Auto-Towing - why is this not more popular?

On Wednesday, October 7, 2015 at 6:06:34 PM UTC-5, Dan Marotta wrote:
As promised, the following clip was copied from raw film shot for an
ESPN show, Secrets of Speed.* The ground launch begins around 30
seconds into the clip but I left the low pass just for fun.* This
shows what happens to the tow car when the glider (me in my LS-6a)
pull too aggressively at the top.



https://www.dropbox.com/s/k9a4v2wbg9...aunch.mp4?dl=0




On 10/6/2015 9:35 AM, Dan Marotta
wrote:




...

I have the raw footage on DVD.* Perhaps I can find a "free" video
editor program and pull out the car pulley sequence and upload to
google drive.* We'll see...



Dan




On 10/6/2015 9:21 AM, Dan Marotta
wrote:




Thanks, Bill.



I only did a couple of pulley tows for the filming of the ESPN
thing.* Some of the raw footage (not shown on TV) shows the rear
end of the car being lifted sufficiently that the driver lost
control of the car.* Fortunately the passenger/observer was
Emerson Fittipaldi and he reached across, took the wheel, and
straightened out the car.* When I released, it was quite a sight
seeing the rope literally slamming down on the runway.* I can
easily imagine the tangles this caused in the pulley system. =-O



Dan




On 10/5/2015 6:18 PM,
wrote:







Dan, a pulley tow launches a glider just fine - but then you need to reset for the next launch. Often, this means untangling the rope. Straight auto tow or winch launch rarely tangles the rope.

There are very few pulley tow operations in the world and cycle time is the usual reason why they gave up on pulleys and moved on to winch launch.


On Monday, October 5, 2015 at 9:16:28 AM UTC-6, Dan Marotta wrote:


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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Dan, 5J




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Dan, 5J




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Dan, 5J

Yep. That's why we had 400 pounds of bricks in the trunk of our autolaunch car.

Frank W. What kind of wire are people using and where to get it, Please. Just now learning about winch use.

On Thursday, October 8, 2015 at 1:27:33 PM UTC-6, Stephen Damon wrote:
Frank W. What kind of wire are people using and where to get it, Please. Just now learning about winch use.

WRT Reverse Pulley, wire was 13 gauge BS5216 'Shiney Bright" piano wire. 10 gauge was tried but the weight caused flats to wear more quickly on the 'memory' coils in the wire, so would break more often. No idea where to get in bulk. Not sure this would be insurable in the US. The Cotswold system was retired a few years ago. There was another system at Essex GC at North Weald also. Rather different design with high inertial pulleys.

Parafil is a sole-source product AFAIK. Google is your friend.

Winching in the US. We formerly used solid wire, then migrated to 3/16" 7/7 galvanized steel wire rope. Not insurable under the SSA Group Plan any longer. Now using Amsteel Blue. I have a vendor that has been pretty consistent with best pricing. However, it may be possible to secure Plasma 12 (virtually the same) for similar but I've never pushed a distributor for best price. UHMWPE ropes come in different flavors. The ropes mentioned are the higher performance brands. Dyneema 75 is the base fiber for Amsteel Blue. Spectra is the base product for Plasma12 There is a Yahoo group called winchdesign. Become a member.

Frank Whiteley

On Monday, October 5, 2015 at 1:27:24 PM UTC-4, Sean Fidler wrote:
Anyway...back to work.

Aaarrggg! Stuff like that gives us nightmares Sean...

One reason winch or auto tows are not more popular is that you are released over the airpark. In an aero tow you can be towed to the lift before releasing. Yes, I know usually on soft days there is a thermal just as one turns downwind to base, but that is not the best place to thermal.

One reason winch or auto tows are not more popular is that you are released
over the airpark. In an aero tow you can be towed to the lift before
releasing. Yes, I know usually on soft days there is a thermal just as one
turns downwind to base, but that is not the best place to thermal.

Hmmm...

I suspect this "truth" is more a statement of "the way aerotows normally are"
than "the realities of usable lift distribution." Reality as a self-fulfilling
prophecy, maybe?

