http://www.hanggliding.org/viewtopic.php?t=28290
Report about fatal accident at Quest Air Hang Gliding
Steve Seibel - 2013/02/13 02:40:40 UTC
tow dynamics
A couple more thoughts--
- I believe that with 3 point towing...
It's fuckin' TWO POINT towing, Steve. Start listening to the people who know what they're talking about and stop listening to the fuckin' idiot pro toads who caused and facilitated this one.
IF the upper point is at the or near the hang point, the bar position is different than with pro tow...
ONE POINT.
...but the bar force is not.
The bar force to WHAT? If you're on a slow pitch stable glider one point behind a fast tug you're gonna be holding a million pounds of bar pressure to hold the glider down into position and your arms are gonna turn to rubber.
In other words the pitch torque experienced by the glider for a given pilot force on the bar is the same as with pro tow. For example when the pilot is exerting no force on the bar, all the tow force ends up being transmitted directly to the hang point. Regardless of whether towing pro-tow or 3-point.
For the last part of that - YES. And now you understand why Donnell Hewett was and is full of shit on his center of mass Skyting "theory" of towing hang gliders and why the hallowed two to one bridle is a useless piece of crap.
- However, with 3-point towing, moving the upper attachment point forward on the keel changes things dramatically.
No, it DOESN'T. It's a gradual incremental change as you move up the suspension and forward on the keel. It's not all that much of a big fucking deal from inch to inch.
In flight, the glider's nose-up pitching tendency is decreased. The pilot needs to exert much less nose-down force on the bar to keep the glider in position.
Yes.
By the same token, a given nose-up bar force by the pilot results in less net nose-up pitch torque on the glider. To exert the same net nose-up pitch torque on the glider, the pilot much push forward much harder when towing 3-point with a forward keel attachment point, than when towing 3-point with the keel attachment point near the hang point, or when towing pro-tow.
OK, let's spread the word to all the new Hang Two Falcon flyers so they'll be aware of the problem they're having with this.
This is extremely relevant to what happens when the cart wheels start shimmying, creating drag, and exerting a nose-down pitch torque on the glider.
SO DON'T USE A CART WHOSE WHEELS START SHIMMYING.
It looks to me like the pilot towing 3-point with a forward keel attachment point should push out hard in this moment, to keep the glider from nosing over.
Jesus H. Christ. With all the REAL problems we've got with towing...
- So we need to be careful to not mix apples and oranges, and if a pilot is towing 3-point with a forward keel attachment point, not to give the same advice about what force to exert on the bar while rolling on the cart, that we would give to a pilot towing with pro-tow, or with 3- point with the upper attachment point at the hang point.
WE WHO?
Put the fuckin' glider on the fuckin' cart, wait a couple seconds after it starts getting buoyant, fly it off.
With the forward keel attachment point, there may be a greater need to push forward hard when the cart wheels generate extra drag and exert a nose-down pitch torque on the glider.
- USE A CART THAT'S *NOT* A PIECE OF CRAP.
- USE A RELEASE THAT *DOESN'T* STINK ON ICE SO IF THE CART *IS* A PIECE OF CRAP YOU CAN ABORT THE TOW INSTEAD OF BREAKING YOUR FUCKING NECK AFTER SLAMMING YOUR HEAD INTO THE KEEL.
- Also, with any bridle configuration, when the cart wheels start shimmying and making drag, this will exert a nose-down pitch torque on the glider. There will always be some requirement for the pilot to push forward harder on the bar in a case of severe shimmying, to hold angle-of-attack constant, i.e. to hold bar position constant. But more so with the 3-point with forward keel attachment.
What did I just say - AGAIN - about carts?
- At the end of the day, bar position equals angle-of-attack. By the time we approach flying speed, we want the glider to be at the correct take-off angle-of-attack, i.e. at the correct bar position for our particular bridle set-up, whether the cart wheels are shimmying or not. Shimmying wheels will mean we have to exert forward bar force to hold that bar position and angle-of-attack, but won't change the bar position associated with that angle-of-attack. It's when we are significantly below flying speed and not at risk of flying off the cart in a stall, that it makes sense to push the bar substantially forward of the take-off position to reduce the odds of a nose-over as we accelerate, especially on soft ground or with shimmying wheels. Especially with 3-point towing with a forward keel attachment point.
Earth to Steve, Earth to Steve...
We just killed a pro toad in no small part because he was being pulled forward and the glider wasn't. Therefore he lost a foot and a half of pull-in range and he couldn't keep the nose down when he REALLY needed to.
And then his:
- Rooney Link kicked in to clearly protect him from an excessive angle of attack
- angle of attack went INSTANTLY through the ceiling
- Wouldn't it help to make the main (upper) V-bridle much longer? The more acute angle might tend to resist sliding on the caribiner.
NO. The line of thrust will be EXACTLY THE SAME.
And don't get into a situation in which the glider's gonna pitch down 'cause if you do you're gonna be fucked.
Also, wouldn't a larger forward component of tow force continue to be delivered to the pilot, even as the glider started nosing forward?
What did I just say?
- My upper V-bridle is longer than average. Not by any special intent. I'll measure it.
You're using a Wallaby Release with the brake lever velcroed to the downtube and a bent pin "backup" release. Fuck what you're using for a bridle.
- This thread has morphed substantially;
Goddam right it has. BY DESIGN. To distract everybody from the fact that this motherfucker was killed 'cause he was being pro toad with a Davis Link.
...by contributing to the discussion re noseovers I don't mean to take anything away from our reflection on the recent tragic accident at Quest.
- You have - exhaustively.
- This wasn't a tragic accident. It was a long overdue godsend.
- The tragedy is that you assholes are derailing the discussion at the critical period in which the non shithead crowd will be able to get through to some of these Jack and Davis Show morons, gut Davis and Rooney, and fix these problems.
- Either get back on your meds or shut the fuck up for a month or so.
That way when a weak link breaks on you, ITS A NON-ISSUE. Genius huh???
