Let's talk ground launching........

[Rusty]

Hello All:
With the price of fuel going up and the price of AeroTows close behind
it I think the need to follow the lead of our brethren in the UK is
close at hand. I have heard talk of the infamous $100.00 tow and know
that I for one can't afford it, I have to work for a living as do most
of you! I and some of my fellow pilots are wanting to start a new club
and are want to use winch, auto tows and reverse pulley launching
exclusively. Let's discuss the different aspects of ground launching as
the only thing that will save our sport and make it inviting once again
to new students.
Thanks
Rusty

[Frank Whiteley]

Rusty wrote:
> Hello All:
> With the price of fuel going up and the price of AeroTows close behind
> it I think the need to follow the lead of our brethren in the UK is
> close at hand. I have heard talk of the infamous $100.00 tow and know
> that I for one can't afford it, I have to work for a living as do most
> of you! I and some of my fellow pilots are wanting to start a new club
> and are want to use winch, auto tows and reverse pulley launching
> exclusively. Let's discuss the different aspects of ground launching as
> the only thing that will save our sport and make it inviting once again
> to new students.
> Thanks
> Rusty

http://groups.yahoo.com/group/winchdesign/
Many of the issues are discuseed here and there are some archival
files/images to review. I'm quite happy to carry on here or in the
group.

There are a few stumbling blocks to ground launching, but most can be
overcome. Space is definitely one. If your launch rope can span
4000ft or more, it's very attractive. Others have done with less
distance. Location helps. Thinking outside the box helps also.

So, where are you? Appears you may be in Texas. That could be
fortunate as there are some ground launch activities there, in case
pilot and instructor qualifications are needed. If you are seriously
considering starting a club in the US, have a look here
http://www.soarcsa.org/ssa/clubs/2005_start_here.htm

Frank Whiteley
SSA Clubs & Chapters Committee member
CSA Winchmeister

[Ken Reynolds]

I did all my training as far as passenger carrying , using a reverse auto
tow system. If there is runway length available, I think nothing will beat
it for speed and low cost.We regularly got 3000 foot launches using 6000
foot of 16 guage piano wire.
Ken Reynolds

[Ian Johnston]

On Fri, 2 Sep 2005 07:26:26 UTC, "Ken Reynolds" >
wrote:

: I did all my training as far as passenger carrying , using a reverse auto
: tow system. If there is runway length available, I think nothing will beat
: it for speed and low cost.

And there is nothing to encourage take off like two tons of pickup
heading towards you at a closing speed of over 100mph ... I think both
the glider and the pilot are launched by fear.

Ian

PS But seriously, did a reverse pulley autotow at Connel a few years
back, very easy smooth launch.
--

[Chris Nicholas]

16 gauge piano wire sounds remarkably thin, unless it was a special high
tensile type. Cotsold GC and Essex GC in the UK used 13 gauge (easier
than 11 gauge to handle, join, etc. but prone to breaks) or later 11
gauge (rarely broke, but harder to tie knots, and needed larger pulley
diameter for reverse pulley). The large diameters required led to
Cotswold going for a non-rotating "pulley" made up from lots of small
rollers round its rim (but it had no guillotine). Essex used two large
rollers, lots of inertia, but it enabled a flat anvil to be between them
so that a spring-loaded chisel could be released to cut the cable in
emergency.

Before reverse pulley, Essex used 13 gauge for straight autotow. It
often broke. Theoretically, the weak link should be weaker than the
cable, but we were using uncalibrated polypropylene rope of uncertain
breaking strain.

Starting over, I would be looking at Dyneema stronger than the highest
rated weak link needed, and the main cable should rarely if ever break.
For reverse pulley, I would look at the Cotswold type but incorporate a
flat part of the "pulley" with an anvil in line with the pivot, like the
Essex set up. The spring loaded chisel would go through the hollow pivot
shaft.

For the benefit of those who have not seen a pulley system, it needs to
pivot about a horizontal axle, and to swing to some extent, to equalise
the angles and allow the cable to run true from the glider (which might
be to one side of the runway, e.g. in a cross wind), into the top of the
pulley, and out from the bottom to the tow vehicle.

Chris N.