In any event, BTDT insofar as brain-picking for "local knowledge" and
"locations of house thermals," but my experience throughout launch sites
(mostly aerotow) in the intermountain west (mostly Colorado and New Mexico)
has me concluding I can't think of one locale where it's *necessary* to "tow
over there" in order to find usable lift. Sure, some plains sites along the
east slope of the Colorado Rockies tend to start later than a tow into nearby
uplands, but my observation has been very few of the locals routinely take
advantage of that fact when time of launch is considered as a function of
release point. IOW, many tows "go to the hills" just because they can, and not
because it's necessary. Every single one of my launch sites has had convective
lift with easy reach of "above pattern height" releases, for ships of the
ubiquitous 2-33-35:1 performance range.

As for auto towing (exposed to that before winching, I was), popularity (or
lack thereof) has to do - so I reckon - with lack of familiarity; neither auto
towing or winching have been "popular" ("common" is probably a better
descriptor) in the U.S. because whatever critical mass may once have existed
disappeared when "cheap towplanes" became the norm after WW-II. Where they
exist(ed), my experience has been both were "hugely popular."

Bob W.

On Friday, October 9, 2015 at 10:05:15 AM UTC-6, Jonathan St. Cloud wrote:
One reason winch or auto tows are not more popular is that you are released over the airpark. In an aero tow you can be towed to the lift before releasing. Yes, I know usually on soft days there is a thermal just as one turns downwind to base, but that is not the best place to thermal.

If you can get 2000' - 2500' over the airport, there's no need for a distant tow. If you disagree, get a turbo.

If you can find a thermal, why aero tow? If you can't, there probably aren't any so why aero tow?

On Friday, October 9, 2015 at 5:59:49 PM UTC-5,
If you can get 2000' - 2500' over the airport, there's no need for a distant tow. If you disagree, get a turbo.

If you can find a thermal, why aero tow? If you can't, there probably aren't any so why aero tow?

Well, if your glider field is only 2400' long, with a highway at one end and a road at the other, you pretty much have to aero tow. We would love to have a winch at SLSA, but our field is just too short, and we have 2 nice Pawnees and a nice 180 Supercub, and our tows are cheap - so THAT is why we don't use a winch (trust me, we have looked at it and done the math...).

But for clubs that have access to a nice long airport, I agree that a modern winch is definitely the way to go!

Kirk
66

I don't think I've ever felt the rear ended get light on my truck. We've used Dodge Ram 2500, my 2007 5.7L Tundra, and a newer Toyota FJ with no reports of rear end lift.
BillT

When I started ground launching, I was told that the glider taking off
often kicks off a thermal is there was a bubble of warm air that the
glider passed through. Because of that, on my ground launch safaris, I
always made a U-turn after release and flew back down the runway. I got
away every time from about 700'. Maybe I was just lucky...

On 10/9/2015 4:30 PM, BobW wrote:
One reason winch or auto tows are not more popular is that you are
released
over the airpark. In an aero tow you can be towed to the lift before
releasing. Yes, I know usually on soft days there is a thermal just
as one
turns downwind to base, but that is not the best place to thermal.

Hmmm...

I suspect this "truth" is more a statement of "the way aerotows
normally are" than "the realities of usable lift distribution."
Reality as a self-fulfilling prophecy, maybe?

In any event, BTDT insofar as brain-picking for "local knowledge" and
"locations of house thermals," but my experience throughout launch
sites (mostly aerotow) in the intermountain west (mostly Colorado and
New Mexico) has me concluding I can't think of one locale where it's
*necessary* to "tow over there" in order to find usable lift. Sure,
some plains sites along the east slope of the Colorado Rockies tend to
start later than a tow into nearby uplands, but my observation has
been very few of the locals routinely take advantage of that fact when
time of launch is considered as a function of release point. IOW, many
tows "go to the hills" just because they can, and not because it's
necessary. Every single one of my launch sites has had convective lift
with easy reach of "above pattern height" releases, for ships of the
ubiquitous 2-33-35:1 performance range.

As for auto towing (exposed to that before winching, I was),
popularity (or lack thereof) has to do - so I reckon - with lack of
familiarity; neither auto towing or winching have been "popular"
("common" is probably a better descriptor) in the U.S. because
whatever critical mass may once have existed disappeared when "cheap
towplanes" became the norm after WW-II. Where they exist(ed), my
experience has been both were "hugely popular."

Bob W.

--
Dan, 5J