Winching: Steel vs. Plasma

Further to Craig Freeman's post of July 28, photos of our new winch are
available at our club web site at http://www.permiansoaring.us/

The winch was conceived and built by Craig in about three months of
spare time work, which is surely remarkable. Even more remarkable, Craig
also wears additional hats as both club president and CFIG.

A short winch description includes a freshly shopped 454 cu.-in. engine
turning a 48-inch by 6-inch drum at about 8.5/1 reduction. As near as I
can learn, the stock 454 engine generates about 325 hp and 350 lb-ft of
torque at 3500 rpm.

In June, we started our new winch operations using 3/16-in. stranded
steel cable. With 5000-ft. of line out, we were averaging about 1200 ft.
of launch height with our 1100-lb. Blanik, using the CG bridle. Craig
wanted to evaluate Plasma rope, so we re-equipped in July. Since then,
our launch heights have been running 1500-ft. or better. All of our
towing so far has been in light winds of 10-15 kt. Since spooling on the
Plasma, we have also enjoyed zero line-handling hassle, as covered by
Craig and Bill Daniels in their recent ras posts.

The physics of the two types of launch cable together with winch
operation are kind of interesting. With steel, we were launching our
Blanik in about four seconds to a speed of 50 kt., at which point climb
was initiated and maintained at about 55 kt. Horizontal acceleration for
the period was about 0.7 G. Total power draw from the engine was
calculated at about 135 hp. With Plasma, the acceleration period was
reduced to about three seconds to reach the same airspeed. Required
engine power was reduced slightly, and acceleration was increased to
about 0.9 G.

During climb to release, which takes about 45 seconds on average, I'm
estimating engine power required is reduced to about 110 hp for both
steel and Plasma, including aerodynamic drag of the glider and towline.

In my calculations, the force accelerating the glider at momentary full
throttle was estimated at 1000-lb. I backed into this figure by
observing the regular acceleration-phase line breaks we were initially
experiencing using certified 1000-lb. poly rope for the weak link. Since
switching to Plasma and 1320-lb. Tost weak links, any line breaks are
occurring in the release area of the launch, where they are supposed to
take place. As Bill Daniels has previously mentioned, it might be
interesting to learn just how much force the glider is actually seeing
during acceleration and climb.

Bob Johnson

explain PLASMA mate,
I always thought plasma would be
the liquid part of blood or
highly ionised gas
is it kind of a rope?
nylon?
kevlar?
latex :-) ?
diameter?
how to repair?
.....

Chris

"Bob Johnson" wrote in message
...
Further to Craig Freeman's post of July 28, photos of our new winch are
available at our club web site at http://www.permiansoaring.us/

The winch was conceived and built by Craig in about three months of
spare time work, which is surely remarkable. Even more remarkable, Craig
also wears additional hats as both club president and CFIG.

A short winch description includes a freshly shopped 454 cu.-in. engine
turning a 48-inch by 6-inch drum at about 8.5/1 reduction. As near as I
can learn, the stock 454 engine generates about 325 hp and 350 lb-ft of
torque at 3500 rpm.

In June, we started our new winch operations using 3/16-in. stranded
steel cable. With 5000-ft. of line out, we were averaging about 1200 ft.
of launch height with our 1100-lb. Blanik, using the CG bridle. Craig
wanted to evaluate Plasma rope, so we re-equipped in July. Since then,
our launch heights have been running 1500-ft. or better. All of our
towing so far has been in light winds of 10-15 kt. Since spooling on the
Plasma, we have also enjoyed zero line-handling hassle, as covered by
Craig and Bill Daniels in their recent ras posts.

The physics of the two types of launch cable together with winch
operation are kind of interesting. With steel, we were launching our
Blanik in about four seconds to a speed of 50 kt., at which point climb
was initiated and maintained at about 55 kt. Horizontal acceleration for
the period was about 0.7 G. Total power draw from the engine was
calculated at about 135 hp. With Plasma, the acceleration period was
reduced to about three seconds to reach the same airspeed. Required
engine power was reduced slightly, and acceleration was increased to
about 0.9 G.

During climb to release, which takes about 45 seconds on average, I'm
estimating engine power required is reduced to about 110 hp for both
steel and Plasma, including aerodynamic drag of the glider and towline.

