Kite Strings

Lisa

So, specifically, what standard de facto methods are now used for tying weak links for hang gliders?

Tracy

Today, there are two generally accepted and widely used methods for tying weak links: (a) Pre-tied and (b) Wrap and Tie (WT). One involves pre-tying the weak link line into a loop before putting it on the V-bridle; the other involves threading the weak link line through the loop at the end of the V-bridle, wrapping it three to five times, and then tying it to make a loop.

- And both of these two generally accepted and widely used methods for tying weak links involve assumptions that, because the knot is hidden from the main tension in the link and excluded altogether from the equation, that the weak link will blow at twice the test strength of the line.

- And none of the morons who've been operating on these assumptions for decades has ever bothered to test these assumptions and find out that the loop blows at about half of what they think it does regardless of the knot configuration.

To make a pre-tied weak link, a short 9-10" length of line...

Nine to ten inches is a SHORT length. Right. I can do a little over half that.

...is tied into a loop with a grapevine knot, then attached to the smaller loop at the end of the V-bridle with a lark's head knot [ref 4]. The resultant loop should be one to two inches long--if longer it can whip and snag on to the tow ring as it passes through the ring at release.

Right. It's gotta be an ABSOLUTE MINIMUM of one inch or you won't be able to get it on your release pin and two inches is short enough to ABSOLUTELY GUARANTEE that it won't weld itself to the tow ring.

Reference 3

Always use an appropriate weak link with a finished length of 1.5 inches or less. Longer weak links are more likely to get tangled on the tow ring upon release.

Or one and a half. Whatever.

Pre-tied weak links made from 130 lb. green spot line work well for many aerotowing operations...

Work well to WHAT?

...are practical and appropriate for those operations...

Well, if they're APPROPRIATE and Reference 3 tells us to always use an APPROPRIATE weak link I guess we're pretty well covered.

...and thus this method has become a de facto standard.

Anything that doesn't kill somebody more than once out of every five or ten flights will become a de facto standard with you shitheads.

The picture to the left shows the length of line, tied into a loop with the grapevine knot, then attached to both a thin Spectra and a thicker polypro bridle with a lark's head knot. Note how much more surface area is provided by the polypro bridle, so that pressure subjected to the weak link by the bridle is spread out over a much a larger area, and is thus reduced per unit area of the weak link which helps to reduce the chance of an inadvertent weak link break.

Makes perfect sense to me. Can't really see much point to loading it up on a test rig.

Some aerotowing operations--particularly ones with more powerful tugs like ours here at Cloud 9--have found that pre-tied weak links fail inconsistently and too frequently.

Yeah?

- HOW did you assholes find that? Did you get data on tow tensions, glider weights, lift to drag ratios, turbulence, cycles of spinnaker shackle gate chewings?

- Define TOO frequently.

Lisa

You and I have flown sailplanes for almost as long as we have flown hang gliders. We own two sailplanes and have two airplanes that we use for towing full-size sailplanes. In all the time that we have flown and towed sailplanes, we have not experienced or even seen a sailplane weak link break.

- What's the PROPER frequency for weak link failures?

Sometimes they perform well by breaking as expected under high loads...

- What's a HIGH load?
- If the load is getting dangerously HIGH what's stopping the pilots from releasing themselves?
- Oh, right. You assholes don't use releases that can be actuated in emergencies.

...and not breaking inadvertently in mild turbulence, but sometimes they fail unexpectedly.

OK, lemme see if I've got this right...
- They break under high loads when they're supposed to.
- They don't break under the moderately high loads one experiences in mild turbulence.
- But under normal tow loads when nothing's going on they start breaking again.

Dude! Somebody's not tying these things right!

This inconsistent weakness is likely caused by (a) the knot in the line that is used to pre-tie the weak link, (b) the garroting action of the lark's head knot, and (c) the ability of the weak link to loosen, shift, and wear. This is exacerbated by use of a Spectra bridle rather than a polypro bridle due to the smaller surface area of the Spectra bridle line and the inability of Spectra to absorb shock.

Yeah, Fisherman's Knots, Lark's Head garroting action, Spectra shock... That's just gotta be the explanation for 130 pound Greenspot blowing at heavy and light but not moderate loads. Gotta hand it to ya, Tracy. Pure genius!

We and some other tow operators get significantly better results by using a Wrap-and-Tie (WT) weak link, made of the same 130 lb. green spot line.

Ya know how *I* get significantly better results with 130 pound Greenspot, asshole? I replace it with 250. Then I don't hafta worry about Fisherman's Knots, Lark's Head garroting action, Spectra shock, and bullshit schemes for positioning the knot so that it's hidden from the main tension in the link and excluded altogether from the equation.

To make this kind of weak link, cut a 12-inch piece of line, thread it through the loop at the end of the V-bridle, wrap it around three to five times, and tie it with a simple overhand knot at the very end.

- Bullshit.
- An Overhand Knot is - by definition - tied in a single strand. So what's holding this piece of string on the bridle?

Then, add two more overhand knot ties, just inside the other ones.

Yeah, when you're using knots that don't do anything it's always best to use lots of them.

Pull the inner loop to use as your weak link, leaving the knots on the inside of the V-bridle loop, so that the knots are separated by the remaining loops as much as possible from the pulling force applied on the weak link in the middle. Here at Cloud 9, we prefer wrapping five times, so that the center loop is used for the weak link, and the knot is separated from the weak link loop by the two additional loops on each side of it.

Get fucked.

The WT style of weak link performs very consistently, likely due to the extra weak link loops snugging down onto the bridle and not shifting around, and because the knot used to make it is separated far from the pulling pressures. Basically, it removes the knot from the actual weak link loop that is used, so it behaves much like a continuous loop of line without a knot in it.

Bullshit.

Lisa

What about a three-line weak link?

Tracy

It is an acceptable method [ref 4]...

