New winch height record

Bill,

At Lasham we still use vehicle retrieves and a 2 drum
main winch set up on days or evenings when demand for
winch launches is low, say when we are operating 5
gliders or less. Also the last launch of the day is
always done without the retrieve winch connected so
that we can wind the cable fully into the main winch.
Although I don't have a large data set, comparisions
between the last two launches of the day suggest that
we lose about 80 feet off a typical 1600 ft launch
due to the retrieve winch, which is 5%. This is using
steel cables on both winches. We have used an all synthetic
cable set up in the past when the losses were almost
negligible. Only problem was that the small diameter
synthetic cable on the retrieve winch wore out within
6 weeks due to ground abrasion!

I can't see that there should be any realistic limits
on the length of retrieve cable, as long as you can
keep it light - see UHMWPE cable below. However sideways
drift in a crosswind needs to be a consideration. You
may need a very wide as well as a very long airfield.
The retrieve cables we use are about half the diameter
of the main cables, so only weigh a quarter of the
amount for a given length. The back pull may initiate
a slightly earlier back release,

Our retrieve winch is fitted with a 1.9 litre industrial
VW engine developing about 90 hp, and even that labours
a bit during the retrieve (even with synthetic cables)
so the starter motor idea, if you will excuse the pun,
is a non-starter!

UHMWPE cable, such as Spectra, Plasma or Dyneema (trade
names) is pretty amazing stuff. It looks like washing
line, but is stronger than steel whilst being 10 times
lighter. Unfortunately it is also about five times
more expensive than the equivalent steel cable and
requires modifications to the winch. For the lengths
of winch run we use, normally about 4200ft, it wasn't
found to give that much improvement in height, less
than 100ft, and was deemed by our Committee not to
be cost effective. It would certainly come into its
own on 5000 feet or longer runs, when steel cable starts
to become significantly heavy.

Del Copeland

At 23:12 28 November 2007, Bill Daniels wrote:
It could be you're right but I'd still like to see
an actual comparison with
and without the retrieve winch at longer and longer
distances. Some
validated metrics would help sell the idea. It has
yet to be determined
just how long ropes can be with a retrieve winch.

What I'm worried about isn't the weight of Dyneema/Spectra
ropes it's the
pull angle at the hook. If the retrieve rope drags
back enough to change
that angle it will adversely affect the height achieved.

I know an engineer who was working on a simple 'spinner
reel' type design
for a retrieve winch that would use 1 or 1.5mm Dyneema.
Calculations showed
that the power required is minimal - you could power
it with a small car
starter motor and a battery. 2000 meters of thin Dyneema
would fit on a
drum not much bigger than a coffee can. With the 'spinner
reel' concept
Dyneema would pay off the retrieve winch with no rotation
of the tiny drum.

On the bright side, using a retrieve winch would cut
the fuel use by half.

Bill Daniels


'tommytoyz' wrote in message
.
com...
Back in Germany we used two twin drum Tost winches
on our field and
launched all day long back to back, as long as there
were planes
needing to be launched. Wires were retrieved with
a retrieve vehicle,
two at a time.

I think the British method of using a single drum
winch in combination
with a retrieve winch to be a very sensible idea -
even for long
fields and high launches.

The cable is being retrieved before it even hits the
ground. So the
retrieve process is shorter and faster than using
a retrieve vehicle
by dragging the entire cable length along the ground.
The winch
retrieve should there for also save on wear and tear
on the cable as
most of th retrieve occurs in the air after the glider
releases.

On very high tows, a long portion of the cable is
never wound up into
the tow drum and there for a high altitude launch
should actually
reduce the cable retrieve process using a cable retrieve
winch. The
light weight of the newer cables makes a launch penalty
negligible.
The retrieve cable need not be very strong or even
in good shape
anyway, as it's only function is to retrieve the cable.

I like this approach and seems the cheapest way to
introduce high
frequency winch operations in the USA. I wish Commercial
Glider
Operators would buy a single drum winch and a retrieve
winch and offer
this launch method. Even at 10-15 a launch - it's
still heaps cheaper
and the operator would probably make more money at
the end of the day.

Not to speak about the fact that winch launches a
far and away more
fun and exiting than aero tows.

On Nov 29, 4:23 am, Del C
wrote:
UHMWPE cable, such as Spectra, Plasma or Dyneema (trade
names) is pretty amazing stuff. It looks like washing
line, but is stronger than steel whilst being 10 times
lighter. Unfortunately it is also about five times
more expensive than the equivalent steel cable and
requires modifications to the winch. For the lengths
of winch run we use, normally about 4200ft, it wasn't
found to give that much improvement in height, less
than 100ft, and was deemed by our Committee not to
be cost effective. It would certainly come into its
own on 5000 feet or longer runs, when steel cable starts
to become significantly heavy.