In my calculations, the force accelerating the glider at momentary full
throttle was estimated at 1000-lb. I backed into this figure by
observing the regular acceleration-phase line breaks we were initially
experiencing using certified 1000-lb. poly rope for the weak link. Since
switching to Plasma and 1320-lb. Tost weak links, any line breaks are
occurring in the release area of the launch, where they are supposed to
take place. As Bill Daniels has previously mentioned, it might be
interesting to learn just how much force the glider is actually seeing
during acceleration and climb.

Bob Johnson

Let me take this since Bob Johnson and I have been talking about his for a
long time.

"Plasma" is a US marketing name for Ultra High Molecular Weight Poly
Ethylene (UHMWPE). It is sold elsewhere as "Dyneema". (The use of the word
"Spectra" makes it hard for search engines to find the stuff.) Spectra has
a specific gravity of about .97 so it is very light. (it floats)

It is available as 12-strand braided cord in a range of diameters. 5mm
diameter seems a good choice for winch launching gliders since it has a
breaking strength of about 5500 pounds. For lighter single-seat gliders,
3mm might work very well. Since it is very strong, light, and has no
tendency whatever to tangle it seems the perfect winch line.

There are two drawbacks. The large one is cost which is three to four times
as much as steel but Plasma promises to last much longer than steel. (The
price seems to be coming down fast) The other is a low melting point of
about 287F with strength starting to diminish above 150F. Both these can be
managed by operational changes.

Splicing is very easy. Just a tuck splice like water ski rope works fine.

Bill Daniels

"CH" wrote in message
...
explain PLASMA mate,
I always thought plasma would be
the liquid part of blood or
highly ionised gas
is it kind of a rope?
nylon?
kevlar?
latex :-) ?
diameter?
how to repair?
....

Chris

"Bob Johnson" wrote in message
...
Further to Craig Freeman's post of July 28, photos of our new winch are
available at our club web site at http://www.permiansoaring.us/

The winch was conceived and built by Craig in about three months of
spare time work, which is surely remarkable. Even more remarkable, Craig
also wears additional hats as both club president and CFIG.

A short winch description includes a freshly shopped 454 cu.-in. engine
turning a 48-inch by 6-inch drum at about 8.5/1 reduction. As near as I
can learn, the stock 454 engine generates about 325 hp and 350 lb-ft of
torque at 3500 rpm.

In June, we started our new winch operations using 3/16-in. stranded
steel cable. With 5000-ft. of line out, we were averaging about 1200 ft.
of launch height with our 1100-lb. Blanik, using the CG bridle. Craig
wanted to evaluate Plasma rope, so we re-equipped in July. Since then,
our launch heights have been running 1500-ft. or better. All of our
towing so far has been in light winds of 10-15 kt. Since spooling on the
Plasma, we have also enjoyed zero line-handling hassle, as covered by
Craig and Bill Daniels in their recent ras posts.

The physics of the two types of launch cable together with winch
operation are kind of interesting. With steel, we were launching our
Blanik in about four seconds to a speed of 50 kt., at which point climb
was initiated and maintained at about 55 kt. Horizontal acceleration for
the period was about 0.7 G. Total power draw from the engine was
calculated at about 135 hp. With Plasma, the acceleration period was
reduced to about three seconds to reach the same airspeed. Required
engine power was reduced slightly, and acceleration was increased to
about 0.9 G.

During climb to release, which takes about 45 seconds on average, I'm
estimating engine power required is reduced to about 110 hp for both
steel and Plasma, including aerodynamic drag of the glider and towline.

In my calculations, the force accelerating the glider at momentary full
throttle was estimated at 1000-lb. I backed into this figure by
observing the regular acceleration-phase line breaks we were initially
experiencing using certified 1000-lb. poly rope for the weak link. Since
switching to Plasma and 1320-lb. Tost weak links, any line breaks are
occurring in the release area of the launch, where they are supposed to
take place. As Bill Daniels has previously mentioned, it might be
interesting to learn just how much force the glider is actually seeing
during acceleration and climb.

Bob Johnson

I saw at your web page, that you winch from a concrete runway.
Doing so with steel cables reduced the lifetime by a factor 10
compared to launching on gras.
How is the abrasive behaviour of this cable?
Do you have a the manufacturers address?
Chris Hostettler
Melbourne
Australia

"Bill Daniels" wrote in message
...
Let me take this since Bob Johnson and I have been talking about his for a
long time.

