Kite Strings

I open this subject to know more about the kind and the placement of the drag device on the tow line.
no reserve (drogue chute) just a cloth spliced and stitched at 3/4 on the tow line, I understood ?
sometimes we can see nothing but the piece of bottle. it seems to be enough..

In US you use a braided Spectra (no stretch) line 2000lbs, not sheathed ? why ? What about mecanic abrasion with the ground ? Vectran seems more vulnerable with abrasion and Kevlar with the UV..

Thanks.

I can't tell you too much on this that you don't already know and I don't think there's too much to the subject anyway.

Yeah, low stretch beyond any other consideration. Maximum control and climb efficiency and no recoil when something breaks or is released.

Length is about 250 feet. Short and control is more critical and lockout more of an issue, long and you have more problems with the two planes being in different parcels of air and increase the chances of something sneaking in behind the tug so the glider doesn't get any warning of what's about to happen to him.

Ridgely uses 2000 pound unsheathed Spectra with a ring spliced to the front end and an aluminum carabiner spliced to the back with no drag device.

Takeoff and landing on the grass parallel to the paved runway with nothing problematic under the departure and approach paths.

The towlines get a lot of use, bake in the sun all season long, and I think they last forever or at least a very long time. I never noted any significant abrasion issues at the carabiner splice (where it would be most problematic), and I never heard of a towline failure - which isn't too surprising seeing as how the front end weak link never permitted more than 400 pounds.

Some operations use a funnel or bottle front end over the line in front of the tow ring and, at the cost of a little more drag on the climb, that will keep the towline higher behind the tug on approach and make life easier on the back end of the towline and carabiner and I've never heard of it created a problem with the bridle clearing at release. (I'm also guessing it would make the towline a lot easier to find if the glider got the towline and dropped it from up high - I think Ridgely lost a couple that way.)

NOBODY puts anything on the towline three quarters of the way back - as per those idiot 1985 regulations.

Maybe Zack can tell you something about issues with pavement at Columbus.

From the Peter Birren Show...

http://groups.yahoo.com/group/skysailingtowing/message/8136
Payout Line Strength?

Nate Wreyford (barw4) - 2012/04/24 02:07:30 UTC
Austin

Curious of opinions on using dyneema/spectra with 1000lbs tensile strength?

(Not interested in hearing about what is available from towmeup, etc)

Sunny Stutzman - 2012/04/24 13:42:24 UTC

What did we use in the days before Spectra, 3/16" Poly? I am trying to put together a boat tow on the cheap and I am considering all the ways to save a buck. (probably not worth it I know) I also didn't know if having something with a bit more stretch on rough waters might make things a bit more pleasant for the pilot.

Danny Hartowicz - 2012/04/24 14:06:38 UTC

I use 3/16 polypro for static towing for a smoother tow for the pilot, and so the driver doesn't have to be schitzofrenic at the wheel, but with payout, the spool just pays out faster and slower in lift and sink. From time to time we have used a polypro leader of two to five hundred feet for a cushion but I am not sure it is needed.

Polypro is a BAD CHOICE for payout because it squeezes the spool and can warp and even explode the sides by multiplying the inward force with every winding. Wrap your finger with a broken rubberband once, then five times then ten... "do you see"?

That thousand pound test spectra sounds great. Wonder what line costs these days? I stocked up five years ago!

Tad Eareckson - 2012/04/24 15:41:43 UTC

Hang Gliding - 1986/11

Rodney Nicholson
Ontario Hang Gliding Association

We have recently experienced three similar towing incidents which we feel should be brought to the attention of all who are involved in towing. You are urged not to tow until you are completely satisfied that your system can safely avoid a recurrence of the type of incident described.

As background information, the system being used involved a truck with payout winch, a center of mass bridle system and a weak link of between 150 and 200 pounds.

In the first incident, shortly after power was applied, the tow line snapped about twenty yards from the glider and the end of the tow rope whiplashed back and hit a spectator, who had been standing at the side of the glider, in the eye, inflicting a black eye.

