Flytec
Wills Wing

Oz Report

Volume 4, Number 53
1 am, Thursday, March 9 2000

https://OzReport.com
"Toto, I have a feeling we're not in Kansas anymore."

to Table of Contentsto next topic Brazilian meets

Wed, Mar 8 2000, 6:00:00 pm GMT

Gordon Rigg|Kathleen Rigg

Gordon Rigg, «Rigg», writes:

Kathleen, Gordon and eight other Brits will be at Valedares, so look out for reports at our League page: http://www.theleague.force9.co.uk/. These will pop up as and when we succeed in sending emails home.  I do not expect to be able to update my own page from Brazil.

The site for the comp is the goup Brazil one: http://www.goup.com.br, email «goup».

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to Table of Contentsto next topic It's Gibbo's Ghostbuster

Wed, Mar 8 2000, 6:00:01 pm GMT

Flight Design Ghostbuster|Mark "Gibbo" Gibson

Gibbo very explicitly wants me to notify Oz Report readers (once again) that I was flying his glider (and not some factory standard glider). Gibbo has tuned it to fly the way he wants it to fly (Gibbo is a glider designer after all).

I thought that I made it clear in the previous report that this was Gibbo's glider.  I also contacted Gibbo right after I landed to see if he had made any changes, because it flew so much different than Campbell's. He emphasized that he pulled the hang strap back.  He also said that turned the turnbuckle a quarter turn (I don't think that this is possible - although half a turn is), tightened the sail slightly, and tightened a few ribs (I didn't notice this).

He may have made other changes that he is not willing to talk about.  He is very competitive and wants to out fly every one else in the upcoming competitions.

Again, according to Gibbo, this is his unique glider.

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to Table of Contentsto next topic Dents on the Ghostbuster

Wed, Mar 8 2000, 6:00:02 pm GMT

Bob Reich|Felix Ruehle|Flight Design Ghostbuster|Matthias Betsch

That said, I hope that the folks at Flight Design don't get bent out of shape about what I write in the Oz Report.  I have written plenty of critical things about the ATOS, and I've never had anything but the most gentlemanly messages and received the most kindly consideration from Felix and Berndt at AIR.  Not a word or a whisper that I might be out of line.

To me it is always surprising and welcome that AIR can except the criticism, and still provide useful answers to my questions, and make changes based on the input they receive from pilots.

That said, I have to report, even though I'm sure that I will get into trouble again for it, that I have recently looked over a Ghostbuster and found the same kinds of dents as I previously found on my ATOS.  To be completely fair, this Ghostbuster had been transported around on a rack that didn't have any padding on it – just four round steel crosspieces.  The rack is now padded (although not nearly as heavily as mine).

I also found a few punctures that had broken the carbon fiber threads.

The dents were quite numerous, and shallow, just like on my ATOS.  They were obviously caused by transporting the glider on an inadequately padded rack.

It is my understanding that both the Ghostbuster and the ATOS use foam cores in their sandwiches of carbon fiber, core, and carbon fiber.  The Exxtacy used honeycomb.  Just as a check, I pulled the sail off this early Exxtacy that I am flying.  No dents.

I've published a discussed the difference between the type of construction used on the Ghostbuster and ATOS and that used on the Exxtacy before.  Let me remind my readers of where we were at with it:

Matthias Betsch, «flightdesign», of Flight Design, the builder of the Ghostbuster wrote:

"In general, we can say that the compression strength of all foams is less strong than the one of honeycombs.  For thin layers of carbon fibre the foam structure is at the end lighter and that’s what the pilots wanted so far."

Felix Ruehle's, «felix», extensive comments can be found at https://OzReport.com/3.137.

The gist of it is that it is easier to detect damage with foam core sandwich construction.  The foam will crush given a strong enough compression.

I'm flying here at Wallaby Ranch with my old friend Bob Reich, former marketing VP for O'Brien water skis.  They made campsite water skis.  He says their experience was that a honeycomb cored ski could not some any damage have experiencing a sharp blow, but that the honeycomb would be broken.  Later, under load, the ski would break right along the broken line in the honeycomb.

I don't have ready advice to pilots regarding when the dents are serious and when you can ignore them.

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to Table of Contentsto next topic Honey, I spun the Ghostbuster

Wed, Mar 8 2000, 6:00:03 pm GMT

Christof Kratzner|Felix Ruehle|Flight Design Ghostbuster|Hansjoerg Truttmann|Michael "Hollywood" Champlin

Penguin, «penguin», very succinctly puts it:

OK, so I'm a PG pilot, but I was an avid modeler for 40+ years also.  Thin at root, thick at tip + CG to rear (i.e. 'tail heavy') is recipe for big trouble.

Hansjoerg Truttmann, «hansjoerg.truttmann», writes:

We had many discussions during the worlds in Italy, especially with Felix Ruehle and Christof Kratzner (who is the official DHV-test pilot for the Guetesiegel-tests) when I heard that rigid wings are not spin-tested in Germany to get the Guetesiegel.

Spinning hang gliders normally is one of the standard procedures during the DHV-tests.  So Christof did it once with the small(?) Exxtacy.  He almost died.

Since that time, Christof doesn't do any spinning tests anymore with rigid wings, as it would be "Russian Roulette", he said (you know the funny game with revolvers …). Therefore I must say, that Ghostbuster isn't spin tested either.  Of course I was very interested in the question, of whether I am in danger flying the Atos, since this glider wasn't "spin-tested".

After many discussions and re-questioning Christof and Felix, I became convinced that - despite the fact that Atos would spin very ugly - there is no danger, because of two facts.

