Bungee at Long Myndd

Hi All, I have flown from the Long Myndd, which at 1600ft asl is the
highest gliding club in UK, situated on a 4 mile long N/S ridge.
So as long as there is more than a 15 knot Westerly wind it does not
really matter how high you get on the winch... you WILL GO UP !
They are the only club still able to use Bungee Launching, to catapult a
glider the 50 or so yards from the ridge top, into the rising ridge lift.

As for the recent Winch Launching debate, we did find that the woven
Dynema cable used on a SkyLaunch winch did break quite often. This was
thought to be because it was used in muddy conditions, or on an abrasive
tarmac runway. It was replaced by some sort of normal 3 strand plastic
rope (8 and 10 mm.) which was easier to splice, and gave better results.
These nylon ropes do stretch a bit first on 'All Out' and can give a
very quick initial acceleration, only limited by the weak link I guess.

A good winch driver is the best 'constant tension' device, he can judge
the tension from the cab, by looking at the bow in the cable. If its too
much he winds it in a bit faster, and if it is as tight as a bow string,
he just backs off the power a little.

Pete

Hi Pete,

What club do you normally fly at, because the Mynd doesn't have an
abrasive tarmac runway, or for that matter much mud except in the Winter;
just nice smooth short grass well lubricated with sheep dropping. Also to
the best of my knowledge they have always used steel cable, rather than
Dyneema.

I'm glad that someone else has found that Dyneema cable doesn't last
very long in adverse conditions, despite the claims of some of its
supporters. Not long enough to justify its five-fold price tag over steel
anyway, although we found it did last a bit longer.

Didn't you know? The Yanks think that winch launching is only possible
with very fancy computer and tension controlled winches! I presume that
you Skylaunch has the normal throttle presets, so there is not that much
reason to watch the bow in the cable, although as a winch driver I still
do, because I used to drive purely manually controlled Tost winches, when
that and too fast and too slow signals from the glider where about all you
had to go on!

Derek Copeland

At 13:30 03 August 2009, Peter Higgs wrote:
Hi All, I have flown from the Long Myndd, which at 1600ft asl is the
highest gliding club in UK, situated on a 4 mile long N/S ridge.
So as long as there is more than a 15 knot Westerly wind it does not
really matter how high you get on the winch... you WILL GO UP !
They are the only club still able to use Bungee Launching, to catapult a
glider the 50 or so yards from the ridge top, into the rising ridge
lift.

As for the recent Winch Launching debate, we did find that the woven
Dynema cable used on a SkyLaunch winch did break quite often. This was
thought to be because it was used in muddy conditions, or on an abrasive
tarmac runway. It was replaced by some sort of normal 3 strand plastic
rope (8 and 10 mm.) which was easier to splice, and gave better results.

These nylon ropes do stretch a bit first on 'All Out' and can give a
very quick initial acceleration, only limited by the weak link I guess.

A good winch driver is the best 'constant tension' device, he can
judge
the tension from the cab, by looking at the bow in the cable. If its
too
much he winds it in a bit faster, and if it is as tight as a bow string,
he just backs off the power a little.

Pete

On 3 Aug, 14:30, Peter Higgs wrote:

As for the recent Winch Launching debate, we did find that the woven
Dynema cable used on a SkyLaunch winch did break quite often. * This was
thought to be because it was used in muddy conditions, or on an abrasive
tarmac runway. *It was replaced by some sort of normal 3 strand plastic
rope (8 and 10 mm.) which was easier to splice, and gave better results.
These nylon ropes do stretch a bit first on 'All Out' and can give a
very quick initial acceleration, only limited by the weak link I guess.

I'd be very nervous about using something as stretchy as nylon for
winching. There's a hell of a lot of energy in a stretched rope, and
it all goes kinetic in a break. In fact, I'd go so far as to say that
for safety reasons I wouldn't go anywhere near a nylon winch cable,
and I certainly wouldn't launch on one.

Ian

Too right about the KE in nylon. I've seen what happens when someone
tried to cut a 1" rope under tension - it explodes.