In the second incident, shortly after launch, the weak link broke and the pilot was hit in the mouth by a metal ring in the end of the bridle. Injuries were minor.

In the third and most recent incident, the weak link broke shortly after launch and the end of the tow rope, with metal ring attached, whiplashed back and hit the spotter/winch operator in the eye. At present the chances appear ninety percent that he will lose the eye completely.

This matter is being given much thought. Could other towing groups please indicate how they handle it?

http://ozreport.com/forum/viewtopic.php?t=1143
Death at Tocumwal

Gregg Ludwig - 2006/01/22 18:15:15 UTC

I just can not understand why operators continue to use poly towlines (for aerotow ops) when spectra towlines are clearly superior. Poly is less expensive... but when considering the cost of a tow plane and HG and the advantages of spectra, a few dollars of savings is foolish.

Gregg Ludwig - 2006/01/23 16:32:52 UTC

Towline elasticity produces a rubber band effect that results in ever changing towline forces that can also produce significant airspeed changes as well. Since Spectra does not offer elasticity (or very little) this effect does not occur and a safer tow results. Trikes normally tow with longer lines of 200 to 250 feet so the advantages of Spectra are even greater.

Steve Seibel - 2006/01/23 20:34:34 UTC

Obviously one of the dangers of an elastic towline is that when it breaks, it can spring back and hit the pilot with much force--I've heard of a (nylon?) towline actually breaking its way through the canopy and into the cockpit of a sailplane after it broke under a heavy load.

Keep elastic materials - nylon, polypro - the hell out of ANYTHING - towlines, "leaders", bridles, releases, weak links - in the system that gets loaded by tow tension. All elasticity does is reduce your ability to control the tow and set you up for something really ugly WHEN your idiot three quarter to one G weak link blows to increase the safety of the towing operation.

P.S. If you have ANYTHING in ANY tow system - static, payout, aero - for ANY kind of aircraft - sailplane, hang glider, paraglider - for ANY level of pilot - Day 1, world aerobatics champ - that blows much under one and a half Gs, you are a MORON. PERIOD.

P.P.S. Anybody tells you anything different is a moron and must be avoided like the plague. (Of course that WOULD make this list an extraordinarily lonely place.)

P.P.P.S. You're also a moron if everything else in the system can't handle twice what the weakest thing can.

Sunny Stutzman - 2012/04/24 16:04:40 UTC

Good info. I have suffered a detached retina myself from monkeying around with a bungee and an old hang glider when I was a kid... I don't need to learn that lesson twice!

And at 2012/04/24 16:56:38 UTC Tad clicks to post:

Tad Eareckson - 2012/04/24 16:56:38 UTC

I have suffered a detached retina...

I hope they were able to put it back OK?

I know someone who wasn't able to have it put back and that was his good eye. He can still see but has a white cane for the street and is legally blind.

(And I took a boomerang in my right eye over 34 years ago and that pupil is permanently dilated. Not much fun.)

The guy for whom the chances of losing the eye completely appeared ninety percent actually ended up with one hundred percent chances. In case anybody missed it that was Mike Robertson and he's got glass where it used to be.

Good info.

WHY is this good info? Who qualified you? And this is a goddam towing discussion group ferchrisake. Why is this not universal Day 1 towing basics as fundamental as pointy end forward?

Why did that hafta happen to Mike in the first place and why were we apparently able to learn zilch even then?

Mike was boat towing a guy whose weak link started out about a third or a quarter of what was needed to do the goddam job and it kept blowing (big surprise) so he kept upping it in hopes that he'd be able to actually get properly airborne. And when it blew with a polypro towline (somebody correct me if I'm wrong) under the tension required to get the glider up the tow system was instantly converted into a medieval weapon.

Combination of elastic materials and this idiot strategy of hang and para gliding culture to use the weak link - which is a structural overload protector - as a lockout and stall protector by dumbing it down to the point at which you're lucky to get five gliders in a row aloft in moderate conditions.