First: to spin an Atos you have to push as far as you can, and stay there.  Felix explained that people of ordinary size (like you and me) usually don't have arms long enough to push as far as you have to, to spin the glider.  The position of the A-frame is designed to prevent pilots pushing to far.  I didn't test it myself.

Christof as well stated that it should be impossible to unwillingly spin an Atos.  Up to now I don't know of anybody reporting a spin-like situation with the Atos.  Do you?

(editor's note: no, although we do have reports of some ATOS's being spirally unstable.)

Second: Felix (a big and heavy guy with long arms as you know) told me, that he once had a situation were he felt he got into spin when he made a test.  He pushed out far and for a quite a long time and at the same time he tried to change roll from one side to the other.  But before spinning really occurred he had obvious signs as the glider slowly started to rotate and he had enough time to react, since the Atos doesn't have a breaking stall.

(editor's note: The key here is fact that the Ghostbuster has a breaking stall, i.e. very quick and without any mushing.)

The reaction needed was very simple: it's enough just to release push-pressure a bit (not even to pull in) and the rising up spinning-effect (not a real spinning yet) immediately stopped.

I think all the pilots out there in the world should be warned now about spinning their rigids and they should be warned about changing their gliders in any way, because it becomes easier to spin their gliders, willingly or not.  There was a broken Exxtacy, two years ago in Geneva, Switzerland because of spinning willingly during aerobatics (as it is told); we know now what happened to you and the death of Michael Champlin is in our mind also.

I am very happy that you survived unhurt and I fear the day, when (again) a deadly accident occurs because of spinning a rigid wing.

In my opinion there should again be an official test to show the Ghostbuster is acting before spinning and what kind of pilot behavior could lead to get into spin.  Your accident is a strong signal to all glider designers and test pilots to keep this aspect on top of the safety priority list.  In my opinion, breaking stalls are (more) alarming with rigid wings (than with flex wings), because the danger of fatal spinning rises (more). If a rigid glider exhibits a breaking stall it shouldn't be allowed to get a Guetesiegel.

It causes anxiety to me reading the stuff on how to get out of spins on a rigid wing (not to critize you!!). After all I heard from Christof Kratzner, it seems just impossible to keep a spinning rigid under control nor to escape by a certain (simple) maneuver.  He had about the same experience as you when he tested the (small?) Exxtacy - it got just chaotic and he didn't know how he escaped at the end.  And I can assure you: if there is one pilot out there who knows how to manage hang gliders in difficult situations, it is Christof Kratzner.

So the solution is not to learn what to do if you're spinning but what to do (and what to fly) not to get into spins.  Or do you know of anybody willingly spinning rigids (especially hybrids!!) and escaping regularly by a certain method.

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to Table of Contentsto next topic Spiral instability on the ATOS

Wed, Mar 8 2000, 6:00:04 pm GMT

ATOS|David "Dave" Sharp|Felix Ruehle|George Ferris|James "Jim" Lamb

George Ferris and I have discussed the issue of spiral instability on the ATOS.  He says that if you lower the tips a small amount, the ATOS becomes spirally unstable.  There are also other configurations in which you can adjust the ATOS and it will become spirally unstable, but they required multiple adjustments.  Felix Ruehle asks that pilots do not adjust their ATOSs outside of manufacturer's specifications.

Jim Lamb, «jlamb», writes:

We've had some great warm weather here in the mid-west this last few days.  I took the ATOS to Whitewater, Wisconsin and had a fun 30 mile flight - good for Mar.  6. During the flight I had an experience similar to Dave Sharp's description.  30+ degree bank, slightly 'pushed' trying to get the glider around quicker, a little turbulence and found myself in a mild, stall/spin.  Mostly the glider just went toward the low wing and it took about a quarter turn to roll level.

It was very easy to get the air moving across the stalled tip and manage the airspeed.  I think there is a big difference in the GB and the ATOS stall/spin characteristics from the EXX consequent to the increased span.  Scott's suggestion that they be 'flown' all the way around turns is certainly appropriate.

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to Table of Contentsto next topic Ailerons Vs Spoilerons

Wed, Mar 8 2000, 6:00:05 pm GMT

Brett Snellgrove

Brett S. Snellgrove, «snell14», writes:

I don't want to hog the forum but I feel compelled to reply to Mr Stephen Morris's last contribution.  He is quite correct to point out that ailerons do impart a pitching moment, however to assert that weight shift control would be insufficient to contain these pitching moments in flying wings is to deny the evidence.

Spoilerons on almost all modern rigids are so close to the trailing edge they could be more correctly termed upward deflecting, split ailerons.  I feel certain they impart a similar pitching moment to an upward aileron.  This is why Joe on his E7 moved the ailerons to the high point of the camber.  The Sunseed also used upward deflecting (but not split) ailerons.  Weight shift has been demonstrated more than adequate to control pitching moments in these instances.

Even though the down going aileron doesn't travel as far as the up going one in a differential set up, it does indeed travel down and must therefore impart some pitch down to partially balance the pitch up moment of the upward aileron.  This does not occur at all with trailing edge spoilerons.  I'd be willing to bet differential ailerons impart less pitching moment then trailing edge spoilerons - and the spoileron controlled rigids fly just fine.  But I'm no expert - we need Alejandro of Aeros in on this one.

We've flown with wing warping "ailerons" on our flex wings for years - why is everyone so scared of them on rigids?

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The Oz Report, a near-daily, world wide hang gliding news ezine, with reports on competitions, pilot rankings, political issues, fly-ins, the latest technology, ultralight sailplanes, reader feedback and anything else from within the global HG community worthy of coverage. Hang gliding, paragliding, hang gliders, paragliders, aerotowing, hang glide, paraglide, platform towing, competitions, fly-ins. Hang gliding and paragliding news from around the world, by Davis Straub.

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