I'd be very nervous about using something as stretchy as nylon for
winching. There's a hell of a lot of energy in a stretched rope, and
it all goes kinetic in a break. In fact, I'd go so far as to say that
for safety reasons I wouldn't go anywhere near a nylon winch cable,
and I certainly wouldn't launch on one.

Ian

At 20:00 03 August 2009, Derek Copeland wrote:
Hi Pete,

What club do you normally fly at, because the Mynd doesn't have an
abrasive tarmac runway, or for that matter much mud except in the
Winter;
just nice smooth short grass well lubricated with sheep dropping. Also
to
the best of my knowledge they have always used steel cable, rather than
Dyneema.


Hi, the club with the tarmac and Skylaunch was the now defunct Denbigh
club. I am not too sure what the replacement plastic rope was, only
that it was a turquoise green colour, and I could very easily splice it
using about 6 'interlocking twists'.
I only ever had one accidental cable break, and that was at 850ft when a
severe attack of turbulent air was encountered, which bust the weak link.

You are quite right about Long Myndd, they use the 4.5mm steel cable, with
a lighter (~ 3mm) retrieve cable to the retrieve winch at the launch end.
If they have gliders lined up, it's about one every two minutes, on their
one and only cable.
The old Sealand club used to have a very large 6 cable winch, which could
launch 6 sequentially, before the land-rover had to bring all the cables
back. I don't know what that winch was, but it may have been the sort
used at other RAF gliding sites.

Pete

We had that Denbigh winch at Lasham for a trial period, before we invested
in two new Skylaunch winches. It was a very nice winch and gave really
smooth launches. On arrival it was fitted with 9.5 mm Skyrope cables,
which I think is polypropylene, but due to our longer runs this was
replaced with 4.5mm stranded steel cable. You can't get enough poly rope
on the drum for much more than about a 1000 metre run. Is was fitted with
an 8.2 litre 'Hi Torque' engine of about 350hp, but due to the power
required to launch our DG1000Ts on still days, our new ones have the 'Hi
Power' engines of 450hp. They are also fitted with pulley heads rather
than rollers.

The Mynd retrieve winch is fitted with 2.5mm stranded steel cable.

The other 6 drum winch sounds like a MEL Van Gelder.

Derek Copeland

At 16:00 04 August 2009, Peter Higgs wrote:
At 20:00 03 August 2009, Derek Copeland wrote:
Hi Pete,

What club do you normally fly at, because the Mynd doesn't have an
abrasive tarmac runway, or for that matter much mud except in the
Winter;
just nice smooth short grass well lubricated with sheep dropping. Also
to
the best of my knowledge they have always used steel cable, rather than
Dyneema.


Hi, the club with the tarmac and Skylaunch was the now defunct Denbigh
club. I am not too sure what the replacement plastic rope was, only
that it was a turquoise green colour, and I could very easily splice it
using about 6 'interlocking twists'.
I only ever had one accidental cable break, and that was at 850ft when a
severe attack of turbulent air was encountered, which bust the weak
link.

You are quite right about Long Myndd, they use the 4.5mm steel cable,
with
a lighter (~ 3mm) retrieve cable to the retrieve winch at the launch end.


If they have gliders lined up, it's about one every two minutes, on
their
one and only cable.
The old Sealand club used to have a very large 6 cable winch, which
could
launch 6 sequentially, before the land-rover had to bring all the cables
back. I don't know what that winch was, but it may have been the sort
used at other RAF gliding sites.

Pete

Peter,
good to see you are still about after the demise of Denbigh.

The poly rope used at Denbigh (and now on one winch at Camphill I believe)
was called "Danline". It's a stronger version than the normal polyethylene
(?)
used in the past.

It took me about 5 minutes to replace a splice or repair a break at Denbigh,
using just a penknife and a bit of insulation tape to hold the strand ends
together.

Wear over the grass areas was of course very good, over the tarmack
obviously
a bit worse.

Cost wise it was better than steel to buy, and much cheaper to repair than
steel.
Against Dyneema the cost benefit was huge.

The only "downside" that I could see was that we got so few cable breaks,
and it
was easy for people to drop out of practice!

Malcolm..