Well yeah, if Dennis and Bill put something in their stupid book it's just gotta be acceptable.

but not necessarily a de facto standard.

No, of course not. Just getting in the stupid book doesn't necessarily make something a de facto standard. In order for something to become a de facto standard it's gotta clear much higher bars than acceptable methods do.

It can be used to make, for example, a 390 lb. weak link from 130 lb. line for use on a tug.

Of course. It's 130 pound test and and three times 130 is 390. Simple. So apparently it doesn't matter whether or not you position the knot so that it's hidden from the main tension in the link and excluded altogether from the equation. That's really good to know.

It requires the use of two knots, one at each end of the weak link to attach it to the bridle or ring, and it doesn't really work on a pilot V-bridle. A practical option would be to just make a 400 lb. WT loop from 200 lb. line.

Idiot.

Lisa

You and I have flown sailplanes for almost as long as we have flown hang gliders. We own two sailplanes and have two airplanes that we use for towing full-size sailplanes. In all the time that we have flown and towed sailplanes, we have not experienced or even seen a sailplane weak link break.

Yeah. Amazing. Ya get in a:

- branch of REAL aviation with REAL standards and regulations, REAL equipment, REAL engineers, and REAL textbooks and you don't have any problems.

- bullshit sport with run by a bunch of stupid lazy quacks studiously and reverently imitating other stupid lazy quacks and shit starts falling apart left and right.

Lisa

Note that we've got two Lisas in a row in this fake discussion. This was undoubtedly supposed to be Tracy, the brilliant engineering professor.

It's not that it doesn't happen, but it is a rare occurrence.

Go figure. Must be 'cause hang glider pilots don't get enough tandem training.

Russell Brown, a founder of Quest Air in Florida and a well-known Dragonfly tug pilot, is also a sailplane pilot, tug pilot, and A&P mechanic for a large commercial sailplane towing operation in Florida.

And a total moron.

He told us that, like us, he has never seen a sailplane weak link break, either.

Dude! They must be making them too strong. Might be a good idea to tie knots in them. (See Reference 4, Page 58.)

Russell owned the first 914-powered Dragonfly ever made--he helped us build the second one, which we still fly. He is the one who, many years ago, showed us the method for making a WT weak link and suggested we use polypropylene rather than Spectra for hang glider V-bridles.

What did I just say about him being a total moron?
This paragraph was probably supposed to be Lisa's.

Jim Lee, two-time US Hang Gliding National Champion and six-time US comp point champion, was our commercial pilot sailplane instructor. He is a sailplane distributor, instructor, and tow pilot in Florida. He recently told us that he has only seen two sailplane weak link breaks, and experienced one himself, when he and the tow plane had to turn sharply on tow to avoid a helicopter that flew into their flight path. He said that his weak link performed properly in that situation.

- Right. That's the purpose of a weak link - to blow when you and the tow plane have to turn sharply to avoid a helicopter. If only Bob Wills had been using a weak link.

- So why didn't he - OR THE TUG - release? 'Cause they didn't need to abort the tow maybe?

Tracy

So, let's look at the purpose of weak links used for sailplanes. The FAA doesn't say much about that in print.

That totally sucks! Boy am I glad I'm in hang gliding where I can read half a magazines worth of lunatic self-contradictory drivel on the many purposes of weak links.

Based on other literature and what we have learned, weak links are primarily...

Yeah. PRIMARILY.

...used to help prevent structural failure of the glider or tow plane when unusually high loads are applied on the towing system.

- As opposed to HELPING to prevent structural failure of the glider or tow plane when unusually low loads are applied on the towing system.
- So what else is HELPING to prevent structural failure of the glider or tow plane when unusually high loads are applied on the towing system?

The SSA specifies the purpose of a weak link as: "designed to break under extreme load to prevent damage" [ref 14].

Yeah Tracy. That's all we really need to say on the issue. So how 'bout shutting the fuck up and ending this nightmare?

They should be weak enough to fail before anything on the tow plane or gliders fails, but not so weak that unintentional breaks occur.

ALL weak link link breaks are UNINTENTIONAL. If you don't wanna be on tow you blow the release. REAL weak links only blow when you've totally lost control of the situation.

In addition to preventing structural failure...

What part of:

So how 'bout shutting the fuck up and ending this nightmare?

did you not understand?

...weak links may break: (a) to prevent loss of control of the tow plane or glider in unusual attitudes

BULLSHIT. When a REAL weak link blows you lost control a long time ago. And there's a real good chance it'll be a long time before you get it back again.

(b) when tow forces increase as a glider gets outside of the cone of safety...

Fuck the "cone of safety". There is no "cone of safety"...

Bill Bryden - 2000/02

Dennis Pagen informed me several years ago about an aerotow lockout that he experienced. One moment he was correcting a bit of alignment with the tug and the next moment he was nearly upside down. He was stunned at the rapidity. I have heard similar stories from two other aerotow pilots.

...for a towed hang glider. Towed hang gliders are ROLL UNSTABLE.

See this:

http://www.youtube.com/watch?v=27yFcEMpfMk


Jamie's IN the goddam "cone of safety" and the only thing that keeps her safe is altitude. And if that kinda shit happens lower and/or more severely she's fucked. And her goddam USHGA recommended nominal one G / 130 pound Greenspot weak link isn't gonna matter worth a rat's ass.

...and (c) sooner or later after a lockout has started.

So what's your fucking point? The goddam weak link blows when the tension hits its breaking point. And there's not a goddam thing you can tell about what the glider was doing before or will be doing after that happens.

A pilot should not expect a weak link to break to prevent a lockout.

