Materialsammlung aus dem Netz II
The Archer's Paradox
"The term "Archer's Paradox" was labeled in the mid 1930s by Dr. Robert P. Elmer, a well-known archery writer. It concerned the question as to why an arrow would hit a target when, from all appearances when placed on the bow, it should strike to the left.
After a number of tests on shooting machines by several individuals and using the high-speed camera of Dr. Clarence Hickman, resultant slow-motion movies at 6600 frames per second produced the following sequence that shows the initial flight of a correctly-spined arrow from a well-designed bow. (A right-handed shooter is assumed).........................
An arrow must be spined correctly to oscillate at just the right frequency to "bend around" the bow. If it is too limber it will strike to the right of the target center. If it is too stiff it will strike to the left of the target center."
Archer's paradox: "In period bows (without a shelf or centre shot) the arrow which is properly shot will fly in the line of aim, although the string propelling the arrow moves directly to the centre of the bow. The arrow in fact bends around the bow after release but after passing the bow returns to its proper line of flight. "
Zitiert aus der Website http://www.bowmen.freeserve.co.uk/terms.htm Jetzt so nicht mehr auffindbar.
Video: unbedingt anschauen
Paradoxe Phänomene beim japanischen Yumi
Stephen Selby's Reflexionen über paradoxes Verhalten beim Yumi:
"I was curious (although this is not a criticism) about the explanation of the step in which the archer has to 'turn the edge of the bow to the left' out of the path of the string at the moment of release to stop the arrow from 'being diverted considerably to the right at the last moment'. Such an action is not required in Chinese archery (or as far as I know, in English longbow shooting), although the arrow-pass is much more pronounced than on a yumi, due to the effect of the 'archer's paradox'.
That archer's paradox is at play in Kyudo is evident from the fact that the string is drawn well behind the archer's ear at full draw, without any risk of the string slicing it off. (I have tried this and I know it to be the case.) I remain to be educated on this point."
http://www.atarn.org/letters/ltr_may02.htm > paradox und yumi
Und Stephen Selby vermutet richtig - Videoaufnahmen beweisen:
Die intensive Verwindungs- und Dreharbeit der linken Hand, das sog. Tsunomi No Hataraki, ist wesentliche Ursache für die Richtung des Pfeilflugs. Angemessen ausgeführt, was Beschaffenheit des Bogens und Pfeils betrifft, wird der Pfeil in die Richtung fliegen, in die der Pfeil vor dem Release zeigt.
Es ist richtig, dass der Pfeil mehr um den Bogen herumgeführt wird, als dass der Bogen dem Pfeil den Weg freigibt. Aber ohne Verwindung des Bogens durch die linke Hand vor dem Release käme es zu keinem Archer’s Paradox-Effekt. Die tatsächliche eintretende, relativ geringe Drehung des Bogens nach links bevor der Pfeil die Sehne verlässt trägt vermutlich ein Letztes dazu bei, dass der Pfeil vollends sicher am Bogen vorbeigeführt wird.
Tsunomi No Hataraki + Verwindbarkeit des Yumi = Archer's Paradox
Mittlerweile verfügen wir über eigenes Material den Archers-Paradox-Effekt beim japanischen Langbogen zu demonstrieren.
Siehe folgende Seite:
............................................................ Der Weg des Pfeils aus dem Bogen
Kleine Illustration zum Thema
paradoxe Phänomene beim Yumi
(yumi = traditioneller japanischer Langbogen) in Form von video (slow motion) und Einzelbildern unter:
.Aus urheberrechtlichen Gründen kann die Szene nicht mehr gezeigt werden. Zu finden ist sie in einem SWR-Film von Willy Meyer aus der Reihe Spiele der Welt zum Thema Kyudo in Japan. Dieser Film ist sehr enmpfehlenswert und eventuell beim SWR erhältlich.
Wieder aus dem westlichen Sportbogenbereich
Tenebrious1 (Deckname) in einer Diskussion über Raketentechnik unter der Überschrift: The science of arrow flight; it is rocket science
Über das Tunen und Befiedern von Pfeilen
"When the arrow leaves the bow, the force is applied to the rear of the arrow. The heavy arrowhead has much more inertia than the rest of the shaft, and thus the shaft bows as it begins to move. As the arrow begins to move, it also has to bend around the side of the arrow (unlike compound hunting and olympic class bows, which are all "center-shot", there is an arrow rest cut into the center of the bow so the arrow is pushed straight through the center in line with the string). If the arrow spine (stiffness) is too high, the arrow pushes off the bow and heads in one direction. If it's too weak, it flexes too much and willows around the bow and heads in the other direction. This is known as "archer's paradox".
Because archer's paradox, the arrow "weaves" it's way to the target as the fletches attempt to straighten the flight of the path. With small fletches, it takes longer to stabilize, but the arrow flies further with less wind resistance. With larger fletches, the flight stabilizes quickly but there is much more drag and more noise (bad for a hunter). The angle you attch the fletches also makes a difference- the more angled, the faster the rotation and more stable the flight, but more drag and less distance.
They have different types of arrows- for pure distance, where accuracy doesn't matter, you see arrows with very small fletches- there's plenty of time for the arrow to correct its flight. For hunting, where shots are taken at less than 20 yards, the fletches are larger and the angle greater. If you try using a 100 yard target arrow with at 10 yards, you'll be off target because the arrow hasn't had time to correct it's flight.
No two arrows are the same. Each is going to have slightly different characteristics, and the challenge of a fletcher is to get the arrow to the same point on the target regardless of the different flight characteristics of the arrow. For "perfect" arrows, there is a good deal of fine tuning because you can't say "this arrow shoots a little high and left, this one shoots a little low". It's an work of art.
For center-shot bows, there is no archer's paradox so you can use much stiffer shafts. There is no weaving from archer's paradox, and the stiff shafts help counter the bending from inertia so you can use much smaller fletches. Still, arrows bought at Wal-Mart aren't going to be good enough for high level competition, you really need the experience of a master fletcher to tune the arrows. "
http://interviews.slashdot.org/interviews/02/07/12/1410203.shtml?tid=160 > ganz weit unten auf der Seite
In period bows (without a shelf or centre shot) the arrow which is properly shot will fly in the line of aim although the string propelling the arrow moves directly to the centre of the bow. The arrow in fact bends around the bow after release but after passing the bow returns to its proper line of flight. See Spine