Releases

[Tad Eareckson]

Hey Antoine,

Delighted to hear from you and REALLY delighted to hear that you've been working on this stuff.

Sixty degrees...

I don't really suggest a sixty degree angle for a primary bridle.

- Sixty degrees is about what one tends to see being used at the flight parks.

- I assume sixty degrees to calculate loads on releases and weak links.

- I advise using a bridle long enough to yield sixty degrees - OR LESS (longer bridle) to reduce loads.

- I decided on an arbitrary standard of ten feet (3.05 meters) for primary bridle length. (And the secondary assembly - of course - adds onto that.)

- Increasing primary bridle length WON'T increase the likelihood of a wrap (snag). Wraps - from everything I've seen and heard - only happen as the end is feeding through the tow ring (almost?) always because of an irregularity in the thickness/stiffness of the construction.

- The trade-off (compromise) is that the longer it is the more line you have to stow or leave trailing (preferably NOT over your basetube).

- So if you want to go longer - go longer.

- But if you want to go longer because your release is up against its limit you have a dangerous problem that going longer isn't going to help much.

4 millimeter Vectran...

I made a bridle for Zack out of eighth inch Samson AmSteel.

AmSteel is Dyneema and Dyneema is similar to Vectran but a little better for the application. Not enough to worry about though.

Eighth inch is 3.2 millimeters so your material is thicker - but I've spliced the entire length of the bridle. It's all double thickness except where the two material ends abut one another near the bottom end - which isn't meant to feed through the tow ring anyway. But I have a little length of heat shrink tubing over that spot anyway to restore the stiffness.

You can see it in Zack's photo at:

http://www.kitestrings.org/post248.html#p248

I'm pretty happy with the way it turned out.

Mixed feelings about your Lookout Release. I'm sorry you had that problem but I didn't like it very much and it's rather nice to hear that it fell apart when fairly new. I've heard way too many people talking about what a godsend it is and now I have some ammunition.

I wish it hadn't been drilled, though. I thought its performance was pretty good and we could've gotten the proper hardware for it. As a matter of fact... Matt should've shipped you a free replacement - the owner's manual doesn't say anything about screws falling out.

Sorry we're still so much on the English system over here - it does make life more difficult.

If you need something to get you by until you build something in, try Joe Street - racingthecloudsatgmaildotcom. I'm pretty sure what he's produced is pretty good and will let you use a heavier weak link without a lot of worry. A double loop of the famous 130 pound will be reasonably good for solo and not much of a headache for tandem.

Keep up the good work.

Best wishes,
Tad

[deltaman]

Thanks it's confortable to have answers so quickly !

Dyneema is similar to Vectran but a little better for the application. Not enough to worry about though.

I began with dyneema, red colored, and the red "varnish" was quickly burned where was the friction with the ring. In doubt, I changed for Vectran which is known to have better friction and temperature resistance. Why do you consider dyneema better?

Primary release]
don't laugh, I was too in a hurry, I ordered (but dont receive actually) a "SteevRelease". Hope it can work with primary bridle top eye directly in the pin rather than a wl.. We use wl on the line, and maybe soon a 150daN tost one for tandem. Hope the Tost carrier enough strong to hit the ground repeatedly (grass) I asked K.Hammon and I wrote a mail to Joe Street yet.

from everything I've seen and heard - only happen as the end is feeding through the tow ring (almost?) always because of an irregularity in the thickness/stiffness of the construction.

I've spliced the entire length of the bridle. It's all double thickness

ok I will consider it and double my 4mm Vectran with a heat shrink tubing where it is "needed".
Could you suggest the same for a secondary short braided bridle with 2 wl at both sides? but hard to choose the right place where the two material ends abut one another. You will advise me the..

Bridle link]
I tried to understand how to build and stitch a bridle link but it's a lot of specific words I have to translate.. You should write a mousetraps version for 10 years old child..

to be continued..

[Tad Eareckson]

Thanks it's confortable to have answers so quickly !

It's not like I've been getting buried in correspondence on this "forum" lately. You don't know how happy it makes me to have somebody besides me post once in a while.

Dyneema versus Vectran...