"Plasma" is a US marketing name for Ultra High Molecular Weight Poly
Ethylene (UHMWPE). It is sold elsewhere as "Dyneema". (The use of the
word
"Spectra" makes it hard for search engines to find the stuff.) Spectra
has
a specific gravity of about .97 so it is very light. (it floats)

It is available as 12-strand braided cord in a range of diameters. 5mm
diameter seems a good choice for winch launching gliders since it has a
breaking strength of about 5500 pounds. For lighter single-seat gliders,
3mm might work very well. Since it is very strong, light, and has no
tendency whatever to tangle it seems the perfect winch line.

There are two drawbacks. The large one is cost which is three to four
times
as much as steel but Plasma promises to last much longer than steel. (The
price seems to be coming down fast) The other is a low melting point of
about 287F with strength starting to diminish above 150F. Both these can
be
managed by operational changes.

Splicing is very easy. Just a tuck splice like water ski rope works fine.

Bill Daniels

"CH" wrote in message
...
explain PLASMA mate,
I always thought plasma would be
the liquid part of blood or
highly ionised gas
is it kind of a rope?
nylon?
kevlar?
latex :-) ?
diameter?
how to repair?
....

Chris

"Bob Johnson" wrote in message
...
Further to Craig Freeman's post of July 28, photos of our new winch
are
available at our club web site at http://www.permiansoaring.us/

The winch was conceived and built by Craig in about three months of
spare time work, which is surely remarkable. Even more remarkable,
Craig
also wears additional hats as both club president and CFIG.

A short winch description includes a freshly shopped 454 cu.-in.
engine
turning a 48-inch by 6-inch drum at about 8.5/1 reduction. As near as
I
can learn, the stock 454 engine generates about 325 hp and 350 lb-ft
of
torque at 3500 rpm.

In June, we started our new winch operations using 3/16-in. stranded
steel cable. With 5000-ft. of line out, we were averaging about 1200
ft.
of launch height with our 1100-lb. Blanik, using the CG bridle. Craig
wanted to evaluate Plasma rope, so we re-equipped in July. Since then,
our launch heights have been running 1500-ft. or better. All of our
towing so far has been in light winds of 10-15 kt. Since spooling on
the
Plasma, we have also enjoyed zero line-handling hassle, as covered by
Craig and Bill Daniels in their recent ras posts.

The physics of the two types of launch cable together with winch
operation are kind of interesting. With steel, we were launching our
Blanik in about four seconds to a speed of 50 kt., at which point
climb
was initiated and maintained at about 55 kt. Horizontal acceleration
for
the period was about 0.7 G. Total power draw from the engine was
calculated at about 135 hp. With Plasma, the acceleration period was
reduced to about three seconds to reach the same airspeed. Required
engine power was reduced slightly, and acceleration was increased to
about 0.9 G.

During climb to release, which takes about 45 seconds on average, I'm
estimating engine power required is reduced to about 110 hp for both
steel and Plasma, including aerodynamic drag of the glider and
towline.

In my calculations, the force accelerating the glider at momentary
full
throttle was estimated at 1000-lb. I backed into this figure by
observing the regular acceleration-phase line breaks we were initially
experiencing using certified 1000-lb. poly rope for the weak link.
Since
switching to Plasma and 1320-lb. Tost weak links, any line breaks are
occurring in the release area of the launch, where they are supposed
to
take place. As Bill Daniels has previously mentioned, it might be
interesting to learn just how much force the glider is actually seeing
during acceleration and climb.

Bob Johnson

Do any changes have to be made to the pay-on rollers, to avoid the
lighter rope slipping and potentially overheating locally? On our
winch, the rollers are heavily scored where generations of steel cable
have slipped a bit and cut into the surface.

These rollers are now about 40 years old, maybe older. While they could
perhaps be renewed with a good surface, they do have considerable
inertia, and a free-running cable suddenly coming into contact with one
of them is bound to take some time to whirl it up to speed. Steel
stands up to that - would Spectra/Dyneema?

Chris N.

"Chris Nicholas" wrote in message
...
Do any changes have to be made to the pay-on rollers, to avoid the
lighter rope slipping and potentially overheating locally? On our
winch, the rollers are heavily scored where generations of steel cable
have slipped a bit and cut into the surface.

These rollers are now about 40 years old, maybe older. While they could
perhaps be renewed with a good surface, they do have considerable
inertia, and a free-running cable suddenly coming into contact with one
of them is bound to take some time to whirl it up to speed. Steel
stands up to that - would Spectra/Dyneema?

