Almost perfect payout winch launch.

On Fri, 10 May 2013 06:19:27 -0700, son_of_flubber wrote:

Okay. I do have a few observations/opinions:

1)That the payout winch payouts more line and keeps line tension
constant when the glider hits lift seems an inherent advantage of this
approach when compared to a traditional winch launch.

As Bill says, a payout winch can't easily compensate for sink or a rear
gust at the start of a launch in calm conditions.

2)Don's suggestion that traditional winch launching is proven and that
there is therefore no reason to experiment with payout winching misses
the point. In a country where beefy pickup trucks are common, the
start-up costs for payout winching are much lower than traditional
winching. Secondly, far fewer humans need to be deployed and
coordinated to run a payout winch. The relevant question is "Which is
better to use on a dry lake bed, 1)autotow with payout winch or
2)traditional autotow? What are the tradeoffs?

As Don mentioned, we've been shown videos of payout winches with *no
gillotine fitted*. Its relatively rare, but cases of failures to release
have happened and are highly liable to be fatal without prompt use of the
guillotine. Even with a guillotine, what are the chances of a solo payout
winch driver noticing the problem in time? Even if he does notice, how
fast can he get to the guillotine's release and operate it?

I wouldn't accept a winch or auto-tow launch if there wasn't a functional
guillotine installed so that its release was instantly accessible to the
driver and/or the person monitoring the launch.


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

Guillotine? How about simply mounting a release mechanism to the back of
the tow vehicle with the release cable within reach of the driver or
observer? That's the way they do it on the dry lake in Nevada and I was not
the least concerned about accepting ground launches. And, of course,
there's always the weak link at the glider end...


"Martin Gregorie" wrote in message
...
On Fri, 10 May 2013 06:19:27 -0700, son_of_flubber wrote:

Okay. I do have a few observations/opinions:

1)That the payout winch payouts more line and keeps line tension
constant when the glider hits lift seems an inherent advantage of this
approach when compared to a traditional winch launch.

As Bill says, a payout winch can't easily compensate for sink or a rear
gust at the start of a launch in calm conditions.

2)Don's suggestion that traditional winch launching is proven and that
there is therefore no reason to experiment with payout winching misses
the point. In a country where beefy pickup trucks are common, the
start-up costs for payout winching are much lower than traditional
winching. Secondly, far fewer humans need to be deployed and
coordinated to run a payout winch. The relevant question is "Which is
better to use on a dry lake bed, 1)autotow with payout winch or
2)traditional autotow? What are the tradeoffs?

As Don mentioned, we've been shown videos of payout winches with *no
gillotine fitted*. Its relatively rare, but cases of failures to release
have happened and are highly liable to be fatal without prompt use of the
guillotine. Even with a guillotine, what are the chances of a solo payout
winch driver noticing the problem in time? Even if he does notice, how
fast can he get to the guillotine's release and operate it?

I wouldn't accept a winch or auto-tow launch if there wasn't a functional
guillotine installed so that its release was instantly accessible to the
driver and/or the person monitoring the launch.


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

The rope on a payout winch is on a drum not simply attached to the rear of a truck. Straight auto-tow uses a release. A payout winch needs a guillotine.

On Saturday, May 18, 2013 10:03:48 AM UTC-6, Dan Marotta wrote:
Guillotine? How about simply mounting a release mechanism to the back of

the tow vehicle with the release cable within reach of the driver or

observer? That's the way they do it on the dry lake in Nevada and I was not

the least concerned about accepting ground launches. And, of course,

there's always the weak link at the glider end...





"Martin Gregorie" wrote in message

...

On Fri, 10 May 2013 06:19:27 -0700, son_of_flubber wrote:



Okay. I do have a few observations/opinions:



1)That the payout winch payouts more line and keeps line tension

constant when the glider hits lift seems an inherent advantage of this

approach when compared to a traditional winch launch.



As Bill says, a payout winch can't easily compensate for sink or a rear

gust at the start of a launch in calm conditions.



2)Don's suggestion that traditional winch launching is proven and that

there is therefore no reason to experiment with payout winching misses

the point. In a country where beefy pickup trucks are common, the

start-up costs for payout winching are much lower than traditional

winching. Secondly, far fewer humans need to be deployed and

coordinated to run a payout winch. The relevant question is "Which is

better to use on a dry lake bed, 1)autotow with payout winch or

2)traditional autotow? What are the tradeoffs?



