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Auto-Towing - why is this not more popular?



 
 
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  #11  
Old October 5th 15, 01:40 PM posted to rec.aviation.soaring
Papa3[_2_]
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Default Auto-Towing - why is this not more popular?

On Monday, October 5, 2015 at 8:30:06 AM UTC-4, Tango Eight wrote:

When I was a student pilot, we did 2-33 "cat shots" off Harris Hill with two old tow ropes spliced together, later with a proper 400' cable, into gentle late afternoon ridge lift, all powered by an old 307 Chevelle with questionable brakes (thanks Dave!). A total gas, never to be forgotten. Driving the car (which I did a lot) was even more exciting than flying the glider. The brow of the hill slopes off in a fashion that makes the nerves a little uneasy... especially with those rusty four wheel drum brakes.

-Evan Ludeman / T8


That reminded me. The far end of our runway had a steep dropoff into a corn field. On one tow, as I eased off the gas and got on the brakes... there weren't any. Or not much. Went all Dukes of Hazard and luckily landed safely on the downslope, ending up with the hood in the corn. Funny now, but actually a pretty dicey situation. So driver/observer safety in the tow vehicle is definitely another consideration depending on the field conditions/configuration.


  #12  
Old October 5th 15, 03:11 PM posted to rec.aviation.soaring
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Default Auto-Towing - why is this not more popular?

On Monday, October 5, 2015 at 7:40:06 AM UTC-5, Papa3 wrote:
On Monday, October 5, 2015 at 8:30:06 AM UTC-4, Tango Eight wrote:

When I was a student pilot, we did 2-33 "cat shots" off Harris Hill with two old tow ropes spliced together, later with a proper 400' cable, into gentle late afternoon ridge lift, all powered by an old 307 Chevelle with questionable brakes (thanks Dave!). A total gas, never to be forgotten. Driving the car (which I did a lot) was even more exciting than flying the glider. The brow of the hill slopes off in a fashion that makes the nerves a little uneasy... especially with those rusty four wheel drum brakes.

-Evan Ludeman / T8


That reminded me. The far end of our runway had a steep dropoff into a corn field. On one tow, as I eased off the gas and got on the brakes... there weren't any. Or not much. Went all Dukes of Hazard and luckily landed safely on the downslope, ending up with the hood in the corn. Funny now, but actually a pretty dicey situation. So driver/observer safety in the tow vehicle is definitely another consideration depending on the field conditions/configuration.


All the winches I flew on in Europe had guillotines to cut the cable in an emergency (mandated in Germany). How do you do that with cars? I witnessed a near fatal accident with hanglider being towed by a car where the pilot flew a neat arc that ended with an impact. When I asked the person on the bed of the towing pickup how he had planned to sever the rope in such an event, he showed me his pocket knife!
  #13  
Old October 5th 15, 03:22 PM posted to rec.aviation.soaring
Steve Leonard[_2_]
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Default Auto-Towing - why is this not more popular?

We do some auto towing at Sunflower in Kansas. Ex Military base, 7000 foot long runway. Surface is roughly the equivalent of The Great Barrier Reef as far as the rope is concerned. The majority of the wear seems to happen when dragging the rope back after the launch, as it does not take too long for all 2000 or so feet to be off the ground. We have cracks in the pavement that has some grass growing up through them, so you can reduce the wear some by pulling the rope back with it in/on that grass. We do not put a chute on the rope, but just let it fall. The fun comes in turning the car around, and trying to be within 50 feet of the end of the rope when it hits the ground. Yep, I have done it. With a full size Chevy G-20 van!

Another option that has been used is a wind up winch on the tow vehicle. Once the vehicle is stopped, the crew goes to the back, operates the wind up winch (have seen both gas and electric version), then drive back, and lay out the rope again.

