suspension

General discussion about the sport of hang gliding
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Tad Eareckson
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Re: suspension

Post by Tad Eareckson »

http://www.youtube.com/watch?v=csDRdqMH3Kk
The flight that almost killed me
Bob Kuczewski - 2019/12/18

The lift and tug method ("always launch with a tight hang strap") is also very good (when safe), but we saw one of its failure modes right here in this video.

Let's face it, ALL of the so-called "fool proof" methods have their failure modes. Complacent reliance on any single method will eventually bite each of us. Extreme vigilance for ourselves and our flying friends is the price we must be willing to pay ... to fly like birds.
And yet....

http://www.ushawks.org/forum/viewtopic.php?f=2&t=802
AL's Second flight at Packsaddle how it went
Rick Masters - 2011/10/19 22:47:17 UTC

Al, there's a lot of noise on this thread but if I can just cut through it, I'd like to provide my observations to your excellently detailed account.

A lot of focus is put on hooking in. Too many pilots have died for no good reason. It was never a problem for me. Before lifting the glider, I would lay down and check my distance from the control bar. I always did this. It was part of my unalterable routine. It just took a moment and then I would shoulder the glider. I would stand and allow the wind to lift the wing. I would stand and fly the wing with gentle tension on my hang strap. Then I would identify the neutral lift attitude where the wing weighed nothing - and hold it.

At that moment, I would banish all concern about launching unhooked. I had taken care of it. It was done. It was out of my mind.
And then two and a half paragraphs later he commits to launch.

Translation...

- Always launch with a tight hang strap.

- For all of your launches there will be a gentle wind which will lift your wing enough to fly it with gentle tension on your hang strap. So no problem with the Zack C / Sport 2 155 combo in which it's physically impossible for the glider to be manually lifted to tight suspension.

- There will never be enough in the way of turbulence, shifts, thermal blasts for any crew to be required. It will ALWAYS be safe.

- You can safely banish all concern about launching unhooked at this point. You have taken care of it. It's done. It's out of your mind. Nothing bad can ever happen beyond this point.

And your response:
Bob Kuczewski - 2011/10/19 22:53:45 UTC

Thanks for bringing us back on topic Rick ... and for the good advice.
Nah, no CONCEIVABLE failure mode to that one. No one who's ever felt tension two paragraphs ago has EVER launched unhooked. 'Cept Garck maybe.

There's no preflight beyond lying down and checking his distance from the control bar. Here's Garck doing that:

087-22822
http://live.staticflickr.com/65535/49206611951_0cabf4084b_o.png
Image

Anybody see any problem with Garck's distance from the control bar? Even with the slight alteration he inadvertently executed in his suspension configuration? Would it have mattered if there had been?
Rob Kells - 2005/12

Not one of us regularly uses either of the two most popular methods outlined above.
Has anybody who has:
- not just altered his configuration ever detected a change in clearance with a hang check?
- just altered his configuration only been alerted to that circumstance in the course of a hang check?
Let's face it, ALL of the so-called "fool proof" methods have their failure modes.
Unless it's total crap from some Owens Valley pioneer asshole Emperor Bob values having in his personality cult. Then it's "good advice" - with no qualifications, reservations whatsoever. Listen to this guy, Al. You'll be fine - just as fine as Jim Keen-Intellect Rooney's first Coronet Peak tandem thrill rider was. Maybe even better.
Complacent reliance on any single method will eventually bite each of us.
And there was absolutely NOTHING in Rick's idiot post that smacked of complacent reliance on a single method...
Extreme vigilance for ourselves...
It was totally OOZING with emphasis on...
At that moment, I would banish all concern about launching unhooked. I had taken care of it. It was done. It was out of my mind.
...extreme vigilance. There's just no more extreme expression of vigilance than putting an issue out of one's mind. Maybe we could get a list of all the other issues Rick puts out of his mind so we muppets can start getting our extreme vigilance ratings up to some level approaching his.
... and our flying friends is the price we must be willing to pay ... to fly like birds.
Where are Rick's flying friends? He's a rugged individualist - up there all by himself. No crew, no crew needed 'cause there was always a gentle straight-in wind to gently lift his wing such that it would transmit gentle tension on his hang strap. Hell, there was nobody else up there even to hold his nose while he was laying down and checking his distance from the control bar.