And what did we start doing differently?

I don't need to learn that lesson twice!

But the culture needs to learn thousands upon thousands of time over and NEVER DOES.

Manned Kiting
The Basic Handbook of Tow Launched Hang Gliding
Daniel F. Poynter
1974

"The greatest dangers are a rope break or a premature release." - Richard Johnson
"A bad flyer won't hurt a pin man but a bad pin man can kill a flyer." - Bill Bennett
"Never take your hands off the bar." - Tom Peghiny

How did we EVER manage to get this far away from the fundamentals and keep drifting backwards?

BUT... Tad has a special little Peter Show asterisk just for him.

* Your message must be approved by the group owner before being sent to the group.

And that post doesn't appear.

http://www.ushawks.org/forum/viewtopic.php?f=2&t=607
Understanding Tow Releases

Peter Birren - 2011/09/18 22:27:52 UTC

Uh, sorry Tad. "TadErcksn@aol.com" is still a member of the Towing List. I did bounce Warren and one other guy but not you. Guess it must be easy to think you're ridiculing someone else when you do it to yourself so easily.

So listen, motherfucker... Neither some halfwitted bottom dweller like you nor any other motherfucker is qualified to APPROVE *ANYTHING* I have to say on these issues. So I'm gonna post over here and you're gonna pay a little more price for this.

Dan Hartowicz - 2012/04/24 17:44:38 UTC

I have aerotowed with spectra and other NON stretch line. I and many others believe in aero, and in static, some stretch is not only a good thing but safer for the pilot.

We can't do this on what you and many others BELIEVE, Dan. We've gotta understand the theory and physics and look at what the data is telling us.

In my 35 years of flying, mostly towing, I have seen or at least heard of most all incidents.

But you weren't the one to tune Sunny into any relevant ones.

If a CHAIN breaks, IT snaps back.

Yep. Steel is elastic. That's why they used it to build the twin towers and that's why they were able to unload wind forces and deal with the initial impact of suicide attackers.

I don't think a chain has much stretch to it.

It doesn't. But you're not gonna reduce the snap-back by INCREASING the elasticity - are you?

Perlon also snaps back.

Also? It's pretty much second only to bungee in elasticity. It's DESIGNED to reduce the shock of a fall in climbing.

We have noticed less whip back with heavy perlon, but it is bulky.

Yeah. A thick rubber band is harder to stretch out than a skinny one.

I have had good luck with spectra...

This game isn't about LUCK.

...but I had a friend that used it and it spun into knots behind the release when ultraline was put under more tension during tow, he ended up flying the glider down with it upside down and backwards steering it with the kingpost in his hand.

- That makes no sense whatsoever. Can you walk us through things a little better?
- So what are you suggesting we do to avoid a recurrence?

Yes, a non stretch bridle is a great idea, and eliminating as much as you can if not ALL hardware in front of the pilot and at the end of a towrope being reeled in at 30 mph is best. I noticed the lighter the hardware, the less momentum it has to cause damage.

Yeah. Sir Isaac noticed that phenomenon as well.

There are many different systems in operation, and there are many things I can point out as dangerous that go on unchanged because of difference of opinion.

Which is why anyone in these sports with an OPINION needs to have his entrails pulled out and burned in front of his face while he's still alive and conscious.

Maybe we can discuss them one at a time...

Who's WE? Peter has already eliminated the one guy most qualified for the discussion from the discussion.

http://groups.yahoo.com/group/skysailingtowing/message/8143
Payout Line Strength?

Dan Hartowicz - 2012/04/24 17:47:42 UTC

Another thing I did was attached a golf ball whiffle ball to the release line at the release (on payout bridle). It dampens any momentum if the weak link breaks.

- Is it worth having a whiffle ball in the airflow on every tow to effect a minor mitigation of a minor recoil after an event which should NEVER HAPPEN?

- How hard are you getting hit? With and without the whiffle ball?