Chris N.

Yes, I would think you should make some changes.

Swiveling pulleys with smooth surfaces where the Spectra rope contacts the
metal should extend the life of the rope considerably.

Bill Daniels

!doctype html public "-//w3c//dtd html 4.0 transitional//en"
html
Hi Chris --
pDue to the high 0.45 USD cost of the stuff, I agree that a careful look
should be made of the rollers, etc. that an existing winch is equipped
with. The photos of our winch on the PSA web site shows the care that has
Craig put into his design. Two large diameter, grooved aluminum sheaves,
running in permanently lubed bearings are set opposed in a close-fitting
housing. Two vertical rollers are arranged to handle cross-wind side loads.
The entire sheave/roller element is free to rotate in sleeve bearings in
the vertical plane in order to keep the pull as uniform as possible. The
narrow  6-inch wide, large diameter drum eliminates any need for a
level-wind, or as you call it, pay-on gear.  
pIt's been my observation that the upper sheave receives most of the
action during climb to release and the lower sheave, as you would expect,
comes into play on the pull-back. The rollers work really well during chute
retrieve, since the wind is seldom exactly favoring. Speaking of the retrieve,
I find that the chute "flew" somewhat better with steel than it does with
Plasma, which is certainly not what I was expecting. 
pAs for the guillotine, we're still working on that one. The 1320-lb.
"Blue" Tost weak links we are using seem to let go easily when the Blanik
encounters a thermal just prior to release, so this is some consolation,
at least.
pAt the risk of splitting the threads, I would like to make the observation
that the unique Blanik bridle tow system allows us to advance the throttle
of our 325-hp engine smartly to the limit on the start, with no complaints
from the flying end of the rope as to "pitch-up" or excessive G's for that
matter . Of course, the throttle has to be just as smartly retarded to
keep things running at about 3500 engine rpm and 410 drum rpm to maintain
a 55 kt climb to transition to release.
pI have no Blanik or Plasma financial interest, but I must confess attempting
to find Cortland's stock ticker symbol.
pBJ
pChris Nicholas wrote:
blockquote TYPE=CITEDo any changes have to be made to the pay-on rollers,
to avoid the
brlighter rope slipping and potentially overheating locally?  On
our
brwinch, the rollers are heavily scored where generations of steel cable
brhave slipped a bit and cut into the surface.
pThese rollers are now about 40 years old, maybe older.  While they
could
brperhaps be renewed with a good surface, they do have considerable
brinertia, and a free-running cable suddenly coming into contact with
one
brof them is bound to take some time to whirl it up to speed.  Steel
brstands up to that - would Spectra/Dyneema?
pChris N./blockquote
/html

Following this thread with interest and I have spoken
to the UK importers.

Some experimental work has been done in the UK. One
identified problem is that the standard winch guillotines
do not cut the plasma cable as efficiently as they
do steel cable and that a strand or strands remain.


Can any user comment on this please.

Dave Martin


At 09:24 12 August 2003, Chris Nicholas wrote:
Do any changes have to be made to the pay-on rollers,
to avoid the
lighter rope slipping and potentially overheating locally?
On our
winch, the rollers are heavily scored where generations
of steel cable
have slipped a bit and cut into the surface.

These rollers are now about 40 years old, maybe older.
While they could
perhaps be renewed with a good surface, they do have
considerable
inertia, and a free-running cable suddenly coming into
contact with one
of them is bound to take some time to whirl it up to
speed. Steel
stands up to that - would Spectra/Dyneema?

Chris N.

"Dave Martin" wrote in message
...
Following this thread with interest and I have spoken
to the UK importers.

Some experimental work has been done in the UK. One
identified problem is that the standard winch guillotines
do not cut the plasma cable as efficiently as they
do steel cable and that a strand or strands remain.


UHMWPE rope is very resistant to cuts - which is a good thing except when
you want the guillotine to cut it fast. Spectra is used in body armor that
protects against cutting weapons.

Taking advantage of the low melting point with a hot-blade guillotine seems
the way to go. Just make a steel blade and mount it solidly next to the
rope path. Use a rubber block to push the rope into the hot blade. Heat
the blade with current from the starting battery. A direct shunt across the
battery should heat the blade to 500C in a second or two.

Bill Daniels