As Don mentioned, we've been shown videos of payout winches with *no

gillotine fitted*. Its relatively rare, but cases of failures to release

have happened and are highly liable to be fatal without prompt use of the

guillotine. Even with a guillotine, what are the chances of a solo payout

winch driver noticing the problem in time? Even if he does notice, how

fast can he get to the guillotine's release and operate it?



I wouldn't accept a winch or auto-tow launch if there wasn't a functional

guillotine installed so that its release was instantly accessible to the

driver and/or the person monitoring the launch.





--

martin@ | Martin Gregorie

gregorie. | Essex, UK

org |

On Sat, 18 May 2013 10:03:48 -0600, Dan Marotta wrote:

Guillotine? How about simply mounting a release mechanism to the back
of the tow vehicle with the release cable within reach of the driver or
observer? That's the way they do it on the dry lake in Nevada and I was
not the least concerned about accepting ground launches. And, of
course, there's always the weak link at the glider end...

The guillotine *is* the winch-end release mechanism. What else can you do
but cut the rope if the glider can't release? Jettisoning the drum and
guides, leaving them swinging beneath the glider isn't a good solution!

And, as others have pointed out, if you're not using a stiff 2-3 metre
strop (4.5mm steel cable inside plastic hose) on the glider's end of the
shock rope, then a hesitation or snatch as the take-off run starts can
wrap the cable round your wheel. That's something that's known to prevent
the glider from releasing its end of the cable.

I've just reviewed the video that started this thread and can't see any
sign that such a strop is in use or any indication that the weak link, if
there is one, at the glider end is correct for the glider. In the UK the
weak link housing is an integral part of the strop and the plastic hose
is colour coded to match the weak link: hence the pilot, or anybody else
at the launch point, can visually check that the correct weak is being
used when the cable is accepted prior to launch.


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

Oops! I was thinking of a straight auto tow. I forgot about the payout
winch part.

You are, of course, correct in the need for a guillotine in this
application.


"Martin Gregorie" wrote in message
...
On Sat, 18 May 2013 10:03:48 -0600, Dan Marotta wrote:

Guillotine? How about simply mounting a release mechanism to the back
of the tow vehicle with the release cable within reach of the driver or
observer? That's the way they do it on the dry lake in Nevada and I was
not the least concerned about accepting ground launches. And, of
course, there's always the weak link at the glider end...

The guillotine *is* the winch-end release mechanism. What else can you do
but cut the rope if the glider can't release? Jettisoning the drum and
guides, leaving them swinging beneath the glider isn't a good solution!

And, as others have pointed out, if you're not using a stiff 2-3 metre
strop (4.5mm steel cable inside plastic hose) on the glider's end of the
shock rope, then a hesitation or snatch as the take-off run starts can
wrap the cable round your wheel. That's something that's known to prevent
the glider from releasing its end of the cable.

I've just reviewed the video that started this thread and can't see any
sign that such a strop is in use or any indication that the weak link, if
there is one, at the glider end is correct for the glider. In the UK the
weak link housing is an integral part of the strop and the plastic hose
is colour coded to match the weak link: hence the pilot, or anybody else
at the launch point, can visually check that the correct weak is being
used when the cable is accepted prior to launch.


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

In article ,
Martin Gregorie wrote:



I wouldn't accept a winch or auto-tow launch if there wasn't a functional
guillotine installed so that its release was instantly accessible to the
driver and/or the person monitoring the launch.



We used to do a lot of ground launching via the "pulley method". We
always had an observer in the tow car watching the launch. Our
"guillotine" was a sharp machete in the hands of the observer. Of course
we were also taught to immediately bank into a tight turn and circle the
tow vehicle if we could not release. I always had my doubts about
recognizing the release failure in time to cut the line or to turn and
get tension off the line before things got out of hand.

All the pulley launch rigs I have seen are just a bare pulley, usually a
truck rim mounted an a trailer hitch. No fairleads or other structure. I
guess a guillotine could be mounted to such a rig. Would be a good Idea,
I think.