Here's what I pulled off the web...

http://www.rigworks.com/running-rigging/vectran-fiber-line.htm

Vectran is an alternative to Dyneema. It has less stretch and creep than Dyneema. Many think Vectran is the ultimate fiber, though it does not have quite the fatigue life or UV resistance of Dyneema. Also it is a little heavier and will not float.

Low stretch is ALWAYS good but in both materials stretch is going to be microscopic - especially when we're using lines with breaking strength ratings in the thousands of pounds to do jobs of two or three hundred pounds at most and usually in the double digit range.

Creep we can forget about.

The fatigue life and UV resistance are the issues that appeal to me.

I suspect the problem you had with the Dyneema bridle had to do with a coating issue rather than the fiber itself.

But if you're doing better with the Vectran then - by all means - stay with it.

It will be interesting to see how Zack's AmSteel bridle holds up - but we're probably not going to learn much without putting one on a tandem glider at a high volume commercial operation.

don't laugh, I was too in a hurry, I ordered (but dont receive actually) a "SteevRelease".

I'm not laughing - I'm more inclined to cry.

That guy does NOT know what he's doing or talking about, there is no indication that that release has been subjected to ANY kind of load testing, it's very poorly designed, and I would be astonished if it functioned much beyond normal tow tension. Please don't put it in the air without load testing it to at least whatever weak link you'll be using with it.

There's no reason that it shouldn't work any worse with the bridle, rather than a weak link, directly engaging it - BUT...

I would predict that whatever is being released is going to be chewed up a little each time and IF you use that release I would recommend that you have a weak link loop on the top end of your bridle so IT gets chewed up. Better to replace a loop of string every now and then than have your bridle degraded and ruined.

I wouldn't be at all happy towing with a 150 daN weak link on a tandem. I'd LIKE a four hundred but, if there were something on the tug end that needed to be protected by a two hundred, I could probably live with that.

I have no doubt whatsoever that you can do a hundred thousand landings on grass without hurting the Tost weak link assembly in the least but...

While they certainly have their places, the back end of a hang glider aero towline isn't one of their better ones. Keeping everything on the glider is a lot better.

ok I will consider it and double my 4mm Vectran with a heat shrink tubing where it is "needed".

It's not really "needed" - just makes me a little happier.

Could you suggest the same for a secondary short braided bridle with 2 wl at both sides?

No. The Bridle Link is so superior for that application that there's no point in even considering anything else.

I tried to understand how to build and stitch a bridle link but it's a lot of specific words I have to translate.. You should write a mousetraps version for 10 years old child..

1. If I want to get through to a lot of US pilots I better shoot for five year old comprehension levels and hope for the best.

2. You should be able to figure them out from the photographs...

http://www.flickr.com/photos/aerotowrelease/sets/72057594141352219/

Language neutral.

3. And/or I can send you one or two or four. They're pretty easy to make, cheap, and light. And they last forever.

Keep me posted.

[Tad Eareckson]

http://www.hanggliding.org/viewtopic.php?t=22233
Looking for pro-tow release

Ann Fawkes - 2011/06/14 17:54:04 UTC
Western Europe

Hello,
I am looking for a website or dealer who is selling the pro-tow release system with three rings.
http://en.wikipedia.org/wiki/3-ring_release_system
I learned to aerotow with this but metamorfosi is apparently not selling them anymore...
All input is welcome. Would be nice if I found it in Europe ...
Thanks!
Fawkes

Please don't refer to it as "pro-tow". It's not. It's the hang gliding equivalent of driving with a compromised steering system.

Casey Cox - 2011/06/14 18:26:32 UTC
Eastern North Carolina

I'm curious why you would want metal rings instead of the barrel, or a three ring that is cord.
Personally, I do not think I would want anything medal that would come back towards me.
Also where would the weak link be located?

Have you EVER heard of someone getting hit in the face by ANY component of ANY one point system following a release or weak link failure?

Marc Fink - 2005/06

Soon after liftoff out of our field, the towline itself failed at the tow ring. The ring remained attached to the bridle and came whizzing back at me and my passenger like a speeding bullet.

If you're so worried about having metal rings in front of you how come you're not worried about the tow ring?

(Hey, Marc... What were you using for your bridles? Poly? Perlon?)