__________________________________________________ _________
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[Rusty]

Hello Again:
Thank you all for the response, it is all very welcome. I do live in
South Texas and we have access to a basically un-used well kept
200'x6000' hard packed grass field. We have recently picked up an
older winch that needs a litte TCL but with a little work will be very
usable. We are also setting up for straight auto-tow and are in the
process of building pulleys for reverse pulley. One of the many
questions I have is this: is a parachute necessary on straight auto-tow
and if so how far from the glider should the parachute be located?
Many more questions later.
Thanks
Rusty

Chris Nicholas wrote:
> 16 gauge piano wire sounds remarkably thin, unless it was a special high
> tensile type. Cotsold GC and Essex GC in the UK used 13 gauge (easier
> than 11 gauge to handle, join, etc. but prone to breaks) or later 11
> gauge (rarely broke, but harder to tie knots, and needed larger pulley
> diameter for reverse pulley). The large diameters required led to
> Cotswold going for a non-rotating "pulley" made up from lots of small
> rollers round its rim (but it had no guillotine). Essex used two large
> rollers, lots of inertia, but it enabled a flat anvil to be between them
> so that a spring-loaded chisel could be released to cut the cable in
> emergency.
>
> Before reverse pulley, Essex used 13 gauge for straight autotow. It
> often broke. Theoretically, the weak link should be weaker than the
> cable, but we were using uncalibrated polypropylene rope of uncertain
> breaking strain.
>
> Starting over, I would be looking at Dyneema stronger than the highest
> rated weak link needed, and the main cable should rarely if ever break.
> For reverse pulley, I would look at the Cotswold type but incorporate a
> flat part of the "pulley" with an anvil in line with the pivot, like the
> Essex set up. The spring loaded chisel would go through the hollow pivot
> shaft.
>
> For the benefit of those who have not seen a pulley system, it needs to
> pivot about a horizontal axle, and to swing to some extent, to equalise
> the angles and allow the cable to run true from the glider (which might
> be to one side of the runway, e.g. in a cross wind), into the top of the
> pulley, and out from the bottom to the tow vehicle.
>
> Chris N.
>
>
>
>
> __________________________________________________ _________
> How much free photo storage do you get? Store your holiday
> snaps for FREE with Yahoo! Photos http://uk.photos.yahoo.com

[GM]

Frank Whiteley wrote:
> Rusty wrote:
> > Hello All:
> > With the price of fuel going up and the price of AeroTows close behind
> > it I think the need to follow the lead of our brethren in the UK is
> > close at hand. I have heard talk of the infamous $100.00 tow and know
> > that I for one can't afford it, I have to work for a living as do most
> > of you! I and some of my fellow pilots are wanting to start a new club
> > and are want to use winch, auto tows and reverse pulley launching
> > exclusively. Let's discuss the different aspects of ground launching as
> > the only thing that will save our sport and make it inviting once again
> > to new students.
> > Thanks
> > Rusty
>
> http://groups.yahoo.com/group/winchdesign/
> Many of the issues are discuseed here and there are some archival
> files/images to review. I'm quite happy to carry on here or in the
> group.
>
> There are a few stumbling blocks to ground launching, but most can be
> overcome. Space is definitely one. If your launch rope can span
> 4000ft or more, it's very attractive. Others have done with less
> distance. Location helps. Thinking outside the box helps also.
>
> So, where are you? Appears you may be in Texas. That could be
> fortunate as there are some ground launch activities there, in case
> pilot and instructor qualifications are needed. If you are seriously
> considering starting a club in the US, have a look here
> http://www.soarcsa.org/ssa/clubs/2005_start_here.htm
>
> Frank Whiteley
> SSA Clubs & Chapters Committee member
> CSA Winchmeister


..... Thinking outside the box helps also....

Frank, well said!
Many folks in the club I recently left in NE Ohio where dead set
against any kind of ground launching for they had heard how dangerous
it is and that you can not soar away out of a winch launch. Most of the
nay-sayers had never ground launched nor had they seen a modern winch
in action.
I think the main obstacle for introducing winch- or ground launching in
the US is to change the perception of what a modern winch is capable of
and at what cost at that.

'Folks - It ain't your daddy's Gehrlein winch anymore!!'

Anybody interested feel free to read up on that issue at (or join)
http://groups.yahoo.com/group/winchdesign/ .

