Kite Strings

In REAL aviation weak link regulations are expressed in terms of a maximum and a minimum. The top figure protects the glider, the bottom its pilot.

And in hang gliding the circumstances in which the glider needs protection are virtually nonexistent.

http://ozreport.com/forum/viewtopic.php?t=22660
What can be learned from this "scooter" towing accident?

Jim Gaar - 2011/01/28 19:33:21 UTC

One thing I haven't read mention of is the actual size (length) of the weaklink "loop" itself. This can have a HUGE affect on how clean the bridle and/or the weaklink itself slips through the tow ring!

I always use an 8 inch piece of weaklink material. I've seen longer weaklinks wrap, and shorter weaklinks break early, way more then weaklinks from an 8 inch line.

One thing I haven't read mention of is the actual weight (strength) of the weaklink "loop" itself.

Towing Aloft - 1998/01

A weak link is the focal point of a safe towing system.

A weak link is a very simple device--typically a loop of line--that is intended to break in the event towline tensions exceed a safe or desired threshold.

A weak link is required that will not break needlessly in response to moderate thermals, or pilot inputs, yet will break at a low enough point to avoid disaster or excessive pilot panic.

"It is infinitely better to have a weak link break too soon rather than too late."
-- Towing Proverb

A weak link is a fuse that protects the equipment--your body!--on an overloaded circuit.

Always use a weak link when towing--WEAK LINKS SAVE LIVES.

Of course, your weak link should break before the lockout becomes too severe, but that assumes a properly applied weak link.

- The towing system wasn't safe. As a matter of fact, if there hadn't been a weak link...

The release bridle got caught in the weak link loop at the end of the tow line.

...the bridle wouldn't have gotten caught in the weak link loop and Shane wouldn't have been killed.

- It didn't break - as intended - when the towline tensions exceeded a safe and desired threshold.

- It didn't break at a low enough point to avoid disaster - and we can probably assume at least appropriate pilot panic.

- It didn't protect his body - and I would hazard a guess that the equipment came out a little worse for wear as well.

- It didn't save his life.

- And the lockout became too severe - so we probably gotta assume in improperly applied weak link.

So how come we're not going nuts about this weak link the way we were - and are - about Robin's?

Or, if all this stuff in Towing Aloft is a heap of shit, how come we're not all going nuts about that?

So Jim,

What's this "weaklink material"? Or am I a total moron for not immediately assuming magic one-size-fits-all 130 pound Greenspot?

What's it hold to when you use an eight inch length? How 'bout a loop from four? Half that? Do you need special gloves to handle a two incher so it doesn't disintegrate before you get it on the rig?

How many tests have you run?

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.

Must've been a little short, huh Jim? Six inches maybe?

http://ozreport.com/forum/viewtopic.php?t=22660
What can be learned from this "scooter" towing accident?

Jim Rooney - 2011/01/30 09:09:45 UTC

A bit of an eye opening experience that I don't suggest you try... this is something taught under very controlled conditions... is "lockout training". Essentially, you slowly get out of position behind a tug. Do it smoothly enough and you'll be surprised how long that little weaklink holds out and how exceptionally fast lockout accelerates from "a little bad" to "holy shit!"

Here's the other side though... don't do it smoothly and you'll see how fast that little weaklink gives up.

NO SHIT? The faster and harder you roll away from the tug the sooner the weak link will blow? And you figured that out all by yourself?

Mitch Shipley - 2011/01/31 15:22:59 UTC

Enjoy your posts, as always, and find your comments solid, based on hundreds of hours / tows of experience and backed up by a keen intellect/knowledge of the issues when it comes to most things in general and hang gliding AT/Towing in particular. Wanted to go on record in case anyone reading wanted to know one persons comments they should give weight to.

How many hundreds of hours/tows did it take someone with an intellect as keen as yours to reach a stunning conclusion like that?