Jim Gaar - 2011/06/14 19:45:12 UTC
Roeland Park, Kansas

Agreed.

Well, that settles it then.

http://ozreport.com/forum/viewtopic.php?t=23813
Threaded bridle system

Jim Gaar - 2011/05/26 15:44:33 UTC

I'm a Rooney follower.

Who's gonna argue with a Rooney follower?

You need to lose the rings and go with 1 or 2 barrel releases and a short bridle. Davis Straub sells a nice spectra bridle and the barrel releases on the Oz Report Classified section.

Definitely. Lose the rings. And go with one or two (simply a matter of personal preference) releases. From Davis. You know it's nice 'cause he says so.

But I've had it once where the pin had bent inside the barrel from excessive tow force. My weaklink was still intact.

The barrel release wouldn't work because we had too much pressure on it.

Doesn't matter if it actually WORKS or not - the important thing is that there's less metal in front of your face and everybody agrees that it's nice.

Ann Fawkes - 2011/06/14 20:10:12 UTC

Guys, I have no idea what you are talking about...

That's OK Ann. Rest assured, neither do they.

...the above is the only thing what I know but it is the PG version. What is a barrel release ?

It's a bent parachute pin on some webbing inside of an old piece of defined tip tubing.

Dennis Wood - 2011/06/14 20:26:19 UTC
Suffolk, Virginia

also check with Steve Wendt @ Blue Sky for a version of a three ring circus release. he also has standard barrel releases such as are used nowadays, and are among other things, less complicated and MUCH MUCH cleaner. or check with OZ report.

http://www.ozreport.com/9.133
Lesson from an aerotow accident report

Steve Wendt - 2005/05/29

The basebar hit the ground first, nose wires failed from the impact, and at the same time she was hitting face first. She had a full face helmet, which helped reduce her facial injuries but could not totallly prevent them.

Yeah, check with Steve Wendt. The important things about a release is that it's standard, used nowadays, and is, amongst other things, less complicated and MUCH MUCH cleaner. It doesn't really matter if it WORKS and/or can be actuated in an emergency...

But that's why we all fly with full face helmets - to reduce, but not totally prevent, your facial injuries. She only needed fifteen hours of reconstructive surgery. Had a good chunk of the day left over for dinner and a movie.

Andrew Stakhov - 2011/06/14 20:37:02 UTC
Toronto

Try this one:
http://estore.hanglide.com/Aerotow_Primary_Release_p/14-9004.htm

http://c2.staticflickr.com/2/1558/25912821781_ced007a9d6_o.jpg

Yeah, loads of help. A one point release with a minimum of metal. (Maybe you can talk to Antoine for a good review.)

NMERider - 2011/06/14 20:46:15 UTC

This is the Pro tow Mini Barrel Release and Bridle, $40 Davis sells:
http://ozreport.com/goodies.php

Yeah Ann, get that one.

It won't accidentally open by hitting your base tube, is small and easily stored, the most aerodynamic one available, thin and gets out of your way right away, easily stored and also creates less drag if you don't put it away and is much stronger than your weaklink.

Ann Fawkes - 2011/06/15 04:54:58 UTC

I just want something very simple and it works for me...

OH! You want something that WORKS! Then why are you talking to these assholes?

P.S. You can't always get something that's very simple AND works. Think about the brake system for your car and your cell phone. Sometimes you hafta make a choice. I'd advise going with works. But I always seem to be in a tiny and extremely unpopular minority inside of this culture.

Casey Cox - 2011/06/15 11:32:49 UTC

Pro-tow is not as safe a tow bridle as a 2 point with aero release. It's just smaller, less drag, shorter bridle that takes a little less time to stow, and looks cooler.

Hurt hang glider pilot joked bravely with friends after a crash landing, unaware that his injuries were fatal.

And, if you wanna look REALLY cool, then joke bravely with your friends after a crash takeoff, unaware that your injuries are fatal.

Ann Fawkes - 2011/06/15 11:50:58 UTC

PS: I am not trying to be smart or so...

Yeah, that would be a BIG mistake on The Jack Show.

...but the other systems are just not used at the airport where I am towing. I just try to stick to something I was taught and that works for me.

Not necessarily the same things.

Way too tricky to try out something new on my own.