I think we have collected the most comprehensive set of information
regarding winch launching in the last year and a half from practical
'how to' knowledge to all sorts of theoretical papers on the physics of
a winch launch.
Lets get to work!

Uli Neumann

[Stefan]

GM wrote:

> Many folks in the club I recently left in NE Ohio where dead set
> against any kind of ground launching for they had heard how dangerous

Frankly, winch launching *is* dangerous if don't have the required
knowledge and aren't dead serious about it. But that's nothing new in
aviation.

> it is and that you can not soar away out of a winch launch.

This depends on your location.

If you think of introducing winch operation at your site, then I suggest
you take the following steps.

1. Answer the following questions: How long will the cable be? How much
height can be achieved with this cable lenghth? Is this enough to get
away? (Always, sometimes, rarely).

2. Is a winch operation feasable at your site at all? (It mixes poorely
with scheduled Airliers.)

3. Calculate the cost.

4. Two or three pilots go somewhere where they have a winch operation.
Try it. Talk to them.

5. Best would be if you could hire a winch for a weekend at your place.
Together with the winch operator, of course, and a flight instructor.
Maybe obsolete if step 4 includes enough pilots.

6. Based on that experience, decide.

7. Most important: If you decide pro winch, get proper istruction, or
you *will* have fatalities. (Not panicking, I love winch launches. But
they *are* serious.)

Stefan

[Chris Nicholas]

Yes, you need a drogue, at least for piano wire cable. If not, it drops
into a terrible snarl-up. Dyneema/Spectra, I don't know - ask people who
have tried it.

For lengths and hardware on the cable, I have seen many different
variations. The most complex was at Dunstable, UK some years ago, which
included many features for which I could understand the reason,
including a long shock rope between drogue and rings. I believe that the
safest arrangement is short (2-6 feet), plastic-tube-covered strop from
Tost rings to Tost weak link; weak link with easy-change connections;
long strop (30-80 feet) from weak link to drogue (to keep billowing
drogue well in front of glider in a power failure situation); swivel;
and then main cable.

It is an official BGA "Recommended Practice" that the shock rope should
be stiffened with plastic hose or similar, to prevent it wrapping round
the wheel axle and being unable to release. There are, however, many
more aspects of the hardware that could usefully be standardised, or at
least listed for guidance so that if people do something different it
should be a conscious decision with good reason, not just ignorance or
lack of experience.

No doubt someone from Dunstable will correct the following if I got it
wrong or it has changed, but my notes of their assembly were as follows,
starting at the glider end:

1. Tost rings

2. wire rope a few feet long.

3. ferrule to secure end of 2 into a loop.

4. plastic hose over 2.

5. ferrule to secure other end of 2 into a loop.

6. oval link with flat section on one side.

7. quick-release hook mating with 6.

8. shackle.

9. weak link assembly.

10. shackle.

11. shock rope about 80 feet long.

12. shackle.

13. triangular ring on end of drogue.

14. drogue.

15. metal end fitting on drogue.

16. shackle.

17. plate on shackle to take the wear.

18. swivel.

19. shackle.

20. oval link with flat section on one side.

21. quick-release hook mating with 20.

22. loop of main winch cable.

23. first ferrule securing 22.

24. plate on loop to take the wear.

25. second ferrule securing 22 and 24.

Most of the hardware is standard off-the shelf stuff. The "plate . . .
to take the wear" looked like a special, and it was oval, about 2x3
inches and 1/4 inch thick (50x75 mm, 6 mm thick) and had two holes
through which the legs of the shackle projected. It had the effect of
being the largest diameter thing on the assembly, so would be the one to
take the wear from running over the ground, hence protecting swivel
etc..

I hope this helps.

Chris N.








