How does an aerotow rope break in two places?

[son_of_flubber]

True story. A couple years ago I ran the wing for a glider that aerotowed into rotor. The rope broke. Both aircraft and both tost rings made it back to the airfield. The rope broke at both ends.

How is that even possible?

[Darryl Ramm]

On Tuesday, October 16, 2018 at 6:38:55 PM UTC-7, son_of_flubber wrote:
> True story. A couple years ago I ran the wing for a glider that aerotowed into rotor. The rope broke. Both aircraft and both tost rings made it back to the airfield. The rope broke at both ends.
>
> How is that even possible?

Rope flailed itself off after it broke.

[Heinz Gehlhaar]

On Tuesday, October 16, 2018 at 6:38:55 PM UTC-7, son_of_flubber wrote:
> True story. A couple years ago I ran the wing for a glider that aerotowed into rotor. The rope broke. Both aircraft and both tost rings made it back to the airfield. The rope broke at both ends.
>
> How is that even possible?

Truly amazing! But would the gliderpilot not release the broken rope with its Toast-beginning, to prevent the remaining, but invisible rope from tangling into the flight controls (flaps, elevator, rudder).
Heinz

[Dan Marotta]

Heinz,

Do you know how much Tost rings cost?Â* At least 100 trillion Zimbabwe
dollars!

I once broke the rope on a ground launch while on a safari.Â* I elected
to keep the ring since I did not know if we had another one with us.Â*
When I landed, the wheel rolled over the rope and back released.Â* I
simply had to walk back and pick it up so we could reattach the ring to
the remaining rope.

I am now prepared for the inevitable flames.Â* Let it begin!

On 10/17/2018 12:52 AM, Heinz Gehlhaar wrote:
> On Tuesday, October 16, 2018 at 6:38:55 PM UTC-7, son_of_flubber wrote:
>> True story. A couple years ago I ran the wing for a glider that aerotowed into rotor. The rope broke. Both aircraft and both tost rings made it back to the airfield. The rope broke at both ends.
>>
>> How is that even possible?
> Truly amazing! But would the gliderpilot not release the broken rope with its Toast-beginning, to prevent the remaining, but invisible rope from tangling into the flight controls (flaps, elevator, rudder).
> Heinz

--
Dan, 5J

[[email protected]]

Must've been one of those rare actually legal tow ropes with a weak link at both ends.

[john firth]

On Tuesday, October 16, 2018 at 9:38:55 PM UTC-4, son_of_flubber wrote:
> True story. A couple years ago I ran the wing for a glider that aerotowed into rotor. The rope broke. Both aircraft and both tost rings made it back to the airfield. The rope broke at both ends.
>
> How is that even possible?

Same reason a piece of spaghetti does that, maybe.
JMF

[James Metcalfe]

At 15:29 17 October 2018, wrote:
>Must've been one of those rare actually legal tow ropes with a weak link
at
>both ends.

Hmmm, never mind the legality, I'm just not sure about the practicality of

looped tow ropes ... could that be "a weak link at each end"?

[Steve Koerner]

On Tuesday, October 16, 2018 at 6:38:55 PM UTC-7, son_of_flubber wrote:
> True story. A couple years ago I ran the wing for a glider that aerotowed into rotor. The rope broke. Both aircraft and both tost rings made it back to the airfield. The rope broke at both ends.
>
> How is that even possible?

That's an interesting puzzle. Here's one way of thinking about it that makes it seem possible...

Polymers are not purely elastic. They have a dynamic modulus. That is to say that stress and strain are not communicated instantaneously. There is effectively a time constant of propagation down the rope. So assuming that the tension in the rope is steeply rising before a break occurs, and assuming that the strength of the rope is pretty well balanced between the two ends; then as the weak end breaks first, the tension at the far end will still be rising for a short period of time while the message is in transit that the rope has already broken. During that propagation interval, the strong end breaks as well as it was only slightly stronger than the weak end. Or, in the limit, the two ends were busy breaking at the same time and neither end knew anything about the trouble at the other end of the rope since the two ends are isolated by the mechanism of the dynamic modulus.