From a winch driver's point of view, I've always thought that the most
appealing aspect of UHMWPE is it's pleasant handling - it's light,
doesn't "ping back" if released under tension (which can be disastrous
with steel), and doesn't cut your hands, and you can use much smaller,
cheaper and more fuel-efficient retrieve vehicles. On the other hand,
from the reports I've heard, the winch needs to be set up *perfectly*
or the expensive cable can be ruined in one launch. It's also a
_little_ trickier to repair when it does break, though nothing that
proper training can't handle.

The main issues with UHMWPE seem to be two-fold: the initial cost of
modifying a winch to use the cable, and the lifetime vs. cost ratio.
Right now, UHMWPE doesn't seem to last as many times longer than
steel, as as many times it costs to buy versus steel.


Dan

"Del C" wrote in message
...
Bill,

At Lasham we still use vehicle retrieves and a 2 drum
main winch set up on days or evenings when demand for
winch launches is low, say when we are operating 5
gliders or less. Also the last launch of the day is
always done without the retrieve winch connected so
that we can wind the cable fully into the main winch.
Although I don't have a large data set, comparisions
between the last two launches of the day suggest that
we lose about 80 feet off a typical 1600 ft launch
due to the retrieve winch, which is 5%. This is using
steel cables on both winches. We have used an all synthetic
cable set up in the past when the losses were almost
negligible. Only problem was that the small diameter
synthetic cable on the retrieve winch wore out within
6 weeks due to ground abrasion!

I can't see that there should be any realistic limits
on the length of retrieve cable, as long as you can
keep it light - see UHMWPE cable below. However sideways
drift in a crosswind needs to be a consideration. You
may need a very wide as well as a very long airfield.
The retrieve cables we use are about half the diameter
of the main cables, so only weigh a quarter of the
amount for a given length. The back pull may initiate
a slightly earlier back release,

Our retrieve winch is fitted with a 1.9 litre industrial
VW engine developing about 90 hp, and even that labours
a bit during the retrieve (even with synthetic cables)
so the starter motor idea, if you will excuse the pun,
is a non-starter!

UHMWPE cable, such as Spectra, Plasma or Dyneema (trade
names) is pretty amazing stuff. It looks like washing
line, but is stronger than steel whilst being 10 times
lighter. Unfortunately it is also about five times
more expensive than the equivalent steel cable and
requires modifications to the winch. For the lengths
of winch run we use, normally about 4200ft, it wasn't
found to give that much improvement in height, less
than 100ft, and was deemed by our Committee not to
be cost effective. It would certainly come into its
own on 5000 feet or longer runs, when steel cable starts
to become significantly heavy.

Del Copeland

We actually tested the power required to retrieve Spectra and the starter
motor is way more powerful than needed. Not sure what your problem is at
Lasham.

The cost of Spectra is more like three times the cost of steel not 5 times -
I checked the prices this morning. It takes a LOT of power to pull steel
cable across an airfield - I can pull a mile of Spectra with one finger.

We need verifiable data from retrieve winches. Your tests at Lasham are not
verifiable since you did no controlled experiments.

Bill Daniels

On Nov 29, 2:57 pm, "Bill Daniels" bildan@comcast-dot-net wrote:
We actually tested the power required to retrieve Spectra and the starter
motor is way more powerful than needed. Not sure what your problem is at
Lasham.

Derek will answer for himself, but I expect they retrieve against the
pay-out brake on the winch, as per normal operation. If you don't, the
drum will keep turning under its own momentum when the retrieve stops
and you'll get cable everywhere. Not good.


The cost of Spectra is more like three times the cost of steel not 5 times -
I checked the prices this morning. It takes a LOT of power to pull steel
cable across an airfield - I can pull a mile of Spectra with one finger.

We need verifiable data from retrieve winches. Your tests at Lasham are not
verifiable since you did no controlled experiments.

Having been to Lasham myself and talked to people there (though not
yet witnessed the retrieve winch itself operating), I'm perfectly
satisfied that what Derek says about the performance of both UHMWPE
and retrieve winches is correct.


Dan

"Dan G" wrote in message
...
On Nov 29, 2:57 pm, "Bill Daniels" bildan@comcast-dot-net wrote:
We actually tested the power required to retrieve Spectra and the starter
motor is way more powerful than needed. Not sure what your problem is at
Lasham.

Derek will answer for himself, but I expect they retrieve against the
pay-out brake on the winch, as per normal operation. If you don't, the
drum will keep turning under its own momentum when the retrieve stops
and you'll get cable everywhere. Not good.

Yes, they certainly pull against the heavy payout brake - they have to,
they're using steel cable. You have to keep steel under tension to prevent
tangles. Spectra/Dyneema doesn't need that tension.

Spectra/Dyneema doesn't ball up and tangle like steel so you use much
lighter braking force. In fact, with tension control used for braking, very
light reverse torque is more than enough to prevent problems so very, very
little force is needed to pull out a Spectra cable from a winch designed to
take advantage of Spectra/Dyneema.