He always did this. It was part of his unalterable routine. It just took a moment. He was NEVER at launch with anyone else. Then he'd fly for a few hours, land out eighty miles a way, walk back to and up the mountain to retrieve his truck.

Me... When I'm at a mountain launch I'm always having to interrupt setup to help people maneuver their gliders to launch and do wire crew. And I'm watching their suspension like a Kestrel watches a mouse.

This asshole doesn't really give a flying fuck about anyone else. Just wants them to crash due to fringe activity towing incidents to help him misrepresent what's actually going on in the real world.

It's a pretty good bet that The Bob Show maxed out a couple years ago and won't achieve anything more than it has already - which ain't a whole helluva lot to write home about. Granted, the original mission of Kite Strings was to reform the sport and that ain't gonna happen in any century on the horizon - given what we now realize we've really been up against since a wee bit after the beginning of time - but we recognize that and have retargeted to do what damage we can.

http://www.ushawks.org/forum/faq.php
Frequently Asked Questions
What will keep the US Hawks from becoming another USHPA or HGAA?
You will ... hopefully. The price of freedom is eternal vigilance. Everyone has to do their part once in a while. If you see something that's not being done correctly, then it's your duty to speak out. One big difference between the US Hawks and other organizations is that the US Hawks really does honor the free speech of its members.
That really doesn't happen on any significant scale and CAN'T. You don't have the critical mass of people with the integrity and brains to make an actual difference. And you won't tolerate any members who DO call you out on crap like this.

Also note that if Emperor Bob ACTUALLY cared about getting and doing things right he wouldn't give a rat's ass whether he was getting called out from within his dictatorship or from anywhere else. He'd respond based on MERIT - regardless of the source. He won't because he can't.

I so did love it when Rooney was shooting his mouth off about me from what he very mistakenly thought was the locked down protection and safety of The Davis Show.
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Tad Eareckson
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Re: suspension

Post by Tad Eareckson »

http://www.hanggliding.org/viewtopic.php?t=36979
Spectra (Dyneema) for Hang Straps
Rob1 - 2021/01/27 14:37:20 UTC

Does anyone use 6mm Spectra (Dyneema) rope for hang straps? It is stronger than standard nylon straps. Is there any advantage to making hang straps from Spectra (using Grapevine knots)? Are there any downsides?
Does anyone use 6mm Spectra (Dyneema) rope for hang straps?
Who gives a rat's ass? The overwhelming majority of your Jack Show douchebag buddies use bent parachute pins as the core component of their easily reachable pro toad releases.
It is stronger than standard nylon straps.
Who gives a rat's ass? Whatever you use is gonna be able to tear your glider apart thirty times ever before it starts breaking a sweat. And if you're not doing hook-in checks - which, statistically, you're not - its strength is likely to be way more irrelevant.
Is there any advantage to making hang straps from Spectra (using Grapevine knots)?
You shouldn't be tying webbing in knots. You should be stitching it - if you give a flying fuck about drag minimization anyway.
Are there any downsides?
Only upsides. It's stronger, more UV resistant, and lower stretch. And that last issue is also gonna give you a performance advantage.

P.S. Red Howard's full o' shit.
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Tad Eareckson
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Re: suspension

Post by Tad Eareckson »

http://www.hanggliding.org/viewtopic.php?t=36979
Spectra (Dyneema) for Hang Straps
CloudDiver - 2021/02/03 20:49:21 UTC

Before I give my .02 cents I will qualify my experience in this area. I'm a professional rigger for sailboats and I specialize in Dyneema Rigging, I've been doing this for close to 7 years now. I replace standing rigging (the wires that support the mast) with heat annealed Dyneema. On the smallest boats like my Nacra 5.2 Cat, its only 4mm. The largest boat I've done is a 56 ft John Alden Ketch that had 22 shrouds & stays. I used 11mm core on the main mast, 7 mm on the mizzen mast. In any case, I use Dyneema sized to account for creep so its usually 1 size larger in mm than the original wire was, but the manufacturer rated tensile strength is about 2x stronger than that 1x19 wire was. I always use a Dyneema cover on the shrouds I make because the life expectancy of uncovered Dyneema is 5 to 8 years of UV exposure. After that time the core loses about 50% of its original rated tensile strength.