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[Frank Whiteley]

Chris Nicholas wrote:
> 16 gauge piano wire sounds remarkably thin, unless it was a special high
> tensile type. Cotsold GC and Essex GC in the UK used 13 gauge (easier
> than 11 gauge to handle, join, etc. but prone to breaks) or later 11
> gauge (rarely broke, but harder to tie knots, and needed larger pulley
> diameter for reverse pulley). The large diameters required led to
> Cotswold going for a non-rotating "pulley" made up from lots of small
> rollers round its rim (but it had no guillotine). Essex used two large
> rollers, lots of inertia, but it enabled a flat anvil to be between them
> so that a spring-loaded chisel could be released to cut the cable in
> emergency.
>
> Before reverse pulley, Essex used 13 gauge for straight autotow. It
> often broke. Theoretically, the weak link should be weaker than the
> cable, but we were using uncalibrated polypropylene rope of uncertain
> breaking strain.
>
> Starting over, I would be looking at Dyneema stronger than the highest
> rated weak link needed, and the main cable should rarely if ever break.
> For reverse pulley, I would look at the Cotswold type but incorporate a
> flat part of the "pulley" with an anvil in line with the pivot, like the
> Essex set up. The spring loaded chisel would go through the hollow pivot
> shaft.
>
> For the benefit of those who have not seen a pulley system, it needs to
> pivot about a horizontal axle, and to swing to some extent, to equalise
> the angles and allow the cable to run true from the glider (which might
> be to one side of the runway, e.g. in a cross wind), into the top of the
> pulley, and out from the bottom to the tow vehicle.
>
> Chris N.
>
When using steel wire and wheels/pulleys, the diameter of the
wheels/pulleys should be 60 times the diameter of the wire to prevent
work hardening. That's why 7/7 wire rope works with much small
diameter rollers and guides on winches.

See http://tinyurl.com/c3pd5

Frank Whiteley

[Frank Whiteley]

Rusty wrote:
> Hello Again:
> Thank you all for the response, it is all very welcome. I do live in
> South Texas and we have access to a basically un-used well kept
> 200'x6000' hard packed grass field. We have recently picked up an
> older winch that needs a litte TCL but with a little work will be very
> usable. We are also setting up for straight auto-tow and are in the
> process of building pulleys for reverse pulley. One of the many
> questions I have is this: is a parachute necessary on straight auto-tow
> and if so how far from the glider should the parachute be located?
> Many more questions later.
> Thanks
> Rusty
>
We did straight autotows for several years with a product known as
parafil. If there's a similar product, it might be a good option for
some. Some prior postings.

http://tinyurl.com/7em69

Frank

[Martin Gregorie]

On Fri, 02 Sep 2005 13:35:49 +0000, Chris Nicholas wrote:

I'm not from Dunstable but.....

I think items 7 and 10 should be swapped so the weak link is part of the
wire strop assembly and item 4 should be selected so its colour matches
the colour of the weak link.

> No doubt someone from Dunstable will correct the following if I got it
> wrong or it has changed, but my notes of their assembly were as follows,
> starting at the glider end:
>
> 1. Tost rings
>
> 2. wire rope a few feet long.
>
> 3. ferrule to secure end of 2 into a loop.
>
> 4. plastic hose over 2.
>
> 5. ferrule to secure other end of 2 into a loop.
>
> 6. oval link with flat section on one side.
>
> 7. quick-release hook mating with 6.
>
> 8. shackle.
>
> 9. weak link assembly.
>
> 10. shackle.
>
> 11. shock rope about 80 feet long.
>
> 12. shackle.
>
> 13. triangular ring on end of drogue.
>
> 14. drogue.
>
> 15. metal end fitting on drogue.
>
> 16. shackle.
>
> 17. plate on shackle to take the wear.
>
> 18. swivel.
>
> 19. shackle.
>
> 20. oval link with flat section on one side.
>
> 21. quick-release hook mating with 20.
>
> 22. loop of main winch cable.
>
> 23. first ferrule securing 22.
>
> 24. plate on loop to take the wear.
>
> 25. second ferrule securing 22 and 24.
>
--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[Stefan]

I said a winch operation wouldn't mix well with airliner. Well, it can
be done, as this picture demonstrates:
http://www.dg-flugzeugbau.de/foto-05-09.html

However it must be said that this aren't scheduled but mostly private
jets (yes, private, not business!) and that the airport is a major
gliding center, so everybody is very willing to cooperate.

