Reasonably good shot of the bullshit sumpin'-fer-nuthin' "floating crossbar" (keel) mutation in our early design evolutionary history related to Donnell Hewett "autocorrecting" "center-of-mass" bridle and Jeff Roberson's Lever Link proposal.
The "thinking" was that with the extended keel pocket and loose-on-the-ground sidewires that the keel (the attachment point for your suspension) would move sideways with a lateral control effort and the force vector would then run perpendicularly up to the wing - thus amplifying the offset for roll control.
The lateral French Connection device actually worked to do something effective in this department. Allowed you to eliminate a lot of the arcing involved in your pendular movement and more efficiently take advantage of your weight shift authority and available leverage (function of control frame length (height) to exert differential sidewires tension.
All this Rube Goldberg floating keel crap does is take the keel out of the plane of where it's supposed to be (and always was prior and always has been since) and throw a lot of junk in the airflow to substitute for what should be just ten inches of hang strap. The junk under the attachment to the center of the wing articulates/pendulums EXACTLY the same.
Coplanar keel, tightish sidewires, high control frame plus hang point raised above the keel. Turns just fine - as fine as you're gonna be able to do with a high L:D wing and no articulating control surfaces anyway.
Taking the liberty of posting our recent and non personal PMs on this...
<BS> - 2015/08/01 17:30:13 UTC
I can't find it, but a couple times you've suggested someone tell Jeff Roberson his Lever Link won't work. If I understand the reason, it's because when towing forces are applied sideways to the keel, the glider goes the opposite direction. In a towing situation like that aren't the changes in victor forces the reason? Isn't the glider being pulled through the air sideways?
Tad Eareckson - 2015/08/01 17:54:12 UTC
WOW!!! I was JUST about to post on this very issue. I wonder if the trigger for us was the same.
Lemme go ahead and post and get back to you. I'd like to discuss this on the forum if it's OK with you.
So, fellow old Comet flyer... Was the trigger the same?
I can't find it...
First page, fifth post of this thread.
...but a couple times you've suggested someone tell Jeff Roberson his Lever Link won't work.
PLEASE!!! SOMEBODY.
If I understand the reason, it's because when towing forces are applied sideways to the keel...
Hopefully just a sidewise vector. If they're being applied fully sideways you're in very deep shit.
...the glider goes the opposite direction.
Yeah, it trims to what it perceives as the gravity vector. If it feels a pull forward it pitches away (up). If it feels a pull to left it rolls away (right).
In a towing situation like that aren't the changes in victor...
...forces the reason? Isn't the glider being pulled through the air sideways?
Nah, the glider's a big wing that can't be pulled sideways. Whichever way it's being pulled it's gonna use the lift it generates to go in the opposite direction. Stability thing.
Looks to me that the Lever Link does just that by turning the entire wing into an articulating control surface.
Yeah, I was afraid I was gonna get in trouble with that when I wrote it. If you wanna get real precise the entire wing IS an articulating control surface...
...AS IS. But I was meaning dedicated articulating control surfaces - ailerons, flaperons, elevators, tip rudders... operated with dedicated strings.
The Lever Link doesn't DO anything. It's just an assembly of Rube Goldberg junk very reminiscent of the Two-To-One / Center-Of-Mass / Hewett / Skyting Bridle. The difference is that the Hewett Bridle actually did SOMETHING intended by its inventor - albeit stupidly, inefficiently, dangerously and ONLY at very shallow tow angles.
Notice that on Jeff's theoretical model:
his pilot doesn't have any arms or hands. I don't know how much flying you've been doing lately but those issues tend to be biggies in turbulence and/or close to the ground. How's he think the pilot is getting and staying over there?
And in these illustrations:
our theoretical pilot has arms, hands, muscles but there's nothing bracing the control frame to the structure of the wing. What's he think is keeping it in place and allowing it to do something?
Jeff's theoretical power steering (perpetual motion) device works for the same reason that Jim Keen-Intellect Rooney's theoretical "bumbel bees" can't fly - they don't bother including various fundamental elements of reality into their equations. Rooney's bumbel bees don't have bumbel bee wings and there's no such thing as airflow.
If you understand the problem please get Jeff in touch with me and/or get him straightened out on The Davis Show.
Boring sled air.
You're flying a hundred feet over the runway and pull yourself forward through the control frame. What's the glider do?
