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Re: Understanding Tow Releases

Postby TadEareckson » Sun Oct 16, 2011 9:44 am

Hey Peter, great to have you back.

Peter Birren

PITCH & LOCKOUT LIMITER

The lockout starts with a bit of roll away from the tow direction. This rolling ultimately makes the glider want to behave like a tail-less kite and turn 'round the line. A short way into the turn there is a high degree of pitch-up attitude relative to the towline, so having a release at the point of too much pitch could automatically release the pilot and hopefully provide the pilot with sufficient recovery time.

How it works:

With the release at the apex release site, a second release line will be attached to the glider's nose. As the glider pitches up relative to the towline, the release gets farther from the nose and tightens the line.

Peter Birren - 2009/05/09

If you want a truly foolproof release, it's got to be one that eliminates the pilot from the equation with a release that operates automatically. Certain tradeoffs would have to be made, like limiting the top altitude of a surface-based tow or having it release within certain limits of pitch, but if you want to legislate safety.... See:

http://www.birrendesign.com/LKOpinions.html

for more details. I am not trying to push the automatic release, definitely not the way you're pushing your setup, but it works.

And here:

http://www.youtube.com/watch?v=IjncKQ02FJ8

we see an actual pitch and lockout limiter in action with an actual pilot in an actual tow situation.

And when there's a high degree of pitch-up attitude relative to the towline it does INDEED automatically release the pilot.

And the pilot IS - along with his driver - TOTALLY eliminated from the equation.

And there IS a tradeoff in that the top altitude of the surface-based tow IS (severely) limited.

But the problem is that when it automatically releases the pilot at the point of too much pitch it DOESN'T provide him with the hoped for sufficient recovery time. In fact, it does the PRECISE OPPOSITE.

Manned Kiting
The Basic Handbook of Tow Launched Hang Gliding
Daniel F. Poynter
1974

"The greatest dangers are a rope break or a premature release." - Richard Johnson

Can you possibly see how Pitch and Lockout Limiter might instantly convert an easily manageable situation into a fatality?

Donnell Hewett - 1981/04

WEAK LINK

Every tension limiting device discussed up to now consists of mechanical components, has a limited range, or relies upon human operation. Every one of these tension limiting devices is subject to failure. Please correct me if I am wrong, but it is also my understanding that there are a large number of tow pilots today who are depending upon smooth air, rope stretch, boat speed, mechanical devices, and ground crews to provide the tension limitation control for their flights. Well, in the author's opinion that is just not good enough. Skyting requires the use of an infallible weak link to place an absolute upper limit to the towline tension in the unlikely event that everything else fails.

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," and that "More people have been injured because of a weak link than saved by one." Well, I for one have been saved by a weak link and would not even consider towing without one. I want to know without a doubt (1) when I am pushing too hard, and (2) what will break when I push too hard, and (3) that no other damage need result because I push too hard.

Furthermore, I will not use a mechanical weak link no matter how elaborate or expensive because there is always the possibility that it may fail to operate properly. In skyting we use a simple and inexpensive strand of nylon fishing line which breaks at the desired tension limit. There is no possible way for it to jam and fail to release when the maximum tension is exceeded. Sure, it may get weaker through aging or wear and break too soon, but it cannot get stronger and fail to break. If it does break too soon, so what? We simply replace it with a fresh one.

A properly designed weak link must be strong enough to permit a good rate of climb without breaking, and it must be weak enough to break before the glider gets out of control, stalls, or collapses. Since our glider flies level with a 50 pound pull, climbs at about 500 fpm with a 130 pound pull, and retains sufficient control to prevent stalling if a weak link breaks at 200 pounds pull, we selected that value. Of course, a pilot could deliberately produce a stalled break at 200 lbs, just as he can stall a glider in free flight. But if he is trying to limit his climb rate and the forces exceed the break limit, the glider simply drops its nose to the free flight attitude and continues flying. If the weak link breaks (or should the towline break) at less than the 200 pound value, the effect is even less dramatic and controlled flight is still present.

Peter Birren

These are Donnell Hewett's original 12 elements of a good tow system. They are as viable today as they were in the early 80's when he wrote them.

Towing Aloft - 1998/01

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

Speed controlled towing is when the speed of the device doing the towing is maintained at a reasonably constant value. Controls, such as throttle, are used to keep the speed of the tow vehicle or tow winch operating at a constant speed. Towline tension can vary dramatically in response to thermals, sink, pilot corrections, etc. Aerotowing is clearly in this category as the tug needs to maintain a minimum speed to prevent stalling. Many of the early towing efforts of the '70s where the vehicle drove at a fixed speed would also fall into this category. Weak links very clearly will provide protection from excessive angles of attack, high bank turns and the like for this form of towing.

Any chance that those pioneer guys mostly knew what they were talking about and Donnell and the a**holes who wrote Towing Aloft mostly didn't/don't have a freakin' clue?
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Re: Understanding Tow Releases

Postby Bob Kuczewski » Thu Sep 22, 2022 2:57 am

Back on the first page of this topic (posted on February 17th, 2011), I was having a hard time interpreting this picture by Tad:

Tads_Barrel_Release_small.jpg
Tads_Barrel_Release_small.jpg (7.71 KiB) Viewed 91 times


I was confused because it looked like the red line (on the right) had wrapped around the pin by one complete turn and was coming back out as the white/green striped line going into the barrel. Despite the color change, I was only seeing one line, and I didn't understand how that could work (I had never seen real towing hardware at that time). But after a little study, I realized what was going on. In my second post (also on February 17th, 2011), I suggested that an animated GIF might be a good idea to help folks understand it more easily:

Bob Kuczewski wrote: ... it might be helpful to generate an animated GIF to use for your avatar (or posts) which shows the deployment sequence ...