Really? Are you sure about that? Here's what it says in Reference 4 on Page 54:

Speed controlled towing is when the speed of the device doing the towing is maintained at a reasonably constant value. Controls, such as throttle, are used to keep the speed of the tow vehicle or tow winch operating at a constant speed. Towline tension can vary dramatically in response to thermals, sink, pilot corrections, etc. Aerotowing is clearly in this category as the tug needs to maintain a minimum speed to prevent stalling. Many of the early towing efforts of the '70s where the vehicle drove at a fixed speed would also fall into this category. Weak links very clearly will provide protection from excessive angles of attack, high bank turns and the like for this form of towing.

Sometimes the pressures...

What PRESSURES, Doctor Tillman?

...produced at the start of a lockout are high, and the weak link may break early.

And it MAY not. So what's the point in writing this crap? Are you getting paid by the word or something?

Sometimes the pressures are not very high at the start of the lockout and don't get high until the lockout progresses much further--in that case the weak link will break later.

Will it break before:
- you slam into the runway?
- slamming into the runway is an inevitability?

In either case, the primary purpose of the weak link is to protect the structure and equipment of the glider and tug by separating them--it is not to prevent a lockout.

The PRIMARY purpose? So the SECONDARY purpose may or may not be to prevent a lockout. So we can continue flying crap Flight Park Mafia equipment because a weak link MAY prevent a lockout.

Lisa

Actually, that is our expectation of performance for weak links on hang gliders here at Cloud 9, too.

Oh good. So if we don't like Cloud 9's expectation of performance for weak links we can go to another flight park...

http://www.wallaby.com/aerotow_primer.php
Aerotow Primer for Experienced Pilots

The Wallaby Ranch Aerotowing Primer for Experienced Pilots - 2012/06/07

If you fail to maintain the correct tow position (centered, with the wheels of the tug on the horizon), the weak link will break before you can get into too much trouble.

...which has higher expectations of performance for its weak links.

Primarily, we want the weak link to fail as needed to protect the equipment, and not fail inadvertently or inconsistently.

What G rating do you use to achieve that goal?

We want our weak links to break as early as possible in lockout situations, but be strong and reliable enough to avoid frequent weak link breaks from turbulence.

Yes Lisa, EVERY fucking moron who tows with shitrigged releases wants a magic weak link which blows at half a G in a lockout but holds to one and a quarter Gs in turbulence and situations in which his ass will be toast if he loses the line. But it's a bit difficult to engineer a device like that.

It is the same expectation of performance that we have for the weak links we use for towing sailplanes.

Lessee...

You and I have flown sailplanes for almost as long as we have flown hang gliders. We own two sailplanes and have two airplanes that we use for towing full-size sailplanes. In all the time that we have flown and towed sailplanes, we have not experienced or even seen a sailplane weak link break.

It's not that it doesn't happen, but it is a rare occurrence. Russell Brown, a founder of Quest Air in Florida and a well-known Dragonfly tug pilot, is also a sailplane pilot, tug pilot, and A&P mechanic for a large commercial sailplane towing operation in Florida. He told us that, like us, he has never seen a sailplane weak link break, either. Russell owned the first 914-powered Dragonfly ever made--he helped us build the second one, which we still fly. He is the one who, many years ago, showed us the method for making a WT weak link and suggested we use polypropylene rather than Spectra for hang glider V-bridles.

Jim Lee, two-time US Hang Gliding National Champion and six-time US comp point champion, was our commercial pilot sailplane instructor. He is a sailplane distributor, instructor, and tow pilot in Florida. He recently told us that he has only seen two sailplane weak link breaks, and experienced one himself, when he and the tow plane had to turn sharply on tow to avoid a helicopter that flew into their flight path.

Sailplane weak links virtually never break and you've never had or even seen one break but your expectation of hang glider weak links is that they break whenever you get in trouble and can't get to your piece of shit releases. I'm a little confused here.

Tracy

Practically, some hang glider aerotow operators may want to use weak links that are at the low end of the legal range, let's say with an actual breaking strength between 80% and 100% of the MCOW of the glider. In this case, they may experience more unintentional breaks, but breaks will occur with less stress applied to the structure of the tow plane or glider.

- Yes. That would limit the stress applied to the structure of the glider to between 1.8 and 2.0 Gs, 30 to 33 percent of its certified capacity. With a one G weak link one would expect to see the damage limited to that typically resulting from a coordinated turn at a sixty degree bank angle - which would be zero.

And with a two G weak link one would expect to see the damage limited to that typically resulting from a coordinated turn at a seventy-one degree bank angle - which would also be zero.

So from this information we can conclude that the damage penalty for increasing the weak link strength from the bottom of the FAA legal limit to the top would be the difference between zero and zero which gives us zero.

That would be a 2.85G weak link, which is 285% of a 1G weak link.

You good with the math on that one, Lisa?

- Have either of you fucking morons considered the implications of what can happen to the structure of the glider AFTER a USHGA recommended nominal one G weak link...

http://www.youtube.com/watch?v=eTKIAvqd7GI

0:50
http://www.youtube.com/watch?v=JR_4jKLqrus


...performs properly?

In this case, there is less likelihood that the tug will experience loss of control or structural failure before a weak link breaks when a glider gets out of the cone of safety.

Idiot.

On the other hand, some operations may want to use weak links that are stronger but legal, primarily to avoid unintentional weak link breaks.

Do you have this kind of absolute lunatic bullshit going on in sailplaning?

Either case is legal if within FAA limits, and can be ethical and practical if it works effectively and safely for that operation.

Are you sure? Maybe we should review the chapter in Reference 7 covering the ethical considerations of weak links.

The strength of the weak link that is appropriate for a particular operation can depend on the power of the tug and resultant climb rate and climb angle of the tow.

NO, it CAN'T - DOUCHEBAG. It depends ONLY on the MAXIMUM CERTIFIED OPERATING WEIGHT of the glider - just like it says in the fuckin' manual.

To be legal, a hang glider pilot should not just use any strength weak link they want to use, it must be within legal limits...

