Winch Launch Stresses on Vintage Gliders

Our club is exploring switching from aero tow to winch launching. Some of
our members own older wooden gliders and have expressed concerns about the
increased stress on the glider's structure resulting from winch launching
vs. aero tow.

Is this a valid concern?
--
Mike Schumann

Bluenose has winched K7 and K8 gliders for twenty plus years. The
gliders are now 35 years old -- no winch related maintenance required.

Mike Schumann wrote:
Our club is exploring switching from aero tow to winch launching. Some of
our members own older wooden gliders and have expressed concerns about the
increased stress on the glider's structure resulting from winch launching
vs. aero tow.

Is this a valid concern?

In message t, Mike
Schumann writes
Our club is exploring switching from aero tow to winch launching. Some of
our members own older wooden gliders and have expressed concerns about the
increased stress on the glider's structure resulting from winch launching
vs. aero tow.

Is this a valid concern?
Just make sure that your winch drivers are trained properly and don't
just launch as though they are coming off an aircraft carrier. Proper
speed control and suitable weak links and it works fine.

We launch T31s T21s K6s Skylark 2s and Oly 2bs with now issues at all.
Remember that a lot of older gliders had compromise hooks which won't
give as high a launch as the more recent designs with real CofG hooks.

Cheers

Robin
--
Robin Birch

In message , Mike Schumann writes
Our club is exploring switching from aero tow to winch
launching. Some of our members own older wooden gliders
and have expressed concerns about the increased stress
on the glider's structure resulting from winch launching
vs. aero tow.

Is this a valid concern?

In addition to Robins well made point the pilots need
a certain amount of training and discipline. Bill Daniel
web site on winch launching contains many useful documents
that may be worth reading. See

http://groups.yahoo.com/group/winchd...guid=180793033

You will have to register to down load the infomation
but it is freely available. If you are in the USA make
contact will Bill he is interested in developing winch
launching.

Dave




Just make sure that your winch drivers are trained
properly and don't just launch as though they are coming
off an aircraft carrier. Proper speed control and
suitable weak links and it works fine.

We launch T31s T21s K6s Skylark 2s and Oly 2bs with
now issues at all.
Remember that a lot of older gliders had compromise
hooks which won't
give as high a launch as the more recent designs with
real CofG hooks.

Cheers

Robin
--
Robin Birch

Dave Martin wrote:
In message , Mike Schumann writes
Our club is exploring switching from aero tow to winch
launching. Some of our members own older wooden gliders
and have expressed concerns about the increased stress
on the glider's structure resulting from winch launching
vs. aero tow.

Is this a valid concern?

In addition to Robins well made point the pilots need
a certain amount of training and discipline. Bill Daniel
web site on winch launching contains many useful documents
that may be worth reading. See

http://groups.yahoo.com/group/winchd...guid=180793033

You will have to register to down load the infomation
but it is freely available. If you are in the USA make
contact will Bill he is interested in developing winch
launching.

Dave




Just make sure that your winch drivers are trained
properly and don't just launch as though they are coming
off an aircraft carrier. Proper speed control and
suitable weak links and it works fine.

We launch T31s T21s K6s Skylark 2s and Oly 2bs with
now issues at all.
Remember that a lot of older gliders had compromise
hooks which won't
give as high a launch as the more recent designs with
real CofG hooks.

Cheers

Robin
--
Robin Birch




Mike,

heed all of the above and check the operating manuals for each glider
you intend to launch. You should find a section regarding the required
weak-link strength. Order the proper weak-links from TOST. Contrary to
'home-made' weak links fashioned from hardware store polypropylene
rope, the TOST links are precision engineered devices with a breaking
strength within a few % of the rating. Also, check what type of
releases your gliders have and buy the appropriate rings.
Regarding the extra stress on the glider: a good rule of thumb is that
a normal winch launch imposes a load about equivalent of 2g onto the
glider.
As Dave Martin already stated - join our yahoo winchdesign group for
all your questions regarding safe winch launching.

