Zack,
Are you saying that John was inadequately trained to fly...
If we can chop the sentence right there I can answer with a simple and rather obvious "Yes."
Beyond that... Some folk pick up glider control quickly and naturally, others suck. Those in the latter category can work extra hard and get things right eventually but it's a headache to deal with them. And whenever I hear about someone "cross (read not) controlling" I know I'm dealing with a B Grouper.
John... I'm just reading what Shane has stated and considering it in the context that he turned back into the hill and killed himself in pretty garden variety conditions. That wouldn't have happened if he had been made to go through the paces doing turns around traffic cones at a hill or off of scooter tow.
And I don't consider flying upright a 'crap configuration'...we launch in this configuration, which would be pretty crazy of us if it was really 'crap', right?
Upright is a necessary evil for getting off a slope, ramp, or cliff most of the time. Not a BFD there though 'cause, unlike the situation at the other end of the flight:
a) you can pick your time and cycle or - choose to scrub;
b) the ground is typically getting farther away;
c) it's a lot quicker and easier to rotate down to the basetube than up to the downtubes;
d) the timing on that transition is virtually never critical.
On landing:
a) your a** is going down and the ground is ALWAYS drawing closer;
b) below a hundred feet there's not much you can do to influence the timing and there's no abort button;
c) people commonly have serious problems rotating to vertical and sometimes get seriously int*rcoursed up as consequences;
d) it's almost always a second best idea to have your hands on the downtubes at the instant of touchdown - sometimes a really distant second.
People staying upright for the whole damn trip to the LZ drives me berserk. People being upright twenty feet over the LZ also drives me berserk.
At Kitty Hawk Kites we threw thousands of inept one-timers off the dunes and they typically did just fine launching on the downtubes, proning out and going to the basetube, then going back up to the downtubes for standup landings or reasonable facsimiles in the courses of flights that didn't make into the double digits on the second hand.
Dunno about that...
1. Go to the local Renaissance festival and steal somebody's chain mail jacket.
2. Put it on and fly to the right of an electromagnet at trim with a light neutral grip on the basetube.
3. You will be pulled / Your weight will be shifted to the left.
Which way will the glider roll?
I don't see it causing a problem for students.
It apparently didn't register very well for John Seward. I'd be inclined to teach students that it's differential wire tension that controls the glider and that weight shift is the way it's effected.
I've never heard anyone say this myself...
http://www.youtube.com/user/maygoli#p/a/f/1/2dvr9P_w5VQ1:36-1:48. Pretty much anybody using a Hewett - sorry, Heewit - Bridle is still stuck in that delusion. And it still keeps spilling over into one point and one to one bridle towing. (And keep listening to see how the weak link will sense when you're getting in trouble and automatically help you out of your particular situation.)
Calling floating crossbars a 'folly' or 'disaster'...
Just folly for the "floating crossbar".
I thought they allowed or at least facilitated wing warping.
Facilitated. People were able to make Seventies gliders with the cross spar fixed to the keel turn just fine. Come to think of it... The Sky Sports Eaglet Kitty Hawk Kites still uses for their trainers has the cross spars fixed to the keel.
Look at a modern topless bladewing.
Crank the VG all the way on and leave it alone to take that complication out of the equation.
The sail is stretched over a frame consisting of three spars - if you count the two joined and pulled back cross spars as one - which they could be if you never needed to put the glider on the car.
1. The leading edge spars define the leading edges of the sail.
2. The cross spar braces the leading edge spars.
3. The keel doesn't do much. It gives you:
-a) an anchor for the cross spars haul-back - but we've already got them fixed and are ignoring that issue;
-b) an anchor point for the tail wires;
-c) something onto which you can bolt your control frame.
The leading edges / cross spar assembly is fixed and immobile inside the sail. The keel runs from nose straight back to and through a rather flat pocket under the trailing single surface area of sail's middle. And it doesn't move much with respect to the other frame components.
Cross spars were originally fixed to keels because it was intuitive to do so (as it was intuitive to connect tow bridles to control frames) but are no longer mainly because it's better engineering not to.
Not having the keel connected to the cross spar allows a little articulation which facilitates a little billow shift but I suspect you might be hard pressed to notice much of a resultant handling advantage. But if Steve Pearson says otherwise go with him.
The folly...
