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Amati

Zero Wind Glider Kite

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Best listened to with Beethoven's Symphony #6

 

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2 line framed single skin kite (surfing):

 

kiteski.jpg

 

Floatation won?

 

But,

 

http://www.peterlynnhimself.com/newsletter/Nov_Nl_13.html

In the early (20 years ago?) days the only Kiter that I saw on SF bay had the same set up, i.e. line reel on the bar and the single surface kite.

The starting routine was to reel in the lines to about 8ft, then hold the kite in the air, and let the lines reel out. Instead of a single board,

he used "trick" water skis. He also had typically a backpack with swim fins and shoes for self rescue. I think the kites with floatation won, as you say, due to greater ease of restart after the kite hit the water.

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From the world of combat flying wing gliders, things are getting bigger and bigger (84" span, 4 lbs), 1.3 epp, which floats

 

https://www.flyingfoam.com/content/mother-ship-0

 

I think the 4 lbs includes battery pack, so lighter without. These things can fly straight into the ground and go back up.

 

There are even bigger ones....

 

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anybody mess with this kite/glider concept for Kite Surfing?

 

http://cdn1.bigcommerce.com/server2500/lu4j0e/product_images/uploaded_images/platz-origional-1.jpg

 

90 year old image- designer was Platz, who was, I think, Fokker's chief designer after 1912.

 

Kind of a cunard/jib/main approach- difficult to stall, very stable. Add a pool noodle to the spar for flotation?

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turns out Platz was a sailor! ed: Fokker Too-

 

(This topic is in: <- Sep.3 Jul.21 Mar.23 Mar.21 )

See the article in the last Oz Report on this glider. Brett Snellgrove <Snelly14> writes:

For some time I've been interested in an early canard glider design by Platz. It preceded the Rogallo by quite a bit. It's a pity our sport didn't evolve from this design rather than the flying wing. His canard was likely stall, tumble and spin resistant with a better static margin, full aerodynamic control and ideal for slow, flying foot launched wings as it was easily folded and transported -- all with primitive materials. The first prototypes of Platz's designs certainly flew far better than early Rogallos.

I've compiled this article from a few letters of Bart Doets on the History of Hang gliding Yahoo forum.

From Bart Doets:

In the hang gliding world it has long been taken for granted that hang gliding was initiated in the fifties by Francis Rogallo. Although it is true that our present day gliders are descendants from Rogallo's flex wing kites, Rogallo was not the first one who thought in this direction, as the pictures with this article clearly show.

For Rogallo, it took a number of years to get from his flex wing kite to the first practical application (the Ryan Fleep, which was the ancestor of all weight-shift powered aircraft, even though it was not weight-shift controlled itself). For Reinhold Platz, the inventor of the early hang glider-avant-la-lettre, it was a matter of months, merely waiting for the right wind; just like in present-day- hang gliding. The first model flew in November 1922, and man-carrying flight succeeded February 1923.

Reinhold Platz was a German technician employed by the Dutch Fokker airplane factory, which had a department in Veere on the peninsula of Walcheren in the southwest of Holland, where hydroplanes were made. Platz had been hired as a specialist in autogenous welding, which was quite a new technique at the time; because of his good technical insight. Anthony Fokker soon put him in charge of assembly.

Although Platz had no knowledge whatsoever of mathematics or mechanics, he was known to find simple solutions for problems that puzzled the Fokker engineers. But then, the combination of technical insight with a certain lack of theoretical basis is a true pioneer quality! Reinhold Platz died in 1966, at the age of 80. He had probably read about Rogallo's exploits, when the Fleep first flew in '62. Surely he must have realized how close he had been to Rogallos invention, thirty years earlier.

Anthony Fokker was a lover of sailing, and so was Reinhold Platz. It is likely that it was on one of his sailing trips in the waters around Veere that Platz got the idea of converting sailboat aerodynamics into sailplane ones. He knew that the course of a sloop-rigged sailing boat can, within certain limits, be controlled by hauling in or paying out the jib sail. He simply transposed the sail-plan of a sloop into the horizontal plane, doubled up to form a symmetrical shape and hypothesized that, like in his sloop, the angle of the two jib sails (the canard, we might say) would control the angle of attack of the main sails.

To try this out, he cut out the planform of his invention from paper, and weighed the nose with a paperclip. It turned out to fly beautifully, and very stable too; and not only could the angle of attack be controlled by varying the jibs, but they also could be set to turn, when one was tilted upward more than the other. In fact, while a normal rudder would function only with sufficient horizontal speed, the "jib rudder" works even if the model is released without any forward speed at all.

As the paper model had shown his theory worked, Platz built a model of his envisioned glider, with a wing span of 1,30 m. and 40 cm² surface. This model was tested from the dunes between Vlissingen and Koudekerke, to find the right settings for the jibs, and to adjust the centre of gravity.

In November 1922 the model soared for some time along an 8 m. high stretch of dune. Before building the final thing, still a lager model was built to make sure of some details. This model had 2,50 m. wingspan and 1,30 m² surface. While the smaller model still had rigid wing surfaces, this time the sails had been made from cloth, and it had to be checked whether they would billow into the desired airfoil shape.

Although all aircraft in those early days were of quite simple construction, nobody -not even Otto Lilienthal- had tried a wing surface without any ribs or rigidification yet. (And afterwards, nobody would until Rogallo, as far as I know.) It is conceivable that, if the sailing boats in his days would have had sail battens like they do now, Platz might have preferred to add them to his glider; as it was, he had never seen a middle way between the rigid wing constructions he knew and the free floating sail of his sailboat.