- How OFTEN are you getting hit?

- Did you hear what I said about one and a half G weak links and people who use them a fraction of the strength they need to be?

- What are you using for bridle material? If it's low stretch there shouldn't be any recoil.

Miller Stroud - 2012/04/24 18:07:28 UTC

Danny Hartowicz - 2012/04/24 14:06:38 UTC

Polypro is a BAD CHOICE for payout because it squeezes the spool.

Forget the spool. Polypro is a BAD CHOICE for any kind of towing.

The secret to mataining a level of safety with any tow system is being able to control line tension. You can not do this with polypro. If you're breaking weaklinks, then slow down, reduce tension, or use a stronger weaklink.

If you're breaking weak links, triple the strength - PERIOD.

If your line is breaking, it's either rotten, damaged, a bad choice, or you don't know what your doing.

Or all of the above.

Also, how many times does hardware have to hit you in the face before you realize that maybe, just maybe you should move the weaklink to between you and the bridle instead of between the bridal and the line???????

IF YOU'RE BREAKING WEAK LINKS HOW LONG SHOULD IT TAKE FOR YOU TO REALIZE THAT THEY THEY'RE A THIRD THE STRENGTH THEY NEED TO BE?

Dan Hartowicz - 2012/04/24 18:24:58 UTC

Miller, if you have ever drivin a truck while static towing you know it is near impossible to keep a steady pressure in midday thermal conditions.

WAY more so with with aerotowing. What's your point?

This makes non stretch line dangerous for static.

Yeah? 'Cause you ASSUME that:
- keeping a steady PRESSURE has same measurable bearing on the safety of the tow; and/or
- that using polypro will HELP you in maintaining steady PRESSURE?

I have towed with poly, ultra, spectra, dacron, kevlar, and cable.

And lotsa people have towed with Wallaby, Quest, Lookout, and Bailey Releases and 130 pound Greenspot standard aerotow weak links. So what's your point?

Why payout pilots always assume what is best for their system is best for all. It makes static towing safer, not more dangerous!

Bullshit. Where's your data on that?

http://groups.yahoo.com/group/skysailingtowing/message/8147
Payout Line Strength?

Miller Stroud - 2012/04/24 18:54:23 UTC

My thoughts have always been that static towing in general is an out of date method for the exact reasons you stated, one cannot control the pressures consistantly with anything other than perfectly smooth conditions...

And this differs from aerotowing how?

With the introduction of payout winches I put static towing right there with an old 18 foot standard hang glider, assuming of course anything over a hundred feet of altitude is your goal. Stretch may make it safer but I won't go as far as to say it makes it safe enough!

No. It makes it more dangerous. PERIOD.

Once your "stretch is stretched", you're back to nothing again, not to mention the projectile mode with a line break.

- And what happens with all that stored energy if - by some miracle - your weak link DOESN'T break?
- So why are you saying that "stretch may make it safer"?

Just my thoughts of what is acceptable for myself.

Fuck that. Physics doesn't give a rat's ass about personalities.

Answer me this. If you had your choice, would you rather static tow or payout winch tow? If you answer payout winch, then your compromizing yourself based upon what equipment is available. I'm not attacking anyone, just expressing some of my life's observations.

Yeah, we've had quite a few deaths to lend credence to that observation.

Dan Hartowicz - 2012/04/24 19:11:42 UTC

OOOOH, ouch! Insults, static towing is like rogollo standard technology! C'mon! It sounds like you have not static towed much. I have thousands of safe tows, many hundreds of them being tandem. Anywhere from 0-30 mph headwinds, 0-90 degree of cross winds. 7/10ths of a mile roads to 4 mile roads. Mostly 2000 feet of altitude and some 4000 feet plus.

- Not crashing over the course of thousands of tows is not great evidence that they're SAFE.
- We're not concerned about road lengths or altitudes much over two hundred feet.

I, at no time on a static line am 5-50 feet over the car I am attached too.

