Auto Tow Information

Does anyone know of a good publication or web site that discusses the
specifics of auto tow launches. In particular, what type of tow vehicles
are appropriate and what release altitudes are possible for various length
runways, etc.....

Thanks,
--
Mike Schumann

http://www.soarcsa.org/thinking_page...ng/default.htm

Couple of items here. John Campbell's notes and Reverse Pulley

Frank Whiteley

Mike:
We've been doing quite a lot of research on the subject as an
inexpensive alternative to aerotowing. Everything I have read
recommends using a pickup truck like a Ford F-150 or equivilent. One
of the best sites we've found to date is
http://www.danlj.org/~danlj/Soaring/GroundLaunch/ also get the book
"Ground Launches" by Derek Piggott. According to what I've read if all
goes right you can expect 70 to 80% of the tow rope length in altitude.
We will be using a 6000ft grass runway with a 2000ft rope. So we are
hoping to get at least a 1400' launch once we get it worked out. Where
are you located? If you would like to contact me direct I can be
reached at (remove both of the * to email) email
me for my phone number if you wish.

Larry Lively, Del Rio, Texas

We found it better to use F250 than F150 - larger, more powerful, engine
and transmission give better acceleration, and we figured more likely to
be reliable if big engine not working too hard rather than small and
going at max output. The last ones we had, in 1988, were fine until we
had to stop autotow for other reasons. We went for "Super engine
cooling" which incorporates an extra oil cooler for the transmission -
launching involves high power at low road speed, and the transmission
oil needs all the help it can get.

The F250 spec we used in 1988 was:

F250 HD 4x2/133 w/base;

Omit radio;

Regular Cab Custom 7.5L V8;

Autotrans;

Super engine cooling;

Rr step bumper;

Spare wheel/tyre/carrier;

LPG conversion.

With a 4x2, it is important to have the tow hook at the back of the cab,
not at the back of the vehicle, so that the cable force does not lift
weight off the rear (driving) wheels. It is easier to get good tyre grip
with reverse pulley launching, where the cable pull is always horizontal
anyway.

You need a Tost or similar release to hook the cable on, to allow rapid
release in emergency.

A window in the roof is advisable.

There is a lot to take into account for reverse pulley launching.
Straight autotow is easier to equip and start operating. Even with that,
you need to follow others' lead in the cable/drogue/weak link/strop set
up and hardware, to avoid reinventing it by trial and error.

Chris N. (Essex, UK)

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At Enstone using parafil, we dispensed with a drogue chute for straight
autotow, to eliminate crosswind drift. XJ6 Jag with Tost release. We
swapped ends each launch to speed up launch rate. 60mph each way,
1500agl from 500m length. L-13 lifted the back of the Jag a couple of
times, so nice to have ballast in the back seat. Four-wheel disk
brakes also helpful at end of tarmac.

Personally feel the Cots reverse pulley system was most elegant and
effective of auto launch systems I've seen in 30 years, including the
Essex GC system.

A lot is made of the room required for ground launching. However, I
know it is quite feasible to establish a ground launch soaring
operation in many areas of the US by leasing, rather than purchasing,
space. Dry pasture and dry agricultural land can be leased cheaper per
acre than my club pays in property taxes, considering our improvements
and the tax basis. In many states, the federal set aside allowance is
greater than beef farmers can pay for grazing (leading to an
interesting observation by ranchers that they are competing against
their own tax dollars for the price of pasture land). Furthermore, a
startup ground launch operation is going to encounter far fewer NIMBY
objections than aero-towing over the local area.

You may find it's possible to winch cheaper than burning up someone's
$40,000+ F250 though, and winching doesn't require as much improved
land.

Frank Whiteley

On the topic of tow vehicles for autotow; we operated an autotow only
operation for 10 years from 1970 - 80 just east of Dallas, TX. We used
approximately 6000ft of dirt road on the top of a low ridge (50ft
elevation). We had our best luck with 10 year old Plymouths ('63 -
'66) with the small V8. We got them used for $200 or so and used them
for a year to two. For us it did not make much sense to get anything
new since the rough road and 50mph speeds beat up suspensions in a
year or two, long before the engine was shot. I would be leery of a
pickup due to the low weight over the backend. At the top of a tow, it
was not unheard of to lift the rear end of our tow vehicle enough to
lose traction.

We used about 1600ft of polypropolyene rope and could get about 1400ft
on a CG hook, and about 800ft on a nose hook.

Good luck.

Bob



On 19 Aug 2005 03:57:04 -0700, "Rusty" wrote:

Mike:
We've been doing quite a lot of research on the subject as an
inexpensive alternative to aerotowing. Everything I have read
recommends using a pickup truck like a Ford F-150 or equivilent. One
of the best sites we've found to date is
http://www.danlj.org/~danlj/Soaring/GroundLaunch/ also get the book
"Ground Launches" by Derek Piggott. According to what I've read if all
goes right you can expect 70 to 80% of the tow rope length in altitude.
We will be using a 6000ft grass runway with a 2000ft rope. So we are
hoping to get at least a 1400' launch once we get it worked out. Where
are you located? If you would like to contact me direct I can be
reached at (remove both of the * to email) email
me for my phone number if you wish.

Larry Lively, Del Rio, Texas

Marc Ramsey wrote:
'It sounds like you are reading too much into the documents
in the Winch Design Group file section. In reality,
the practical design discussions have all been about
two drum winches, mounted on (and obtaining power from)
commonly available large pickups or small trucks with
250 to 300 HP turbo diesels. Discussion has slowed
for the past few months, as it is soaring season in
the northern hemisphere.