Though unbattoned, the larger model flew well; like the small one, it could soar the dune lift band and stay at altitude for some time. So finally, back at the Fokker factory the definitive glider was made. It measured 6,60 m. span, 16 m² surface, and tethered loading with a 100 kg man had proven the structure generated sufficient lift.

A close look at the photographs reveals that, between the tethered tests and the free flights, somehow a correction had been made to the jib assembly. Not only has the upturned front part of the keel been cut down some, but the jib sail seems to hinge on a point behind the leading edge. Of course, originally the pilot had been supporting a certain percentage of the lift with his hands; by moving the hinge point back, the force needed to hold the control surfaces in position could be largely diminished. Finally, the glider was considered safe enough for free flight. On a day in February 1923, on the Dutch coast near Vlissingen, the glider soared for some time along the dunes.

The glider weighed 40 kg; quite heavy for nowadays standards, but then, the materials were canvas sails, wooden booms and some iron hardware. Even though, it may well have been one of the lightest gliders for years; and surely it was the very first with a cantilever wing!

A comment in Flight, a British magazine, of March 1924: "Personally, we fail to see why the spars do not fold up, as they are very improperly braced." (typical British understatement.) Platz emphasized the point that his construction was cheap, and also could be very swiftly rigged and de-rigged, and that the folded glider could easily be carried by one man and eventually transported on bicycle or on a passenger train. He may have had a dream of groups of people coming to a hillside, each with his own folded glider, rig, and soar the aerial currents. A prophet!

Platz-glider-on-bike.jpg

To ensure directional stability and to do away with a tailfin, which due to the absence of adverse yaw did not require a rudder to anyway, Platz had chosen to give the structure quite a lot of dihedral. On the model gliders this had proven to work well.

The keel construction (no hang glider keel ever deserved that name more than this one!) was a bent iron tube at front, with a wooden boom stuck into it for the aft end; at the junction, two butts of tube were welded on at right angles, to stick the wooden wing booms into.

The only moving part of the glider was the connection of the jib sails. They had a pivoting anchor point at the front end of the keel, and the aft ends were hand held by way of controls. Surely, compared to early Rogallo hang gliders which measured up to 20 m², the wing surface of 16 m² was quite small; especially considering the tips were very pointed, like on the first Rogallos, and thus must have been quite ineffective.

However, with his canard stabilo wing, the was no need for Rogallo wing billow, rather, as in the sailing boats that inspired the concept, he had every reason to make the sail as tight as possible, as the pictures show. This, of course, is an advantage over early Rogallo type wings.

It is a pity that none of the documentation gives a clue as to how the glider was launched; a catapult start would seem logical in those days, but the pictures do not even show anything that looks like a towing hook anywhere under the keel. So we must assume the thing was lifted by a group of men and shoved off the dune top. Though a hip harness to the glider would have made it foot launchable, there's no evidence of such in the photos.

All the reports say that the glider was fully controllable; stable and with sufficient performance to soar dunes for prolonged periods decades before Rogallos evolved to a comparable level. It was easily broken down and transportable on a bicycle, as the pictures show, but alas soon forgotten afterwards.

Other, more serious airplanes had to be made by the Fokker plant. Although, in the thirties, it had been suggested in several sailplane magazines that the Platz glider might be a good and cheap trainer for sailplane clubs, to my knowledge and in spite of its many successful flights and truly revolutionary construction, no second Platz sailplane has ever been built.

Bill Berle <auster5> writes:

The Platz glider of 1923 in the photo was the subject of some great scheming, planning, and dreams of mine about a year or two ago. I was just absolutely certain that I wanted to build one, and hordes of great thoughts came rolling along...carbon fiber tubes making the whole thing weigh 70 pounds...powered paraglider backpack engine on the pilot...being able to market the world's simplest rigid ultralight.

With my first 16 inch span free flight stick and tissue model I found out the same thing that Reinhold Platz found out in 1923, it doesn't fly well at all. I rigged up a trim system in which you cold position the canards (jibs in sailboat speak) in any position to trim the thing for level flight. That barely worked, but was manageable.

When I tried to use the differential position of the canard/jibs to make it turn, the little glider would have no part of it! Even a 20-25 degree differential angle on the canards made almost NO difference, and it droned along in a straight line into the nearest wall. This insurmountable problem occurred with and without the micro electric motor and propeller.

All I can suspect is that the mild turning force of the canards (when positioned at a differential angle) was completely offset by either adverse yaw, or the drag of closing off one aerodynamic "slot" between the canard and main wing. It was the equivalent of a car going in a straight line with the driver madly turning the wheel one way and another, with the front wheels turning one way and another, and making no difference to the trajectory at all.

The problem is fix-able, if anyone out there wants to build a Platz Glider, but it will not be an accurate replica. You need a movable vertical rudder, that is attached to the control system. You'll need to rig it up with a stick that moves the rudder left and right, and then moves the canards up and down equally like an airplane's elevator. I strongly suspect that this would make it flyable and controllable, however it will not be a three axis control.

It does not matter what that book's caption, or anyone else's hopes and dreams claimed the Platz Glider configuration is not controllable with the minimalist canard grips alone, as cool as that might have been.

Platz' more successful designs all had rudders, and were noted for their excellent maneuverability and controllability. His Fokker D-VII was the only aircraft so feared and respected by the enemy (Allies) that they were specifically ordered to be turned over at the end of WW1 as part of the armistice.

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