Not nearly as tricky as finding out on your own that something old that you were taught and works for you doesn't always work for you. Just ask Mike Haas and Jeremiah Thompson.

Furthermore a differentiating system would only confuse the start assistant that hooks me in when I am on the cart...

Tell him to get used to it. Better him confused on the ground than you confused in the air - and, shortly after, dead on the ground.

Davis Straub - 2011/06/15 12:50:03 UTC

Pro-tow is not as safe a tow bridle as a 2 point with aero release.

Do you have any references that back up your opinion here?

http://ozreport.com/pub/fingerlakesaccident.shtml



The way total assholes configure them they're equally deadly.

What is an aero release?

Maybe you shoulda figured that out before you started shitrigging and selling them.

I would suggest that this statement is in fact false.

Yeah. Why should anyone waste time with outright false statements when misleading ones can be so much more effective?

But this one happens NOT to be false.

Ya ever wonder why nobody EVER does his first solos one point? It's 'cause it's not as SAFE as two point - and never will be no matter how much of a "pro" you are.

You want a reference?

Dennis Pagen - 2005/01

Soon after lift-off the trike tug and I were hit by the mother of all thermals. Since I was much lighter, I rocketed up well above the tug, while the very experienced tug pilot, Neal Harris, said he was also lifted more than he had ever been in his heavy trike. I pulled in all the way, but could see that I wasn't going to come down unless something changed. I hung on and resisted the tendency to roll to the side with as strong a roll input as I could, given that the bar was at my knees. I didn't want to release, because I was so close to the ground and I knew that the glider would be in a compromised attitude. In addition, there were hangars and trees on the left, which is the way the glider was tending. By the time we gained about sixty feet I could no longer hold the glider centered - I was probably at a 20-degree bank - so I quickly released before the lockout to the side progressed. The glider instantly whipped to the side in a wingover maneuver. I cleared the buildings, but came very close to the ground at the bottom of the wingover.

astronaut - 2011/06/15 13:18:56 UTC

If you are looking for a simple and durable pro tow release I would recommend buying a Koch-2 release from Finsterwalder in Germany.
They have been on they market for years. Are incrediably reliable and sold in millions Never heard anyone complain about them.
They are a bit expensive though, but you get what you pay for
http://shop.finsterwalder-charly.de/index.php?page=product&info=442

1. It IS durable and reliable.
2. It is NOT particularly simple. It is, in fact, the most complex release commercially available for the hang gliding market.
3. It's a damn good two stage release.
4. It sucks as a one point aerotow release. (But I'd still take it over the bent pin crap like Steve and Davis sell 'cause it'll at least work under load.)

Davis Straub - 2011/06/15 13:29:07 UTC

I have complained about them. :-)

Why? 'Cause you can't make and don't sell them? 'Cause stitching a bent pin onto a piece of webbing and cutting a chunk of aluminum tubing is already really taxing your abilities?

Dennis Wood - 2011/06/15 13:31:15 UTC

what part of K.I.S.S. is so danged hard to understand

It's EASY to understand. Especially for assholes like you who never in their entire useless lives have ever designed and built anything of value to put into the air.

http://www.hanggliding.org/viewtopic.php?t=11497
Aerotow release options?

Scott C. Wise - 2009/04/13 17:56:51 UTC

What some are missing with the K.I.S.S. comments is that the USE of the release must also fit within the Keep It Simple, Stupid principle. But it can be a real trick to make both the mechanism and trigger simple AND easy to use (while not removing your hand from the base tube).

Ann Fawkes - 2011/06/15 13:50:23 UTC

Tried that one. Very good and durable system but it is not easy/quick to fix to your harness.
Quite a big metal piece, not very advisable if you make a bellylanding once very now and then. Rib cracker...

Yes, it is a big metal piece. And it's an overbuilt piece of crap in one point aerotow application.

They have been on the market for years. Are incrediably reliable and sold in millions Never heard anyone complain about them.

But, in the 26 years they've been in widespread use, can you cite a single instance in the history of hang gliding in which one has actually cracked a rib - or caused any injury whatsoever - in a CRASH, let alone a belly landing?

