Releases

[Tad Eareckson]

Please stay on topic and not attack or mention Jim.

That'll be a LITTLE tough 'cause the bulk of your post is quotes from him, but... OK, I'll try. I get to use quotes though.

And - truth in advertising - I was in the middle of disemboweling him on an entry I'm trying to get up on the "fiends" thread before I lose power.

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

Jim Rooney - 2011/08/26 17:34:33 UTC

My point is that everything has issues. Everything. Period.

Bullshit.

The Dragonfly tow release - which is essentially an adaptation of a Schweizer sailplane release - DOES NOT HAVE ISSUES. It's well designed, built in, and more than up to the job it needs to do - releasing the BOTTOM END of the tow bridle. (There are certainly issues with some of the things that can and do happen AFTER that end is released but that ain't the fault of that part of the system.) You will NEVER hear about a Dragonfly release failure.

Tommy Crump - 1986/10

The release that I am using works every time and is mechanically sound. You need not have an additional release in case this one fails. A good mechanical release, under most all circumstances, is going to release every time. There are some things that you must rely on hundreds of thousands of times without failure. A release mechanism that is properly designed can do that.

This "everything has issues" crap is just a line the Flight Park Mafia goons feed everyone to lessen their chances of their getting sued out of existence when the cheap shoddy junk the sell everyone malfunctions at an inopportune time in one or two the several ways they know it WILL.

Will I fly with a straight pin release? Sure.

Well that's reassuring. Flight park goons will fly and put students and pilots up on ANYTHING. (I didn't mention Ji-... that person.)

Does it have the track record of the curved pins? No.

We're gonna skip that one 'cause - as you're well aware - "track records" are totally meaningless. Especially when the commercial interests are the ones supplying the records.

Does it have limitations that the curved pins don't? Yes, yes it does.

Bullshit. This is like saying an aluminum baseball bat has limitations a rubber one doesn't. This is actually worse. If you use a rubber bat in an electrical storm you're less likely to get killed. The idiot bent pin crap is NOTHING but downsides. You can't grip it, you can't pull it...

Her hand slipped on the metal tube as she was expecting a light pull.

...it WILL fail under load...

http://www.flickr.com/photos/aerotowrelease/sets/72057594066304861/

...it's bulky, uses more material, and is more likely to auto actuate if it gets dragged forward over the basetube.

It was "DESIGNED" by a total moron.

Try fitting a straight pin release with anything but weaklink. (it doesn't quite fit the same) OH! Right.

Bullshit.

Try fitting a 350 pound pilot on a Falcon 3 145. It won't climb or do no wind landings quite the same. OH! Right.

Try engaging an aircraft carrier docking hawser with a Wallaby Release. You'll have a hard time closing the spinnaker shackle gate. OH! Right.

My system doesn't use conventional weak links. My barrel releases are intended to engage Bridle Links. The pin closes over 3/32 Dacron leechline and the standard Bridle Link can be graduated up to a 648 pounds towline. That's 1.6 times the deadly double loop and two and a half times the nice safe single.

I can blow 648 with a sixteen pound pull. A bent pin - if it survived that long - would require 52.

Just might be that we've thought of that eh?

http://www.hanggliding.org/viewtopic.php?t=21033
barrels release without any tension except weight of rope..

Bart Weghorst - 2011/02/25 19:06:26 UTC

But I've had it once where the pin had bent inside the barrel from excessive tow force. My weaklink was still intact. The tug pilot's weaklink broke so I had the rope. I had to use two hands to get the pin out of the barrel.
No stress because I was high.

Yeah, right. Good thinking. (Oops, I'm starting to drift into attack mode.)

they can jam. I've had one do so, so he can get stuffed, he's wrong. It has to do with how they're built...

Unlike the gliders, harnesses, parachutes, and launch dollies we use - which are just thrown together from whatever junk happens to be lying around in the garage. WELL DUH!!! (Sorry, can't help myself.) Solution: Don't let total fucking morons build them.

...specifically, the line on the pilot end crunches up cuz it's too tight of a tolerance for the small barrel that's necessary to use with a straight pin.

This is just UN FUCKING BELIEVABLE!

http://www.flickr.com/photos/aerotowrelease/8306296899/


http://www.flickr.com/photos/aerotowrelease/8312399698/

Absolute psychopathic lunacy. (Oops.)

What are the limitations of straight pin releases?

1. Using available and off the shelf materials you risk damaging the pin (which is my limiting factor) as you close to 400 pounds direct loading. That's 800 towline or over two and a quarter Gs for a 350 pound glider. NOT an issue. (And even at 800 it's still gonna work OK (twenty pound pull).) Normal 914 Dragonfly tow tension for a solo is about 125, I recommend limiting it with a 700 pound weak link (two Gs for a heavy solo).

2. If you do a lot of high load bench testing the recoil will cause the leechline base to be abraded as it retracts into the barrel. But if you just use it for towing the thing will last forever.

