Wanting to start a new glider club

At 20:43 28 April 2018, Chris Rowland wrote:
I did most of my ab initio training and learning to be an instructor
o
autotow.

I'd suggest avoiding reverse pulley because it's difficult for both
the to
car driver and pilot to know when to finish the launch. With
straigh
autotow it's easy, stop sufficiently before the end of the runway
that yo
can drive forward and lay the cable out.

Another issue is cross winds. The cable will drift downwind and
looking a
Ronan on Google Earth there are fields with irrigation equipment
there. Th
farmers will take a dim view of the launch cable being dragged
throug
their irrigation kit.

Chris



Don't see what the problem is at all with reverse pulley - had many
launches that way - the other end of the runway is just as easily
visible to the tow car driver and as speed decays the glider pilot
pulls off - think you creating an issue where none exists.

If you have a straight reverse pulley system and set it up properly,
with removable strops t both ends the cable is waiting for the next
glider, the car drives back and connects to the other end of the cable
and your ready to launch again.

Some reverse pulley systems where just way over the top -KISS is
the answer. Doubt these guys will be doing hundreds of launches a
day.

Crosswinds are something every ground launching site has to
contend with and 1000's of sites around the world seem to manage
ok with proper training - seem to remember the advice was to have
at least 80m width of clear land to launch from.

On Sunday, April 29, 2018 at 3:30:06 AM UTC-6, Paul T wrote:
At 20:43 28 April 2018, Chris Rowland wrote:
I did most of my ab initio training and learning to be an instructor
o
autotow.

I'd suggest avoiding reverse pulley because it's difficult for both
the to
car driver and pilot to know when to finish the launch. With
straigh
autotow it's easy, stop sufficiently before the end of the runway
that yo
can drive forward and lay the cable out.

Another issue is cross winds. The cable will drift downwind and
looking a
Ronan on Google Earth there are fields with irrigation equipment
there. Th
farmers will take a dim view of the launch cable being dragged
throug
their irrigation kit.

Chris



Don't see what the problem is at all with reverse pulley - had many
launches that way - the other end of the runway is just as easily
visible to the tow car driver and as speed decays the glider pilot
pulls off - think you creating an issue where none exists.

If you have a straight reverse pulley system and set it up properly,
with removable strops t both ends the cable is waiting for the next
glider, the car drives back and connects to the other end of the cable
and your ready to launch again.

Some reverse pulley systems where just way over the top -KISS is
the answer. Doubt these guys will be doing hundreds of launches a
day.

Crosswinds are something every ground launching site has to
contend with and 1000's of sites around the world seem to manage
ok with proper training - seem to remember the advice was to have
at least 80m width of clear land to launch from.

http://coloradosoaring.org/thinking_...ey/default.htm

I've had a couple of chats with John Foster. There are raised runway lights. Reverse pulley allows a lot more control of the line than direct auto tow, so could be an option. Today, UHMWPE ropes, spectra, dyneema, or polyolefin drag line might work for reverse pulley, though I'm unaware of an operation doing so.

Frank Whiteley

On Sunday, April 29, 2018 at 4:22:59 PM UTC-6, Frank Whiteley wrote:
On Sunday, April 29, 2018 at 3:30:06 AM UTC-6, Paul T wrote:
At 20:43 28 April 2018, Chris Rowland wrote:
I did most of my ab initio training and learning to be an instructor
o
autotow.

I'd suggest avoiding reverse pulley because it's difficult for both
the to
car driver and pilot to know when to finish the launch. With
straigh
autotow it's easy, stop sufficiently before the end of the runway
that yo
can drive forward and lay the cable out.

Another issue is cross winds. The cable will drift downwind and
looking a
Ronan on Google Earth there are fields with irrigation equipment
there. Th
farmers will take a dim view of the launch cable being dragged
throug
their irrigation kit.

Chris



Don't see what the problem is at all with reverse pulley - had many
launches that way - the other end of the runway is just as easily
visible to the tow car driver and as speed decays the glider pilot
pulls off - think you creating an issue where none exists.

If you have a straight reverse pulley system and set it up properly,
with removable strops t both ends the cable is waiting for the next
glider, the car drives back and connects to the other end of the cable
and your ready to launch again.

Some reverse pulley systems where just way over the top -KISS is
the answer. Doubt these guys will be doing hundreds of launches a
day.

Crosswinds are something every ground launching site has to
contend with and 1000's of sites around the world seem to manage
ok with proper training - seem to remember the advice was to have
at least 80m width of clear land to launch from.

http://coloradosoaring.org/thinking_...ey/default.htm

I've had a couple of chats with John Foster. There are raised runway lights. Reverse pulley allows a lot more control of the line than direct auto tow, so could be an option. Today, UHMWPE ropes, spectra, dyneema, or polyolefin drag line might work for reverse pulley, though I'm unaware of an operation doing so.