If not then how 'bout giving the "rib cracker" thing a rest and start paying more attention to the Holly Korzilius and Steve Elliot face and neck cracker issues that actually DO happen in real life - and death?

Check out my pictures:
http://www.flickr.com/photos/aerotowrelease/
http://www.flickr.com/photos/aerotowrelease/8305308635/

Secondary Bridle Assembly

Stop talking to those assholes on The Jack Show and start talking to this one instead. This one knows what he's talking about.

[deltaman]

Tad,
About the case of a towed glider which climbed high and strong before the tug took of. There is a known risk for the tug never reach to take off. Are your 1.4G recommended wl not a complication in this case ?
Thanks

[deltaman]

I re-try to read Bridle link on mousetraps, I think I have 10 years old now ! I understood and it wasn't so hard.
I bought dental string today but the thief of pharmacist told me "floss" doesn't exist anymore since ..I wasn't born. False! and give me this one:
http://www.cocooncenter.co.uk/Fluocaril-Dental-Floss-with-Fluorine!10312.html
nonetheless it's written "floss" here. I will test it (no less than 5 runs on the overlap, right ?) with 5, 6, 7, 8 and will see what happend..

Could you imagine a dyssimetric bridle with a longer part of leechline (but still 125mm overlap) on the other side of the release ("port" or "starboard" ?). I want to connect it directly to my harness webbing loop.
Something to say on that ?
RE-Thanks
---
Tad Eareckson 2022/03/28 14:15:00 UTC

Updated link:
http://www.cocooncenter.co.uk/fluocaril-dental-floss-30m/66028.html
Fluocaril Dental Floss 30m

[Tad Eareckson]

1.4 G weak link...

- Sometimes the air does stuff - often, in our areas of concern, as a consequence of a thermal or dust devil - that makes ANY situation with a low hang glider - launching off a ramp, tow launching, or coming in for a landing - unsurvivable.

- Usually it's better to be off tow before you get hit - but not always.

- If you get hit WHILE on tow it's often - a lot more commonly than people think (or admit) - a lot better for your health to stay on tow, keep climbing, and ride it out as best as possible.

- Lockouts commonly hit so hard and so fast that - I don't care who you are or how good your equipment is - you can't react and release before they're almost over, even if it IS to your advantage.

- So you can't really afford to launch into a powerful thermal or dust devil.

- Your best strategy to keep from doing that is to have ribbons along the runway and check them before rolling - kind of like they do at mountain launch ramps.

- John Dullahan (the victim of that security clearance / lie detector bullshit that I just found out about on the Oz Report) had a monster thermal break off behind him on 2006/02/06 at Quest just before launch, got locked out, reacted and released quickly, and flew recovery as best as could be done but still broke a wrist. So to really do things right ribbons should be checked behind launch as well. (People behind John were aware of what was going on and the danger it presented - the situation WAS predictable and preventable.)

- If, however, you DO launch into a powerful thermal or dust devil and...

- You get rolled and locked out... Release or have a weak link blow immediately - you may still die. It's just a matter of being lucky enough to have enough air to recover from the stall. John was flying with a piece o' crap Wallaby release with the brake lever on his downtube and he STILL beat his loop of 130 pound Greenspot. If he had waited for it to blow he could've ended up just as dead as Mike Haas did in a similar aerotow incident with the same release and weak link.

- You go straight up like a rocket... There are several things you REALLY don't want in that situation.

Wings! - 1982/07

Brian Wooltorton's Flexiform Vector entered an ever steeper climb until the weak link in the fixed line towing system broke, an inquest at Aylesbury heard.

-- one G weak link

1978/04/06 - Bill Flewellyn - 31 - Toowoomba - Queensland - Moyes Stinger

Vehicle tow during exhibition, rope broke at a hundred feet, dived in. Hang IV pilot. Had flown over Mount. Fuji, balloon dropped from 23,000 feet.

-- worn out towline

Doug Hildreth - 1990/09

Apparently the angle caused an "auto release" of the towline from the pilot, who completed a hammerhead stall and dove into the ground.

-- release lanyard on your wrist

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

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

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

-- total idiot on the Dragonfly

Dennis Pagen - 2005/01

By the time we gained about sixty feet I could no longer hold the glider centered - I was probably at a twenty degree bank - so I quickly released before the lockout to the side progressed. The glider instantly whipped to the side in a wingover maneuver.