3. It can/will auto release if it's dragged forward over the basetube. I COULD develop a safety system to prevent that from happening but it's just not enough of a real life issue to be worth worrying about. If it were the idiots using those stupid flared Bailey Releases would be dropping like flies.

4. It requires you to take a hand off the basetube to actuate. That's why you launch with a Four-String Emergency Release trigger in your teeth.

5. It requires several pounds of towline tension to blow with one hand. But there's NO good excuse for the two pilots to allow a slack line situation to develop (and those situations are deadly). If you DO have a slack line situation you can blow the Four-String with one hand or the barrel with two.

Thanks for asking.

[miguel]

I was looking through the junk box and found a 3 string release that I bought from GW many years ago. Never had a problem with it.
What are the limitations of this type release?
No need to trash GW.

[Tad Eareckson]

Arguably. But whenever the opportunity presents itself...

At one of the Kitty Hawk Spectaculars in the Nineties Bill Robertson asked me if I had asked GW something like what time something or other was gonna start. I replied, "No, I never speak to or have any contact with GW unless it's absolutely necessary." Bill immediately turns to his wife and says "SEE?"

Believe me - it ain't just me on this one.

Limitations on three-strings...

- They wear through use.

- The mechanical advantage at the high end is paid for by a lot of compromise of its slack line performance.

- They pretty much require a lanyard for actuation and that generally makes them a little harder to fire than a barrel and less suitable for installation at the end of a shoulder-to-shoulder or hip-to-hip bridle.

- They're best used engaging the tow ring directly rather than an eye at the end of a bridle. And I prefer to have releases engaging bridle ends because bridles are pretty much mandatory in hang gliding so you might as well take advantage of the fact that they cut the load to a mechanism at an end nearly in half.

But...

None of those issues is really a BFD in the environment in which they're most commonly used - platform towing.

They handle high end loading really well and people rarely release until after they've topped out and the tension is light.

When tension is light there's less burning and if the tension is so light that it won't dump the towline - what the hell, you're at altitude, slack lines tend to be dangerous only in aerowtowing, and you can usually just shake or jerk the bridle to clear it.

The Mason Release flavor of the three-string is kinda cool 'cause it's got a nice spring loaded pin and the strings are easily replaceable - making the burning a non issue.

And I really like the way the Hearne (Texas) guys have incorporated the weak link as an add-on to / extension of the third loop (the one that engages the tow ring). That makes the burning even more of a non issue. (I also really like the strength they use - five to six hundred pounds - because it so flagrantly violates the good rule of thumb that weak links be about one G.)

Back to negatives...

Conventional three-strings have zero place in aerotowing (although the modification concept Steve Kinsley came up with for an emergency release is brilliant) 'cause barrels do the job better and for less cost and structure.

Three-strings are always fixed at the apex of the bridle and directly engage the tow ring. The good news is that you eliminate the possibility of a bridle wrap, the bad news is that you can load the bridle halves and their attachments unevenly so you need to configure such that each half can safely handle the full tension allowed by the weak link.

And there are no conventional three-string configurations which allow the pilot to blow tow with both hands on the basetube.

Even immediately and still today after the 1990 Brad Anderson and Eric Aasletten fatalities people are still stupid enough to put release lanyards on their wrists (such that when the glider pitches up the lanyard tightens). Others run the lanyard to a shoulder strap - which is considerably less insane way to configure but still has the low pitch - slack / high pitch - taut lanyard problem.

The right(est) way to configure - which nobody does - is to use a split lanyard and anchor the ends - along with the bridle halves - at your hips so the lanyard freeplay is unaffected by glider attitude and you can access the lanyard with either hand.

http://www.flickr.com/photos/aerotowrelease/8322057772/

http://www.flickr.com/photos/aerotowrelease/8320997427/

http://www.flickr.com/photos/aerotowrelease/8320997523/


Summary...

Don't get your hopes up to high about your prospects for survival if you have a serious problem down low and need to take a hand off the basetube to blow tow. But platform towing can be pretty easily managed such that you needn't have a serious problem down low.

The three-string mechanism itself I don't really have any serious problems with in a platform environment.

[miguel]

Good explanation and write up.
Thanks

[Zack C]

But there's NO good excuse for the two pilots to allow a slack line situation to develop (and those situations are deadly).

Then how do you prevent it? I've had the line go slack on me (briefly) several times towing in rough conditions.

Zack

[Tad Eareckson]

miguel,

Thanks and you're more than welcome.
And thanks really go to Bill Booth - the Florida skydiving dude who developed the three-ring concept in the Seventies.

Zack,

"(Briefly)" is not a problem. You don't need or want to release when the line goes a bit slack for a second and a half when you're being bounced around by turbulence almost certainly at altitude.