[[email protected]]

On Thursday, October 18, 2018 at 1:56:38 PM UTC-4, Steve Leonard wrote:
> On Thursday, October 18, 2018 at 12:06:08 PM UTC-5, Steve Koerner wrote:
> > On Tuesday, October 16, 2018 at 6:38:55 PM UTC-7, son_of_flubber wrote:
> > > True story. A couple years ago I ran the wing for a glider that aerotowed into rotor. The rope broke. Both aircraft and both tost rings made it back to the airfield. The rope broke at both ends.
> > >
> > > How is that even possible?
> >
> > That's an interesting puzzle. Here's one way of thinking about it that makes it seem possible...
> >
> > Theory snipped...
>
> Or, the tow pilot snagged it in the trees at the approach end of the runway.
>
> Steve Leonard
> Have seen and recovered more than one tow rope from the trees at the approach end of the field.

That was my guess.
UH

[SF]

Its usually the simplest explanation that's correct. While I love the stress propagation delay theory for it's intellectual elegance, my money is on the towpilot snagged it on something.

SF

[Bret Hess]

Direct observation of a simultaneous break on both ends:

Three years ago I was flying in the front seat of a Grob 103 (nose tow hook) with an instructor for a spring checkout. He wanted me to try a slack rope recovery method that was very different from normal (and later we agreed was not the right approach). When I did the maneuver, we had a spectacular rope break...I could see the rope break simultaneously at the tow plane end and the glider end and fall away.

This has an aerodynamically interesting ending.

The instructor could hear the broken rope segment on our end making noise against the fuselage. We had plenty of height, so we let the tow plane land, and moved over the runway to drop our short length of rope so the tow ring, etc could be recovered easily. When I pulled the nose tow release to drop the rope, a second or two later I noticed something at the open canopy window to my left. There was a foot or less of rope flapping around just inside the cockpit, so I pulled gently on it, and the entire three feet or so of the broken rope segment with the tow ring on the end came in through the window. It was trapped in some low pressure region against the fuselage which was connected to the flow through the window!

I agree with the wave/propagation idea.

[2G]

On Friday, October 19, 2018 at 8:46:48 AM UTC-7, Bret Hess wrote:
> Direct observation of a simultaneous break on both ends:
>
> Three years ago I was flying in the front seat of a Grob 103 (nose tow hook) with an instructor for a spring checkout. He wanted me to try a slack rope recovery method that was very different from normal (and later we agreed was not the right approach). When I did the maneuver, we had a spectacular rope break...I could see the rope break simultaneously at the tow plane end and the glider end and fall away.
>
> This has an aerodynamically interesting ending.
>
> The instructor could hear the broken rope segment on our end making noise against the fuselage. We had plenty of height, so we let the tow plane land, and moved over the runway to drop our short length of rope so the tow ring, etc could be recovered easily. When I pulled the nose tow release to drop the rope, a second or two later I noticed something at the open canopy window to my left. There was a foot or less of rope flapping around just inside the cockpit, so I pulled gently on it, and the entire three feet or so of the broken rope segment with the tow ring on the end came in through the window. It was trapped in some low pressure region against the fuselage which was connected to the flow through the window!
>
> I agree with the wave/propagation idea.

Before the rope breaks, it is stretched a considerable percentage, storing energy in the fibers. When the rope breaks at some point, this energy is released in the form of a travelling wave from the point of breakage in both directions with the long portion having the greatest energy. Upon reaching either end, it encounters an impedance discontinuity (the tow release) and is reflected backwards along the rope. This reflection can add to the still oncoming wave, amplifying its magnitude. If this exceeds the ultimate strength of the rope at this point, it will, too, break.

This travelling wave phenomena also occurs in electronics, and is exploited in antennas.