And, of course, since we've established that a single loop of 130 pound Greenspot blows at 260 pounds beyond a shadow of a doubt there's just no way a solo glider can go wrong using one.

...and coordinated with the weak link used at the tug end of the rope.

Fuck the tug. The glider is legally entitled to use anything between 0.8 and 2.0 and it's the tug's job to stay over it. If he can't do his job he should find another one.

We have very powerful tugs here at Cloud 9 with very large and efficient Prince P-tip propellers. The diameter of the propellers we use on our Rotax 914 engines is the same diameter as the propellers we have on our Skymaster 225 hp engines--in fact, because of the P-tip, the effective diameter is increased by 6 inches, to 84 inches, which is 7 feet [ref 15].

What does any of this have to do with the issue of weak link strength?

The climb rate we get is amazing.

Is it too amazing to express in terms of feet per minute?

Weather permitting, we tow on a daily basis here through most of the flying season, but we only see a few weak link breaks here each season.

Why do you see ANY?

Most of our solo pilots here at Cloud 9 use the 130 lb. line, so that they are towing with a 260 lb. nominal 1G WT weak link on a polypro V-bridle, which equates to using an actual 1.7G weak link on the towline.

Yeah Tracy. See if you can get into the Guinness Book for stuffing the greatest amount of bullshit into the least amount of sentence.

Tracy

Dr. Lionel D. Hewitt, professor of physics and developer of the 2-to-1 center-of-mass Skyting bridle for surface towing, is well respected for his knowledge of towing, bridles, and weak links [ref 4].

- It's spelled HewEtt.

- There' no such thing as a center of mass bridle.

- Donnell didn't develop the two to one bridle for surface towing. He developed it for TOWING. Aerotowing - for all practical purposes - didn't exist in the early Eighties.

- Neither you nor anyone you know uses two to one bridles.

- The reason you don't use two to one bridles is 'cause there's no appreciable difference between two and one to one bridles.

- Two point bridles offer an advantage ONLY at low tow angles.

- And aerotowing is constantly at or near zero tow angle.

- Two to one bridles were NEVER used in aerotowing on any scale worth mentioning. Aerotowing went from one point to one to one two point and, for some portion of higher performance gliders, back to one point.

- The only people who use two to one bridles are Donnell and some of his old cult members who never figured out that two to one bridles don't do anything that can't be better accomplished with one to ones.

- Donnell's understanding of weak links was totally fucking clueless in 1980 and largely remains so.

- Ditto with respect to his understanding of towing and bridles.

His position on weak link strength for aerotowing of hang gliders seems to be consistent with ours.

His position on weak link strength for aerotowing of hang gliders - MOTHERFUCKER - is ENTIRELY based on and derived from...

Donnell Hewett - 2009/03/26

Let me lend my support to Tad Eareckson's proposal to improve the SOPs of aerotowing by setting a weak link standard of a minimum of 1 g, a maximum of 2 g's, and an optimum of 1.5 g's. Although this proposal violates Skyting Criterion 7 (which specifies a maximum of 1-g), it is necessary to help compensate for the way that aerotowing violates Criterion 2 (constant tension). Since aerotowing uses air speed to try to regulate towline tension on a short towline, the probability of breaking a 1-g weak link is relatively high for aerotowing compared to most other forms of towing. And because a premature, unexpected, or unwanted weak link break can often be more dangerous than staying on line, non-essential weak link breaks should be minimized as much as possible. And, finally, since aerotowing should never be performed solo by an inexperienced pilot, any pilot qualified to aerotow should be able to handle the proposed weak link standard without difficulty. Therefore, the proposal is consistent with the intent of Skyting Criterion 7 which states, "Breaking point should be appropriate for the weight and experience of the pilot."

Tad should be commended for his tireless effort to improve the safety of aerotowing.

...MY position on weak link strength for aerotowing of hang gliders. His previous position on weak link strength for aerotowing of hang gliders was that they should be one G max and under what surface towers use because aerotowing tensions are less than surface towing tensions for any given climb rate. And that approach was and is total bullshit. And may you rot in hell for perpetrating it with all of your bullshit about engines, propellors, and climb rates.

He has acknowledged that we especially need to avoid inadvertent weak link breaks while aerotowing, because much of aerotowing takes place over unlandable terrain.

Which is pure, unadulterated, lunatic BULLSHIT. It's like saying no one should launch off Kagel or Henson because you have to fly over unlandable terrain.

These aren't cinder blocks, douchebag - they're GLIDERS. They can fly over unlandable terrain and GLIDE back to landable terrain - like an AIRPORT. I'da thunk a really sharp flight park operators such as yourselves might have been able to grasp a concept like that - even if Dr. Lionel D. Hewitt, professor of physics and developer of the two to one center-of-mass Skyting bridle and respected expert on towing, bridles, and weak links, couldn't.

That, along with recognizing that towing pressures...

As clueless on towing as Donnell was and is, he has NEVER degenerated to the point of referring to TENSIONS as PRESSURES - asshole.

...vary considerably while on aerotow, has led him to suggest the use of a weak link that breaks in the neighborhood of 1.5G of towline pressure [ref 16].

Fuck you.

This is near to what actually results when a USHPA-recommended nominal 1G weak link is placed at the top end of a V-bridle used for aerotowing.

Fuck you.

Lisa

We know that some aerotow hang gliding operations and pilots experience a relatively high incidence of weak link breaks. Why do you think that happens?

Haven't we already established that Tracy is totally incapable of thinking?

Tracy

There are many reasons, but for most pilots it is not because the standard 130 lb. green spot Dacron line used to make weak links for hang gliders is too weak.

No, of course not. Even CONSIDERING that POSSIBILITY is TOTALLY ABSURD. So let's start droning on again with the crap about positioning the knot so that it's hidden from the main tension in the link and excluded altogether from the equation, garroting action, and shock loading.