Pay Out winch probably works better for hang gliders than for our sailplanes, as the car has to go faster than the glider in order to pay out any line.. And in light winds, the glider may need the car to run 60 MPH or more for straight towing, so even faster for pay-out towing. Faster yet for higher elevations (Sunflower is 1500 feet MSL). Gary Boggs has used a pay-out system quite successfully, so it is not impossible to do. Just maybe not so good for the planes that need a bit more speed, unless operating from a drive lakebed.

Fixed pulley at the upwind end opens up lots of possibilities. Especially since the glider can no longer pick up the tow car! Bring on the Z06 Corvettes if you have got pavement! You wanted winch acceleration, now you have got it!

As to wear and tear on the vehicle and its drive train, do an auto tow with a vehicle with an auto transmission that also has a tachometer. Then, drive in the same gear (count shifts from start) at the same speed without the load of the glider. You will probably discover that the torque converter is not locked up when launching the glider (much higher RPM during the glider tow). So, you are generating a lot of extra heat in the transmission on each tow. Best bet for auto tow would be a big block with a manual transmission, and ability to start out in second gear, so you don't have to shift..

It is fun. Get a new car. Get the extended drive train warranty. When the tranny goes out, don't mention you have been launching gliders. :-)

Steve Leonard


  #14  
Old October 5th 15, 03:23 PM posted to rec.aviation.soaring
Papa3[_2_]
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Default Auto-Towing - why is this not more popular?

On Monday, October 5, 2015 at 10:11:57 AM UTC-4, wrote:


All the winches I flew on in Europe had guillotines to cut the cable in an emergency (mandated in Germany). How do you do that with cars? I witnessed a near fatal accident with hanglider being towed by a car where the pilot flew a neat arc that ended with an impact. When I asked the person on the bed of the towing pickup how he had planned to sever the rope in such an event, he showed me his pocket knife!


We had a very nice rig for that. The car end had Schweizer tow release mounted on a steel plate. The plate was hinged for freedom in the vertical axis. The plate and associated structure was mounted on a ball coupling that rode on the car's towball, allowing freedom in the horizontal axis. The rig had the usual Schweizer release rope (same as a towplane), so the back seat observer held the release rope in his hand and pulled it in an emergency. We also had a crash-ax mounted in back as an extra safety measure.
  #15  
Old October 5th 15, 03:28 PM posted to rec.aviation.soaring
Tango Eight
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Default Auto-Towing - why is this not more popular?

On Monday, October 5, 2015 at 10:11:57 AM UTC-4, wrote:
On Monday, October 5, 2015 at 7:40:06 AM UTC-5, Papa3 wrote:
On Monday, October 5, 2015 at 8:30:06 AM UTC-4, Tango Eight wrote:

When I was a student pilot, we did 2-33 "cat shots" off Harris Hill with two old tow ropes spliced together, later with a proper 400' cable, into gentle late afternoon ridge lift, all powered by an old 307 Chevelle with questionable brakes (thanks Dave!). A total gas, never to be forgotten. Driving the car (which I did a lot) was even more exciting than flying the glider. The brow of the hill slopes off in a fashion that makes the nerves a little uneasy... especially with those rusty four wheel drum brakes.

-Evan Ludeman / T8


That reminded me. The far end of our runway had a steep dropoff into a corn field. On one tow, as I eased off the gas and got on the brakes... there weren't any. Or not much. Went all Dukes of Hazard and luckily landed safely on the downslope, ending up with the hood in the corn. Funny now, but actually a pretty dicey situation. So driver/observer safety in the tow vehicle is definitely another consideration depending on the field conditions/configuration.


All the winches I flew on in Europe had guillotines to cut the cable in an emergency (mandated in Germany). How do you do that with cars?


We had a Schweizer tow hook mounted in place of a hitch ball.

-Evan
  #16  
Old October 5th 15, 03:42 PM posted to rec.aviation.soaring
Steve Leonard[_2_]
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Default Auto-Towing - why is this not more popular?