Ok, that said and based on some of the statements above;
- The average strength of 1 inch Nylon Flat webbing is 4200 lbs
- 6 or 7mm Dyneema would be way overkill and massive windage.
-There are many 'flavors' of Dyneema (SK 75, 78, 90, 99) and all of these can come plain or heat annealed. So determining which size to use that meets or exceeds 42000 lbs in tensile depends on what brand and type you want to use.
- Knots: Dyneema should always be spliced, knots should be avoided in any load bearing application. Dyneema is very slippery compared to other ropes, large sizes do not hold knots well. Its super easy to splice Dyneema into an infinite loop.
- UV cover; Sure you can, but its not a big deal in this application. Wings spend the majority of their lives packed into their bags, not in direct sunlight 12 hours a day. The 5 to 8 years metric I mentioned above is for constant UV exposure on the deck of sailboat, 12 hours a day. The size of Dyneema that would be good for hang-loops (I'd use 5 mm if it were not heat annealed) is so cheap that I would realistically just replace the hang loop every 5 years and that would be a very, very generous safety margin.

I would generally say that while Dyneema has more than adequate strength for hang-loop application and I would have absolutely no reservations about flying with one that I made for myself I still wouldn't recommend it over sewn Nylon flat webbing and here is why;

Windage: Even if I use the smallest size SK99 heat annealed core that meets or exceeds 4200 lbs, probably 3 mm, it will still have more drag compared to flat webbing pointed into the wind. Given the amount of surface area we are talking about its probably insignificant to noticeable performance, but drag is drag.

Shock Loading: Dyneema has very, very, very low stretch compared to nylon webbing. For the application of hang-loops, stretch is a good thing. This is the same reason why Rock-Climbers use dynamic (stretchy) ropes instead of static ropes for fall protection... ask any climber that has taken a big whipper. For nylon webbing the back-up hang-loop should only be 1/8 to 1/4 inch longer than the back up. The idea is that you shouldn't be anticipating that the primary actually breaks before the back up is engaged, the primary can stretch without breaking to the point where the back-up is engaged. Since Dyneema has so much less stretch this dynamic would totally change. Further, and this greatly depend on how the hang loops are attached to the frame, a smaller diameter Dyneema loop will focus its load on a smaller area where 1 wide flat webbing distributes it over a larger area. Obviously I'm talking about single surface wings with the simple Lark's head around the keel. I doubt seriously that any amount of pilot weight amplified through bouncing in turbulence or any other flight condition would put enough force on the loop to break the keel, but IF it could happen it would be more likely to happen from a small diameter Dyneema loop that is static than it would be likely to happen from flat webbing that is dynamic. If anyone brings up reserve chute deployment, just stop right there... that's not how it works.

So in summary.... Dyneema isn't BAD per se, definitely more than capable in terms of tensile strength. Simply put, flat nylon webbing works great and has better windage in profile, so there is no need to try Dyneema loops. I wouldn't want to do it on a Falcon for reasons I stated above, plus the the CG will be easier to slip out of position. My old Sport 2 is in storage so I can't look at it and my new Sport 3 is being built. When I get the new Sport 3 maybe I'll take a closer look and make a sample/feasibility test.

- Luke - H2, USHPA #101609
Before I give my .02 cents...
.02 cents is 0.0002 dollars - one fiftieth of a penny. But yeah. That IS closer to what this post is worth.
I will qualify my experience in this area.
I don't give a flying fuck about your EXPERIENCE in this area. This issue has ZILCH to do with experience - it's all about theory and engineering. And you've flunked before you've started.
I'm a professional rigger for sailboats...
Yeah sailboats. Float around with their hulls in one fluid medium and their sails and rigging flying in another. And the only place they're not bending over backwards to eliminate or minimize flex and elasticity is their anchor line - the thing that stops them from doing what they're designed and built to do.
Ok, that said and based on some of the statements above;
- The average strength of 1 inch Nylon Flat webbing is 4200 lbs
The minimum strength of an HGMA or equivalent certified glider is about six Gs. And for a 250 pound hook-in guy we're talking about 16.8 Gs. And that's before we start thinking about the issue of it being DOUBLED to form a LOOP - which, by the way, you NEVER do in this post.
- 6 or 7mm Dyneema would be way overkill and massive windage.
And the factory gear of course isn't. But let's...
Mike Meier - 2005/08/~18