Tom

[Steve Koerner]

On Friday, October 19, 2018 at 4:12:53 PM UTC-7, 2G wrote:
> On Friday, October 19, 2018 at 8:46:48 AM UTC-7, Bret Hess wrote:
> > Direct observation of a simultaneous break on both ends:
> >
> > Three years ago I was flying in the front seat of a Grob 103 (nose tow hook) with an instructor for a spring checkout. He wanted me to try a slack rope recovery method that was very different from normal (and later we agreed was not the right approach). When I did the maneuver, we had a spectacular rope break...I could see the rope break simultaneously at the tow plane end and the glider end and fall away.
> >
> > This has an aerodynamically interesting ending.
> >
> > The instructor could hear the broken rope segment on our end making noise against the fuselage. We had plenty of height, so we let the tow plane land, and moved over the runway to drop our short length of rope so the tow ring, etc could be recovered easily. When I pulled the nose tow release to drop the rope, a second or two later I noticed something at the open canopy window to my left. There was a foot or less of rope flapping around just inside the cockpit, so I pulled gently on it, and the entire three feet or so of the broken rope segment with the tow ring on the end came in through the window. It was trapped in some low pressure region against the fuselage which was connected to the flow through the window!
> >
> > I agree with the wave/propagation idea.
>
> Before the rope breaks, it is stretched a considerable percentage, storing energy in the fibers. When the rope breaks at some point, this energy is released in the form of a travelling wave from the point of breakage in both directions with the long portion having the greatest energy. Upon reaching either end, it encounters an impedance discontinuity (the tow release) and is reflected backwards along the rope. This reflection can add to the still oncoming wave, amplifying its magnitude. If this exceeds the ultimate strength of the rope at this point, it will, too, break.
>
> This travelling wave phenomena also occurs in electronics, and is exploited in antennas.
>
> Tom

To invoke any theory involving waves there needs to be a reason to think that there is a wave created of some sort. Waves necessitate two forms of energy storage with oscillation between them. I'm not seeing how that works in the towrope. It seems like the energy stored in the elastic rope will get dissipated as heat as the rope progressively shortens after breaking. I can visualize that at the breaking impulse maybe a wee bit of energy would get spit out as transverse displacement wave but that would be second order and not significant; the main happening is longitudinal. What wave are we talking about?

[2G]

On Friday, October 19, 2018 at 7:45:29 PM UTC-7, Steve Koerner wrote:
> On Friday, October 19, 2018 at 4:12:53 PM UTC-7, 2G wrote:
> > On Friday, October 19, 2018 at 8:46:48 AM UTC-7, Bret Hess wrote:
> > > Direct observation of a simultaneous break on both ends:
> > >
> > > Three years ago I was flying in the front seat of a Grob 103 (nose tow hook) with an instructor for a spring checkout. He wanted me to try a slack rope recovery method that was very different from normal (and later we agreed was not the right approach). When I did the maneuver, we had a spectacular rope break...I could see the rope break simultaneously at the tow plane end and the glider end and fall away.
> > >
> > > This has an aerodynamically interesting ending.
> > >
> > > The instructor could hear the broken rope segment on our end making noise against the fuselage. We had plenty of height, so we let the tow plane land, and moved over the runway to drop our short length of rope so the tow ring, etc could be recovered easily. When I pulled the nose tow release to drop the rope, a second or two later I noticed something at the open canopy window to my left. There was a foot or less of rope flapping around just inside the cockpit, so I pulled gently on it, and the entire three feet or so of the broken rope segment with the tow ring on the end came in through the window. It was trapped in some low pressure region against the fuselage which was connected to the flow through the window!
> > >
> > > I agree with the wave/propagation idea.
> >
> > Before the rope breaks, it is stretched a considerable percentage, storing energy in the fibers. When the rope breaks at some point, this energy is released in the form of a travelling wave from the point of breakage in both directions with the long portion having the greatest energy. Upon reaching either end, it encounters an impedance discontinuity (the tow release) and is reflected backwards along the rope. This reflection can add to the still oncoming wave, amplifying its magnitude. If this exceeds the ultimate strength of the rope at this point, it will, too, break.
> >
> > This travelling wave phenomena also occurs in electronics, and is exploited in antennas.
> >
> > Tom
>
> To invoke any theory involving waves there needs to be a reason to think that there is a wave created of some sort. Waves necessitate two forms of energy storage with oscillation between them. I'm not seeing how that works in the towrope. It seems like the energy stored in the elastic rope will get dissipated as heat as the rope progressively shortens after breaking. I can visualize that at the breaking impulse maybe a wee bit of energy would get spit out as transverse displacement wave but that would be second order and not significant; the main happening is longitudinal. What wave are we talking about?

