Surface towing for teaching

[Tad Eareckson]

Mike Lake - 2013/07/12 01:28:08 UTC

I think the problem with the mechanical twin release is it got to the point where it was good and, like so many things, got stuck on good enough.

[MikeLake]

... but having now used a Koch for a few years I have softened up a bit.

Paul Edwards - 2012/10/17 15:41:42 UTC

While launching I had no way of releasing from the tow line.

I don't understand why anyone who surface tows would not use a setup like this when it's so easily doable.
If the technology exist why not use it?

I do not wish to unduly knock this over/under mouth release system, as I said before I have not used one so I can only comment from what I can see in the videos.
I sincerely hope it turns out to be the best ever solution and if it does I want one.

What I do see is ropes, loops, wrappy stuff, two different release mechanisms, a possible third method for dumping everything and a pilot floundering (by comparison) for his first release.

Compare this with a typical video of a Koch type. What you see is a clean, neat and effortless system. No need to look, reach or find a moving target when you want to first or second release or abort. The hand off requirement is minimal and strength and reliability are about as good as it gets. It is also very difficult to connect incorrectly.

Of all the release systems this is by far the most reliable solution (so far) with the longest track record and, despite the claims of a few w***ers with an agenda, chest crushing is not one of the attributes this release is known for.

But of course you do need to remove your hand from the base-bar to operate and this puts it a notch or two down from an ideal solution.

However, the whole tow package must be considered and there is little that can substitute a correctly trained and on the ball winch-man.
The fact is while the ability to release with a spit is a desirable attribute the situations where this might be the correct thing to do at low level are not that clear cut.

A correctly trained winch-man has the ability to ease the tension (or is it pressure, torque, load, spin or maybe squeeze) and often carry on with the tow at the first sign of trouble. This is nearly always a preferable method of tow control than a sudden and one way removable of all tension, even when initiated by the pilot.

Paul Edwards situation would certainly have been improved with a mouth release, but so would it if he had had a decent ground crew not willing to launch him downwind with probably a tow hardly able to scrape him off the ground.
Preventing crashes is always preferable to trying to improve them!

So, I'm not convinced the trade-off is worth it, but would be delighted to be proven wrong.

[Tad Eareckson]

What I do see is ropes, loops, wrappy stuff, two different release mechanisms, a possible third method for dumping everything and a pilot floundering (by comparison) for his first release.

Even if it's a bit clunky, it's a good basic concept. And once you have a good basic concept it's almost always pretty easy to clean things up and improve efficiency.

Steve Kinsley's initial version of the multi-string looked like something a third grader had whipped together between getting home and dinner - and he'd be the first to tell you that. But the concept was brilliant and it was a lark to reengineer it...

http://www.flickr.com/photos/aerotowrelease/8305333309/


So much of a lark, in fact, that I reengineered it to the point that it wouldn't work...

http://www.kitestrings.org/post3241.html#p3241

... until deengineering it a bit.

Of all the release systems this is by far the most reliable solution (so far) with the longest track record and, despite the claims of a few w***errs with an agenda, chest crushing is not one of the attributes this release is known for.

It IS *KNOWN* for crushing chests. This is hang gliding and hang gliding is opinion based aviation and the fact that it DOESN'T actually crush chests is of very minimal importance.

However, the whole tow package must be considered and there is little that can substitute a correctly trained and on the ball winch-man.

When:
- whatever's going on with the glider can be fixed by giving it the rope
- using an appropriate weak link as the safety focal point of the system
- whatever bad happens to the glider is its own fault
- waivers have been signed and secured
just how much training does a winch-man need?

A correctly trained winch-man has the ability to ease the tension (or is it pressure, torque, load, spin or maybe squeeze) and often carry on with the tow at the first sign of trouble. This is nearly always a preferable method of tow control than a sudden and one way removable of all tension, even when initiated by the pilot.

This is why aerotowing is so dangerous - especially Rooney Link based aerotowing. Three tension settings:
- normal
- high and increasing
- off
often in that order.

A little bit of offset due to the tug's ability to maneuver to stay in front of the glider in some situations but that's a very little bit.

Paul Edwards situation would certainly have been improved with a mouth release, but so would it if he had had a decent ground crew not willing to launch him downwind with probably a tow hardly able to scrape him off the ground.