One problem for them could be use of a pre-tied weak link, which has both a grapevine knot and garroting lark's head knot that can cause the weak link to break inconsistently.

If someone is using the SAME:
- bridle
- pre-tied weak link
- Fisherman's Knot
- garroting Lark's Head
how can that POSSIBLY cause the weak link to break INCONSISTENTLY? Asshole.

Sailplane weak links avoid using knots, and the WT style of weak link effectively doesn't have a knot near the working weak link, which allows the line to maintain its integrity...

And when you BENCH TESTED this bullshit hypothesis of yours I'm guessing that you found that your wonderful wrapped and tied weak links blew at 260 pounds plus or minus three percent and crappy pretied weak links blew at 180 pounds plus or minus forty percent. Did I get that about right?

...and break reliably as needed.

Oh. The WT style of weak link breaks reliably AS NEEDED.

Your sailplane weak links NEVER break and neither of you assholes has been killed yet so apparently your sailplane weak links are NEVER needed. Kinda like my parachute.

But your hang glider weak links break RELIABLY as needed so that means blows are common and - minus the blows - somebody would die.

So how many times in a typical weekend is someone's life saved by the reliable blow of a WT style weak link?

Do they reliably blow to prevent the glider from breaking up?

Given that gliders are certified to six Gs wouldn't the thousand pound spliced quarter inch polypro sailplane weak link work just as well to keep even a max loaded baby Falcon 3 from breaking up?

Or are your WT style weak links breaking RELIABLY to prevent lockouts?

What percentage of your WT style weak link blows occur before a lockout progresses enough to be dangerous?

What's the maximum altitude loss one can expect to experience following a reliable WT style weak link blow?

Mike Haas and Roy Messing were UNDOUBTEDLY using 130 pound Greenspot on their two point bridles.

There's a slim chance that they were using WT style weak links which blow reliably as needed but they were almost certainly chintzy garroting pretied weak links which blow unreliably WAY before they're needed.

So how come they're both dead?

Why aren't Cloud 9 pilots RELEASING THEMSELVES AS NEEDED? Why are they hanging around on the end of the rope like cud chewing passengers waiting for the fucking WT style weak link to break reliably AS NEEDED?

Sounds to me like they need a lot more tandem training.

Tracy

Another factor is the size and material used for the pilot's V-bridle. A Spectra bridle has almost no stretch, so sharp, impact loads are transferred directly to the weak link, while a polypro bridle has a reasonable amount off stretch and can act as a shock absorber and reduce the intensity of the impact load.

I use nothing but the lowest stretch materials between me and the tug that I can get my hands on and I've never once experienced a sharp impact load - asshole.

Lisa

Without shock absorption, a Spectra bridle acts somewhat like an impact wrench on the weak link.

Yeah Lisa. It's like using an impact wrench to remove a lag bolt from the middle of an eighteen inch two by four floating in a bathtub. Halfwit.

Tracy

Right. It just hammers away at it.

I know what you're talking about, Tracy. Whenever I flew low stretch bridles I'd hafta get out the wrenches and retighten all my nylocks a three quarters turn. The hammering was just terrible. Good thing my 130 pound Greenspot nominal one G weak link blew about half the time on a good thermal day before I cleared five hundred feet. I shudder to think of the consequence if I had been allowed to continue all the way up to a workable altitude.

A Spectra bridle typically has a relatively small diameter and thus applies a type of garroting action on the weak link, compared to a larger diameter polypro bridle, which spreads the pressures over a larger area of the weak link. Also, the shorter the V-bridle, the more stress is applied to the weak link due to the resultant vector of force. The worst performance comes from a relatively short Spectra or thin pro-tow bridle...

How very odd.

Tracy

The situation is different when the weak link is attached to one end of a V-bridle, such as at the top of the V-bridle, where it connects to the primary release. To break at a certain towing load, the strength required of the weak link on the V-bridle would be half of that load, plus about 15% due to the vector angle of the bridle.

I'da thunk that the worst performance would come from a weak link subjected to an additional fifteen percent over half the towline tension. But, OBVIOUSLY...

http://groups.yahoo.com/group/skysailingtowing/message/612
hang gliding Comments on outlandish release/bridle/weak link

Tracy Tillman - 2001/05/25 01:01:56 UTC

I use 150 lb. for pro-towing, but Lisa still uses 130 lb. for pro-towing. I use 130 lb when using my regular towing bridle.

...I have that entirely backwards.

...especially when the weak link is attached directly onto the thin curved pin...

The thin curved pin selected as the ideal release gate based on several decades of experience and hundreds of thousands of tows conducted by experts in the field and numerous aerotow operators across the county.

...of the secondary release...

So are you using secondary weak links on secondary releases?

http://groups.yahoo.com/group/skysailingtowing/message/549
Weaklinks/bridles; was: high wire act world news

Tracy Tillman - 2001/05/16 15:14:55 UTC

We (and many others) do not recommend using a second weaklink on the non-released end of the bridle. That weaklink is just as likely to break as the one on the other end. If the lower weak link breaks, the bridle could get caught in the towline ring, and pull the glider from the 'biner or keel, causing it to tuck. The other weaklink (on top) may not break prior to the tuck.

The weaklink should be on the released end of the bridle, and the bridle should release from the top. That way, if the bridle does get caught on the ring, it is pulling from the body, rather than from the glider, and the glider may still be controllable--in which case you can use your secondary release (or hook knife if that fails) to release.

I was under the impression that you (and many others) saw no value whatsoever in the secondary weak links I tried to push in the magazine over fifteen years ago.

...which imparts high loads over a very small area of the weak link.

- If your:

-- secondary weak link is the same as your primary weak link and engaged by a secondary release it's physically impossible for it to be loaded highly unless your bridle has wrapped following a release or primary weak link blows

-- primary bridle wraps after you release you want the secondary weak link to blow

-- primary bridle wraps after your primary weak link blows the secondary WILL blow - whether you want it to or not.