You're coming off a launch dolly with a one point (pilot/shoulders only) bridle and exerting no force on the basetube - flying hands off for all intents and purposes. You've got a 125 pound of straight forward tension pulling you straight forward through the control frame to the exact same extent you were doing through your effort in free flight. What's the glider do?
Boring sled air.
You're flying a hundred feet over the runway and you use block and tackle to pull the keel towards the crossbar leading edge juncture on the right side. What's the glider do?
Fold up and plummet 'cause keels are totally useless for anything other than compression loading.
Short of that my best guess is that you'd make the airframe and thus sail asymmetrical, put more weight to the right, and induce a right roll and turn.
We could do a similar version of the same experiment by just running a heavy cord from a saddle between the leading edge and cross spar end down to our hips or any point up on the suspension and jam cleating ourselves over. That would pivot the keel sideways and offset our weight. But that would just be a variation of what we're doing on normal control efforts. The advantage would be that we'd be using no cost line strain versus high cost muscle strain to hold the input. The disadvantage would be that we'd be committed for a longer time than might be advisable.
The French Connections and Speed Rails of the early Eighties worked 'cause they reduced the amounts of up we'd hafta use to get and hold ourselves fore and aft and left and right. I recall that Speed Rails had to be carefully installed to make sure they didn't work TOO well - glider not returning to normal trim before you slammed into something hard.
But we threw these devices away 'cause we reduced pitch and roll control pressures by reducing washout, lengthening control frames, raising suspension points, making cleaner and faster wings, and adding VG systems so's we could make in-flight tradeoffs between handling and performance.
And show me how any of these design strategies of Jeff's are doing ANYTHING to reduce the effort and movement involved in getting the wing to go where we want it to.
Read his Abstract:
About 30 years ago, designers provided a full-span aerodynamic roll control surface for flex wing hang gliders when they cut the fixed connection between the keel and the crossbar (i.e. The Floating Keel or Floating Crossbar). By allowing the keel to float relative to the crossbar/leading edge structure, true wing warping roll control became possible. However, strong sail tension has for decades hidden the true potential of this aerodynamic roll control surface because the sideways force of the pilot on the keel is relatively weak. The Lever Link hang system described in this article provides the missing piece to this puzzle: a control linkage which connects the full pilot's weight directly to the full-span wing warping control surface in a levered manner to easily overcome the inherent stiffness due to large sail tension. This device should provide significantly improved roll control authority to flex wing hang gliders, resulting in improved safety, performance and ease of flight.
The Floating Keel/Crossbar was/is well intentioned but absolutely clueless RUBBISH that had two accidental spinoff benefits that stayed around after they had the good sense to chuck that idiot extended keel pocket - allowed more billow shift after they got the keel back up where it belonged and made the gliders a lot quicker and easier to set up and break down.
And speaking of enhanced control authority... The raised kingpost suspension point advantage for roll gets neutralized as soon as the webbing contacts a side of the keel - hence the spreader. Neither the assholes who sell and fly these things...
...appear to be able to grasp that concept. And Jeff wants manufacturers to build and certify Lever Link option gliders? Good freakin' luck. I can't even get any of those motherfuckers to build my cheap and easy VG system mirror aerotow release system into their gliders 'cause none of them will admit that there's no such things as easy reaches and one handed flying control compromises during low level lockouts and that appropriate weak links with a finished lengths of 1.5 inches or less are just more toxic snake oil.
Our problems are not having difficulties in delivering sideways force to the keel at its hang point and having limited keel pivot ranges. Our problem is that we're controlling our wings by pushing and pulling ourselves around in our swings with and against the bracing structure under the wing and that takes muscle and there's just so much we can do to reduce the effort and pretty much everything that can be done has already been done decades ago.
We've got pretty good wings that we can stay safe on in some pretty nasty conditions and if they're not good enough for us we can start pouring money into them, increasing our setup and breakdown times and efforts and turning them into sailplanes. But I can one hundred percent guarantee you that there will never be a Lever Link glider that gets off the ground and that if one did there'd be no discernable handling advantage - undoubtedly a disadvantage after you've fucked this:
up enough to accommodate the requisite engineering.
And just a gut level intuitive thing... Show me something on a modern intermediate to high performance glider that doesn't really look like it was really designed to fly. Do these proposals blend in with anything else anybody's put in the air at any time within the past thirty years?