Stefan

[Frank Whiteley]

Stefan wrote:
> GM wrote:
>
> > Many folks in the club I recently left in NE Ohio where dead set
> > against any kind of ground launching for they had heard how dangerous
>
> Frankly, winch launching *is* dangerous if don't have the required
> knowledge and aren't dead serious about it. But that's nothing new in
> aviation.
>
> > it is and that you can not soar away out of a winch launch.
>
> This depends on your location.
>
> If you think of introducing winch operation at your site, then I suggest
> you take the following steps.
>
> 1. Answer the following questions: How long will the cable be? How much
> height can be achieved with this cable lenghth? Is this enough to get
> away? (Always, sometimes, rarely).
>
> 2. Is a winch operation feasable at your site at all? (It mixes poorely
> with scheduled Airliers.)
>
> 3. Calculate the cost.
>
> 4. Two or three pilots go somewhere where they have a winch operation.
> Try it. Talk to them.
>
> 5. Best would be if you could hire a winch for a weekend at your place.
> Together with the winch operator, of course, and a flight instructor.
> Maybe obsolete if step 4 includes enough pilots.
>
> 6. Based on that experience, decide.
>
> 7. Most important: If you decide pro winch, get proper istruction, or
> you *will* have fatalities. (Not panicking, I love winch launches. But
> they *are* serious.)
>
> Stefan
(previously posted under another thread)

http://members.tripod.com/~thrift/soaring/psa2.html

2000ft launches
BLM land access
non-profit (social)
Located several miles from local airport according to map.


Frank Whiteley
p.s. cool animation

[Chris Nicholas]

Martin Gregorie wrote [snip] " . . .I think items 7 and 10 should be
swapped so the weak link is part of the wire strop assembly and item 4
should be selected so its colour matches the colour of the weak link."

Some clubs, including mine, do that - change the strop with weak link
attached, to suit the glider. Some have several weak links on the cable
and just switch the same strop from one to another. Some may just change
the weak link, with quick releases either side, so only one strop is
needed.

Chris N.






__________________________________________________ _________
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[Bruce]

Scary thought that. I have a total of three aero tow launches representing less
than 1% of my flying yet somehow have managed to thermal away many times. In
fact well enough that my average flight time is 33 minutes. Considering I do a
fair amount of intro flights of 5 to 10 minutes that is not a bad average for a
launch type that is so difficult.

One thing we notice at our club, by the time we send someone solo, they can find
thermals and get away pretty efficiently. Nothing like being 1,500" AGL to focus
the mind on finding lift...

Maybe we are just spoiled with good conditions.

GM wrote:
> Frank Whiteley wrote:
>
>>Rusty wrote:
>>
>>>Hello All:
>>>With the price of fuel going up and the price of AeroTows close behind
>>>it I think the need to follow the lead of our brethren in the UK is
>>>close at hand. I have heard talk of the infamous $100.00 tow and know
>>>that I for one can't afford it, I have to work for a living as do most
>>>of you! I and some of my fellow pilots are wanting to start a new club
>>>and are want to use winch, auto tows and reverse pulley launching
>>>exclusively. Let's discuss the different aspects of ground launching as
>>>the only thing that will save our sport and make it inviting once again
>>>to new students.
>>>Thanks
>>>Rusty
>>
>>http://groups.yahoo.com/group/winchdesign/
>>Many of the issues are discuseed here and there are some archival
>>files/images to review. I'm quite happy to carry on here or in the
>>group.
>>
>>There are a few stumbling blocks to ground launching, but most can be
>>overcome. Space is definitely one. If your launch rope can span
>>4000ft or more, it's very attractive. Others have done with less
>>distance. Location helps. Thinking outside the box helps also.
>>
>>So, where are you? Appears you may be in Texas. That could be
>>fortunate as there are some ground launch activities there, in case
>>pilot and instructor qualifications are needed. If you are seriously
>>considering starting a club in the US, have a look here
>>http://www.soarcsa.org/ssa/clubs/2005_start_here.htm
>>
>>Frank Whiteley
>>SSA Clubs & Chapters Committee member
>>CSA Winchmeister
>
>
>
> .... Thinking outside the box helps also....
>
> Frank, well said!
> Many folks in the club I recently left in NE Ohio where dead set
> against any kind of ground launching for they had heard how dangerous
> it is and that you can not soar away out of a winch launch. Most of the
> nay-sayers had never ground launched nor had they seen a modern winch
> in action.
> I think the main obstacle for introducing winch- or ground launching in
> the US is to change the perception of what a modern winch is capable of
> and at what cost at that.
>
> 'Folks - It ain't your daddy's Gehrlein winch anymore!!'
>
> Anybody interested feel free to read up on that issue at (or join)
> http://groups.yahoo.com/group/winchdesign/ .
>
> I think we have collected the most comprehensive set of information
> regarding winch launching in the last year and a half from practical
> 'how to' knowledge to all sorts of theoretical papers on the physics of
> a winch launch.
> Lets get to work!
>
> Uli Neumann
>


--
Bruce Greeff
Std Cirrus #57
I'm no-T at the address above.