That's wonderful. Now tell us about all the carnage that's resulted from payout gliders being five to fifty feet over the car you're attached to.

P.S. You're not ATTACHED to the car on payout. You're attached to a line coming off of a constant tension winch. If you wanna be attached to a car - try static towing.

People ask me "What is the safest method of flying a hang glider" (Pay out, static tow, aero tow, ridge soaring in higher winds, mountain launchs, boat towing)?

How 'bout we run this one by Zack?

Zack C - 2011/03/04 05:29:28 UTC

I now feel platform launching is the safest way to get a hang glider into the air (in the widest range of conditions). You get away from the ground very quickly and don't launch until you have plenty of airspeed and excellent control.

I tell them what I have witnessed to be fact.

Bullshit. These issues aren't determined by watching whatever happens to be in front of one and making statements.

Whatever they are most experienced with.

Yeah? I'd hazard a guess at this point that people are WAY more likely to get mangled and killed on the flavor of towing with which they're most experienced than on something else. And that includes owners and staff of aerotow operations and they were probably a lot more experienced with aero than platform.

You show me ANY type of flying and I will shoot holes in it on how many things can go wrong.

How much effort have you made to plug any holes or even adopt the plugs that other people have provided? Just kidding.

I flew my static system next to seven payout tow teams in Arizona years ago, I got higher, faster, and my vehicle was back at launch reeled in in less time. I fly both ways, but I like that I can safely look around more on a 2000-3000 foot static line with less possibility of occilation than on a payout system. Each system has its good and bad points. I usually prefer static.

Fine. But cite some incidents - or even some reasonable scenarios - resulting from people launching on payout.

I never stated that you cannot control pressure with static in unstable air. I said it is easier with at least SOME polypro, or a line with some give to it.

You're getting a smoother feel - but your control of the tension (and thus glider) sucks.

Otherwise if you tow into a thermal you have to get a car doing 30 mph to stop its 4000-5000 pounds down to 10 mph in one second.

WHY? OR WHAT?
- So you don't blow your idiot fucking weak link?
- Why can't you just let the glider climb like in aerotow?
- If the tension needs to be dumped in a second why can't the pilot do it?

That is where the payout system shines.

The payout shines at liftoff and initial climbout.

Each system demands a different criteria in training a driver.

Why?

http://www.chgpa.org/forums/viewtopic.php?f=2&t=2467
weak links

Jim Rooney - 2007/08/01 13:47:23 UTC

Whatever's going on back there, I can fix it by giving you the rope.

Doesn't sound all that complicated to me.

All our pilots, 30-50, learned how to drive, and only on the most thermic turbulent days did they say it was difficult. I am sure you could learn and do it safely and change your opinion.

http://groups.yahoo.com/group/skysailingtowing/message/8149
Payout Line Strength?

Dan Hartowicz - 2012/04/24 19:14:36 UTC

Oh, I forgot to mention, we have two systems built into our trucks to aid us in keeping a steady line tension when lift and sink are abound. A BRAKE and a GAS PEDAL!

That's one more control than a Dragonfly has.

http://www.chgpa.org/forums/viewtopic.php?f=2&t=2467
weak links

Jim Rooney - 2007/08/01

Whatever's going on back there, I can fix it by giving you the rope.

It's more of this crappy argument that being on tow is somehow safer than being off tow.

Unless you count the lever on the joystick the asshole up front is always poised to use to make a good decision in the interest of your safety.

Miller Stroud - 2012/04/24 19:37:53 UTC

You are correct. I have not static towed much. In fact it's been over twenty years. I guess my relm of thinking has been the payout system is more forgiving of human tow operators. I think about pulling in a big bass on six pound line. I'm glad I have a drag on the reel.

Maybe if you used a fishing line rating one and a half times the weight of the bass instead of half it would be a whole lot easier to lift the bass from the surface.