"Peter Higgs" wrote in message
...
At 20:00 03 August 2009, Derek Copeland wrote:
Hi Pete,

What club do you normally fly at, because the Mynd doesn't have an
abrasive tarmac runway, or for that matter much mud except in the
Winter;
just nice smooth short grass well lubricated with sheep dropping. Also
to
the best of my knowledge they have always used steel cable, rather than
Dyneema.


Hi, the club with the tarmac and Skylaunch was the now defunct Denbigh
club. I am not too sure what the replacement plastic rope was, only
that it was a turquoise green colour, and I could very easily splice it
using about 6 'interlocking twists'.
I only ever had one accidental cable break, and that was at 850ft when a
severe attack of turbulent air was encountered, which bust the weak link.

You are quite right about Long Myndd, they use the 4.5mm steel cable, with
a lighter (~ 3mm) retrieve cable to the retrieve winch at the launch end.
If they have gliders lined up, it's about one every two minutes, on their
one and only cable.
The old Sealand club used to have a very large 6 cable winch, which could
launch 6 sequentially, before the land-rover had to bring all the cables
back. I don't know what that winch was, but it may have been the sort
used at other RAF gliding sites.

Pete

The rope is polyproplene, we have been using it on our Skylaunch at
Camphill for over 12/15 months. Drum capacity is a problem at over 1000
yds, and it cannot be used on the smaller capacity Tost winch drums. It
seems to wear as well as steel on grass, and is cheaper.
BTW, Camphill too still bungee launches, but usually only at Vintage
glider meetings.
Dave


At 16:45 04 August 2009, Del C wrote:
We had that Denbigh winch at Lasham for a trial period, before we
invested
in two new Skylaunch winches. It was a very nice winch and gave really
smooth launches. On arrival it was fitted with 9.5 mm Skyrope cables,
which I think is polypropylene, but due to our longer runs this was
replaced with 4.5mm stranded steel cable. You can't get enough poly
rope
on the drum for much more than about a 1000 metre run. Is was fitted
with
an 8.2 litre 'Hi Torque' engine of about 350hp, but due to the power
required to launch our DG1000Ts on still days, our new ones have the
'Hi
Power' engines of 450hp. They are also fitted with pulley heads rather
than rollers.

The Mynd retrieve winch is fitted with 2.5mm stranded steel cable.

The other 6 drum winch sounds like a MEL Van Gelder.

Derek Copeland

At 16:00 04 August 2009, Peter Higgs wrote:
At 20:00 03 August 2009, Derek Copeland wrote:
Hi Pete,

What club do you normally fly at, because the Mynd doesn't have an
abrasive tarmac runway, or for that matter much mud except in the
Winter;
just nice smooth short grass well lubricated with sheep dropping. Also
to
the best of my knowledge they have always used steel cable, rather
than
Dyneema.


Hi, the club with the tarmac and Skylaunch was the now defunct Denbigh
club. I am not too sure what the replacement plastic rope was, only
that it was a turquoise green colour, and I could very easily splice it
using about 6 'interlocking twists'.
I only ever had one accidental cable break, and that was at 850ft when
a
severe attack of turbulent air was encountered, which bust the weak
link.

You are quite right about Long Myndd, they use the 4.5mm steel cable,
with
a lighter (~ 3mm) retrieve cable to the retrieve winch at the launch
end.


If they have gliders lined up, it's about one every two minutes, on
their
one and only cable.
The old Sealand club used to have a very large 6 cable winch, which
could
launch 6 sequentially, before the land-rover had to bring all the
cables
back. I don't know what that winch was, but it may have been the
sort
used at other RAF gliding sites.

Pete

On Aug 3, 7:30*am, Peter Higgs wrote:
Hi All, I have flown from the Long Myndd, which at 1600ft asl is the
highest gliding club in UK, situated on a 4 mile long N/S ridge.
So as long as there is more than a 15 knot Westerly wind it does not
really matter how high you get on the winch... * you WILL GO UP !
They are the only club still able to use Bungee Launching, to catapult a
glider the 50 or so yards from the ridge top, into the rising ridge lift.