Uli Neumann

Look at vintage glider winch launch video at Nijmegen Aero Club website.
http://www.nijac.nl/galerij/zweefvlieg.wmv
Vintage glider winch launch is no problem as long as you know what you (or your winch driver) are doing. (of course the oximoron for everything)
This is the originating club of the Van Gelder / MEL winch.
You can winch launch anything from hangglider/paraglider to fully ballasted DG505 (again, if you know what you are doing)

Originally Posted by Mike Schumann

Our club is exploring switching from aero tow to winch launching. Some of
our members own older wooden gliders and have expressed concerns about the
increased stress on the glider's structure resulting from winch launching
vs. aero tow.

Is this a valid concern?
--
Mike Schumann

If the vintage wooden glider is truly airworthy and
you use the specified weak link (usually white or blue),
then no. We launch vintage gliders by winch most of
the time in the UK (America's fixed aircraft carrier,
just off Europe - if you don't know where that is).


However, winch launches can put a strain equivalent
to a 3.5g turn on the mainspar, and sometimes the tail,
without any obvious g loading on the pilot. If you
have a very powerful modern winch, then you need to
brief the winch driver to apply the power fairly gently
at the start. Placarded speed limits need to be strictly
observed.

Cheers,
Derek Copeland (part owner of several vintage gliders)


At 18:18 22 January 2006, Mike Schumann wrote:
Our club is exploring switching from aero tow to winch
launching. Some of
our members own older wooden gliders and have expressed
concerns about the
increased stress on the glider's structure resulting
from winch launching
vs. aero tow.

Is this a valid concern?
--
Mike Schumann

Mike Schumann wrote:
Our club is exploring switching from aero tow to winch launching. Some of
our members own older wooden gliders and have expressed concerns about the
increased stress on the glider's structure resulting from winch launching
vs. aero tow.

Is this a valid concern?
We fly almost exclusively vintage aircraft at our club. All launches are winch,
and the safety and maintenance record is excellent. (30,000 vintage trainer
launches at last count) The two principal trainers are a 1965 Bergfalke III and
a 1955 Bergfalke II/55. with 13,000 and 19,000 launches respectively.

Like with any mechanical system it is possible to damage an aircraft with winch
launches if you do not follow correct procedures. Conversely, simple procedures
can ensure safe operation.

My Advise is -
1] some engineer put a lot of work into designing and specifying the weak link
system. Use the right weak links and your chances of overstressing are minimal.
2] make sure your winch drivers are pilots and visa versa. That way there is a
lower risk of over exuberance...
3] Teach a progressive rotation into the steep climb, slamming the tail of a
wooden glider into the ground with full up elevator can result in a lot of work.
(if you are lucky) One pilot who did this at our club flew for 2:30 with a
cracked rudder and broken frame under the elevator hinge. He didn't think it was
a "loud bang..."
4] The point on the launch that exposes the structure to greatest stress is the
top of the launch where you have maximum downward force from the winch and
cable, often together with higher speed if the winch driver is insensitive. Add
a pilot who is bending the stick to wring the last bit of height out of a launch
(last year someone - different club - managed to spin off the cable) and you
have the limiting force being the down force on the elevator.

Respect the speed limits and use appropriate equipment and winching is no
problem for vintage types. Conversely, the sustained flexing on the wings of
some of the newer glass ships can result in premature gell coat crazing, and
some owners refuse to winch launch for this reason.

--
Bruce Greeff
Std Cirrus #57
I'm no-T at the address above.

Someone please correct me if I am wrong,

But as I recall the weak link is supposed break before it carries twice
the gross weight of the glider.
So during the launch the wings must lift at a maximum the weight of the
glider plus up to 2 times weight of the glider through the weak link.
So the maximum load you should be able to put on the glider is 3G's.

I don't think I would want to fly a glider that could not withstand
3G's.

Brian

In article t,
"Mike Schumann" wrote:

Our club is exploring switching from aero tow to winch launching. Some of
our members own older wooden gliders and have expressed concerns about the
increased stress on the glider's structure resulting from winch launching
vs. aero tow.

Is this a valid concern?

Not really. If your glider is likely to be damaged by a winch
launch, then it's also likely to be damaged by a 3G pullup.

If a 3G pullup is going to harm it, perhaps you should check your
maneuvering envelope and consider grounding the aircraft for
good. :-)

- mark