If you're right - and, as exciting as this new hypothesis is, we still need independent testing and confirmation - the implications are mind boggling. This would almost certainly mean that if you swung a bat harder and faster at a ninety mile per hour pitch the ball would go faster and farther! You'd be more likely to hit it out of the park! Does anyone have Mark McGwire's email address? The same might also apply to a stationary ball when hit with a golf club! DUDE!!! I'm thinkin' Stockholm!

Of course what he means is that a 130 pound weak link blows at much less than 130 pounds if a load is applied quickly, reminiscent of the lunacy expressed and supported at:

http://www.hanggliding.org/viewtopic.php?t=13864
My new wing

Keith Skiles - 2009/10/05 16:44:40 UTC

It does matter. Have you ever heard the terms "impact" and "impulse" or the biggie, "shock loading"? A force of 75lbs applied over 3 seconds is merely 75lbs. A force of 75lbs applied over the fraction of a second it takes you to stomp is a lot more. I wish I had my old fracture mechanics book and I would show you just how much difference there is. Needless to say, your 75lbs of "stomping" could easily break a 300lb rated wire.

(And it's a 920 pound wire, by the way.)

So what Jim's saying is that all of us weekend warriors have been doing it WRONG - for decades. We've all been resisting the roll and pulling in. What we SHOULD be doing is ignoring our releases - 'cause we can't get to them anyway and they probably won't work even if we did - and accelerating the lockout 'cause that'll get us off tow faster.

And - ignoring the few good no-hands releases out there - he's absolutely right! It WILL get you off tow faster! We're just not being told how that's gonna do us any good when and after it does.

Because he only does this in - and is able to "think" about it occurring under - "very controlled conditions", i.e. in smooth air, a deliberate roll away from the tug, a half mile up... in circumstances in which there are no consequences for anything you do.

Meanwhile, back in the REAL world with REAL lockouts in REAL air at, occasionally, REAL altitudes...

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.

- The weak link doesn't blow 'cause you're not rolling away from the tug as in the classic smooth air fake lockout.

Almost immediately the glider went into a lockout and the weak link broke just as I hit the release. I almost got it around but couldn't quite pull it off, so the left corner of the control frame dug into the ground taking out the right downtube and fractured a small bone in my wrist (the ulnar styloid).

- The weak link only blows as it's being shredded by the notch on the spinnaker shackle after you've opened it - and you still crash hard.

I heard a snap, and then just like the sound of a WWII plane just shut down hurdling to the ground, only the ball of fire was missing. The tug weak link broke off at 1000ft, in less than a second the glider was at 500ft.

- The weak link blows in the course of the lockout, you go down like a brick, and you die if you're below five hundred.

Then, at around fifty to sixty feet, the glider pitched up radically and started arcing to the left. Somewhere around this time the weak link broke. The glider continued rotating left and dove into the ground, first hitting the left wing tip, then nose.

- The weak link blows in the course of the lockout, you go down like a brick, and you DO die because you ARE below five hundred.

The pilot launched with his Litespeed and climbed to about forty feet when he encountered a thermal that lifted him well above the tug. After a few moments, the glider was seen to move to the side and rapidly turn nose down to fly into the ground, still on tow, in a classic lockout maneuver. The impact was fatal.

- You lock out and slam in and the weak link lives longer than you do.

Eric Aasletten launched at about 14:43 into strong conditions and was unexpectedly hit by a powerful updraft at about fifty feet. From the front it looked as though he went into a whip stall and hit the pavement at a violent rate.

I talked to a lot of pilots at Hobbs, and the consensus was that in the course of Eric Aasletten's accident, had a weak link break occurred instead of the manual or auto release that apparently did occur, the outcome would have been the same.

Analyzing my incident made me realize that had I released earlier I probably would have hit the ground at high speed at a steep angle. The result may have been similar to that of the pilot in Germany.

- You come off tow under light tension when tension - light or high - is the only thing keeping you alive.

http://groups.yahoo.com/group/skysailingtowing/message/4607
Weaklinks - What force are you trying to break them with ?

Michael Derry - 2005/02/09 11:10:14 UTC

What I think is missing from this analysis is that the force on the weak link if a glider banks up into a lockout is some squared relationship to the speed.