First, before breaking, the rope is stretched considerably beyond its resting length - this undeniably stores energy in the rope (the same as a spring). Second, when the rope breaks this stored energy is released by accelerating the end of the rope, like the cracking of a whip or an earthquake starting a tsunami. This energy travels the rope until it reaches the terminated end, where it is reflected in the opposite direction.
Here is a video of a steel rope breaking; single-frame from 33 sec to see the wave-like action:
https://www.youtube.com/watch?v=W6gZawDnthI

Tom

[Steve Koerner]

On Friday, October 19, 2018 at 10:01:22 PM UTC-7, 2G wrote:
> On Friday, October 19, 2018 at 7:45:29 PM UTC-7, Steve Koerner wrote:
> > On Friday, October 19, 2018 at 4:12:53 PM UTC-7, 2G wrote:
> > > On Friday, October 19, 2018 at 8:46:48 AM UTC-7, Bret Hess wrote:
> > > > Direct observation of a simultaneous break on both ends:
> > > >
> > > > Three years ago I was flying in the front seat of a Grob 103 (nose tow hook) with an instructor for a spring checkout. He wanted me to try a slack rope recovery method that was very different from normal (and later we agreed was not the right approach). When I did the maneuver, we had a spectacular rope break...I could see the rope break simultaneously at the tow plane end and the glider end and fall away.
> > > >
> > > > This has an aerodynamically interesting ending.
> > > >
> > > > The instructor could hear the broken rope segment on our end making noise against the fuselage. We had plenty of height, so we let the tow plane land, and moved over the runway to drop our short length of rope so the tow ring, etc could be recovered easily. When I pulled the nose tow release to drop the rope, a second or two later I noticed something at the open canopy window to my left. There was a foot or less of rope flapping around just inside the cockpit, so I pulled gently on it, and the entire three feet or so of the broken rope segment with the tow ring on the end came in through the window. It was trapped in some low pressure region against the fuselage which was connected to the flow through the window!
> > > >
> > > > I agree with the wave/propagation idea.
> > >
> > > Before the rope breaks, it is stretched a considerable percentage, storing energy in the fibers. When the rope breaks at some point, this energy is released in the form of a travelling wave from the point of breakage in both directions with the long portion having the greatest energy. Upon reaching either end, it encounters an impedance discontinuity (the tow release) and is reflected backwards along the rope. This reflection can add to the still oncoming wave, amplifying its magnitude. If this exceeds the ultimate strength of the rope at this point, it will, too, break.
> > >
> > > This travelling wave phenomena also occurs in electronics, and is exploited in antennas.
> > >
> > > Tom
> >
> > To invoke any theory involving waves there needs to be a reason to think that there is a wave created of some sort. Waves necessitate two forms of energy storage with oscillation between them. I'm not seeing how that works in the towrope. It seems like the energy stored in the elastic rope will get dissipated as heat as the rope progressively shortens after breaking.. I can visualize that at the breaking impulse maybe a wee bit of energy would get spit out as transverse displacement wave but that would be second order and not significant; the main happening is longitudinal. What wave are we talking about?
>
> First, before breaking, the rope is stretched considerably beyond its resting length - this undeniably stores energy in the rope (the same as a spring). Second, when the rope breaks this stored energy is released by accelerating the end of the rope, like the cracking of a whip or an earthquake starting a tsunami. This energy travels the rope until it reaches the terminated end, where it is reflected in the opposite direction.
> Here is a video of a steel rope breaking; single-frame from 33 sec to see the wave-like action:
> https://www.youtube.com/watch?v=W6gZawDnthI
>
> Tom

