Experiences with Dyneema

This started from a thread on winch cable breaks, but I thought I should
start a new thread:

On Tue, 28 Jun 2005 20:20:23 +0000, Andreas Maurer wrote:

Flying on the same airfield as the Landau Aero Club, I'd like to add a
few comments:
- There have been lots of cable breaks with Dyneema ropes now (also of
other Dyneema cable users - these plastic cables are used by many
clubs in Germany now). At the moment my club is not sure if the
Dyneema cable is really cheaper to operate than steel cable on the
long run.

I have been wondering when we would start getting real feedback about
Dyneema. I never really believed that it would work out cheaper than
steel on a life cycle cost per launch basis. But I had hoped that it would
suffer less from cable breaks and snarl-ups etc and be easier to handle,
which would make winch launching more user friendly. (After a day of
winching it sometimes feels like we spend more time farming than flying.)

What does concern me is:

- it may be more susceptible to damage due to being mishandled (eg damaged
by rubbing on steel parts) leading to a shortening of its useful life.

- that on high wear surfaces (eg gravel or tar) it will wear out long
before the high capital costs can be recovered.

If anybody has first hand experience, please pass it on.

Thanks

Ian

Ian wrote:
This started from a thread on winch cable breaks, but I thought I should
start a new thread:

On Tue, 28 Jun 2005 20:20:23 +0000, Andreas Maurer wrote:


Flying on the same airfield as the Landau Aero Club, I'd like to add a
few comments:
- There have been lots of cable breaks with Dyneema ropes now (also of
other Dyneema cable users - these plastic cables are used by many
clubs in Germany now). At the moment my club is not sure if the
Dyneema cable is really cheaper to operate than steel cable on the
long run.


I have been wondering when we would start getting real feedback about
Dyneema. I never really believed that it would work out cheaper than
steel on a life cycle cost per launch basis. But I had hoped that it would
suffer less from cable breaks and snarl-ups etc and be easier to handle,
which would make winch launching more user friendly. (After a day of
winching it sometimes feels like we spend more time farming than flying.)

What does concern me is:

- it may be more susceptible to damage due to being mishandled (eg damaged
by rubbing on steel parts) leading to a shortening of its useful life.

- that on high wear surfaces (eg gravel or tar) it will wear out long
before the high capital costs can be recovered.

If anybody has first hand experience, please pass it on.

Thanks

Ian



Ian --

We call it Spectra but it's the same material. There is hardly any
comparison between our use of 5000 ft (1500 m) stranded steel vs.
Spectra working off of a hard-surfaced runway. We have had zero breaks
in four or five hundred starts as compared to one break every three or
four starts using steel. The Spectra is still not even getting fuzzy
after two years of use.

The pavement wears out the bottom of the waves in the steel whereas the
Spectra is so light it practically floats over the surface on pull-back.
On grass steel may work fine, but I don't have any first-hand experience.

As far as getting higher tows goes, we don't see a lot of improvement,
about 1700 ft (500 m) either way. This is with about 1600 to 2000 lb
(700 to 900 kg) of line tension (as best as I can estimate) and 15 kt
headwind using a Blanik L-13 and its wishbone cg harness.

Bob

hello,
now we have more than 2800 starts with each drum of dyneema ( 5mm )
and we have somes breaks in the cable with big gliders ..
We project to change dynnema by new and we doen't want to use steel
cable because if the preise per start is more , for security, and for
repar and so one dynnema is the best and our winch is like new : no
impact in the winch ..

see you
Pascal internet site : www.planeur-stflo.net

"Ian" wrote in message
news
This started from a thread on winch cable breaks, but I thought I should
start a new thread:

What does concern me is:

- it may be more susceptible to damage due to being mishandled (eg damaged
by rubbing on steel parts) leading to a shortening of its useful life.

- that on high wear surfaces (eg gravel or tar) it will wear out long
before the high capital costs can be recovered.

If anybody has first hand experience, please pass it on.

Thanks

Ian

The feedback I have been getting is that the stuff lasts longer on almost
any surface. The key, as Bob Johnson pointed out, is that the weight
bearing down on the runway is far less with Spectra/Dyneema. On turf, the
stuff should last much longer.

Breaks, when they occur, are almost always due to the material getting
nicked by a sharp edge - usually where the termination hardware attaches.
There seems to be some room for improvements in attachment hardware.

It's clear that with extremely long cables, Dyneema delivers higher launches
but the benefit is much smaller with short winch runs. If you are fortunate
enough to have 2000 meters or more, really high launches are possible.

Bill Daniels

My very limited experience with Spectra (Dyneema, etc), about 50
launches, was very positive. I've driven maybe 2000+ launches with steel
cable. One of the nicest things about the synthetic lines is that they
have very little tendency to throw themselves into a tangle when there
is a sudden release of tension on the launch (cable break or simulated
cable break). Also, a drum of synthetic has much lower inertia than a
drum of steel cable so it's easier to control.