[Martin Gregorie]

On Fri, 02 Sep 2005 21:56:11 +0000, Chris Nicholas wrote:

> Martin Gregorie wrote [snip] " . . .I think items 7 and 10 should be
> swapped so the weak link is part of the wire strop assembly and item 4
> should be selected so its colour matches the colour of the weak link."
>
> Some clubs, including mine, do that - change the strop with weak link
> attached, to suit the glider. Some have several weak links on the cable
> and just switch the same strop from one to another. Some may just change
> the weak link, with quick releases either side, so only one strop is
> needed.
>
> Chris N.
>
Apologies, Chris. I thought that you'd gotten confused with all the
shackles - the sort of thing I'd do.

The only club I've visited that swapped the weak link but not the strop
was Auckland, NZ - and they use a really long strop, at least 5 m, and
aero-tow rope in place of steel cable on the winch.

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

[Ian Johnston]

On Fri, 2 Sep 2005 10:15:14 UTC, Chris Nicholas
> wrote:

: For reverse pulley, I would look at the Cotswold type but incorporate a
: flat part of the "pulley" with an anvil in line with the pivot, like the
: Essex set up. The spring loaded chisel would go through the hollow pivot
: shaft.

Who operates the guillotine in these systems? Do you need someone
stationed by the pulley, or is there some sort of remote actuation?

Personally, I think it's time we stopped messing about with spring
loaded cutters and went to explosive ones, but that's incidental here!

Ian

[Chris Nicholas]

Ian Johnston wrote:[snip]Who operates the guillotine in these systems?
Do you need someone stationed by the pulley, or is there some sort of
remote actuation? [snip]

The pulley was mounted on the back of a large, heavy truck, chocked to
stop the forces dragging it down the runway. The guillotine control was
a knob in the back of the cab (seat reversed on the passenger side IIRC)
which released the spring loaded chisel if required. We always had a
chopper person there during launching as a safety precaution, and they
had to be in the cab because of the danger of thrashing wire after a
break or chop.

They also served to speed up the launching process, by gathering the
drogue and strop etc. to hook onto the tow truck when it drove up.

For fastest turnaround, two tow trucks are used. One does the launch,
carries on to the launch point after glider release and delivers that
end to the next glider. The other follows the launched glider up the
runway, passes the launching truck half way, and arrives at the pulley
in time for the chopper person to hook on. The cable is double ended, of
course, with drogues and rings etc. at both ends. An extra ring on the
main cable goes to the tow truck Tost release, so no wear and tear on
the drogue etc. at that end when launching. At its best, it gives
similar turnaround to the Long Mynd's cable retrieve winch system - 20
or more launches per hour.

It is only worth doing all this if you need a lot of launches. Straight
autotow is quicker and cheaper to establish, needs less training and
manpower to operate, but is a bit harder to get a quick turnaround. You
can use two tow trucks to speed it up, if you have a wide runway - one
retrieves the cable it has launched with and returns to the launch
point, while the other does the next launch. Safety precautions need
some care with this - we did it in the 1970's when there were fewer
legal cases likely in the event of nasty incidents.

Chris N.






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[Frank Whiteley]

Ian Johnston wrote:
> On Fri, 2 Sep 2005 10:15:14 UTC, Chris Nicholas
> > wrote:
>
> : For reverse pulley, I would look at the Cotswold type but incorporate a
> : flat part of the "pulley" with an anvil in line with the pivot, like the
> : Essex set up. The spring loaded chisel would go through the hollow pivot
> : shaft.
>
> Who operates the guillotine in these systems? Do you need someone
> stationed by the pulley, or is there some sort of remote actuation?
>
> Personally, I think it's time we stopped messing about with spring
> loaded cutters and went to explosive ones, but that's incidental here!
>
> Ian
The Cotswold Reverse Pulley had no guillotine and the reasoning was
that none was needed. The design was such that the tow vehicle end
would release if there was a release failure and the glider would pull
wire and tackle back through the pulley, as needed. IIRC, there were
two release failures in the 30 years of operation and that both
recovered okay.