-- release actuator on your shoulder or downtube

So to answer your question...

Yes, my 1.4 G recommended weak link may INDEED be a complication in such a case. In a situation like that I'd want something 2.0 or heavier to give me one less thing to worry about.

There's never been a weak link that forced somebody to stay on tow when he didn't want to be.

There've been a hell of a lot of weak links that have forced people off tow and crashed and occasionally killed them.

A weak link can ONLY complicate a situation by failing.

Damn. My computer crashed just as I was about to get off a response. Had my work saved but you got another post in ahead of me before I recovered.

Glad you figured out the Bridle Link. Like the other flavors of Shear Link it's just two elements sewn together with a known number of stitches.

I tested several US brands of floss - they seemed to be the same stuff with different labels on the packaging and dispensers and produced consistent results. I hope the same holds for stuff available in Europe. Check with a magnifying glass for broken fibers. I did get a spool once that I wasn't happy with but I suspect any difference would have been negligible at worst.

Yes, minimum of five stitches per run. And I don't thing there's really any need for low end Bridle Links below Ten (five plus five). There aren't any gliders or reasonable releases that require anything lighter than that in any configuration.

Note... There's some stuff in Mousetraps that doesn't reflect my current thinking on the two point bridle system.

What I'm recommending now is to eliminate the secondary weak link at the bottom of the Primary Bridle, just install a sailmaker's thimble in the bottom eye, and use a Bridle Link 120 percent - or a little more - of the (top end) Primary Weak Link.

Could you imagine...

Sure, you could do that. But why not just have barrel releases on both sides? They're cheap, they don't weigh anything, they stow easily, and you've got more grab options in an emergency.

Really happy that you're working on this stuff. Any questions, keep 'em coming.

[deltaman]

Hi,

Bridlelink
I was trying to build my first bridlelink yesterday night and my test results wasn't the ones I should expect.. (example 6+6 = 97kg, directly tested) I observed that stitched bindings weren't enough parallel all together to distribute the tension evenly.
I miss the right way to stitch the overlap correctly..
What I understood:
1- boil the leechline to shrink it cause you will have to do it again if you put a shrink tubing fairing (bridlelink in a 1:1)
(my leechline is a 2mm dyneema)
2- stitch close (1mm) the first 4th or 6th runs from the end sides of the overlap

I need a technic to reach to tight evenly the 4 strands of the overlap before to stitch them !!
Should stitches be strictly perpendicular to the leechline ?
1 every 2mm, that's right ?
What important do I forget ?

Help me to raise doubt: floss stitch have to break when loaded above the wl tension and not untie ?

1.4G
I read this answer you did on your favorite Davis' forum:

Well, I can recall a time when having a weaklink was very useful for me, here. If you come off the cart early and hit the ground, you'd like the tow rope to break so that you are not pulled along the ground anymore than necessary.

Actually - you want the tow rope to HOLD so that you ARE pulled along the ground rather than slamming to an instantaneous stop. Nobody's ever been injured to a noteworthy degree in an AT incident by being dragged. Peter Birren was half killed by coming to an instantaneous stop when his weak link failed in a dolly wreck.

We had a dramatic accident in 2004 in AT in France. I wasn t there. First AT for a pilot in a 1:1 dolly start. As he believed he has to pull hard right after leaving the dolley, he did it and hit the ground ..and was dragged before the wl break. He is tetraplegic now.
I try to be the devil's advocate before accept to use 1.4G as I never break my greenspot 130lb (between harness loop and vectran bridle eye (grapevine and lark's head knots) including taking off in strong conditions in Australia and Namibia. I'm 120kg wing loaded : pilot+harness+glider. As I tested this greenspot on the same condition with the right angle and find an average of failure at 100+ kg on the tow line, this wl is a 0,83G for me...

To be continued..

[Tad Eareckson]

...example 6+6 = 97kg, directly tested...

If by "directly tested" you mean you stretched it out straight (pulled at the ends) - which I'm pretty sure you do - you NAILED IT.

My numbers for the Bridle Links are for the TOWLINE TENSIONS at which they will blow when towing one point (pilot only). If you got 97 kilograms end to end you'd have twice that - 194 kg - in flight.