- If you:

-- are towing one point your "secondary" release is your primary release.

-- had ever ACTUALLY LOOKED AT a weak link blown off of a barrel release you'd have noticed that it didn't blow at the pin. It blew at the point at which one of the two strands exits the bridle. Thus the issue of the pin is totally irrelevant.

- Load a release to two hundred pounds. The stress on the weak link AT ANY POINT of the protruding loop is EXACTLY one hundred pounds. Either strand at any point between the bridle and pin or at any point rounding the pin. So shove the crap about the pin imparting a high loads over a very small area of the weak link back up your ass from where you got it.

The best performance...

OH!!! The BEST weak link performance being synonymous with the MOST resistance to breaking. So we're REALLY not worried about weak links...

Lisa

We want our weak links to break as early as possible in lockout situations...

Tracy

Practically, some hang glider aerotow operators may want to use weak links that are at the low end of the legal range, let's say with an actual breaking strength between 80% and 100% of the MCOW of the glider. In this case, they may experience more unintentional breaks, but breaks will occur with less stress applied to the structure of the tow plane or glider. In this case, there is less likelihood that the tug will experience loss of control or structural failure before a weak link breaks when a glider gets out of the cone of safety.

...protecting us in lockout situations, stress applied to the structure of the tow plane or glider, or the loss of control or structural failure. That's REALLY good to know.

...comes from three-point...

Two point - asshole.

...bridle using an appropriately long primary V-bridle made from 1/4" or 5/16" diameter polypro.

Good ol' polypro. Where would we be without it.

The overall length of a three-point bridle system is much longer than that of a short pro-tow bridle, and thus will have more stretch and shock absorbing quality.

So why not just make ten foot long "pro-tow" bridles?

Come to think of it...

Tracy

For the Blanik, we use 3/8" polypro as the towline...

You're using a polypro towline for the sailplane and it's pretty fucking obvious that you're using a Spectra towline for hang gliders.

Why? Why not use the best towline for hang gliders too?

Then it would make absolutely no difference whatsoever what any glider used for a bridle. EVERYBODY - Spectra, long and short two point, one point - would have EQUAL and AWESOME shock absorbency. Your weak links would almost NEVER break.

Could the reason possibly be that...

Lisa

It is important to realize that most sailplane operations use polypro for the tow rope rather than Spectra. Unlike Spectra, polypro has some stretch to it under load--and can stretch up to 20% before breaking.

...hang gliders are already enough of a dangerous bitch to try to control on aerotow...

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

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 200-250 feet so the advantages of Spectra are even greater.

...without throwing a giant rubber band into the equation and...

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.

...there's no canopy between the towline and the pilot's face?

Here at Cloud 9, we experience the most reliable weak link performance by using WT style weak links and three-point polypro primary and secondary bridles.

Idiot.

The use of a Spectra bridle is an accepted de facto standard, and works well for many towing operations. It just does not work well for our towing operation here at Cloud 9.

Yeah Tracy, the Newtonian physics over Webberville, Michigan are NOTHING like they are at most other aerotow operations. Must have something to do with stupidity waves. Have you tried lining your helmets with lead foil?

Lisa

We used to see more weak link breaks happen here at Cloud 9 in the past, when more visiting pilots flying here were using pre-tied weak links and Spectra bridles.

- Define "MORE".

- What's your data? When somebody blows a weak link do you record glider model, flying weight, thermal conditions, relative positions of tug and glider, headings, one versus two point bridle, bridle material and diameter, release mechanism, weak link material type, weak link installation method, condition of weak link prior to tow?

You're full o' shit, Lisa.

Because Spectra is slippery, we also used to see their bridles sometimes slip apart on tow.

Yeah, there's just no reliable way to splice Spectra so it won't fall apart. Poly just keeps coming out on top in any equation into which you wanna put it.

Some bridle makers are sewing their Spectra bridles now.

You mean the shit that Davis sells?

We just have not had a problem with our polypro bridles slipping apart.

And I just have not had a problem with my Dyneema bridles slipping apart. The downside is that I need to spend more than two or three minutes pumping out a copy.

Tracy

There are other factors that affect weak link performance. Faster tows create more drag, which increases load on the weak link, and makes the turbulence impart a sharper impact load on the weak link. Higher climb rates and climb angles impart more load on the weak link, as does towing in a position that is too high or low, or too far to the side, rather than in the center of the cone of safety.

Yeah Tracy, we all know all about the scores of factors which endanger our fucking loop of 130 pound Greenspot.

Now let's replace it with something that holds to two thousand pounds, use nothing but Spectra between the tug and glider.

So how much damage to the glider should we expect to sustain from faster tows, more drag, more turbulence, higher climb rates, higher climb angles, and being outside of your idiot cone of safety?

Towing without a fin decreases directional stability and smoothness of the tow, which increases load and wear on the weak link.

Doesn't increase the wear on MY weak link - asshole. Won't increase the wear on an appropriate Tost weak link either.

Likewise, pro-towing decreases smoothness and the ability to control the tow...

OH!!! So:
- "pro-tow" DECREASES the ability to control the tow.
- "pro-towing" INCREASES your likelihood of being killed on launch - no matter who you are.
- then what's the "thinking" of the "pros" who use it?

...and can increase loads on the weak link, as described earlier.

- But DOESN'T *EVER* increase the loads on the GLIDER - which is what we SHOULD BE talking about - to any extent worth mentioning.

- Unless the glider is locking out and uncontrollable, and the tow isn't salvageable.

- In which situation an ACTUAL two G weak link will blow within a few milliseconds of what a bullshit loop of 130 would have and guarantee that the damage to the glider will be limited to the same it would be with a half G weak link.

These factors lead to a relatively high frequency of weak link breaks at aerotow hang gliding competitions. An inadvertent weak link break places a pilot at a competitive disadvantage and can increase the chance of personal injury or damage to their glider--which is also a competitive disadvantage.