Frank Whiteley

[Chris Nicholas]

There are other risks than the glider hook hanging up. At North Weald,
we broke a child's leg when the drogue dropped into a group of young
football players and dragged one of them along the ground - the chopper
man decided not to pull the release but should have done. (Agreed there
were others things that should have avoided such accidents, but Sod's
law says that if something can go wrong it will if you keep trying long
enough.)

The requirement for a guillotine should not be dismissed lightly.

We also had a fatal accident on the ground - one end of the cable
snagged during retrieve, got very tight, and snapped back when a man at
the launch point went to release it, pulling him over, resulting in a
fractured skull. Tow truck driver didn't know there was a problem. The
victim forgot his training, to ensure the cable was slack before
releasing it from the truck. (If the chopper man had cut it when it
snagged, it would not have hurt anyone.)

Launch systems can bite, and will, if safety is not taken very
seriously.

Chris N.




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[Robin Birch]

In message >, Chris Nicholas
> writes
>Martin Gregorie wrote [snip] " . . .I think items 7 and 10 should be
>swapped so the weak link is part of the wire strop assembly and item 4
>should be selected so its colour matches the colour of the weak link."
>
>Some clubs, including mine, do that - change the strop with weak link
>attached, to suit the glider. Some have several weak links on the cable
>and just switch the same strop from one to another. Some may just change
>the weak link, with quick releases either side, so only one strop is
>needed.
>
Fairly common practice that I have seen at all of the clubs I regularly
fly from (Cotswold, Mynd, Port Moak) go Tost Rings - shock rope - weak
link - quick change link.

The logic for this is that if you do break the weak link then you stand
a chance of finding the tost rings as they will have the shock rope that
is usually covered by a brightly coloured plastic pipe.

The shock rope length is about 6 to 10 feet long, port moak's is
shorter. Some clubs also choose coloured pipe to match the weak link
colour.

For What It's Worth. I fly from Cotswold and witnessed the last couple
of years of the reverse pulley system. It was simple to use but -

It was extremely tough on the vehicles with high maintenance costs and
effort;
The single strand wire broke very readily;
It was hard to get a good launch for heavier gliders;
The knots had to be cut out and re-made every morning before flying;
There was a significant dip in the launch just after rotation as the
truck gearbox changed gear.

We averaged 1,000 to 1,500 ft launches but did get to much higher on
occasion. (1 Mile Runway). We replaced the system with a Skylaunch
winch using stranded steel wire. This is much more repeatable and gets
launches between 1,400 and 1,800 feet with a much greater availability.

We fly gliders ranging from K8s to Duo Discus's and get good launches
with lots of good cross countries. We do have a tug on site which gets
used a fair amount but most people winch. One of our full cats managed
to get 30 mins with a T31 on Friday so it can't be that bad and he only
came down thinking that the owner (me) wanted it back.

Seriously, winching works well if you have a ridge within a straight
glide and if you have reasonable thermal sources around the airfield but
do get good instruction on it as it is easy to get into very bad habits
masked by the power of modern winches which will then bite you.

Hope this helps

Robin
>Chris N.
>
>
>
>
>
>
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--
Robin Birch

[Martin Gregorie]

On Sat, 03 Sep 2005 23:40:08 +0100, Robin Birch wrote:

> We averaged 1,000 to 1,500 ft launches but did get to much higher on
> occasion. (1 Mile Runway). We replaced the system with a Skylaunch winch
> using stranded steel wire. This is much more repeatable and gets launches
> between 1,400 and 1,800 feet with a much greater availability.
>
I was once winched in an SF-25 there. It was pretty calm
but we still made 1300 ft. The ride up was quite odd: climbing out
steeply with a stationary three-blader in front. We glided around for
400 feet before hitting the starter and flying back to Nympsfield.

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

[Don Johnstone]

At 09:36 03 September 2005, Ian Johnston wrote: (snip)
>Personally, I think it's time we stopped messing about
>with spring
>loaded cutters and went to explosive ones, but that's
>incidental here!
>
>Ian

Er.......you are kidding, right?