Frank Whiteley

Sorry to dig up this old thread, but now that winter has set in, I'm starting to think and plan more on this project. Do you happen to know where one could get one of these "polyolefin drag lines"? I've looked around a bit, but haven't seen any links for such. I'm also considering various designs for the pulley system. The one that you have linked from the Cotswold GC in Great Britain looks like it would take some effort to build. I've wondered about conscripting an old motorcycle wheel for this purpose and welding up a frame with guides for it to attach to a tow hitch of a pick-up truck. Any proven designs out there like this?

On Friday, December 28, 2018 at 8:33:58 PM UTC-7, John Foster wrote:
On Sunday, April 29, 2018 at 4:22:59 PM UTC-6, Frank Whiteley wrote:
On Sunday, April 29, 2018 at 3:30:06 AM UTC-6, Paul T wrote:
At 20:43 28 April 2018, Chris Rowland wrote:
I did most of my ab initio training and learning to be an instructor
o
autotow.

I'd suggest avoiding reverse pulley because it's difficult for both
the to
car driver and pilot to know when to finish the launch. With
straigh
autotow it's easy, stop sufficiently before the end of the runway
that yo
can drive forward and lay the cable out.

Another issue is cross winds. The cable will drift downwind and
looking a
Ronan on Google Earth there are fields with irrigation equipment
there. Th
farmers will take a dim view of the launch cable being dragged
throug
their irrigation kit.

Chris



Don't see what the problem is at all with reverse pulley - had many
launches that way - the other end of the runway is just as easily
visible to the tow car driver and as speed decays the glider pilot
pulls off - think you creating an issue where none exists.

If you have a straight reverse pulley system and set it up properly,
with removable strops t both ends the cable is waiting for the next
glider, the car drives back and connects to the other end of the cable
and your ready to launch again.

Some reverse pulley systems where just way over the top -KISS is
the answer. Doubt these guys will be doing hundreds of launches a
day.

Crosswinds are something every ground launching site has to
contend with and 1000's of sites around the world seem to manage
ok with proper training - seem to remember the advice was to have
at least 80m width of clear land to launch from.

http://coloradosoaring.org/thinking_...ey/default.htm

I've had a couple of chats with John Foster. There are raised runway lights. Reverse pulley allows a lot more control of the line than direct auto tow, so could be an option. Today, UHMWPE ropes, spectra, dyneema, or polyolefin drag line might work for reverse pulley, though I'm unaware of an operation doing so.

Frank Whiteley

Sorry to dig up this old thread, but now that winter has set in, I'm starting to think and plan more on this project. Do you happen to know where one could get one of these "polyolefin drag lines"? I've looked around a bit, but haven't seen any links for such. I'm also considering various designs for the pulley system. The one that you have linked from the Cotswold GC in Great Britain looks like it would take some effort to build. I've wondered about conscripting an old motorcycle wheel for this purpose and welding up a frame with guides for it to attach to a tow hitch of a pick-up truck. Any proven designs out there like this?

The Essex GC one had a reverse pulley set up. However the rig had a lot of stored energy in the pulley wheels. So a wire break could involve quite a mess. I launched on this rig a few times. I think the Cotswold rig was better. In both iterations, solid wire needs considerably more safety area than other methods.

The Cotswold GC was 200 members and 70 gliders. They also owned tow planes, mostly for wave days.

Now, they did pack in the reverse-pulley for a winch. Not sure exactly why, but cost was not the first consideration.

Frank Whiteley

At 03:33 29 December 2018, John Foster wrote:

Sorry to dig up this old thread, but now that winter has set in, I'm
starti=
ng to think and plan more on this project. Do you happen to know where
one=
could get one of these "polyolefin drag lines"? I've looked around a
bit,=
but haven't seen any links for such. I'm also considering various
designs=
for the pulley system. The one that you have linked from the Cotswold
GC
=
in Great Britain looks like it would take some effort to build. I've
wonde=
red about conscripting an old motorcycle wheel for this purpose and
welding=
up a frame with guides for it to attach to a tow hitch of a pick-up
truck.=
Any proven designs out there like this?

Don't underestimate the loads involved - I doubt if a motorcycle wheel
could cope! The load on the rope from pulley to glider could be up to the

weak link strength and the same load will be in the rope from the pulley to

the towcar. This means that the pulley frame and the anchor point (or
anchor truck) has to withstand twice the weak link break load.