OH!!!

- So a weak link that blows for no reason...

http://ozreport.com/forum/viewtopic.php?t=24846
Is this a joke ?

Davis Straub - 2011/08/26 14:04:52 UTC

We had six weaklink breaks in a row at Zapata this year.

...can put one at a competitive disadvantage.

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

Jim Rooney - 2007/07/22 22:30:28 UTC

I've heard it a million times before from comp pilots insisting on towing with even doubled up weaklinks (some want no weaklink). I tell them the same thing I'm telling you... suck it up. You're not the only one on the line. I didn't ask to be a test pilot. I can live with your inconvenience.

Who'da thunk?

- And a weak link that crashes a glider...

http://ozreport.com/9.011
2005 Worlds

Davis Straub - 2005/01/13

Tom Lanning had four launches, and two broken weaklinks and a broken base tube. He made it just outside the start circle.

...can ALSO put one at a competitive disadvantage. And here I've been thinking that that would give someone an unfair edge.

- And personal injury can - under certain very specific circumstances - have a negative effect on your daily standings. But still...

http://ozreport.com/forum/viewtopic.php?t=24846
Is this a joke ?

Jim Rooney - 2011/08/26 02:44:10 UTC

The "purpose" of a weaklink is to increase the safety of the towing operation. PERIOD.

...I find it terribly hard to believe that a weak link blow could POSSIBLY...

http://ozreport.com/forum/viewtopic.php?t=24846
Is this a joke ?

Jim Rooney - 2011/09/02 19:41:27 UTC

Please note that the weaklink *saved* her ass. She still piled into the earth despite the weaklink helping her... for the same reason it had to help... lack of towing ability.

...make ANY tow situation WORSE.

To be safer and tow more smoothly, a comp pilot could use a small fin [ref 17] on his/her glider...

You mean the fin that increases directional stability? So in order to protect his precious weak link for four minutes of tow the comp pilot is gonna be flying the rest of the afternoon turning into and inside of thermals and adjusting his roll to optimize climb on a glider with extra directional stability. Sounds like a plan to me!

...and use a three-point V-bridle instead of a pro-tow V-bridle.

- Yeah, comp pilots just LOVE throwing all that crap into the airflow.

- And Industry Standard two point releases...

miguel - 2012/05/31 22:57:42 UTC

The glider had a bicycle handle release. When it came time to release, it would not release and in fighting with it, it came loose on the downtube, rotating around it. Fighting with it put the glider in the beginnings of lockout so I flew the glider. I noticed that the truck had stopped but the reel was free wheeling. I had done step towing before so I flew large circles around the towline and landed into the wind. I kissed the ground and swore never to tow a hang glider again.

...all have such GREAT reputations for safety and reliability.

If they want to stick with a pro-tow bridle, they could reduce the likelihood of an inadvertent weak link break by: (a) using a polypro rather than Spectra bridle, to reduce the intensity of the shock load placed on the weak link;

Bullshit.

(b) making their bridle a bit longer so that the force vector on the weak link has the effect of making the weak link stronger;

Bullshit. The apex angle on ANY one point bridle is so acute that making it longer won't make a bug fart's worth of difference.

(c) using a slightly stronger weak link, such as 160 lb. rather than 130 lb. line...

Let's not go nuts here.

- That translates to an extra sixty pounds of towline tension.

- And on the 260 pound maximum certified operating weight glider that just about all of us fly that's almost an extra quarter G. No telling WHAT might happen with that much extra PRESSURE.

...but only if that stronger weak link is coordinated with the weak link used by the tug;

Yeah, ya just gotta coordinate with the tug.

He's expecting to tow a 260 pound glider using a USHGA recommended nominal one G weak link - not a 320 pound glider using a one G weak link. And these are the guys who've been perfecting aerotowing over the course of decades and hundreds of thousands of tows, forbidding us to use any equipment that doesn't have a huge track record, keeping us on the very safest of weak links, and selflessly risking their lives to get us airborne. So let's show a little consideration. It's the very least we can do.

...and/or (d) using a WT-style weak link rather than a pre-tied weak link, so that it will more consistently break at its intended strength.

Shove it up your ass.

Cone of safety, flying with a fin is better for your weak-link, too many other examples from the last few pages.
What a load of shit.
Who are these people?

Total quacks. And the people controlling US hang gliding - and moving it backwards as fast as they can manage.

Lisa

Finally, everyone should know that thorough aerotow training and currency results in a more proficient aerotow pilot who can tow more smoothly and can stay more precisely in the center of the cone of safety [ref 18]. When hang glider pilots can fy their gliders on tow as smoothly as a sailplane flies on tow, it is less likely that they will experience an inadvertent weak link break. Is that it for this article?

So what are you saying, Lisa? That people who fly sailplanes are naturally gifted and people who fly hang gliders inherently suck?

Three points...

Steven Kinsley - 2006/11/23 03:38:11 UTC

Sailplanes are a piece of cake to tow. Much easier than a hang glider.

- Hang gliders will NEVER be a fraction as easy to tow as sailplanes. We've gotta use muscle and the towline is hooked up to our control system. (Funny Steve was able to figure that out but you - AND TRACY - weren't.)

- But any halfway competent fuckin' Hang Two - barring a lockout, from which NO ONE is immune - can in soaring conditions keep a hang glider in position just as well as a sailplane.

- There are TWO reasons hang gliders blow weak links.

-- First and foremost, you inbred flight park pigfuckers are putting them up on weak links half to a third of what you're telling them they are and a third to a quarter of what they should be.

-- You inbred flight park pigfuckers are putting them up on crap releases that NOBODY can operate SAFELY or AT ALL when the shit hits the fan.

Tracy

We could get into details of lab testing weak links and bridles, but this article is already getting long.