To get all the benefits of Spectra/Dyneema, you have to not only modify the
winch, you have to change operational techniques. Just throwing it on an
old steel cable winch and using steel cable operating techniques is
guaranteed to fail - as it did at Lasham.


The cost of Spectra is more like three times the cost of steel not 5
times -
I checked the prices this morning. It takes a LOT of power to pull steel
cable across an airfield - I can pull a mile of Spectra with one finger.

We need verifiable data from retrieve winches. Your tests at Lasham are
not
verifiable since you did no controlled experiments.

Having been to Lasham myself and talked to people there (though not
yet witnessed the retrieve winch itself operating), I'm perfectly
satisfied that what Derek says about the performance of both UHMWPE
and retrieve winches is correct.


Derek says Dyneema doesn't work because it's too expensive, wears out faster
than steel and doesn't provide any aditional height. Evedence from many
other sites successfuly using Dyneema is to the contrary on all points. The
difference is that successful sites did their homework and made all the
neccessary changes.

Bill Daniels

On Nov 29, 5:38 pm, "Bill Daniels" bildan@comcast-dot-net wrote:
Yes, they certainly pull against the heavy payout brake - they have to,
they're using steel cable. You have to keep steel under tension to prevent
tangles. Spectra/Dyneema doesn't need that tension.

The pay-out brake is not to keep the line under tension, it's to stop
the drum when the retrieve stops, or the drum keeps turning and paying
out cable which forms great big loops hanging down from the drum. A
drum of UHMWPE will of course be much lighter than a steel one, but
the drum itself is heavy enough. If the brake is weak you have to tow
very slowly, which is frustrating.


Derek says Dyneema doesn't work because it's too expensive, wears out faster
than steel and doesn't provide any aditional height. Evedence from many
other sites successfuly using Dyneema is to the contrary on all points. The
difference is that successful sites did their homework and made all the
neccessary changes.

Lasham isn't the only club that tried UHMWPE and abadonded it.
Pocklington tried it too - with a brand new Skylaunch winch - and also
abandoned it. Another club I know well is only using up their current
stock of it before reverting to steel. A number of sites had initially
very favourable results with UHMWPE but I've never seen any follow-up
results, which were promised by the BGA but have never materialised
(afaik).


Dan

"Dan G" wrote in message
...
On Nov 29, 5:38 pm, "Bill Daniels" bildan@comcast-dot-net wrote:
Yes, they certainly pull against the heavy payout brake - they have to,
they're using steel cable. You have to keep steel under tension to
prevent
tangles. Spectra/Dyneema doesn't need that tension.

The pay-out brake is not to keep the line under tension, it's to stop
the drum when the retrieve stops, or the drum keeps turning and paying
out cable which forms great big loops hanging down from the drum. A
drum of UHMWPE will of course be much lighter than a steel one, but
the drum itself is heavy enough. If the brake is weak you have to tow
very slowly, which is frustrating.

I bet it's frustrating. Why don't you re-engineer it so it works right.

You need to re-think tension. Steel needs to be kept under tension any time
you are moving it. If it is just laying in the grass, it's still under a
little tension due to friction with the grass.

If it takes 70hp to pull out the cable, you're using way too much brake.
Tension control winches use the hydraulic motor to provide light reverse
torque, not a brake. It takes very little reverse torque to prevent over
runs with UHMWPE.



Derek says Dyneema doesn't work because it's too expensive, wears out
faster
than steel and doesn't provide any aditional height. Evedence from many
other sites successfuly using Dyneema is to the contrary on all points.
The
difference is that successful sites did their homework and made all the
neccessary changes.

Lasham isn't the only club that tried UHMWPE and abadonded it.
Pocklington tried it too - with a brand new Skylaunch winch - and also
abandoned it. Another club I know well is only using up their current
stock of it before reverting to steel. A number of sites had initially
very favourable results with UHMWPE but I've never seen any follow-up
results, which were promised by the BGA but have never materialised
(afaik).


The start of this thread was about some very talented folkes in Belgium who
set a release height record using UHMWPE on a winch designed for it. UHMWPE
is a spectacular success as a winch rope. It beats steel on all counts
including wear and life. In fact it lasts long enough to actually be
cheaper than steel on a per launch basis. BUT, you have to understand it
AND you winch has to be designed for it.

Skylaunch is a great steel cable winch. However, it would need a lot of
modifications to make it a successful UHMWPE winch. I sincerely hope they
do this since it would be easier than trying to convince the world that
UHMWPE doesn't work.

UHMWPE has never failed anyone but some people trying to use it have failed
to use it properly. If you want to know how to use it right, talk to the
people who succeeded not the ones who failed. Make a call to Belgium.

Bill Daniels