On Saturday, December 29, 2018 at 2:45:04 AM UTC-7, James Thomson wrote:
At 03:33 29 December 2018, John Foster wrote:

Sorry to dig up this old thread, but now that winter has set in, I'm
starti=
ng to think and plan more on this project. Do you happen to know where
one=
could get one of these "polyolefin drag lines"? I've looked around a
bit,=
but haven't seen any links for such. I'm also considering various
designs=
for the pulley system. The one that you have linked from the Cotswold
GC
=
in Great Britain looks like it would take some effort to build. I've
wonde=
red about conscripting an old motorcycle wheel for this purpose and
welding=
up a frame with guides for it to attach to a tow hitch of a pick-up
truck.=
Any proven designs out there like this?

Don't underestimate the loads involved - I doubt if a motorcycle wheel
could cope! The load on the rope from pulley to glider could be up to the

weak link strength and the same load will be in the rope from the pulley to

the towcar. This means that the pulley frame and the anchor point (or
anchor truck) has to withstand twice the weak link break load.

Yes. I expect this would be the case. Do you think a rig similar to the Cotswold design, but made from many roller blade wheel bearings would be able to withstand the forces involved? I would think the more bearings there were, the more the load would be spread out, but I'm not an engineer, so I don't know for sure.

I'm seriously looking at a reverse auto tow set-up to cut the costs down when starting up the club and am playing around with design concepts in my head. As far as rope goes, I am really impressed with Dyneema as a rope material, and from what I can gather, Samson Amsteel Blue Dyneema has a breaking strength of 1400 lbs for a rope only 7/64" diameter. That's about the thickness of a string! I can get a spool of it 3280 feet in length. Our runway is about 4,800, so we'd probably need to splice some additional length to be able to utilize the full length of the runway and maximize the height of the launch. Would need to use a weak link on each end though. For this application, would a single axle wheel like a motorcycle wheel rim work better for the pulley, or would something like the Cotswold design work better? The rope wouldn't have the extra mass that the piano wire did that they used in Cotswold.

On Sunday, December 30, 2018 at 10:02:46 PM UTC-7, John Foster wrote:
I'm seriously looking at a reverse auto tow set-up to cut the costs down when starting up the club and am playing around with design concepts in my head. As far as rope goes, I am really impressed with Dyneema as a rope material, and from what I can gather, Samson Amsteel Blue Dyneema has a breaking strength of 1400 lbs for a rope only 7/64" diameter. That's about the thickness of a string! I can get a spool of it 3280 feet in length. Our runway is about 4,800, so we'd probably need to splice some additional length to be able to utilize the full length of the runway and maximize the height of the launch. Would need to use a weak link on each end though. For this application, would a single axle wheel like a motorcycle wheel rim work better for the pulley, or would something like the Cotswold design work better? The rope wouldn't have the extra mass that the piano wire did that they used in Cotswold.

1/8" for 2400lbs. Not sure is the small diameters are easily spliced buy I have a spool of 1/8", so well let you know.

You might get away with a 14" wheel. I wouldn't bother with a motorcycle wheel.

Have to grok on this a bit.

Frank Whiteley
Been there, done that

On Sunday, December 30, 2018 at 11:02:46 PM UTC-6, John Foster wrote:
I'm seriously looking at a reverse auto tow set-up to cut the costs down when starting up the club and am playing around with design concepts in my head. As far as rope goes, I am really impressed with Dyneema as a rope material, and from what I can gather, Samson Amsteel Blue Dyneema has a breaking strength of 1400 lbs for a rope only 7/64" diameter. That's about the thickness of a string! I can get a spool of it 3280 feet in length. Our runway is about 4,800, so we'd probably need to splice some additional length to be able to utilize the full length of the runway and maximize the height of the launch. Would need to use a weak link on each end though. For this application, would a single axle wheel like a motorcycle wheel rim work better for the pulley, or would something like the Cotswold design work better? The rope wouldn't have the extra mass that the piano wire did that they used in Cotswold.

Forget the "reverse auto tow" and you don't need Dyneema to start (although it has definite advantages). My club, Southern Eagles (aka Sufferin' Eagles) started with 4000 feet of dacron rope and a truck wheel mounted on a steel bar the went into a hitch receiver on the back of a very old Ford LTD with an automatic trans. One end of the rope goes to an anchor (another vehicle or big metal stake in the ground). The rope goes over the pulley and to the glider. The car pulls from the middle of the rope, thus giving a 2:1 mechanical advantage. We would just put the old LTD in low gear and leave it there. Launching a 2 seater, the car would get up to maybe 28 miles per hour at most, then slow down from there. We were usually going about 18 mph when the glider was at the top of the launch. We got hundreds of launches off that dacron and that was on asphalt pavement. I think this is the best autolaunch system. The car is going slow so it's easily controllable and you can do this on less than smooth surfaces. Acceleration at the glider end of the rope is very fast, pretty much just like a winch. Simple, simple, simple. We sometimes got our single seat gliders to 2000 agl with a bit of headwind. Email me at if you want details.

John, you should oversize the launch line, so as it wears from abrasion and uv it won't become the weak link in the system.

RR