And when you ARE rapidly rolling away from the tug, the difference in time between a three quarter and one and a half G weak link blowing - and the attitude of the glider when one does - ain't gonna be worth talking about.

Essentially, you slowly get out of position behind a tug. Do it smoothly enough and you'll be surprised how long that little weaklink holds out...

Really?

My weak link broke for no obvious reason at about two thousand feet as Zach was pulling me in a wide turn to get back into a thermal he had found earlier.

Then I switched to the Falcon and the birds were singing in tune again. Until the brand new weak link vaporized at about a thousand feet for no apparent reason.

One broke while aerotowing just as I was coming off the cart. Flared immediately and put my feet down only to find the cart still directly below me.

Maybe we should all try slowly getting out of position 'cause what always astonishes me is that little weak link holding long enough to get a glider fifty feet off the runway while people are staying in perfect position.

http://www.chgpa.org/forums/viewtopic.php?f=2&t=3600
Weak link question

Janni Papakrivos - 2008/11/05 23:03:26 UTC

I probably witnessed fifty broken weak links this summer at Highland.

Obviously almost always in the course violent lockouts.

Jim Rooney - 2011/01/31 19:16:54 UTC

Hi Mitch!
Welcome to the circus

For those who don't know Mitch... in addition to many other hats (including sub commander and professor)... he's an instructor at Quest Air.

Yeah, that WAS Mitch Shipley.

He's got a very level head and is a good friend.

Pick one, Jim. Those are mutually exclusive conditions.

http://ozreport.com/forum/viewtopic.php?t=9945
Launched unhooked

George Stebbins - 2007/10/26 16:05:20 UTC

The weak link is NOT there to prevent the glider from being overstressed on tow. OK, it serves that function too, but its main purpose is to release if you get too far off-line or some other issue causes the forces to become stronger than you, the pilot, can control. The forces become too strong for the pilot to overcome LONG BEFORE the glider gets overstressed. Does the weak link always do its job? Nope. On the other hand, making it too weak is a danger too. The key is to minimize risks. A reasonable weak link does that. It will seldom (but not never) break when it shouldn't. It will usually (but not always) break when it should. Different forms of towing use different strengths. And tandems need stronger ones regardless, because the tow forces are higher.

There are some folks who tow with very strong weak links. They are asking for trouble, IMO.

http://www.questairforce.com/aero.html
Aerotow FAQ

Quest Air Hang Gliding

Weak Link

The strength of the weak link is crucial to a safe tow. It should be weak enough so that it will break before the pressure of the towline reaches a level that compromises the handling of the glider but strong enough so that it doesn't break every time you fly into a bit of rough air. A good rule of thumb for the optimum strength is one G, or in other words, equal to the total wing load of the glider. Most flight parks use 130 lb. braided Dacron line, so that one loop (which is the equivalent to two strands) is about 260 lb. strong - about the average wing load of a single pilot on a typical glider. For tandems, either two loops (four strands) of the same line or one loop of a stronger line is usually used to compensate for nearly twice the wing loading. When attaching the weak link to the bridle, position the knot so that it's hidden from the main tension in the link and excluded altogether from the equation.

IMPORTANT - It should never be assumed that the weak link will break in a lockout.
ALWAYS RELEASE THE TOWLINE before there is a problem.

http://ozreport.com/forum/viewtopic.php?t=12512
Weak Links

George Stebbins - 2008/07/13 21:01:44 UTC

I've always been happy with the Quest Air links, and only once did one break when it annoyed me seriously, and for no apparent reason. (Just as I crossed the treeline. I had to whip a 180 before I ran out of altitude to do so. Then I had an interesting landing, not really having room to turn back into the wind...)

I've had enough links break when they should to think mine is ok...

Lookout Mountain Flight Park - 2009/07/12

The new GT aerotow release is designed to be used with a V bridle and a 130-pound green stripe Dacron tournament fishing line weak link. At this time it is not recommended to use this release with a higher value weak link. We are confident that with an ultimate load of 130 pounds at the release point, the new GT aerotow release works better than all cable releases that we have experience with.

http://www.hanggliding.org/viewtopic.php?t=20756
How is Zach Etheridge doing?