It shouldn't matter whether the backup is in front or behind, because it should be longer than the main such that it is always slack in flight. An argument could be made that IF the main hang loop broke, you'd rather have the backup in front because the most likely scenario in which you'd break the main would be pulling high positive G's, and in that case you'd rather have the pitch trim become more nose down than become more nose up, but on a Falcon 2 that's not really a consideration. As far as where the backup "usually" goes, we usually put it behind the main because that's usually where there's room for it. If the main is properly maintained, and periodically replaced, it is never going to fail anyway, so the backup is sort of pointless. Years ago we didn't even put backup hang loops on our gliders (there's no other component on your glider that is backed up, and there are plenty of other components that are more likely to fail, and where the failure would be just as serious), but for some reason the whole backup hang loop thing is a big psychological need for most pilots.
...back it up anyway just to be on the safe side.
-There are many 'flavors' of Dyneema (SK 75, 78, 90, 99) and all of these can come plain or heat annealed. So determining which size to use that meets or exceeds 42000 lbs in tensile depends on what brand and type you want to use.
Yeah, let's use that 21 ton figure as our yardstick. Really hard to go wrong that way. It's not like the hang gliding industry guys just grabbed some off-the-shelf climbing gear and pronounced it standard. Nah, we arrived at all this stuff after years of careful engineering studies, flight testing, incident analysis, and an incredible degree of trail and error on top of all that.
- UV cover; Sure you can, but its not a big deal in this application. Wings spend the majority of their lives packed into their bags, not in direct sunlight 12 hours a day. The 5 to 8 years metric I mentioned above is for constant UV exposure on the deck of sailboat, 12 hours a day. The size of Dyneema that would be good for hang-loops (I'd use 5 mm if it were not heat annealed) is so cheap that I would realistically just replace the hang loop every 5 years and that would be a very, very generous safety margin.
Probably also be a good idea to change your hang glider's sail every two and a half years 'cause those things are getting a lot more UV exposure per square inch and the material's a fraction of the thickness of the strap.
Shock Loading:...
Yeah, Shock Loading...

http://ozreport.com/forum/viewtopic.php?t=24846
Is this a joke ?
Jim Rooney - 2011/08/28 19:39:17 UTC

Weak links break for all kinds of reasons.
Some obvious, some not.

One of the biggest bits that seems to be under appreciated is the bit that weaklinks break under shock loading.
They can take a hell of a lot more force if they're loaded slowly... which is exactly what happens in a lockout.
One of the biggest bits that seems to be underappreciated is that materials fail at much lower loads when they're surprised by the suddenness of the application and are deprived of the opportunity to start bracing themselves adequately.
Dyneema has very, very, very low stretch compared to nylon webbing.
Which makes it much more vulnerable to the shock loads we often encounter when flying through turbulence. So let's back it up just to be on the safe side.
For the application of hang-loops, stretch is a good thing.
Obviously. What other reason would we have for using nothing but nylon for our glider and harness suspension from the beginning of time up to the present? Just imagine the number of gliders we'd have torn to shreds flying through turbulence otherwise.
This is the same reason why Rock-Climbers use dynamic (stretchy) ropes instead of static ropes for fall protection... ask any climber that has taken a big whipper.
Rock climbers - you moron - are anchoring themselves to 1500 foot tall slabs of granite that haven't moved more than an inch and a half over the course of the past fifty thousand years. And they're falling fifty feet. Not quite the same thing as what's going on with hang glider suspension. The most we can fall is maybe three and a half feet between getting slammed against the keel and full suspension. And if we're in a situation like that the strength and elasticity of our hang loop are at the absolute bottom of our list of concerns.
For nylon webbing the back-up hang-loop should only be 1/8 to 1/4 inch longer than the back up. The idea is that...
...it's a big psychological need for most pilots.
...you shouldn't be anticipating that the primary actually breaks before the back up is engaged, the primary can stretch without breaking to the point where the back-up is engaged.
- Wow! Pure genius! Your talents are being totally wasted as a sailboat rigger. I'da thunk that you'd have been snatched up by a top glider manufacturer years ago.