Yeah, and we'd MUCH rather hear about how you two assholes lead the Seal Team 6 raid on bin Laden's compound last year. That would be SO MUCH more interesting.

That would be a good topic for an article in the future.

I can hardly wait. So when are you pathologically disingenuous pieces of shit planning on putting a loop of 130 pound Greenspot on a test rig and coming back and telling us what a load of absolute rot you've perpetrated on this sport with this work of fiction?

Besides, with our backgrounds in formal research, you and I both know that lab tests may produce results with good internal validity, but are often weak in regard to external validity--meaning lab conditions cannot completely include all the factors and variability that exists in the big, real world.

- Fuck your backgrounds in formal research. Neither one of you has the brains, honesty, integrity, or respect for process to be allowed anywhere near a fifth grade science project competition.

- There is NOTHING that can be safely learned about weak links which includes all the factors and variability that exist in the big, real world.

- Here's what it says in Reference 4, Page 56:

The only way to ensure safe, consistent weak links is to test each batch of new weak link material with the same equipment (release, rings, bridles, etc.) for breaking strength.

That's what you NEED to do and that's ALL you need to do.

- And neither one of you lazy irresponsible motherfuckers has EVER ONCE tested a SINGLE loop from a SINGLE batch of ANYTHING.

What we have covered in this article is practical information and knowledge gleaned from the real world of aerotowing, developed over decades and hundreds of thousands of tows by experts in the field.

What you have covered in this work of fiction is load of rot a bunch of incredibly stupid self glorifying air jocks pulled out of their asses on Day One a couple of decades ago and carved into granite.

This information has practical external validity. Hopefully, someone will develop methods and technology that work better than what we are using as standard practice today.

Hopefully you'll both break your fucking necks at the ends of whipstalls induced by failures of USHGA recommended nominal one G 130 pound Greenspot weak link blows.

Like the methods and technology used today, it is unlikely that the new technology will be dictated onto us as a de jure standard.

Meaning the technology I'VE developed and refined, right Tracy? Straight pin releases that can handle loads and be actuated without loss of control, Steve Kinsley's multi-string, wrap proof and resistant bridles, shear links?

Yeah, it's about as unlikely that you'll be forced to use equipment which complies with existing regulations as it is that you'll even bother to look at it, motherfucker. You scumbags have done what you do best - wormed your ways into positions of control and crushed every effort for advancement onto which you could get your crosshairs.

Rather, to become a de facto standard, that new technology will need to be made available in the marketplace, proven in the real world, and then embraced by our sport.

I REALLY can't see that happening. What we have now is practical information and knowledge gleaned from the real world of aerotowing, developed over decades and hundreds of thousands of problem free tows using 130 pound Greenspot by experts in the field. That information has practical external validity. And if someone had developed methods and technology that worked better than what we are using as standard practice today we'd have been using it already.

FUCK YOU.

Lisa

I m looking forward to that.

I'll bet you are, Lisa. I can tell by the way you're always seeking out the best technology and putting it in the air - the way Antoine does. At the rate you're going in only twenty years you'll be using the same spinnaker shackle, brake lever, cable, velcro, bent pin, 130 pound Greenspot crap that people were using forty years before.

You were right; this has been a serious and technical discussion.

In the way one might have a serious and technical discussion about evolutionary biology at Liberty University.

FUCK YOU.

So to finish, I have another joke...

The entire fuckin' article was a joke. Damn near all of it a hundred times funnier than the intentional stuff at the beginning and end.

An old weak link walks into a bar and sits down next to a string. The string says, 'This is a string bar, they don't serve weak links here. Aren't you a weak link?" To which the weak link replied: "No, I'm a frayed knot!"

Quit your day job.

Tracy

You know, you've got to be kind of weird to tell a joke about weak links.

- Hey. Did you hear the one about the Hang Glide Chicago student who was killed instantly - along with his "instructor" - when the tandem trainer whipstalled after the front end weak link blew?

- A frayed knot.

Lisa

And just as weird to understand it!

Sure is a good thing you assholes understand this much. So maybe you could explain to me how the issue of frayed knots was relevant to the issue of aerotow weak links - 'cause I've never seen them in the field and there was absolutely nothing about them in this epic load of crap you just fed us.

This article was peer-reviewed and approved for publication by the USHPA Towing Committee.

You're goddam right it was PEER reviewed. And for a really good definition of what a peer is let's have a look-see at Reference 8:

A person who has equal standing with another or others, as in rank, class, or age: children who are easily influenced by their peers.

So maybe you should get this rot reviewed by someone who DOESN'T have total shit for brains.

http://groups.yahoo.com/group/skysailingtowing/message/7067
AT SOPs - proposed revisions

Subj: Re: [Tow] AT SOPs - proposed revisions
Date: 2009/05/10 02:08:52 UTC
From: cloud9sa@aol.com
To: skysailingtowing@yahoogroups.com
cc: GreggLudwig@aol.com, lisa@lisatateglass.com

This information would also be very helpful in convicing the USHPA and others to take your complaint seriously. Most of the individuals who serve on the USHPA Towing Committe have most of the credentials listed above, so it will be great for you to let them know about your similar credentials and depth of experience, too. If you do not have those credentials, it will be a simple matter for the USHPA Tow Committee to respond to the FAA to discount your complaint, so it will be very important for you to present this information in your letter to the FAA and to others now.

The best way to make change is to get involved, and join the Tow Committee at its meetings. That's what people who really care do to make change. Such is the nature of the great opportunities we have to make a difference in the US (although it means having to spend time, money, and effort, compared to the ease of just sitting in front of a computer.)

Good luck with your endeavor, and regards,

Dr. Tracy Tillman
USHPA Director, Region 7
FAA Detroit FSDO FAAST Aviation Safety Counselor

If I had a magic wand your fucking heads would be on fucking pikes - right along with those of all the other motherfuckers who signed off on this rot.