Tom: As you know, cracking a whip happens because the whip is excited with a transverse wave. We're not doing that; our excitation is longitudinal. As I said before, there is likely a small amount of incidental motion that goes to making a transverse wave as there is in the video you reference; but that's second order and I think too small to matter.

I don't see that there is anything about the longitudinal accelerating rope that can then oscillate energy back into stored state as rope tension. Hence, you do not have a longitudinal wave scenario. Without a wave mechanism, you don't get to talk about reflection. The energy in the rope just goes to heat.

The basic problem is that you can't push a rope. If we were talking about a spring, then yes, you could push on a spring and get energy stored in compression and have a longitudinal wave with energy oscillating between longitudinal kinetic motion and compression. Such wave would reflect at the far end and maybe do something interesting. But when you push on a rope, you get nothing.

[Steve Koerner]

On Saturday, October 20, 2018 at 12:35:33 AM UTC-7, Steve Koerner wrote:
> On Friday, October 19, 2018 at 10:01:22 PM UTC-7, 2G wrote:
> > On Friday, October 19, 2018 at 7:45:29 PM UTC-7, Steve Koerner wrote:
> > > On Friday, October 19, 2018 at 4:12:53 PM UTC-7, 2G wrote:
> > > > On Friday, October 19, 2018 at 8:46:48 AM UTC-7, Bret Hess wrote:
> > > > > Direct observation of a simultaneous break on both ends:
> > > > >
> > > > > Three years ago I was flying in the front seat of a Grob 103 (nose tow hook) with an instructor for a spring checkout. He wanted me to try a slack rope recovery method that was very different from normal (and later we agreed was not the right approach). When I did the maneuver, we had a spectacular rope break...I could see the rope break simultaneously at the tow plane end and the glider end and fall away.
> > > > >
> > > > > This has an aerodynamically interesting ending.
> > > > >
> > > > > The instructor could hear the broken rope segment on our end making noise against the fuselage. We had plenty of height, so we let the tow plane land, and moved over the runway to drop our short length of rope so the tow ring, etc could be recovered easily. When I pulled the nose tow release to drop the rope, a second or two later I noticed something at the open canopy window to my left. There was a foot or less of rope flapping around just inside the cockpit, so I pulled gently on it, and the entire three feet or so of the broken rope segment with the tow ring on the end came in through the window. It was trapped in some low pressure region against the fuselage which was connected to the flow through the window!
> > > > >
> > > > > I agree with the wave/propagation idea.
> > > >
> > > > Before the rope breaks, it is stretched a considerable percentage, storing energy in the fibers. When the rope breaks at some point, this energy is released in the form of a travelling wave from the point of breakage in both directions with the long portion having the greatest energy. Upon reaching either end, it encounters an impedance discontinuity (the tow release) and is reflected backwards along the rope. This reflection can add to the still oncoming wave, amplifying its magnitude. If this exceeds the ultimate strength of the rope at this point, it will, too, break.
> > > >
> > > > This travelling wave phenomena also occurs in electronics, and is exploited in antennas.
> > > >
> > > > Tom
> > >
> > > To invoke any theory involving waves there needs to be a reason to think that there is a wave created of some sort. Waves necessitate two forms of energy storage with oscillation between them. I'm not seeing how that works in the towrope. It seems like the energy stored in the elastic rope will get dissipated as heat as the rope progressively shortens after breaking. I can visualize that at the breaking impulse maybe a wee bit of energy would get spit out as transverse displacement wave but that would be second order and not significant; the main happening is longitudinal. What wave are we talking about?
> >
> > First, before breaking, the rope is stretched considerably beyond its resting length - this undeniably stores energy in the rope (the same as a spring). Second, when the rope breaks this stored energy is released by accelerating the end of the rope, like the cracking of a whip or an earthquake starting a tsunami. This energy travels the rope until it reaches the terminated end, where it is reflected in the opposite direction.
> > Here is a video of a steel rope breaking; single-frame from 33 sec to see the wave-like action:
> > https://www.youtube.com/watch?v=W6gZawDnthI
> >
> > Tom
>
> Tom: As you know, cracking a whip happens because the whip is excited with a transverse wave. We're not doing that; our excitation is longitudinal. As I said before, there is likely a small amount of incidental motion that goes to making a transverse wave as there is in the video you reference; but that's second order and I think too small to matter.
>
> I don't see that there is anything about the longitudinal accelerating rope that can then oscillate energy back into stored state as rope tension. Hence, you do not have a longitudinal wave scenario. Without a wave mechanism, you don't get to talk about reflection. The energy in the rope just goes to heat.
>
> The basic problem is that you can't push a rope. If we were talking about a spring, then yes, you could push on a spring and get energy stored in compression and have a longitudinal wave with energy oscillating between longitudinal kinetic motion and compression. Such wave would reflect at the far end and maybe do something interesting. But when you push on a rope, you get nothing.