On Monday, October 5, 2015 at 9:11:57 AM UTC-5, wrote:

All the winches I flew on in Europe had guillotines to cut the cable in an emergency (mandated in Germany). How do you do that with cars? I witnessed a near fatal accident with hanglider being towed by a car where the pilot flew a neat arc that ended with an impact. When I asked the person on the bed of the towing pickup how he had planned to sever the rope in such an event, he showed me his pocket knife!


Yikes! Like the others, we have a Schweizer hitch on a swivel so it is always line up with the rope tension, and a cable or cord to operate it. On my setup, I also have a hydraulic cylinder between the car and the hitch, with a gauge up front so I can see line tension and use this to help set the right speed.

Steve Leonard

  #17  
Old October 5th 15, 03:51 PM posted to rec.aviation.soaring
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Default Auto-Towing - why is this not more popular?

On Sunday, October 4, 2015 at 10:57:33 PM UTC-6, Sean Fidler wrote:
I had an interesting conversation with a pal about auto-tow glider launching method recently. It seems academic really.

When cost is considered, auto-towing has to be far more affordable than even winching. Maybe $1.50 per tow, max? In aviation, the cost is always critical. Especially in gliding club environments. Aerotows are $30-50 per tow. Winches are extremely expensive to purchase, to maintain, and insure and require skilled operators.

Auto-tow procedure seems fairly simple. 1) Steady strong acceleration until the glider comes airborne, then 2) add 5mph and 3) hold that speed until you hear differently from the pilot. Of course, 4) stop at the end of the runway :-).

Why is auto-towing not a mainstream method of getting gliders airborne?

I saw auto-towing happen regularly at Hobbs this year (my first visit). It was quite graceful and almost exotic. To be honest, it looks even more fun than winching.

I am very interested in learning what you know, your thoughts and your opinions.

Sean
7T


Sean, I've done a lot of both auto tows and winch launches. The low cost of auto tow is illusionary because people tend to ignore the costs associated with the tow car. Auto towing is really, really hard on a car. Modern gliders need 60 - 65 knots to safely rotate into the climb phase so the tow car is doing full throttle 0 - 75 mph on every tow followed by maximum effort braking to stop. It's basically drag racing so maintenance and tire replacement become a huge cost. Auto tow operations typically use a noob's car - until the owner figures out the wear and tear his vehicle is subject to..

As other poster pointed out, it also takes a LOT of room. To get decent height you need a long rope which takes up a large chunk of runway before anything gets rolling. Then, you need the acceleration distance for the car before the glider can start the climb. Finally, the tow must end so as to leave enough distance for the tow car to stop before running off the end of the runway.

If unlimited space is available as on Mojave dry lakes, then auto tow sorta makes sense but with any runway less than 5500 feet long, winches will get you higher and cost you less money doing it.
  #18  
Old October 5th 15, 04:10 PM posted to rec.aviation.soaring
Dan Marotta
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Default Auto-Towing - why is this not more popular?

Not quite as exciting as winching since the power to weight ratio is
less but as effective if you have the room. Still, it's a heck of a lot
of fun! Definitely cheaper than a winch since somebody always has a
capable vehicle.

I've been on two ground launch safaris with my partner and our LS-6a.
We used his Jeep Grand Cherokee once and my Ford F-150 the other time.
We would take turns flying and driving (pulling the trailer) and every
flight was a straight out adventure. Everywhere we went we were well
received by airport management and never had problems with departing any
airport. Over 6-8 days we would fly a large circuit around the
southwest USA.

I'll be ground launching off of Roach Dry Lake south of Las Vegas, NV in
a couple of weeks during the LVVSA's twice annually ground launch
weekend. What a hoot!

Dan, 5J

On 10/4/2015 10:57 PM, Sean Fidler wrote:
I had an interesting conversation with a pal about auto-tow glider launching method recently. It seems academic really.

When cost is considered, auto-towing has to be far more affordable than even winching. Maybe $1.50 per tow, max? In aviation, the cost is always critical. Especially in gliding club environments. Aerotows are $30-50 per tow. Winches are extremely expensive to purchase, to maintain, and insure and require skilled operators.