Joey Quillen - 2011/02/04 01:34:54 UTC
Nashville

Does anyone know how Zach Etheridge fared after his accident late last year? He was being aerotowed at LMFP when his line released near the end of the LZ. He unsuccessfully tried to recover from the stall and turn around to land. He impacted and went unconscious. I happened to be across the LZ with some friends and we ran out to help, but he was out cold.

I tried calling the hospital but could never get through. Does anyone have any info on his status?

Bob Flynn - 2011/02/04 05:51:15
Jacksonville, North Carolina

I don't think I heard about this accident. I hope he recovered from his injuries.

Joey Quillen - 2011/02/04 10:01:30 UTC

I want to say it was in late August or early September. I had made my first mountain flight that day and I was so excited, then we saw him crash. It was a terrible sight. He is a middle aged gentleman, white beard, a slight belly, very nice guy, flies a North Wing Freedom, lives in Georgia (I think). I will post a pic of him when I can find one.

Diev Hart - 2011/02/04 10:25:40 UTC
Santa Cruz

This is what really bugs me, when things happen and the word never gets out...
SOOOOOO uncool as a school / organization / instructor...
(I'm not saying this wasn't reported though...(but I don't remember it either)...

http://www.hanggliding.org/viewtopic.php?t=14230
pro tow set-up

Jack Axaopoulos - 2009/11/09 14:44:23 UTC

Tad, your continual bashing in general and bashing of HG schools has gotten really old. AT parks have solid safety records, so what you say and reality seem to be quite far apart.

You dominate the ignore report here http://www.hanggliding.org/ignorereport.php
Ever ask yourself why???

You do nothing but bring negativity here. My finger is on the ban button.
This is your last warning.

If you continue rubbing everyone the wrong way with your harsh, know it all tone, you are out of here.

http://www.hanggliding.org/viewtopic.php?t=17092
Crash at Questair

Alfie Norks - 2010/06/03 12:24:40 UTC
Brazil

Speedy recovery to the pilot in question.
It could have been worse. It could have happened at...the other place (but nothing happens there. ) Good luck if it does. No 911 calls allowed. My friend was lucky, the nurse on hand convinced the owner not to move him, this after he snatched and threw her phone away. She was trying to dial 911. My friend suffered lower back injury.

http://www.hanggliding.org/viewtopic.php?t=20756
How is Zach Etheridge doing?

Bob Flynn - 2011/02/04 11:26:34 UTC

Lookout keeps this kind of stuff under their hat. You never hear of accidents there. But every time I go there, I hear about quite a few. Blown launches, tree landings, etc.

Joey Quillen - 2011/02/04 15:20:23 UTC

OK, I just called LMFP and asked about Zach. Apparently he made a full recovery after his accident and is back flying. He was there a week ago, even! That is a load off...

Christmas in February...

George,

The weak link is NOT there to prevent the glider from being overstressed on tow. OK, it serves that function too, but its main purpose is to release if you get too far off-line or some other issue causes the forces to become stronger than you, the pilot, can control...

Bullshit.

http://groups.yahoo.com/group/skysailingtowing/message/4633
Weaklinks and aerotowing (ONLY)

Steve Kroop - 2005/02/10 04:50:59 UTC

Weak links are there to protect the equipment not the glider pilot. Anyone who believes otherwise is setting them selves up for disaster.

If you're gonna sing the praises of Quest's idiotic weak link policy then at least listen to one of the clowns down there who occasionally says something right.

Better yet - especially after listening in absolute astonishment to Mitch's assessment of Jim... Forget Quest ever existed and listen to these guys.

http://www.dynamicflight.com.au/WeakLinks.html
Weak Links - Dynamic Flight Hang Gliding School

Dynamic Flight - 2005

The purpose of a weak link is solely to prevent the tow force from increasing to a point that the glider can be stressed close to or beyond its structural limits.

...but its main purpose is to release if you get too far off-line or some other issue causes the forces to become stronger than you, the pilot, can control.

