Yes!
Hey! He asked Terry! You can't answer that!
Oh, what the hell, I'd rather have someone who can read and write anyway.
A weak link has more than one function.
Tost Flugzeuggeratebau
Weak links protect your aircraft against overloading.
Steve Kroop - 2005/02/09
A weak link is there to protect the equipment - not the pilot. Anyone who believes otherwise is setting himself up for disaster.
Dynamic Flight
The purpose of a weak link is solely to prevent the tow force from increasing to a point that the glider can be stressed close to or beyond its structural limits.
It should be stressed tested to the breaking limit while hooked to the tow bridle it is to be used with.
1. Assuming the weak link is a loop of string installed on a bridle, yeah. So?
2. And just how many people do you know who acually do that?
3. Hell, how many flight parks do you know who actually do that?
Should any tow ring, carabineer, release, or other hardware be snapped back that could hit a pilot, should they be in line with the tow bridle, this weaklink, tow, bridle combination cannot be used safely. (This hazard should be self evident. It has caused injury and blindness.)
Can you cite an incident of anybody who getting so much as bruised when using all low stretch materials for towline and bridle/release system components?
Simply increasing the breaking strength of a weak link for heavier pilots, larger gliders, or tandem flights without consideration of the stretching of a tow bridle or the maximum working load of a release is inadequate planning.
1. Never use elastic materials for elements of a tow system - even if you have read the lunacy Donnell published in the Eighties or...
Material should be a no-stretch line like perlon, spectra, or a particular 900-pound test like I found at a skydiving supply house.
...on Peter's website.
2. The weak link protects the release system from overloading. The release system is part of the aircraft. The definition is solid.
A weak link used only for the sole purpose of preventing damage to the vehicle (glider) can be too strong. It could easily break at so high of a speed that the glider would pitch up beyond the pilots ability to prevent the start of a loop or result in a break stall, tuck, tumble and collapse.
1. If it's too strong how can it "easily break"?
2. What G rating can you use to ensure that a glider can't pass VNE? Weak links tend not to break when gliders are going fast - they're most likely to break when they're doing the precise opposite.
Peter Birren - 2008/10/27
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.
3. Name a G rating you can use to prevent a pitch-up beyond the pilot's ability to prevent the start of a loop or break stall, tuck, tumble, and collapse.
Think about it, dude. Gliders pitch-up beyond the pilot's ability to prevent the start of a loop or stall, tuck, tumble, and collapse just fine in free flight. How are you gonna use a weak link to prevent bad stuff from happening on and/or just off tow?
The weak links' maximum breaking strength should not be so high that it is beyond the pilots ability to prevent a stall when it separates.
http://www.youtube.com/watch?v=vb4nUTAJXTkhttp://www.youtube.com/watch?v=bTa6XL16i0Uhttp://www.youtube.com/watch?v=JR_4jKLqrushttp://www.youtube.com/watch?v=eTKIAvqd7GIPeter Birren - 2005/02/08
This scenario is in my opinion what happened with Mike Haas at Cushing Field last year. His weaklink broke at a low altitude and he rolled off the stall.
Same weak link, similar G ratings.
ANY WEAK LINK CAPABLE OF GETTING SOMEONE AIRBORNE IS CAPABLE OF KILLING HIM EITHER BECAUSE IT BLOWS OR BECAUSE IT DOESN'T.
There are more considerations for weak link strength but they pertain to ground based towing and the response above was made with aero-towing in mind.
No. The sole purpose of a weak link is to prevent overload and it makes no difference what angle the towline's pointed when that overload is being approached.
All towing should be done with the idea that you have more options available in free flight than when under tow.
It most assuredly SHOULD NOT.
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
That's never gonna stop being true. That especially didn't stop being true when Donnell decided to reinvent aviation and the laws of Newtonian physics and throw logic and common sense to the winds.
A glider on tow thirty feet over the runway is virtually always going and/or having the option to go UP. A glider thirty feet over the runway with a broken weak link is ALWAYS going DOWN - often very quickly and sometimes sideways.
There most certainly ARE times when it's better to be off tow than on but they are EXTREMELY rare and virtually always avoidable down in the kill zone. And that's a good thing 'cause if you allow yourself to get get in a critical situation down low there's a real good chance you're gonna be killed equally dead whether or not you get off tow. And if you're waiting around for the weak link to do the job you should've done with your release two seconds ago... GOOD FREAKIN' LUCK.
Should a tow stop for any reason like motor failure due to a multitude of causes, unintended release, line breaking, weak link break, stupidly pulling the release when the pilot meant to pull a zipper cord or VG cord...
With the possible exception of engine failure, every one of those issues is one hundred percent avoidable and inexcusable.
...you should now be in a situation where you haven't flown yourself into a corner.
Right, you SHOULDN'T be. But we're all human, lotsa times you've got someone on the other end of the string who's pathologically human, sometimes Ma Nature throws us really nasty curveballs, and s*** happens. And sometimes there are two or three other things going wrong at the same time and we really don't need two or three hundred pounds of thrust instantly and irreversibly removed from the equation at a time not of our choosing.
At any second during the tow you should have planed to be off tow and be able to land safely.
Yeah, you SHOULD.
1. But hang glider people don't have great records of landing safely even when they get to start planning what they're gonna do from a couple of thousand feet.
2. And it's a lot easier to go up without hurting yourself or bending something than it is to come down without hurting yourself or bending something.
3. A landing following an engine, towline, or weak link failure is - by FAA definition - an EMERGENCY LANDING. And we can expect to see a lot more bad things happening in emergency landings than in vanilla ones. And, in fact, we DO - no ands, ifs, or buts.
Not down wind...
http://www.youtube.com/watch?v=bTa6XL16i0UWinds shift - especially in really good soaring conditions.
...on a nude sunbather...
That one needs more consideration. I'll get back to you.
...on the dolly...
Shane Nestle - 2010/09/17
So far I've only had negative experiences with weak links. One broke while aerotowing just as I was coming off the cart. Flared immediately and put my feet down only to find the cart still directly below me. My leg went through the two front parallel bars forcing me to let the glider drop onto the control frame in order to prevent my leg from being snapped.
...into the electrical sub station...
You don't need to come down into any of that stuff to hurt or kill yourself. A nice soft grass strip will do the job just fine.
Keith Skiles - 2011/06/02
I witnessed the one at Lookout. It was pretty ugly. Low angle of attack, too much speed and flew off the cart like a rocket until the weak link broke, she stalled and it turned back towards the ground.
And someone who may not be launching perfectly doesn't deserve to be punished for a flawed launch technique on a single occasion by getting the crap beaten out of her.
Davis Straub - 2005/01/13
Tom Lanning had four launches, and two broken weaklinks and a broken base tube.
And I know Tom and like him a lot. And he's a competition pilot and - aside from allowing himself to be brainwashed and/or bullied by SCUM like Davis into using 130 pound Greenspot - knows what he's doing. And if you're blowing three quarter G weak links every other other tow 'cause they can't handle world class thermal conditions in Australia you WILL crash a lot of gliders and do a lot of damage for NO REASON beyond trying to use the weak link for something other than the only job it can safely do.
Home