From a mechanical perspective, the main things that
are preventing a couple of groups from 'cutting metal'
this fall, are the lack of a source for inexpensive
and reliable split-shaft power takeoff units, and a
simple workable design for drum clutches. If you or
anyone else has any ideas, we'd love to hear them...

Marc'

No, Marc. most of my reading has been in the messages
section. And I guess I need to ask again, does a typical
US Operation really need multiple drums? And does
a typical US operation really need 250 to 300 HP turbo
diesels? If we want this much, it is available from
Europe right now. We are not buying them because the
initial cost is higher than the initial cost of most
towplanes. And some clubs look into renting their
towplanes (not those with Pawnees, most likely) for
additional income during the off season for trips by
members or others. Cannot do that with a winch!

For economical launching to take hold in the US, you
have to find a way to get the 'buy in' cost down.
Multiple drum setups and big, expensive engines just
do not accomplish this. Bad information about ground
launch safety and high 'buy in' costs are what is keeping
it out of the US.

If you have the space to do straight auto towing, look
in your local paper in the 'Used cars under $600' section.
Find one that is really cheap because they don't have
the title. Drive it until it drops, then get $25 or
$50 from the local salvage yard when you haul it in.
You might be surprised at how long it will last.
Or, if it just refuses to die, enter it in a local
demolishion derby and go buy another!

Fly Safe and Have Fun!

Steve

Steve Leonard wrote:
No, Marc. most of my reading has been in the messages
section. And I guess I need to ask again, does a typical
US Operation really need multiple drums?

Single drum winches have a long launch cycle time, two drums help. That
said, two drums do add more mechanical complexity than I (and others)
expected.

And does
a typical US operation really need 250 to 300 HP turbo
diesels?

Many in the group fly in the western US, where summer density altitudes
range up to 10,000 feet. Yes, the numbers I've run indicate that we
need at least a 250 HP turbo diesel (not so much for the HP as the
torque) to be able to launch something as mundane as a Grob 103 with two
aboard.

If we want this much, it is available from
Europe right now. We are not buying them because the
initial cost is higher than the initial cost of most
towplanes.

Agreed, the point behind the group is to try to substantially reduce the
initial cost (over buying new $75,000+ dual drum winches from Europe),
by building on a reasonably priced used vehicle readily available here
in the US (i.e., heavy duty pickups and light trucks).

If you have the space to do straight auto towing, look
in your local paper in the 'Used cars under $600' section.

Auto tow has its places (but not that many here in the land of high
priced real estate), but so does winch launching. What we desperately
need is alternatives to aero tow, which if it continues to be the
default launch solution, will kill the sport in the US due to
fuel/maintenance costs and noise.

Marc

Single drum turn around time is similar to autotow. If you retrieve
your rope at 15mph, it will take 5+minutes to get the rope back to the
launch point on a 6000ft run and another minute to get the tow car back
to the other end. Then the launch take up and launch you are talking
10 minute cycles or 6 launches per hour. If you're flying one Blanik,
or 5-6 gliders in a small club, this is fine. With parafil, we ran 4-6
minute cycle times. Similar to our single drum winch cycles with a
good retrieve driver and launch crew. Cotswold GC with the reverse
pulley managed 3-minute launch rates, but that was a club with about 70
gliders and 200 members. They also had a second RP rig and a tow plane
(used for those elusive wave days). Now a winch is their primary
launch method. Essex GC at one time claimed 90 sec launch intervals
with two vehicles on an RP system, but that was not the standard rate.
It was a somewhat shorter run the Cotswold.

Unless some care is taken with the installation of a Schweizer release,
it is possible to get it into a position where it can't release at the
tow vehicle, just like in the tow planes. We happened to have a TOST.
We knew it would work if fired in anger. The Cotswold RP release is a
homebuilt type. It's not an expensive system, but does require someone
with machine skills to construct and maintain it. The real plus is
that the large diameter 'pulley wheel' doesn't store any substantial
energy, unlike some other designs with large wheels. Similarly, it
doesn't 'steal' any power to get the launch up and running. Like
autotow, it's best suited for 5000-6000ft run, to allow about 1000ft
for landback and staging and high performance. You do need a clear
safety zone at the pulley end also, in the event of a wire break.

There are plenty of Yank tanks out there that could allow a small club
with a rope to do plenty of flying on a budget with a small learning
curve. So if you're a group of ten with a Blanik and bridle hooks,
that's a way forward. But it has it's limitations built in and a club
can outgrow it's capacity pretty quickly. I found the linked article
about autotow provided earlier in this thread a bit one dimensional and
containing some assertions based on ignorance and second hand
information about winch launching. An alternative is something like
http://www.permiansoaring.us, if you want to grow and make better use
of your available space.

But there is a lot of difference in what you can ramp up in the near
term and aim for in the future. Go for the solution that makes sense,
but plan for the next stage. BTW, we eventually took the engine and
transmission out of the XJ6 Jag and put it into an ex-ATC winch and
converted entirely to winch launching from the parallel turf runway.
Why? Because the new owners of the airfield started an ever increasing
pattern of annual rent increases for the paved runway. The club had
senior rights to the parallel turf run, so abandoned auto tow as an
economic imperative. FWIW, the winches gave higher launches over less
distance. We used less distance because light single's like K-8's,
K-6's, and Oly463's were more subject to adverse wing loading carrying
the weight of the steel wire rope if the length were too long and there
was also a practical limit to wire capacity of the winch drums.

Frank Whiteley

Any idea why it isn't done today?

Frank Whiteley