So what you're saying is that if you use a half G weak link (and I haven't heard you mention anything about either Gs or pounds of tow tension (and people who make these arguments never do)) you'll either always be able to control the glider on tow or you won't be on tow?

The forces become too strong for the pilot to overcome LONG BEFORE the glider gets overstressed.

I got some REAL bad news for you. The forces can easily become too strong for the pilot to overcome LONG BEFORE a fuzzy loop of 130 gets mildly concerned about its survival.

Does the weak link always do its job?

What's its job, George? You need to understand the difference between the pilot/release combo and the weak link.

Nope.

Bullshit. Its job is to blow at its breaking strength. It will ALWAYS do that.

YOUR job is to ignore all the bullshit you've learned from Donnell, Dennis, Bill, the assholes at Quest, Wallaby, Florida Ridge, Lookout, Ridgely, Whitewater, Hang Glide Chicago, Adventure Air, Cowboy Up, You-Name-It Flight Park... determine an appropriate breaking strength for YOUR GLIDER, and acquire something that'll get you within a hundred pounds of your target.

On the other hand, making it too weak is a danger too.

Define "TOO WEAK". We really need to start hearing less about Quest and more about Gs at this point.

The key is to minimize risks. A reasonable weak link does that.

- Bullshit. You minimize risks by keeping the glider pointed in something approaching the right direction while on tow and CHOOSING to get off when being on is no longer in your best interest.

- A light, "REASONABLE", or heavy weak link may or may not do that. And the weak link on your glider or the air bag on your steering wheel blowing is a REAL good indication that you've done a shit job of minimizing risks.

- Define "REASONABLE".

Different forms of towing use different strengths.

Why? Does a glider fold up under fewer G's when aerotowed than when it's platform launched?

And tandems need stronger ones regardless, because the tow forces are higher.

But all solos should use the same one 'cause nobody's talking about Gs or pounds, right?

There are some folks who tow with very strong weak links. They are asking for trouble, IMO.

- Yeah, since we're not talking Gs, pounds, standards, or anything remotely resembling reality and are instead doing:
-- too far off-line
-- stronger than you can control
-- too strong for the pilot to overcome
-- too weak
-- reasonable
-- seldom
-- usually
-- should
-- different
-- stronger ones regardless
-- tow forces are higher
-- very strong
we can make this issue all about your OPINION - just like hang gliding has always operated with respect to weak links in particular and tow equipment in general.

- Who are these folk towing with "very strong weak links" - whatever the hell those are?

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.

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.

Are they clueless reckless Twos or the pilots who have enough intuitive feel for what's going on, think something's wrong with this picture, and are tired of total asshole flight park operators and tug drivers dictating policy?

- You got any data to support your OPINION? Who's actually HAVING trouble?

http://www.hanggliding.org/viewtopic.php?t=6911
Sunday flying at Florida ridge. -

Axel Banchero - 2008/05/22 04:19:39 UTC

Doc's body wasn't moving and we were shitting our pants until he started talking confused. The first thing I saw was his eye bleeding and swollen the size of an 8 ball. There was sand and dirt inside. Looked like he lost it at first until he could open it a little bit.

Or is this just a nice socially acceptable position to take? (Fly safe - don't go too high or too fast.)

Just as I crossed the treeline.

He was being aerotowed at LMFP when his line released near the end of the LZ.

I had to whip a 180 before I ran out of altitude to do so.

He unsuccessfully tried to recover from the stall and turn around to land.

Then I had an interesting landing, not really having room to turn back into the wind...

He impacted and went unconscious. I happened to be across the LZ with some friends and we ran out to help, but he was out cold.

I've had enough links break when they should to think mine is ok...

- That's great that your magic Quest weak links consistently blow to do your job for you, but sometimes all you need to do is lose the tow at a time not of your choosing ONCE to get really fucked over. So ONCE is WAY too many times. A competent pilot is unlikely to EVER blow a weak link.

OK, I just called LMFP and asked about Zach. Apparently he made a full recovery after his accident and is back flying. He was there a week ago, even! That is a load off...