On Monday, May 20, 2013 9:19:03 AM UTC-5, WB wrote:
In article , Martin Gregorie wrote: I wouldn't accept a winch or auto-tow launch if there wasn't a functional guillotine installed so that its release was instantly accessible to the driver and/or the person monitoring the launch. We used to do a lot of ground launching via the "pulley method". We always had an observer in the tow car watching the launch. Our "guillotine" was a sharp machete in the hands of the observer. Of course we were also taught to immediately bank into a tight turn and circle the tow vehicle if we could not release. I always had my doubts about recognizing the release failure in time to cut the line or to turn and get tension off the line before things got out of hand. All the pulley launch rigs I have seen are just a bare pulley, usually a truck rim mounted an a trailer hitch. No fairleads or other structure. I guess a guillotine could be mounted to such a rig. Would be a good Idea, I think.

If you're using a pulley why not just have a release on the tow vehicle?

In article ,
Tony wrote:



If you're using a pulley why not just have a release on the tow vehicle?

Hi Tony,

I was unclear about the pulley launch. The pulley is on the tow vehicle.
One end of the line is anchored, the line goes over the pulley to the
glider. The tow vehicle is pulling from the middle of the rope, going in
the same direction as the glider. The advantages are that acceleration
at the glider is almost as fast as a winch launch and the tow car only
has to go 25-30 mph maximum to launch the glider. No gear changes
required, and the low vehicle speed means it can be done on less than
paved surfaces. Launching with 4000 feet of dacron rope and an old LTD
with 500 lbs of bricks in the trunk used to get our Ka-8 to 2000' if we
had a bit of headwind.

A release can be put at the anchor point, but that's a long way from
where the action is.

There are some other disadvantages to this type of ground launch as
well. Turn around time is fairly long. Switching ends of the rope after
each launch can speed things up especially if the anchor point is
another vehicle. Rope recovery can be problematic since a chute is
usually not part of the rope end hardware, so the rope tends to fall a
ways downwind.

On Monday, May 20, 2013 9:52:58 AM UTC-5, WB wrote:
In article , Tony wrote: If you're using a pulley why not just have a release on the tow vehicle? Hi Tony, I was unclear about the pulley launch. The pulley is on the tow vehicle. One end of the line is anchored, the line goes over the pulley to the glider. The tow vehicle is pulling from the middle of the rope, going in the same direction as the glider. The advantages are that acceleration at the glider is almost as fast as a winch launch and the tow car only has to go 25-30 mph maximum to launch the glider. No gear changes required, and the low vehicle speed means it can be done on less than paved surfaces. Launching with 4000 feet of dacron rope and an old LTD with 500 lbs of bricks in the trunk used to get our Ka-8 to 2000' if we had a bit of headwind. A release can be put at the anchor point, but that's a long way from where the action is. There are some other disadvantages to this type of ground launch as well. Turn around time is fairly long. Switching ends of the rope after each launch can speed things up especially if the anchor point is another vehicle. Rope recovery can be problematic since a chute is usually not part of the rope end hardware, so the rope tends to fall a ways downwind.

ah i see, i was thinking of a fixed pulley.

On Monday, May 20, 2013 11:00:54 AM UTC-4, Tony wrote:
On Monday, May 20, 2013 9:52:58 AM UTC-5, WB wrote:

In article , Tony wrote: If you're using a pulley why not just have a release on the tow vehicle? Hi Tony, I was unclear about the pulley launch. The pulley is on the tow vehicle. One end of the line is anchored, the line goes over the pulley to the glider. The tow vehicle is pulling from the middle of the rope, going in the same direction as the glider. The advantages are that acceleration at the glider is almost as fast as a winch launch and the tow car only has to go 25-30 mph maximum to launch the glider. No gear changes required, and the low vehicle speed means it can be done on less than paved surfaces. Launching with 4000 feet of dacron rope and an old LTD with 500 lbs of bricks in the trunk used to get our Ka-8 to 2000' if we had a bit of headwind. A release can be put at the anchor point, but that's a long way from where the action is. There are some other disadvantages to this type of ground launch as well. Turn around time is fairly long. Switching ends of the rope after each launch can speed things up especially if the anchor point is another vehicle. Rope recovery can be problematic since a chute is usually not part of the rope end hardware, so the rope tends to fall a ways downwind.



ah i see, i was thinking of a fixed pulley.

Yes, fixed pulley has some advantages: quick turnaround, can use a chute, driver
is facing the action. The disadvantage is that you drag the whole rope the
length of the field at speed. I would think that would wear out Spectra
pretty fast. There's some places that use multiple pulleys that can
mitigate some of that. Check out the pulleylaunch Yahoo group for that.

Matt