We need to look at the big picture. Yes, if you have competent people it both ends of the string doing their jobs properly the chances that a max capability release will ever pay for itself is something real close to zero. Steve Wendt has demonstrated that if you:
- tow on a huge, well groomed, flat putting green
- keep:
-- good control of the winch
-- a good eye on the conditions
you can do tens of thousands of student tows on the crappiest possible release equipment and never skin a knee (at least until all those scooter tow students you've acclimated to the crappiest possible release equipment start aerotowing in thermal conditions).
- But the same can be said with respect to helmets and parachutes.
- And even if you just have one Bob Buxton every twenty years you can justify a lot of extra two hundred dollar expenditures on release equipment.

Preventing crashes is always preferable to trying to improve them!

Especially when the outcome of a crash will almost certainly include a crushed chest.

So, I'm not convinced the trade-off is worth it, but would be delighted to be proven wrong.

I think the only major trade-off would be for someone who already owns a Koch two stage. I think this Russian two stage can be produced a lot cheaper and you should be able to blow a good first stage with no more difficulty than with a proper aerotow barrel release.

[Tad Eareckson]

A somewhat new thought occurred to me subsequent to my last post.

Aero is inherently - hands down - the most dangerous flavor of towing (assuming, of course, you throw out anything in which Peter Birren is involved).

I took a skim through all of the significant aero disasters I can recall and reached a conclusion.
- halfway competent people on both ends of the string
- two point bridle properly trimmed and routed
- six hundred pound weak links at both ends
- solid dolly
- stowed harness lanyards
- reasonable prelaunch conditions check
- tug aborts tow upon encountering significantly nasty low level crap

We don't need releases for aero. We can use hook knives or wait for two G weak links to blow.

- The best release on the planet is very unlikely to keep one alive in a severe low level lockout.

- Virtually all of our aero crashes are consequences of Rooney Link pops.

- A good chunk of what's left is caused by a tug driver making a good decision in the interest of the glider's safety while a situation is in progress.

- The vast majority of aero launches are conducted with, for all intents and purposes, no release on the glider. The Industry Standard crap that the vast majority of aero launches employ give the glider about zero chance of beating any weak link or the tug and, barring something else stupidly and majorly fucked up, it doesn't make any difference. As per the Ben Dunn incident one would be better off just fighting the lockout and waiting for the tug or weak link.

Put a gun to my head.
- Three hundred pound towline weak link and my release system.
- Five hundred pound towline weak link and my release system is inoperable until after I clear the kill zone.

I'm going with "B". I'm a lot more likely to be killed on the drive to Ridgely than on "B".

P.S. Ask yourself when the last time you saw a dolly launched two point deliberately aborted below two hundred feet was.

[Steve Davy]

Thanks for the thoughtful replies Mike and Tad, I really appreciate them.

Next up I need to get this built and tested. I'm sure I'll have some more questions along the way.

[Tad Eareckson]

Making better releases is SO Early Eighties. Try doing a one string, pronouncing it to be state-of-the-art, packaging it with ten feet of 130 pound Greenspot, a hook knife, and a pitch limiter, and selling to Mission Soaring Center for a hundred bucks a kit.

[Steve Davy]

I made a pin 60mm from tip to center of the eye then ran a second loop (ending 10mm past the opened pin tip) and got something like a two string/barrel release. Loaded it to 80 kg with my finger on the tip of the pin I'd say it took about 1 to 2 kg to hold it shut.

I won't be able to do much more until I get some sewing stuff (need to stitch line) and some cable.

[Tad Eareckson]

Be careful not to make the same mistake I did with the Four-String and boost the mechanical advantage to the point that it hangs up at normal tow tension - 'cause it takes a lot less than normal tow tension pulling sideways to lock a glider out and kill it.

Damn near everything in this game is a tradeoff - even Peter's Linknife which becomes progressively less effective as the tension drops.

If you can dump 600 pounds with a fifteen pound actuation force and still lose 75 without having to jump through an extra hoop I'd call that pretty reasonable.

[Steve Davy]

http://lh5.googleusercontent.com/-GjRUYbVOJpk/UfPhhXHy9AI/AAAAAAAAACk/lCXAymMqoVQ/w503-h377-no/DSC00071.JPG


Finally figured out how to get photos on here!!

[Steve Davy]

http://lh6.googleusercontent.com/-QUoBgXoIwvI/UfPUiMKAMAI/AAAAAAAAABw/ROPsBWxJ2o8/w503-h377-no/DSC00054.JPG


First stage release un-boosted.