I predict about 18 pounds per stitch end to end or 36 pounds towline tension so for six plus six - 432 pounds / 196 kilograms. 99 percent. Pretty damn good!

I observed that stitched bindings weren't enough parallel all together to distribute the tension evenly.

Sounds like you did plenty good enough - but take your time and do everything as carefully and precisely as you can. The nice thing about Bridle Links is that, since they get doubled, there aren't that many stitches to worry about.

Boiling the leechline...

I boil ALL my Dacron leechline before making anything out of it because it significantly and permanently shrinks when you do and I found out the hard way that you can really mess things up where measurements are critical.

Bridle Link measurements aren't critical and I don't know how Dyneema reacts but it's probably not a bad idea to heat up a coffee mug's worth of water and do it for the stuff you're using.

Should stitches be strictly perpendicular to the leechline?

Yes.

1 every 2mm, that's right ?

Right. Not terribly important but a good standard.

2- stitch close (1mm) the first 4th or 6th runs from the end sides of the overlap

Yeah, but for the Bridle Links you're not doing much more than six stitch runs - so don't worry about it. It's not all that important. The thought behind it is to help ensure that the end stitches blow by reducing their tendency to pull through. So maybe bias a couple of stitches at the ends of the runs a little closer but it really doesn't matter much (if at all).

What important do I forget ?

Based upon that test result - NOTHING.

Help me to raise doubt: floss stitch have to break when loaded above the wl tension and not untie ?

By "untie" I think you mean "pull through"? Yeah.

1.4G

I picked 1.4 Gs some years back because the FAA (Federal Aviation Administration) specifies a 0.8 to 2.0 G range for sailplanes and I picked the middle of it because that was their "safety" range and I figured they knew what they were talking about. They don't - EVERYTHING should be kept well over one G.

So now I just say one and a half Gs or better up to two and am not very worried about precision.

We had a dramatic accident in 2004 in AT in France.

I really wish we knew about these things. I'm sure we miss a lot of important data from outside of the English speaking world (north North America, UK, Australia, New Zealand).

He is tetraplegic now.

I am VERY sorry to hear that.

I try to be the devil's advocate...

EXCELLENT. That's EXACTLY what you should be doing - all the time, for everything and everyone, including / especially me.

But for the purposes of this discussion I don't have much useful data on that incident.

- What was:
-- the glider model and size?
-- his hook-in weight?
-- he using for a weak link and where was it installed?
- When was he injured and why? He could've:
-- sustained all the damage the instant he hit the ground and the matter of his being dragged would have had zero bearing
-- been injured when he hit the ground and had the dragging increase the severity
-- sustained all the damage at some time DURING the dragging (although I think that unlikely)
-- been fine after the initial impact and during the dragging until the weak link finally blew, the glider stopped, and he swung into the keel
-- been paralyzed or killed if the weak link blew at the instant of impact and he had swung into the keel harder than he would have if he hadn't been dragged a while first

http://ozreport.com/pub/fingerlakesaccident.shtml



- What was he using for a release, how was it actuated, why didn't he blow it?
- Did he have adequate wheels and, if not, would they have made a difference?

I never break my greenspot 130lb (between harness loop and vectran bridle eye (grapevine and lark's head knots) including taking off in strong conditions in Australia and Namibia.

I fly with a cross spar which has a big dent in the middle of it such that it will fail at about 2.5 Gs. For years I've taken off and flown in really strong winds and thermal conditions in the Owens Valley and it's never broken.

Does that mean those flights have been safe? (I haven't done that.)

Do you want to be going up like a rocket (on a one point bridle) with the bar stuffed to your knees fifty feet off the runway with a 0.83 G weak link?

I don't want a goddam piece of fishing line - or tug driver - making my decisions for me. If I want to stay on I want to stay on and if I want to get off I'm perfectly capable of getting off.

We use wl on the line, and maybe soon a 150daN tost one for tandem.

Here's everything Tost has to say about the purpose of a weak link:

Weak links protect your aircraft against overloading.

You can trust them on that one. That's it. If you try to use a weak link for ANYTHING ELSE you are asking for trouble.