"Hi, Matt. Joey. Do you know how Zach is doing?"
"Who?"
"Zach. Zach Etheridge."
"Who?"
"Guy who crashed real bad in the LZ late year."
"Can you narrow that down a bit for me?"
"Late August or early September."
"Uhhh... Just a second. Got a call on the other line. I'll get right back to you.
...............
Oh yeah. ZACH!!! Yeah, he's fine. They just took him in for precautionary reasons and released him in under an hour. Looked a lot worse than it was. Great guy. He was here just a week ago. Three hours, five K, thirty miles... You shoulda been here! Great hearing from you, Tony! I'll tell him you said hi. Fly safe."

Jack,

Fuck you.

Revised thinking on hang glider weak links...

We're not using weak links to protect gliders. The strength of the gliders is ridiculous. Six Gs minimum.

We're using weak links to keep releases from being overloaded.

All gliders use the same releases.

Barrel releases based on M111S parachute pins can handle 350 pounds of direct loading no problem.

A two point release feels 345 pounds when the towline tension is 600.

A 600 pound weak link keeps a max loaded Falcon 3 Tandem a bit over a G.

Baby gliders are proportionally stronger than big ones - same tubing, wires, sail material, lighter pilots, shorter wingspans, less square footage.

A max loaded Falcon 3 145 about to blow 600 pounds of towline tension is feeling three and a half Gs. BFD. Make it 500 and you're a little over three Gs total and two of towline tension.

The pinbrains who've been running aerotowing for twenty years have been using one-size-fits-all 130 pound Greenspot to put virtually all gliders on the ragged edge of sustainable tow.

We could do 500 pound weak links for all smaller gliders and 600 for the big ones. Flip a coin for the stuff in the middle.

I'm not following you here, Tad. You've been advocating glider-appropriate weak links, and now you're suggesting one-size-fits-all (or two sizes)? Why?

I also don't get your statement that "all gliders use the same releases." I've seen a lot of different release configurations. Very few are using M111S pin releases. Is 345 lbs excessive for cable-actuated spinnaker releases?

As for my thinking on 600 lb (tow line tension) weak links...

One of the Wills Wing presentations I attended was about operating limitations and glider certification. Steve discussed how gliders are tested to twice the loadings indicated by their operating limitations. I asked if they ever test to failure and he said generally no, but they know the gliders can take a lot more than they test them to. So I asked 'isn't the safety factor actually more than 2, then?' His response was that yes, on a new glider it is, but things like kinked or frayed side wires or previously bent downtubes can reduce a glider's load capability.

That's the kind of thing makes me nervous about putting 3.5 Gs on a wing. Our wings aren't required to receive any kind of periodic recertification. Maybe it's an unreasonable phobia...even a compromised (to the extent that you might not be aware of it) wing shouldn't have trouble with 3.5 Gs...but since tow forces shouldn't get anywhere near that I see no disadvantage capping them at, say, 2.5 Gs (other than requiring more weak link flavors).

And if we use 600 lb glider weak links, we'll need 700 for the tug end to comply with USHPA's recommendations.

Zack

Why?

Because the day before I was talking to Joe Street about the issue of Shear Links needing to be color coded so you didn't mix them up and said that "that could make things a little dangerous."

Then I thought, "Would it really? What's the worst that could happen?" And then I concluded, "Not much."

As I explained above, smaller gliders can take more Gs than larger gliders so you're not any more likely to blow up a little one using the weak link for a big one. I'd actually predict you'd be LESS likely. The hook-in weight range is specified for reasons relating to control and performance - not load capacity.

I also don't get your statement that "all gliders use the same releases."

I'm saying that when you order a release from Wallaby, Quest, or Lookout you don't get asked your glider size or flying weight and they have the same thing they're selling you on their tandems - primary and "backup".

Is 345 lbs excessive for cable-actuated spinnaker releases?

I dunno. What kind of luck have you been having at a fifth of that?

If you rig it the way God intended - the way I did - yeah, I can handle that much no problem. And you can always step up the capacity with pulleys.