But wait just a minute, Steve: Certainly a rope under tension can support a longitudinal wave. We all know about the tin can telephone that works by longitudinal waves when a string is tensioned.

Yesterday, Steve, you were putting forth how it takes time for the tow rope to relax after breaking. If the speed of relaxation is slower than the speed of wave propagation (it probably is), then wouldn't there be a brief period after breaking that an impulse generated longitudinal wave can propagate to the other end of the rope and do mischief?

[2G]

On Saturday, October 20, 2018 at 6:52:11 AM UTC-7, Steve Koerner wrote:
> On Saturday, October 20, 2018 at 12:35:33 AM UTC-7, Steve Koerner wrote:
> > On Friday, October 19, 2018 at 10:01:22 PM UTC-7, 2G wrote:
> > > On Friday, October 19, 2018 at 7:45:29 PM UTC-7, Steve Koerner wrote:
> > > > On Friday, October 19, 2018 at 4:12:53 PM UTC-7, 2G wrote:
> > > > > On Friday, October 19, 2018 at 8:46:48 AM UTC-7, Bret Hess wrote:
> > > > > > Direct observation of a simultaneous break on both ends:
> > > > > >
> > > > > > Three years ago I was flying in the front seat of a Grob 103 (nose tow hook) with an instructor for a spring checkout. He wanted me to try a slack rope recovery method that was very different from normal (and later we agreed was not the right approach). When I did the maneuver, we had a spectacular rope break...I could see the rope break simultaneously at the tow plane end and the glider end and fall away.
> > > > > >
> > > > > > This has an aerodynamically interesting ending.
> > > > > >
> > > > > > The instructor could hear the broken rope segment on our end making noise against the fuselage. We had plenty of height, so we let the tow plane land, and moved over the runway to drop our short length of rope so the tow ring, etc could be recovered easily. When I pulled the nose tow release to drop the rope, a second or two later I noticed something at the open canopy window to my left. There was a foot or less of rope flapping around just inside the cockpit, so I pulled gently on it, and the entire three feet or so of the broken rope segment with the tow ring on the end came in through the window. It was trapped in some low pressure region against the fuselage which was connected to the flow through the window!
> > > > > >
> > > > > > I agree with the wave/propagation idea.
> > > > >
> > > > > Before the rope breaks, it is stretched a considerable percentage, storing energy in the fibers. When the rope breaks at some point, this energy is released in the form of a travelling wave from the point of breakage in both directions with the long portion having the greatest energy. Upon reaching either end, it encounters an impedance discontinuity (the tow release) and is reflected backwards along the rope. This reflection can add to the still oncoming wave, amplifying its magnitude. If this exceeds the ultimate strength of the rope at this point, it will, too, break.
> > > > >
> > > > > This travelling wave phenomena also occurs in electronics, and is exploited in antennas.
> > > > >
> > > > > Tom
> > > >
> > > > To invoke any theory involving waves there needs to be a reason to think that there is a wave created of some sort. Waves necessitate two forms of energy storage with oscillation between them. I'm not seeing how that works in the towrope. It seems like the energy stored in the elastic rope will get dissipated as heat as the rope progressively shortens after breaking. I can visualize that at the breaking impulse maybe a wee bit of energy would get spit out as transverse displacement wave but that would be second order and not significant; the main happening is longitudinal. What wave are we talking about?
> > >