Tad,

What are your thoughts on static line towing? Is your only issue with it the launch method? If you launch with a dolly, do you consider it any more dangerous than aerotowing? Does the payout winch's ability to automatically keep a constant tension have a significant impact on the safety of the tow? You once said

Tad Eareckson wrote:...it's about a hundred time easier to have a serious lockout "accident" on static than payout.

Why is that?

Zack

- Launch it off a dolly if the terrain permits.

- The launch is mostly safer than aero (which is a flavor of static) because you can slow the vehicle down to whatever you want.

- But there's a bit of an offset because you can't maneuver left or right to help the glider out.

Does the payout winch's ability to automatically keep a constant tension have a significant impact on the safety of the tow?

- Talk to Bill Bryden about Debbie Young - 1999/12/11. It's by no means a given that she'd have been fine on payout but it pisses me off and makes me a bit suspicious that Bill never even gets around to broaching the issue. And let's note that static towing of hang (but not para) gliders is illegal in the UK.

- But if you have people at both ends who know what they're doing I don't have a problem with it.

- And if you don't have aero available and static is gonna get you higher than payout in your circumstances and conditions, hell, go for it.

http://groups.yahoo.com/group/skysailingtowing/message/8151
Payout Line Strength?

Jim Gaar - 2012/04/26 05:15:46 UTC

We have been towing for 25+ years (both AT and PL) with 3/16 and 3/8 poly.

Well, if you've been doing something one way for that long that OBVIOUSLY means you're doing it RIGHT!

The correct combination of tow operator and tow pilot procedure all aid in the tow. We found the stretch ploy provides (especially on AT) is a built in safety device.

How did you find that out? Did you kill fewer people per month using ploy than you did using Spectra?

Doesn't mean it can't be used in an unsafe manner!

WHOA!!! Lemme write that down so I don't forget.

The stretch diminishes after the first few tows. One needs to be aware if they are on a new line.

So the more the stretch diminishes the more the safety increases. I better write that one down too.

Our PL systems control "line tension" with breaking pressure on the drum. We never measure actual line tension. We use appropriate weak links.

OF COURSE YOU DO!

Wills Wing

Always use an appropriate weak link with a finished length of 1.5 inches or less.

EXACTLY like Wills Wing says. Hard to go wrong when you just read the fuckin' manual.

http://www.hanggliding.org/viewtopic.php?t=13689
eating dirt

Jim Gaar - 2009/09/18 19:23:44 UTC

Hell I've literally shoved the control frame out in front of me to avoid a whack when it got a little ahead of me in a light DW landing, similar to when I've had to slide it in on my belly (did that once after a weaklink brake coming off a launch cart.

1.5 inches or less, right?

I've never in all these years heard of a drum, using the ATOL type system getting crushed (I'm sure it's possible).

I would think that for PL a combo of mostly spectra (whatever) with the poly would be a great way to reduce weight and give a little, even if Miller gets a little kweezy thinkin about it!

Idiot.

Dan Hartowicz - 2012/04/26 05:36:04 UTC

Thanks, Jim!

Yes, where would we be without Jim - and all the other shitheads Peter cultivates on his forum?

A thick layered winding of Poly has a higher tendancy of blowing the sides off a spool as many spools do not have a lot of strength in that direction. It is probably quite unlikely that it might crush inward on a round cylinder. Kind of like trying to break an egg in your hand by squeezing. It depends how they were machined to attach to the spool.

I do recall we used to pre-stretch our line when new. We did extensive testing on weak links and registered a noted difference in breaking strength between weak links that we preloaded with pressure first, and others that we just took up to breaking pressure. As I recall, a high percentage of "unseated" links seamed to break at the knots, where seated ones broke somewhere else on the link. Notes may be buried in our archives somewhere.

Wanna tell us anything about Gs?
Never mind, as long as they're appropriate, under an inch and a half, and blow with tight tolerances I guess we're OK.

Miller Stroud - 2012/04/26 12:31:00 UTC

I guess my worries come from my background of Rescue with the fire dept. Before we start, I know, we're flying, not rescueing.