Tost doesn't say it's there to keep a plane from getting out of control, crashing, or being dragged or to keep a pilot from getting hurt or killed. It's there ONLY to keep the plane from being overloaded - in the air and under positive stress.

It's not there to keep somebody who doesn't know how to fly and/or is using dangerous equipment from flying into the ground and breaking his neck and/or killing himself.

My glider is rigged so that if I move my hand ON or it's torn OFF the basetube...

http://www.flickr.com/photos/aerotowrelease/8306300488/


...I'm off tow. I don't have to wait for the nose to slam into the runway and the weak link to blow.

If I'm towing one point...

http://www.flickr.com/photos/aerotowrelease/8306152861/


...all I have to do is stop biting the string.

And if you want to prevent a repeat of that terrible 2004 crash the best things you can do are:
- Publicize it as much as possible with as many details as possible.
- Make sure that nobody gets on a cart alone unless he knows what he's doing.
- Keep working on better equipment (exactly like you're doing now) and getting it into widespread use.
- Get people like Davis, Tracy Tillman, Matt Taber, Steve Wendt, Adam Elchin, Jim Rooney out of circulation.

Viva la France. Wilbur and Orville were pretty much first but your country took the basic idea and ran with it - really fast and well. Keep up the tradition.

[deltaman]

My numbers for the Bridle Links are for the TOWLINE TENSIONS at which they will blow when towing one point (pilot only). If you got 97 kilograms end to end you'd have twice that - 194 kg - in flight.

I should take more time before to write !!
Happy to have the key now to build bridlelinks, is that your proper genious idea ? If yes, well done !

mousetraps ~21 :

#04. Low End Modifications

A Run of Strength Stitching does not fall below five (the point at which the Floss fails rather than pulls through). Therefore, for ratings from seven to nine, the Strength Stitching is effected entirely on the port end of the Overlap and the starboard end is secured with three stitches which do not significantly increase the breaking strength. However, since the load tends to be distributed very evenly amongst the stitches, these Bridle Links tend to fail at points above average and it is advisable to bias selection on the low side.

please help me to understand this sentence:

it is advisable to bias selection on the low side.

I don't understand this word "bias"
with 3 stitches, they can pull through easily. overlap don't stay tight on this side.

Is it necessary to stitch the 2 strands before the eyes too ? On how long (minimum) if I build an dyssimetric bridlelink (if it s important, I don't see why it should be)

As we do tandem, and our runway (grass) is surrounded by fields. I feel more and more the necessary not to have a failure at the exit of the take off and have to land with the extension of keel (which not permit to land on our feet) on high cultures.. So my bridlelink will be stronger that what we practiced before with the more reliable Joe street release as a primary and barrels+bridlelinks as a chance to save a wrap.

Our microlight (Cosmos/single surface) is 190kg weaklink (and I don't know why they choose this limit). So if we have to keep this value, you recommend 190kg - 23kg (50lb) = 167kg as a max wl for the tandem to respect the necessary difference between glider and tug wl. I know that's far from what you would recommend to us.. Actually, I asked for better understanding of the 190kg value and am waiting for answers..

Tost wl

Rather than a tost+carrier, can you imagine to protect a shear link on the line from the ground with a transparent hose which may be stopped by a rapid link on the tug side and the ring on the glider side for example.
Tost: the one of K.Hammond is 150kg max (UK law, he said)

Weak links protect your aircraft against overloading.

and limit the force to the confortable release actuation tension before. right?

French accident

I have no more reliable and objective datas to give. But the pilot I knew wasn't really skilled enough and too hurry to belong to the top level. It was a training before our national championship. He was stressed with the manner to do.

your country took the basic idea and ran with it - really fast and well.

We didn't practice the 2:1 at this time or not everywhere in France.. He flew his usual glider, an old laminar. And pull strongly after leaving the dolley cause he was afraid being over the microlight as he should have been (you see, not objective) at the briefing. If the way to learn was surely bad, he made the mistake ..not sure he had wheels. For sure he didn't feel concern about its wl as he didn't practice AT before. don't know about its release but not sure he had time to actuate one.

Viva la France.

An action against the federation was attempted and not already finished..
The matter of being dragged and potentially increase the injury was the reason of this story..

I thank you again for your help..