Dyneema Cable

[Martin Roberts]

We have been using 1 Dyneema cable @ Bowland Forrest
for the
past 12 Months - on grass with rubble hardned tow out
track

After initial teathing troubles - Finding the most
durable cable
manufacturer and modifying linkages and shock ropes
etc it has
now settled down and we have converted both drums to

Dyneema.

The cable lifts free of the ground as soon as tension
is put on it
therefore wear and tear on the ground is minimal either
at cable
retrieve or launch

Launch hight are regularly 200ft higher than stranded
steel cable
and there are significantly less cable breaks.

Care has to be taken not to land across thc line of
cables as the
cable can stand above the surface of the grass especially
in dips
or hollows or when the cable is under any kind of
load - ie cable
retrieve - hand pulling of cable to obtain slack to
attach to a
glider etc. (This is potentially far more hazardous
than steel
which tends to bed into the grass.

Also worth noting is the potential for the cable to
fly in windy
conditions - so care must be taken on the retrieve
to make sure
cables do not cross and that a very large seperation
is used @
the departure point.

[Frank Whiteley]

Interesting comments about the rope resting on the grass and the snag
hazards.

What is the length of your launch run?

Frank Whiteley
Martin Roberts wrote:
> We have been using 1 Dyneema cable @ Bowland Forrest
> for the
> past 12 Months - on grass with rubble hardned tow out
> track
>
> After initial teathing troubles - Finding the most
> durable cable
> manufacturer and modifying linkages and shock ropes
> etc it has
> now settled down and we have converted both drums to
>
> Dyneema.
>
> The cable lifts free of the ground as soon as tension
> is put on it
> therefore wear and tear on the ground is minimal either
> at cable
> retrieve or launch
>
> Launch hight are regularly 200ft higher than stranded
> steel cable
> and there are significantly less cable breaks.
>
> Care has to be taken not to land across thc line of
> cables as the
> cable can stand above the surface of the grass especially
> in dips
> or hollows or when the cable is under any kind of
> load - ie cable
> retrieve - hand pulling of cable to obtain slack to
> attach to a
> glider etc. (This is potentially far more hazardous
> than steel
> which tends to bed into the grass.
>
> Also worth noting is the potential for the cable to
> fly in windy
> conditions - so care must be taken on the retrieve
> to make sure
> cables do not cross and that a very large seperation
> is used @
> the departure point.

[Martin Gregorie]

Martin Roberts wrote:
>
> The cable lifts free of the ground as soon as tension
> is put on it
> therefore wear and tear on the ground is minimal either
> at cable
> retrieve or launch
>
Out of curiosity, have you tried any lowish level simulated power
failures with it? My own observation is that during a power fail the
weight of steel cable keeps the drogue and shock cord well out of the
way below the glider, but I've wondered what happens with Dyneema.

The possibility of it not being heavy enough to keep the drogue etc.
clear of the glider is my only worry about taking a launch on it.

I don't remember this point being discussed here.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Frank Whiteley]

Martin Gregorie wrote:
> Martin Roberts wrote:
> >
> > The cable lifts free of the ground as soon as tension
> > is put on it
> > therefore wear and tear on the ground is minimal either
> > at cable
> > retrieve or launch
> >
> Out of curiosity, have you tried any lowish level simulated power
> failures with it? My own observation is that during a power fail the
> weight of steel cable keeps the drogue and shock cord well out of the
> way below the glider, but I've wondered what happens with Dyneema.
>
> The possibility of it not being heavy enough to keep the drogue etc.
> clear of the glider is my only worry about taking a launch on it.
>
> I don't remember this point being discussed here.
>
>
I've posted here and on the winchdesign group about the 'float' we
experienced. However, we also used our normal chute and strop
arrangement. Powered off, the strop falls first, causing the chute to
collapse and the rig falls out of the way taking the rope with it. The
remaining rope did fall rather slowly, but it would take, in my
estimation, quite an effort to get under it.

That being said, the new plastic disk design and other light weight
solutions might lead to longer hang times for the rope in the event of
the launch failure.

Frank Whiteley

[Ian]

On Tue, 27 Jun 2006 14:02:30 +0000, Martin Roberts wrote:

> After initial teathing troubles - Finding the most
> durable cable
> manufacturer and modifying linkages and shock ropes
> etc it has
> now settled down and we have converted both drums to

Which cable worked (diameter, construction and supplier), and which did
not?

> The cable lifts free of the ground as soon as tension is put on it
> therefore wear and tear on the ground is minimal either at cable
> retrieve or launch

What is the vertical curvature of your field - is there a convex shape
which assists in holding the cable off the ground during tow back?

> Also worth noting is the potential for the cable to fly in windy
> conditions - so care must be taken on the retrieve to make sure cables
> do not cross and that a very large seperation is used @ the departure
> point.

What chute, strop and weak link arrangement are you using? What mods did
you do to the winch (guillotine etc).

Anybody else been down this road who can provide feedback? We have a
winch which need new cables and I am trying to collect as much information
as possible so that we can make good decisions.


Thanks

Ian