- What are you imagine is going on with the glider and pilot and as things are transitioning through thirty Gs? Adam Parer would've been a good individual to consult on issues like these but we can't anymore.
Since Dyneema has so much less stretch this dynamic would totally change. Further, and this greatly depend on how the hang loops are attached to the frame, a smaller diameter Dyneema loop will focus its load on a smaller area where 1 wide flat webbing distributes it over a larger area. Obviously I'm talking about single surface wings with the simple Lark's head around the keel.
- A keel heavily sleeved in the relevant area. But we should do some bench testing anyway to see what it takes to choke it to the point of deformation with webbing over a range of widths.

- You're flying gliders with kingpost suspension. And most of the gliders doing most of the flying in most of the demanding conditions and situations aren't flying with crap Lark's Headed around the keel. They're flying like you are - with kingpost or rocker hardware connections.
I doubt seriously that any amount of pilot weight amplified through bouncing in turbulence or any other flight condition would put enough force on the loop to break the keel, but IF it could happen it would be more likely to happen from a small diameter Dyneema loop that is static than it would be likely to happen from flat webbing that is dynamic.
And no glider has ever failed in the course of a tumble or blown aerobatic maneuver so we have no fuckin' clue as to which structural components start snapping first - which are the outboard leading edge sections and cross spars.
If anyone brings up reserve chute deployment, just stop right there... that's not how it works.
You should've stopped before you started.
So in summary.... Dyneema isn't BAD per se, definitely more than capable in terms of tensile strength. Simply put...
http://www.chgpa.org/forums/viewtopic.php?f=2&t=2871
speed link
JD Guillemette - 2008/02/07 12:51:57 UTC

For these same reasons, It just bothers me when people try to "improve" upon Bobby Bailey's designs ... simply put, the designs are at the maximum of efficiency and safety. So I'm right back to where I was. I see no problem in the way things are currently done and creating overly complicated mouth actuated releases is just a waste of time.
...flat nylon webbing works great...
Wow. just like the Standard Aerotow Weak Link. If it ain't broke... Don't worry. It will be at the worst possible time...
Donnell Hewett - 1980/12

Now I've heard the argument that "Weak links always break at the worst possible time, when the glider is climbing hard in a near stall situation"...
...when the glider is climbing hard in a near stall situation.
...and has better windage in profile...
What's the windage profile of a fluttering backup loop?
...so there is no need to try Dyneema loops.
Yeah, if it ain't broke... See above.
I wouldn't want to do it on a Falcon for reasons I stated above...
Has anyone on a lower performance glider ever been in a situation in which he needed every inch of performance he could get to make it to a safe field or keep himself from being blown over the back? Lower performance gliders are flown because they're cheaper, lighter, require lighter effort. So hell, let's just keep throwing more useless crap into the airflow 'cause we're never gonna be able to match a topless bladewing anyway.
...plus the the CG will be easier to slip out of position.
- So the existing configuration allows the connection to slip, but not as easily as it most assuredly would using Dyneema rather than nylon. Has there ever been any documentation of this actually happening?

- And there'd be no freakin' way we could glue a rubber strip along the top of the relevant area of the keel to eliminate any possibility of any material being able to slip when loaded.

- A one and a half ton Speed Link...




Image

...will break at a quarter the load a six ton steel carabiner will hold. So obviously we should all be flying with the six ton carabiner 'cause that's four times as safe. Maybe use a backup for good measure.
My old Sport 2 is in storage so I can't look at it and my new Sport 3 is being built. When I get the new Sport 3 maybe I'll take a closer look and make a sample/feasibility test.
I can hardly wait. It's through the efforts of individuals such as yourself that this sport constantly evolves to hitherto unimaginable heights. And you're managing to do this without pissing off Jack and or any of his other coffee shop patrons.
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Tad Eareckson
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Re: suspension

Post by Tad Eareckson »

http://www.hanggliding.org/viewtopic.php?t=22079
Hanging from velcro.........
Matt Christensen - 2011/06/02 00:21:46 UTC
Vienna, Virginia

I thought I should pass on a lesson learned from the HG Spectacular. As you may know, many of us were flying borrowed gliders at this event. After two days of flying, one of the pilots flying a borrowed glider requested a hang check, which he had done prior to every flight. During the hang check it was noticed that something looked odd with the hangstrap. Upon closer inspection it was found that the hang strap was attached to the keel using only velcro! A little tug on the velcro and the pilot dropped free.
Real good thing the lesson was learned, huh Matt?

http://www.kitestrings.org/post4439.html#p4439
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