As for the recent Winch Launching debate, we did find that the woven
Dynema cable used on a SkyLaunch winch did break quite often. * This was
thought to be because it was used in muddy conditions, or on an abrasive
tarmac runway. *It was replaced by some sort of normal 3 strand plastic
rope (8 and 10 mm.) which was easier to splice, and gave better results.
These nylon ropes do stretch a bit first on 'All Out' and can give a
very quick initial acceleration, only limited by the weak link I guess.

A good winch driver is the best 'constant tension' device, he can judge
the tension from the cab, by looking at the bow in the cable. *If its too
much he winds it in a bit faster, and if it is as tight as a bow string,
he just backs off the power a little.

Pete

Pete,

Dyneema/Spectra is so light that it doesn't' bow enough for the winch
driver to get much tension information from it. There has to be an
automatic method of limiting or controlling rope tension. Anyway,
tension recordings show it changes way too fast for a human to react.

I spent today walking and inspecting the Spectra (Plasma rope) on the
Hydrowinch prototype and found it to be in very good shape. It was
still soft and pliable - almost like new. I'd predict at least 3000
launches on this rope and maybe 5000. That's in line with other good
winch designs.

The airfield is a mix of about 2500 feet of old rough asphalt (tarmac)
plus 6000 feet of rough weeds, wild grass and cactus patches. Most
people wear protective footwear.

Spectra/Dyneema provides considerable warning of airfield surface wear
- it gets very fuzzy long before the strength deteriorates to where it
would need to be replaced. This is caused by individual micro fibers
snagging on the rough surface. I don't know of anyone who has
replaced Dyneema for this reason

Damage due to poor winch design is also easy to see. The rope gets
hard, stiff, squared off and shiny due to local overheating on
cylindrical rollers or poorly designed sheaves. There will be cut
strands visible where the rope gets nicked on sharp metal edges. Rope
breaks will be experienced at about 100 launches. This will limit the
useful live to only a few hundred launches which makes it uneconomic
to use with old steel wire winch designs.

The winch itself is by far the worst source of rope damage.
Airfields, even very bad ones, do little damage.

Strange therefore how our winch drivers at Lasham, including the amateur
volunteers, managed to cope perfectly well with a synthetic cable when we
tried it out on a purely manual driven Tost winch without ANY automatic
gizmos! You still have the climb rate, glider appearance, and any signals
from the pilot to go on. UHMWPE cable does bow a bit, but less than steel.
It also drifts a long way sideways in a crosswind after release. We got
just over 2500 launches from it, with most of the wear being caused by
ground abrasion where it was pulled across our rough concrete cross
runways.

Derek Copeland



At 23:20 14 August 2009, bildan wrote:

Dyneema/Spectra is so light that it doesn't' bow enough for the winch
driver to get much tension information from it. There has to be an
automatic method of limiting or controlling rope tension. Anyway,
tension recordings show it changes way too fast for a human to react.

I spent today walking and inspecting the Spectra (Plasma rope) on the
Hydrowinch prototype and found it to be in very good shape. It was
still soft and pliable - almost like new. I'd predict at least 3000
launches on this rope and maybe 5000. That's in line with other good
winch designs.

The airfield is a mix of about 2500 feet of old rough asphalt (tarmac)
plus 6000 feet of rough weeds, wild grass and cactus patches. Most
people wear protective footwear.

Spectra/Dyneema provides considerable warning of airfield surface wear
- it gets very fuzzy long before the strength deteriorates to where it
would need to be replaced. This is caused by individual micro fibers
snagging on the rough surface. I don't know of anyone who has
replaced Dyneema for this reason

Damage due to poor winch design is also easy to see. The rope gets
hard, stiff, squared off and shiny due to local overheating on
cylindrical rollers or poorly designed sheaves. There will be cut
strands visible where the rope gets nicked on sharp metal edges. Rope
breaks will be experienced at about 100 launches. This will limit the
useful live to only a few hundred launches which makes it uneconomic
to use with old steel wire winch designs.

The winch itself is by far the worst source of rope damage.
Airfields, even very bad ones, do little damage.