Allowing so much slack that the towline can tie itself around a wire or tip is a BIG problem. And that only happens when someone on one or both ends of the line has screwed a major pooch - high glider diving on the tug or tug suddenly accelerating to the inside of a turn.

[deltaman]

Tad,
you will laugh.. some voices ask to impose your barrel release for the French Championship 2012 in the flats near Poitiers. And we will invite the Brits in a FAI cat2 event..
Not really sure it will happend but stay tuned..

[Tad Eareckson]

Really happy to hear that. But...

- Towing one point is always more dangerous than two.

http://groups.yahoo.com/group/skysailingtowing/message/6726
Weaklinks

Peter Birren - 2008/10/27 23:41:49 UTC

Imagine if you will, just coming off the cart and center punching a thermal which takes you instantly straight up while the tug is still on the ground. Know what happens? VERY high towline forces and an over-the-top lockout. You'll have both hands on the basetube pulling it well past your knees but the glider doesn't come down and still the weaklink doesn't break (.8G). So you pull whatever release you have but the one hand still on the basetube isn't enough to hold the nose down and you pop up and over into an unplanned semi-loop. Been there, done that... at maybe 200 feet agl.

- You have to take your hand off to blow tow and you can't always expect to be able to take a hand off and live.

- It's pretty cheap and easy to make a one point release actuated by a string or mechanism in your teeth.

- I hope it's going to be all dolly launched. That's by far the most important thing you can do to enhance the safety of the tow.

And I hope we can get the weak links up to where they should be. It would be a great venue to get Bridle Links into circulation but even a tacky double loop of 130 pound Greenspot would keep everybody safe and happy.

If you do Bridle Links I'd be happy if you would adhere to my color coding standard - but without color coding it's fairly easy to separate the Base Runs a little, count stitches, and then tighten things back up.

And, if you want, I can gear up into production mode and help with supplies.

Thanks zillions for sticking with this stuff. It's great to be able to have a realistic hope of things getting better on some significant scale.

[deltaman]

dolly launch, yes

- It's pretty cheap and easy to make a one point release actuated by a string or mechanism in your teeth.

another set up than 4-strings emergency release ?
4-strings: Can I modify the length of the strings if I want something shorter ?..

I did a barrel release with Ø2,5mm dyneema as leechline without any stitch, did a "spliced" knot in one place on the aft part and put a small nail through the tube and between the 2 strings of dyneema on the rear which can stop the tube by pulling in a manner you can close the pin just the right way. no trick available.
I introduce a 2cm string Ø3mm spliced inside 1 string of the dyneema to add friction with the tube

[Tad Eareckson]

another set up than 4-strings emergency release ?

I REALLY like the Four-String. It's powerful as hell (virtually unaffected by tow tension), light, fairly cheap in terms of materials and labor, and can be armed and released in a millisecond.

Downside...

The one time installation is a bit of a pain. But I could probably make it somewhat less so.

Can I modify the length of the strings if I want something shorter ?

No.

The Trigger Line MUST come straight up from the bridle assembly (behind the helmet's chin guard) to your teeth with your head tilted up at a normal comfortable angle. That length can't be reduced - and you need to add to it to be able to look around a little.

And the first (smallest, inner) loop has to be safely longer than the Trigger Line, and the second loop has to be safely longer than the first loop, and the third loop has to be safely longer than the first second loop.

I'm pretty anal about minimizing lengths but if you push your luck you'll end up with something that locks.

And anyway... I end up with a pretty comfortable overall length. The shorter the secondary bridle/release assembly is the more it pulls your shoulder straps together. So why do you want to make it shorter anyway?

In the past I've customized the Four-String to the individual pilot to make the Trigger Line - and thus the entire mechanism - as short as comfort allows. If it turned out to be less than perfect on a flight test I'd take it back and make another one with the Trigger Line a few more or less centimeters. That's too labor intensive an approach.

Better to just use a standard Trigger Line length long enough to accommodate anyone, lock it such that the mechanism takes up the excess, and settle for an overall length maybe a couple of inches longer than a custom job.

If that didn't make any sense...

http://www.flickr.com/photos/aerotowrelease/8312914326/


Feed the some of the length of the Trigger Line down through the Clamcleat and out through the front (right) so that you have the desired length between the Clamcleat and your teeth.

I did a barrel release...

http://www.flickr.com/photos/aerotowrelease/8312402264/


If you used a machine screw and nut instead of a nail you could rig it as I have my shoulder mounted Remote Barrel Release.

You could also just configure with a Linknife on the end of the string in your teeth.

It would be easiest to rig and cut most efficiently going straight down to a sacrificial element near the (call it) left end of your bridle assembly - but that would leave a lot of length to feed through the tow ring.

You could also route the lanyard through a pulley - as I've done with the Remote Barrel - to position the Linknife just aft of the left end of a Bridle Link to eliminate any wrap potential and I'm sure that would cut quite effectively enough as well.

And whatever you do would be better than nothing.