be very careful doing that as it is very easy to to create a situation where
a hangup can occur .
gary
"Mark Zivley" > wrote in message
m...
> We've done a few winch launches w/ our club's twin lark and when the
> winch driver starts to reduce power at the release point on the launch
> the cable back releases w/ a solid bang. I haven't had a chance to take
> a look and see if it is possible to rotate the CG release so that the
> cable has to be unloaded a bit more before it can back release. Does
> anyone out there know?
>
> Thanks,
>
> Mark
>

[Bill Daniels]

It's supposed to do that. My Twin Lark did the same thing. It's a neat
safety feature. Don't even THINK about modifying it. (You'd have to remove
way too much stuff to get to it anyway.)

The problem isn't the release, it's the weight of the cable. The cable sags
as the power is reduced slightly and that causes the angle of the cable at
the release to exceed 70 degrees and BANG! - away goes the cable.

Buy some Spectra - it's much lighter and won't sag as much. You'll get
another 15 - 20% over the height you are getting now. It will still
auto-release when the power is reduced but at a higher altitude.

Bill Daniels


"Mark Zivley" > wrote in message
m...
> We've done a few winch launches w/ our club's twin lark and when the
> winch driver starts to reduce power at the release point on the launch
> the cable back releases w/ a solid bang. I haven't had a chance to take
> a look and see if it is possible to rotate the CG release so that the
> cable has to be unloaded a bit more before it can back release. Does
> anyone out there know?
>
> Thanks,
>
> Mark
>

[Robin Birch]

In message <D2bUc.25951$TI1.2218@attbi_s52>, Bill Daniels
> writes
>It's supposed to do that. My Twin Lark did the same thing. It's a neat
>safety feature. Don't even THINK about modifying it. (You'd have to remove
>way too much stuff to get to it anyway.)
>
>The problem isn't the release, it's the weight of the cable. The cable sags
>as the power is reduced slightly and that causes the angle of the cable at
>the release to exceed 70 degrees and BANG! - away goes the cable.
>
If it is getting too bad then the problem may also be the springs in the
hook getting tired and it's time for a service, 2000 launches springs to
mind as the normal interval (I'm probably wrong there)

Robin

>Buy some Spectra - it's much lighter and won't sag as much. You'll get
>another 15 - 20% over the height you are getting now. It will still
>auto-release when the power is reduced but at a higher altitude.
>
>Bill Daniels
>
>
>"Mark Zivley" > wrote in message
m...
>> We've done a few winch launches w/ our club's twin lark and when the
>> winch driver starts to reduce power at the release point on the launch
>> the cable back releases w/ a solid bang. I haven't had a chance to take
>> a look and see if it is possible to rotate the CG release so that the
>> cable has to be unloaded a bit more before it can back release. Does
>> anyone out there know?
>>
>> Thanks,
>>
>> Mark
>>
>

--
Robin Birch

[BTIZ]

> >
> If it is getting too bad then the problem may also be the springs in the
> hook getting tired and it's time for a service, 2000 launches springs to
> mind as the normal interval (I'm probably wrong there)
>
> Robin

And you have to keep in mind that it is 2000 launches (actuations) of the
release, every time you pull the forward release, you are exercising the
springs on the winch (CG) release. Provided you have more than one.

Maybe it's time to replace both. But the heavy cable sagging back will make
it back release.

BT

[Mark Zivley]

I don't think this is due entirely to the weight of the cable. We fly
the same cable w/ our Duo and it back releases nicely with a much softer
"ka-clink" that you can hear. On the Lark it's a loud bang and the
cable is definitely much more taught when it does back release. This is
what makes me suspicious that it's the angle that the release is
installed at, but I'm definitely looking for other considerations.

This Lark is relatively low time so I don't think it's a spring issue,
but good thought.

Mark

Mark Zivley wrote:

> We've done a few winch launches w/ our club's twin lark and when the
> winch driver starts to reduce power at the release point on the launch
> the cable back releases w/ a solid bang. I haven't had a chance to take
> a look and see if it is possible to rotate the CG release so that the
> cable has to be unloaded a bit more before it can back release. Does
> anyone out there know?
>
> Thanks,
>
> Mark
>

[Bill Daniels]

"Mark Zivley" > wrote in message
...
> I don't think this is due entirely to the weight of the cable. We fly
> the same cable w/ our Duo and it back releases nicely with a much softer
> "ka-clink" that you can hear. On the Lark it's a loud bang and the
> cable is definitely much more taught when it does back release. This is
> what makes me suspicious that it's the angle that the release is
> installed at, but I'm definitely looking for other considerations.
>
> This Lark is relatively low time so I don't think it's a spring issue,
> but good thought.
>
> Mark

I noticed exactly the same thing comparing my Lark to a Grob Twin II. The
Lark was much louder and released with more tension. That's just the nature
of the animal.

As the winch driver launching my own Lark with a friend at the controls I
noticed that the back release occurred exactly when I wanted it to. As soon
as I cut the power, the cable fell free of the glider - I liked that. On
the other hand, the Grob would hold the cable until the pilot pulled the
release, sometimes dropping the cable way too close to the winch.

Now, if the cable is coming off the CG hook BEFORE the winch driver cuts the
power, THEN you have a problem with the release.

Carbon/Glass reinforced resin with a PVC foam core is a great sound
deadener - any composite structure will be quiet. Aluminum is a great
conductor of sound. The Lark back release will always be loud especially
since it is mounted directly to the sub-structure beneath the rear cockpit.

Note that the Lark nose hook will also back release. Sit in the cockpit and
have someone pull back on a rope until the hook back releases. It will be
loud too although not as loud as the 2-32 nose hook.

Bill Daniels

[Mark Zivley]

Bill,

Thanks for the good info. I'm sure the metal structure also makes it
louder, but we can tell by watching the cable/parachute that it's under
a lot more load then when the Duo lets go. I guess that's just the way
it is.

Mark

Bill Daniels wrote:
> "Mark Zivley" > wrote in message
> ...
>
>>I don't think this is due entirely to the weight of the cable. We fly
>>the same cable w/ our Duo and it back releases nicely with a much softer
>>"ka-clink" that you can hear. On the Lark it's a loud bang and the
>>cable is definitely much more taught when it does back release. This is
>>what makes me suspicious that it's the angle that the release is
>>installed at, but I'm definitely looking for other considerations.
>>
>>This Lark is relatively low time so I don't think it's a spring issue,
>>but good thought.
>>
>>Mark
>
>
> I noticed exactly the same thing comparing my Lark to a Grob Twin II. The
> Lark was much louder and released with more tension. That's just the nature
> of the animal.
>
> As the winch driver launching my own Lark with a friend at the controls I
> noticed that the back release occurred exactly when I wanted it to. As soon
> as I cut the power, the cable fell free of the glider - I liked that. On
> the other hand, the Grob would hold the cable until the pilot pulled the
> release, sometimes dropping the cable way too close to the winch.
>
> Now, if the cable is coming off the CG hook BEFORE the winch driver cuts the
> power, THEN you have a problem with the release.
>
> Carbon/Glass reinforced resin with a PVC foam core is a great sound
> deadener - any composite structure will be quiet. Aluminum is a great
> conductor of sound. The Lark back release will always be loud especially
> since it is mounted directly to the sub-structure beneath the rear cockpit.
>
> Note that the Lark nose hook will also back release. Sit in the cockpit and
> have someone pull back on a rope until the hook back releases. It will be
> loud too although not as loud as the 2-32 nose hook.
>
> Bill Daniels
>