Well ... over a decade later, I finally got around to making such an animated GIF myself. It's not perfect (and I see a number of flaws), but I think it would help people (like myself) understand the barrel release a little more easily. Here's my animation:

Release_Animation_640.gif
Release_Animation_640.gif (255.19 KiB) Viewed 91 times


Sorry it took so long (11+ years?). The good news is that I was able to get it done while Tad is still alive and posting on his forum. Tad, if you're reading this, please feel free to use that animation in any of your posts on your forum or elsewhere. :thumbup:
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Re: Understanding Tow Releases

Postby JoeF » Thu Sep 22, 2022 10:36 am

Very nice addition to the literature, Bob! Thanks.
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Re: Understanding Tow Releases

Postby Craig Muhonen » Fri Sep 23, 2022 11:28 am

H0 me again,
Bill, after watching many videos, I really do feel the rush that tow launching provides a would be Hang Glider Pilot, or one who just wants to train.
Foot Launching is the best but Tow Launching is more available and the "pattern work" that the flyers get to do is so value packed.
Bill Bennett told me in 1968, (that's another story) that the "release point" was the hardest thing.

Next step is a portable Hang Glider Flight Simulator,
with video recording, in a 20 knot wind machine. :thumbup:

So many people don't live in the "gentle hills", and I think your Tow Launching and training influence on Hang Gliding is on the cutting edge and becoming more available to pilots, people do forget that it's all about the
"SAFE" flying, and Training Training Training.
TY.
Hope all the hard work you do on the insurance front pays off, being an instructor pilot is tuff I would imagine.
Craig




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"You gotta' push the stick forward while you're lookn' at the ground
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Re: Understanding Tow Releases

Postby Craig Muhonen » Sat Sep 24, 2022 9:18 am

Outta the Blue and dum luck


I was on R & R, It was Dec 22nd 1968, on a river North of Sydney' I was sitting across the campfire from Bill Bennett and his friends, only knowing that they were showing me the wettest 3 days of my life, Solid skiing, and all the Fosters and steak we could eat. Hot showers and a bed and some "round eyes",
after 375 days of "scary hard", and breathing water most days.
Bill and his family picked us up at the airport and I was in heaven.
I got in so many hours on one ski, next to Bill. He showed me how to barefoot ski, but one fall and that was that.
They were talking about the ski kites that they built and the boats to pull them, and how they worked, each one of them said the release was by far the scariest part,
and they couldn't pull in far enough to get good pitch control some times. Bennett said, the flying was easy but I'm pretty banged up from "Falling, and not Flying".
They were on a very long line being towed by very powerful boats getting quite high in the air the hard part, the easy part Bill said, was flying, and it was getting better and better each flight. We all know how Bill progressed through Hang Gliding, but when he started in a motorized tandem Hang Glider he went away from the fun of being a single pilot flying his Hang Glider.
watching a lot of videos
Looks like Tow launches in a great Hang Glider that you don't have to purchase number one, number two , Master pilots at your side and towing you, and three, you get to feel the absolute rush of 20 + miles per hour
then the take off right away and what you do with the control bar is up to you.

Here is a tow launcher I pictured, a wide flat trailer going 20 mph,
with one student Hang Glider standing in the middle with a safety link, a nose tether and two wing, an instructor pilot and two wingmen with safety harnesses . And cameras rolling, with helmet to helmet communication.
Wouldn't the glider want to fly up and down, left right depending on speed? and wouldn't the look on peoples faces, "hey I can do this", nobody will believe I flew a Hang Glider, but I have my video.
a mobile wind tunnel. Pilots could take off and land with their tethers flying, many times an hour, and maybe catch a little up lift.
Take off's and landings are the real master trade I think, flying is easy.
I think this set up would work, only if you had a good tow driver and a piece of flat ground,
and charge accordingly
the tuff part


what you think?
Good on ya Bill, keep on truckn'
Enjoy,
this is the coolest Hang Glider video, what training, you can get a masters in low flying with your friends, and never get too high.
But I imagine that high wind, slow flying training, puts them ahead of other students, right away, and the muscle memory must stay with you for a long time, these fliers make it so easy, but it's not I would guess.
https://www.youtube.com/watch?v=oh947seXs5c


Craig
"You gotta' push the stick forward while you're lookn' at the ground
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Re: Understanding Tow Releases

Postby Bob Kuczewski » Sun Sep 25, 2022 1:45 pm

Thanks for sharing your great memories of Bill Bennett.

Also thanks for sharing that video. It's really great!!
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Re: Understanding Tow Releases

Postby Craig Muhonen » Sun Sep 25, 2022 2:41 pm

Bob, a story I've kept to myself, but I almost "kilt" Bill.
On our last day of skiing I carelessly flung my tow rope over to him, it got tangled in his arm and down he went hard dragging him into a boat at the dock,
I thought he was a goner for sure.
They took him to the hospital and I got on a plane the next morning not knowing, but with a heavy heart, mainly because I was headed back to the war zone. What a 7 days that was though.
He was a "monster man" and recovered to ski and fly again, and in 1974 he came to a fly-in along with Dave Cronk and others. Dave, by the way, won our contest that year, and then promptly went to Austria the next year and became World Champion. Torrance Beach did rule.
Thanks for US HAWKS.

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