> > > First, before breaking, the rope is stretched considerably beyond its resting length - this undeniably stores energy in the rope (the same as a spring). Second, when the rope breaks this stored energy is released by accelerating the end of the rope, like the cracking of a whip or an earthquake starting a tsunami. This energy travels the rope until it reaches the terminated end, where it is reflected in the opposite direction.
> > > Here is a video of a steel rope breaking; single-frame from 33 sec to see the wave-like action:
> > > https://www.youtube.com/watch?v=W6gZawDnthI
> > >
> > > Tom
> >
> > Tom: As you know, cracking a whip happens because the whip is excited with a transverse wave. We're not doing that; our excitation is longitudinal. As I said before, there is likely a small amount of incidental motion that goes to making a transverse wave as there is in the video you reference; but that's second order and I think too small to matter.
> >
> > I don't see that there is anything about the longitudinal accelerating rope that can then oscillate energy back into stored state as rope tension. Hence, you do not have a longitudinal wave scenario. Without a wave mechanism, you don't get to talk about reflection. The energy in the rope just goes to heat.
> >
> > The basic problem is that you can't push a rope. If we were talking about a spring, then yes, you could push on a spring and get energy stored in compression and have a longitudinal wave with energy oscillating between longitudinal kinetic motion and compression. Such wave would reflect at the far end and maybe do something interesting. But when you push on a rope, you get nothing.
>
> But wait just a minute, Steve: Certainly a rope under tension can support a longitudinal wave. We all know about the tin can telephone that works by longitudinal waves when a string is tensioned.
>
> Yesterday, Steve, you were putting forth how it takes time for the tow rope to relax after breaking. If the speed of relaxation is slower than the speed of wave propagation (it probably is), then wouldn't there be a brief period after breaking that an impulse generated longitudinal wave can propagate to the other end of the rope and do mischief?

Steve,
It is a well known effect (hazard) that when a steel cable breaks under tension, it comes flying back, snaking all over the place. Now, steel stretches very little at failure, so this snaking is due to a transverse wave being induced. I suspect that the same thing can occur in a poly rope.
Tom

[Tom[_21_]]

As this has happened to me (rope broke in severe turbulence) and both the glider and towplane returned with their respective rings, the rope is in the woods somewhere - my guess is that the rope broke at the weakest points, the 180 degree bend at both ends.

Regards Tom

[Steve Koerner]

> It is a well known effect (hazard) that when a steel cable breaks under tension, it comes flying back, snaking all over the place. Now, steel stretches very little at failure, so this snaking is due to a transverse wave being induced. I suspect that the same thing can occur in a poly rope.
> Tom

I think I can see why steel cable does what it does on breaking and why towrope wouldn't really behave the same. Upon breaking, the stretch of steel cable is released with a lot of acceleration and because of its momentum, it overshoots its neutral length. The cable has rigidity and buckles energetically when it recoils and pushes upon itself throughout its length. By contrast, poly rope has no need of buckling; it can go placid as it arrives at neutral length. Once placid, it won't support wave propagation in transverse or longitudinal mode. So, if there's any waves generated at the first breakage, those waves need to finish their work before the rope finishes unstretching.