Auto-tow procedure seems fairly simple. 1) Steady strong acceleration until the glider comes airborne, then 2) add 5mph and 3) hold that speed until you hear differently from the pilot. Of course, 4) stop at the end of the runway :-).

Why is auto-towing not a mainstream method of getting gliders airborne?

I saw auto-towing happen regularly at Hobbs this year (my first visit). It was quite graceful and almost exotic. To be honest, it looks even more fun than winching.

I am very interested in learning what you know, your thoughts and your opinions.

Sean
7T


--
Dan, 5J

  #19  
Old October 5th 15, 04:14 PM posted to rec.aviation.soaring
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Default Auto-Towing - why is this not more popular?

The Douglas County Composite Squadron (Minden) of CAP has one or two auto-tow clinics every year. We find them a good way to introduce ground launch operations to the CAP members, but also find them pretty labor intensive, hard on tow vehicle and rope, and more of a novelty than a good way to launch gliders.

By labor intensive, I mean we have at least three people in the tow vehicle (a 4WD pickup truck with auto transmission in tow mode so it doesn't try to shift into 4th gear). The three people are driver, person beside driver who communicates with glider and launch crew, and person in the back who can release the rope in an emergency or at the end of the run. Then we have a wing runner, a signal person beside the wing runner to communicate between the truck and the glider, and a driver for a retrieve vehicle that hooks onto the glider end of the rope to pull it back to the launch position. That's a lot of people, and we could ideally operate with one or two less, but in CAP we want to involve everyone.

We use a 2000' long rope on a 6000' long runway (we actually use a hard dirt area beside the runway because there are lights on the runway that would suffer if we tried to auto tow there). We generally get 900-1100' altitude on launch, depending on wind and the pilot's skill. We have a specially fabricated tow hook that fits into the truck's receiver hitch. It has a swivel so the hook is always aligned with the rope and a Tost release at the end.

Having the pilot drop the rope where it will fall over the tow area is essential for us, as we have obstacles to each side (runway lights to the north and a chain link fence to the south). I remember one retrieve when the pilot dropped the rope in such a place that the wind carried it over the chain link fence. That one lasted one and a half hours.

Despite the fact that most flights are 5-10 minutes long (we are, after all, practicing launch, not soaring) we generally don't get more than 15 launches out of an 8 hour day. I think the most we've ever gotten was 25 launches. That gives you an idea of how long staging, launching, retrieving and re-staging takes. Not as efficient as we might be, but we've been doing it for 3 years so we aren't neophytes at it.

Bottom line for me: it is a good way to introduce CAP members to a different method of launch, and it adds a lot of flights to the glider (CAP wants us to get 200 flights a year in order to keep the glider), but it has its own limitations and is not quite as easy as it might sound.

Fred

  #20  
Old October 5th 15, 04:16 PM posted to rec.aviation.soaring
Dan Marotta
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Default Auto-Towing - why is this not more popular?

I once flew for an ESPN video on flying (Secrets of Speed). One of the
launch methods used was an auto pulley tow wherein the pulley was
mounted to the receiver on the back of the car and the cable was staked
to the ground near mid field. The car drove in the takeoff direction
during the launch and, with the 2:1 advantage of the pulley, it was
every bit as exciting as a winch. The car drove at about 1/2 the speed
of the glider. We were using a 3,400' runway and I don't recall the
release height, though it was not as high as a winch with a full runway
length of cable.

On 10/5/2015 5:01 AM, GB wrote:
Good question. Seems to me reverse car tows(fixed pulley windward car drives toward the glider) would be the way to go. Has there been any sailplane work with car mounted pay out winches? Pay out winches are what the hangglider and paraglider community have mostly settled on using. Both of these solutions somewhat mitigate the space needed to auto tow.


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Dan, 5J

 




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