That's the kind of thing makes me nervous about putting 3.5 Gs on a wing.

So we should dumb down weak links so people can maybe get away flying kinked and/or frayed sidewires and/or bent downtubes a little longer?

Lemme tell ya something about frayed wires I probably shouldn't admit.

Maybe about twenty years ago I noticed a single broken strand on one of my Comet 165's tail wires at the nico at the keel. I thought, "Eh, it's a tail wire. It's not taking any load, I'll take care of it after another flight or two." After another flight or two I checked it again. HOLY SHIT!!! I was hanging on by a thread. I had heard those things propagate like hell after just one strand but I sure never thought a tail wire would work that way.

If a glider's not safe to tow with a two G weak link it's not safe to fly in thermal conditions.

Our wings aren't required to receive any kind of periodic recertification.

That sidewire stomp preflight test you're doing isn't a bad facsimile.

Suggestions...

- Also put a foot on the keel just aft of your sail and pull back hard on the upper tail wire to check for problems with longitudinal wires.

- Before you start breaking down do POSTflight tests on the lateral and longitudinal wires. That way if you pop anything you have a week to get it replaced instead of finding out at noon on Saturday that you're screwed for the weekend and you're better covered if you forget that part of the preflight next time.

Maybe it's an unreasonable phobia...

Once you've straightened out a leading edge by putting it between a couple of closely spaced tree trunks and using the other end as a lever arm you tend to get a whole lot less paranoid. If that doesn't work for you just look at the grotesque distortion of the wings when the glider is undergoing a certification load test on a truck.

Three Gs is about what a glider is feeling at the bottom of a properly executed loop and that's not that big of a deal. If your wires are OK and you haven't gotten too ridiculous with a downtube you're gonna be OK.

...but since tow forces shouldn't get anywhere near that I see no disadvantage capping them at, say, 2.5 Gs...

I'm not saying you HAFTA go over that. I'm just saying you CAN and it won't make any difference.

And if we use 600 lb glider weak links, we'll need 700 for the tug end to comply with USHPA's recommendations.

- Yes. And?

- Since when did anybody start worrying about USHGA's
-- recommendations?
-- regulations?

- At six hundred pounds I'm really not all that worried about anything blowing anywhere. It just ain't never gonna happen.

- With those two weak links - five and six hundred pounds - you just BARELY stray beyond the EXISTING USHGA two G maximum on only the very smallest of gliders - which are the ones in which that would be least problematic.

Zack C wrote:I'm not following you here, Tad. You've been advocating glider-appropriate weak links, and now you're suggesting one-size-fits-all (or two sizes)? Why?
Zack

YES one size fits all!

I posted this on my local forum during a weak-link discussion.
I am pleased to say these things get an airing every once in a while at our club.

I was a bit of a lone ranger on this one but was trying to make a point.

.....

"** IMHO ** and no doubt controversial.

Find the biggest, fattest f****r in the club (this is not a competition) and give him a weak-link strong enough so that it never ever ever breaks (ok never say never acknowledged).
Anyone smaller than the biggest, fattest f****r in the club can then enjoy the EXTRA safety margin this would give you at the time when you really need it.

This is at the expense of the weak-link breaking at a few dozen pounds closer to the enormously generous 6.5G limit of the glider and losing the ability (according to the USA) to deliberately break the weak-link by the fantastically optimistic practice of pushing out hard in a lockout."

.....

This thinking (ok this example was a bit over the top) originated around 1979 and I have seen nothing since that has persuaded me that we should be working from the bottom up.

Gawd. This is SOOO depressing.

I've spent tens of thousands of hours breaking, crashing, reading, thinking, developing, testing, explaining, fighting weak links. Weak links are the primary reason I've been kicked out of hang gliding.

Took me till Saturday to get back to that simple, common sense, obvious understanding of the issue. Thirty one or two years.

Thanks Donnell.

Tad Eareckson wrote: ....Thirty one or two years.
Thanks Donnell.

Not just Donnell.