At some point in the late Seventies somebody got the idea that if you cut the keel free from the middle of the cross spar and ran it through a deep keel pocket that when you moved to the (call it) left the keel would be allowed to articulate to the left and thus you'd be effectively suspended from a bit outboard to the left and your roll authority get a boost.
And the "floating crossbar" became all the rage for a number of years. My first glider, the UP Comet, was an expression of this thinking.
The problem with this thinking was that it didn't matter where you put the keel - all that mattered was where the wing/sail was feeling the transmission of the load. And all that was relevant to that issue was where the keel pocket - irrespective of its depth or near total lack thereof - was stitched to the sail. And - as long as you anticipate a need to fly straight and be able to turn in BOTH directions - that's always gonna be at the centerline.
I believe that it was Wills Wing who started suspecting that the "floating crossbar" wasn't actually doing anything and put a glider up with a camera on the keel and watched what was going on with the geometry - which was, effectively, nothing.
And, of course, there never was any "floating crossbar" in any case. That was an optical illusion resulting from the narrow perspective of the person standing under the glider. The entire wing was floating left and right in relation to the keel which was bolted to the control frame which was parked on terra firma.
The "floating crossbar" was a scheme whereby people attempted to get something for nothing and it hit just a little before Donnell came out with his Skyting Bridle - believing that it would do the same thing. On Page 5 of the 1982/09 edition of his Skyting newsletter...
In addition to the above mentioned roll and yaw tendencies, there is some sideways force on the pilot due to the body line. This is illustrated below:
PILOT WEIGHT SHIFT
Back View
As can be seen, this sideways force tends to pull the pilot over to the correct side to make the glider turn naturally in the proper direction.
But it doesn't. It, if fact, does the PRECISE OPPOSITE. Keep it up for another second or two and you've got a lockout.
I've really never understood how hang glider roll control is effected...
It's fairly simple and not all that different from what was going on with the Wright Flyer or is with the Cessna 152 - but it really helps to think about what's going on in terms of differential control wire tension rather than weight shift.
01. You shove the basetube to the right (pull yourself to the left).
02. The left sidewire tension increases while the right is reduced.
03. Thus there's more of a downward pull on the left wing (at the leading edge / cross spar junction) and less of a downward pull on the right.
04. Thus there are more pounds per square foot of left sail than there are pounds per square foot of right sail.
05. Whether or not the keel is bolted to the cross spar some slop WILL be pulled out of the right sail and transferred to the left.
06. This slop transference simultaneously allows the trailing area of the left wing to deflect up while the right wing has its trailing area pulled down.
07. Think ailerons. Think ailerons deflected using control cables which act in opposition to each other.
08. The left wing will thus be generating less lift (and aerodynamic drag) as its angle of attack is lowered and will sink while the right wing will thus be generating more lift (and aerodynamic drag) as its angle of attack is raised and will climb.
09. So the glider will roll the way you want it to.
10. The stuff in the parentheses will cause the glider to yaw adversely but the sweep will take care of that problem for you.
As for pitch, I've always thought it was 100% weight shift.
Do the chain mail / electromagnet experiment again but this time flying directly at and away from it. And be careful to maintain a minimum ten foot separation.
Or, if that's too much trouble, tow one point behind a tug and see which way the glider pitches when the towline tension shifts your weight forward.
...and some of them don't have nose wires.
I don't know this construction. But if you've got a control frame it has to be braced somehow and the force you apply to the control frame will be transmitted through the bracing.
You totally lost me there.
See electromagnet, Hewett Bridle, and one point bridle above. No differential wire tension, the glider does the opposite.
Bob,
I believe that Tad is a very knowledgable person about many things. His life experience has likely confirmed that he's often (if not usually) right in most disucssions. I think this has led to a false sense of infallibility with regard to what he says and it has led him to assume he's right in situations where he is clearly not. This makes it very difficult to change his mind once he's committed himself to an idea.
1. If I'm batting .501 I'm probably a force for the positive and others should be able to take up the slack and neutralize me where I'm wrong.
2. Rather ironic spelling of "discussions" in a paragraph about infallibility. (And may even be problematic with respect to FCC regulations.)
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by Nobody » Sat Nov 12, 2011 10:05 pm 
“Lift and tug is MANDATORY *IF* the pilot believes it can be done without exposure to additional risks.”