No, rescuing is what we do AFTER we start flying in a culture in which nobody has a freakin' clue what he's talking about.

But we use static type of rope instead of dynamic to remove any stretch in our operations. This is to eliminate the variable of stretch.

But that would take so much of the EXCITEMENT out of hang glider towing.

We want want absolute control of the physics in play.

HEY! Didn't you just hear Jim tell you that they found the stretch ploy provides is a built in safety device? And now you're gonna start talking PHYSICS?!

I too, many years ago towed with poly in a static mode, and I remember the stretch upon takeoff and then the big surge that followed. Wasn't too bad, in fact it was pretty smooth. By using Aims steel or spectra I assumed we were doing the same thing, removing one variable.

It's Amsteel, by the way.

I can see how a length of poly in the system could act like a shock cord.

Yeah, just what we need.

I'd just have to think about it.

Make sure you've got the qualifications first.

Presently in our payout system technique, communication has been the greatest improvement in tow efficiency and smoothness.

Nah, you don't want PEOPLE doing this. Take a hint from Jim and throw some stretch back in the equation.

This spring we have been able to reduce our tow pressures...

Oh good, I see we're already getting safely away from the realm of physics.

...climb rates (which have been too high), and vehicle speed through good communication from the pilot to the driver. This has extended our times on the rope giving us higher and more efficient climb rates.

Hey, if poly is working for you guys, great. Ninety percent of this towing is knowing your system and how to make it work for you.

Yep, isn't it wonderful the way the physics of hang gliding adapts to different personalities and levels of intelligence.

http://dir.groups.yahoo.com/neo/groups/Airchairgroup/conversations/messages/5759
2500 foot runway launching

Sunny Stutzman - 2007/09/04

Forget bungee... been there done that with a hang glider years ago. I lost vision in one eye for a day or so and now have an eighty percent chance of developing glaucoma later in life.

Another friend strapping stuff to the roof wasn't so lucky and lost his eye.

If you want to be experimental there are other options for self launch. The best one I have heard is a remote controlled winch. Set up a winch at the end of the field and a transmitter in the cockpit to control the speed. It wouldn't be that hard with three axis. Others have done it with a hang glider and mouth control. The interesting possibility here is that you could go electric and have a green launch.

http://dir.groups.yahoo.com/neo/groups/Airchairgroup/conversations/messages/5791

Sunny Stutzman - 2007/09/07

3000 feet of Spectra will cost $615 and 3/16" poly will cost somewhere between $200 and $400 depending on the type. It will be half the strength and probably close to twice the weight before you even start talking about drag and stretch and lifespan. You won't want to tow paragliders with it because it stretches too much and you will need to fabricate a custom spool because it won't fit on a scooter/motorcycle rim. I'm sure you could get by with poly, but since even the guys raiding junk yards for old scooters (to be used as winches) are using Spectra I'm quite sure the benefits outweigh the difference in price.

As for which makes for an easier tow, I've aerotowed behind both and the poly, even at 150 to 200 feet has a far greater amount of stretch. At 3000 feet it must feel like a bungee.

While the stretch does have a tendency to equalize tow forces, it also can whip you once you leave a thermal. You end up catching up with the tug, then stalling a bit while trying to hold altitude, then zoooming again once the slack has been taken up.

I'm not sure if this would be a concern with a ground based winch and a sailplane. It's more of a problem on aerotow with a higher performance glider I believe. With an auto tow I can see poly as actually having some benefits, because a car really can control pressures as easily as a winch, and HP is obviously not a concern.

One last thing, then I'll shut up about tow lines...

Even if the difference in drag is say 25 pounds, this is still relevant. On my hang glider the difference between level flight and 200 feet per minute sink (the sink rate of my glider) is about 30 pounds of drag. With my powered harness, total thrust is about 100 pounds, and if that drops to 70 or 80 pounds I eat dirt... and grass... maybe a bug or two...

Continued at:
http://www.kitestrings.org/post2140.html#p2140
instructors and other qualified pilot fiends