This is what REALLY happened, dramatised for effect.
Imagine a small experimental tow group in the very early '80s.
Any names used are purely coincidental.
....
....

"Ok guys, what about the extra load on all this stuff?"

"Yes, we really need to start looking at other things now and have a bloody good tidy up, things are starting to come together nicely."

"How much extra load? What about beefing up the Xtube?"

"Don't be silly, we don't want to be modifying too much, these aren't Bog Rogs any more. Besides, we have that new fandangle automatic tension limiting device, we are never going to put THAT much load on anything."

"I beg to differ old boy, what if the winch brake locks up as we are trundling down the runway?"

"PAUL! What car did you cannibalise for a winch brake?"

"German."

"Small chance then."

"No no, I can see the point. A small chance is still too big.
Sorry I missed that one. I'm just so excited now we don't have to be very nearly tipping upside-down every few flights."

"We could think about putting in a weak-link now, just like the big glider boys."

"Yes, nice and simple and make it easy to break."

"Hang on hang on STOP. I don't want anything breaking when I fly, thank you very much. Certainly when I'm near the ground I don't want to stop flying. Are you mad? That concrete runway looks a lot harder than my face."

"Oh pi**off Lakey, always the pessimist."

"Just saying, that's all."

"No no, a weak-link, it's called a weak-link but it doesn't have to be THAT weak - just weaker than all the other stuff.
A better name would be 'equipment fuse' or perhaps 'Glider Protection System' yes 'GPS' that has a nice ring to it, not that that is ever going to catch on."

"What value should we use then? Paul, you are good with numbers what do you think?"

"F*** off and do me a favour, how on earth am I supposed to work that one out you bunch of c***s. Not even Albert E himself could do that one. Too many variables not enough data.
Even if I had my own computer, and there is a zero chance of that ever happening, it could only ever be a best guess. Do some f***ing tests and find something that works."

"Well if we are going to have one I still think it might as well be a very weak one. Think of all that extra protection."

"Err... extra protection how come, as long as it breaks before anything else?"

"No, I don't mean just things breaking. I mean, what if, say, I drop a wing on take off and my wing tip just touches the ground, the weak-link would break and ...."

"Hang on, hang on, STOP. I don't want anything breaking ESPECIALLY if my wingtip is just touching the ground. That concrete runway looks a lot harder than my face and I don't want to be stopping off anywhere near it."

"Oh pi**off Lakey, pessimist again. You will be expecting everyone to fly with a parachute next."

"A what?"

"Never mind."

"Ok what if the release fails, the weak-link might help you out.... On second thoughts, it might be better to just avoid s**t rig releases."

"S**t rig releases. Work to be done on this one too chaps. What else is there about, anything worth investigating? How do they rate?"

"I've heard of one made completely of string and rings and stuff, nice and cheap."

"Did it work ok?"

"Well, only tested with two flights. On the first flight it operated perfectly, and on the second something jammed up on a ring and the guy was killed."

"Score that release as 'average' then."

(laughter)

"Back to the weak-link then. I'm afraid it's down to suck it and see again chaps."

"To conclude we need some kind of weak-link value as a starting point. I have this nice round number floating around in my head, can't remember where it came from. I seem to remember something about 'one G' and 'never to be exceeded'. It's probably as good a guess as anything."

"Great, now we need a test dummy, where's Thompson?...."
....
....

And somehow that nice round, best guessed number stuck.

How could ANYONE in the early '80s do anything other than make a best guess?
How is a best guess likely to be spot on first time?
How is any value likely to be relevant 30 years on?
How likely is it to fit in with such a nice round number?
Why 'never to be exceeded'. Does 20, 30, 40, 50lbs extra really make THAT much difference other than reducing unwanted weak-link breaks?

The fact is had that nice round number been shifted up by the equivalent of a couple of bags of shopping no one would have noticed anything any different, except for the reduction in weak-link breaks, except that wouldn't have been noticed, because there would be nothing to notice.

And you Tad might now be flying with your buddies giving them a never ending stream of abuse because they insist on using sh** rig releases.