My only problem, and a very slight one at that, with the synthetic line
is that it doesn't sag under it's own weight on launch. The sag of steel
cable is a prime indicator of tension. Too much sag means you need to
add power, too little means you have too much power on. With the
synthetic, this clue is lost. It just looks like a laser beam from the
winch to the glider.

I still miss the winch...

--
Take out the airplane for reply

On Thu, 30 Jun 2005 05:19:05 -0700, jouanarp wrote:

now we have more than 2800 starts with each drum of dyneema ( 5mm )
and we have somes breaks in the cable with big gliders ..
We project to change dynnema by new and we doen't want to use steel
cable because if the preise per start is more , for security, and for
repar and so one dynnema is the best and our winch is like new : no
impact in the winch ..

This is a good indication of what to expect. This is the kind of
information we need to justify the investment. Can you please give me
some more details:

Are you still using the original cable after 2800 launches?

Are their any plans to replace it yet?

How many launches per break do you get now with the worn cable?

What surface do you operate from (it looks like smooth grass from the
photo on your web site)?

How long is your runway?


Thanks

Ian

In message , Ian
writes
On Thu, 30 Jun 2005 05:19:05 -0700, jouanarp wrote:

now we have more than 2800 starts with each drum of dyneema ( 5mm )
and we have somes breaks in the cable with big gliders ..
We project to change dynnema by new and we doen't want to use steel
cable because if the preise per start is more , for security, and for
repar and so one dynnema is the best and our winch is like new : no
impact in the winch ..

This is a good indication of what to expect. This is the kind of
information we need to justify the investment. Can you please give me
some more details:

Are you still using the original cable after 2800 launches?

Are their any plans to replace it yet?

How many launches per break do you get now with the worn cable?

What surface do you operate from (it looks like smooth grass from the
photo on your web site)?

How long is your runway?

And a set of equivalent answers from someone using it on a tarmac
runway, ideally with it going across another one would be very useful as
it would map directly to our site.

Robin

Thanks

Ian


--
Robin Birch

At 16:30 30 June 2005, Wallace Berry wrote:
(snip)
My only problem, and a very slight one at that, with
the synthetic line
is that it doesn't sag under it's own weight on launch.
The sag of steel
cable is a prime indicator of tension. Too much sag
means you need to
add power, too little means you have too much power
on. With the
synthetic, this clue is lost. It just looks like a
laser beam from the
winch to the glider.

Does anyone have any experience of what happens with
a 'low' cable break. One of the advantages of a 'heavy'
wire is that it assists in preventing the tendency
of the launch parachute to fly up or is the parachute
unecessary with synthetic line?

Ian wrote:

This started from a thread on winch cable breaks, but I thought I should
start a new thread:

On Tue, 28 Jun 2005 20:20:23 +0000, Andreas Maurer wrote:

Flying on the same airfield as the Landau Aero Club, I'd like to add a
few comments:
- There have been lots of cable breaks with Dyneema ropes now (also of
other Dyneema cable users - these plastic cables are used by many
clubs in Germany now). At the moment my club is not sure if the
Dyneema cable is really cheaper to operate than steel cable on the
long run.

I have been wondering when we would start getting real feedback about
Dyneema. I never really believed that it would work out cheaper than
steel on a life cycle cost per launch basis. But I had hoped that it would
suffer less from cable breaks and snarl-ups etc and be easier to handle,
which would make winch launching more user friendly. (After a day of
winching it sometimes feels like we spend more time farming than flying.)

What does concern me is:

- it may be more susceptible to damage due to being mishandled (eg damaged
by rubbing on steel parts) leading to a shortening of its useful life.

- that on high wear surfaces (eg gravel or tar) it will wear out long
before the high capital costs can be recovered.

If anybody has first hand experience, please pass it on.

Thanks

Ian
I don't think anyone really ever said it would be cheaper.

On a winch launch, rope weight and rope diameter are the only two variables
that will have an impact on launch performance (given that there is
sufficient power and length). The longer the run, the more impact.

All Dyneema/Spectra ropes are not equal. There are more expensive products
that have superior strength and abrasion resistence. Superior strength
means even less weight and diameter.

The performance variables are most significant at the glider end of the
rope. Cheaper and larger diameter ropes may enable cost savings at the
winch end without impacting launch performance.

We have some limited experience with exactly this, steel wire rope at the
winch end and a Spectra sample at the glider end. 1000ft or so over a mile
run. We achieved 200-400ft/launch improvement. There are several
opportunities for improving on this concept.

Frank Whiteley

The August-September issue of Sailplane & Gliding (out
July 25 in UK)
includes a report from the first UK club to trial Dyneema.

Helen
Editor, S&G
www.gliding.co.uk