As control frame, rigging frame, undercarriage, combination of these: The A-frame, the triangle control frame .. has had a long history in aviation beginning with at least Leonardo da Vinci. Tracing that history enlightens to many nuances. The development of the A-frame for hang gliding is an ongoing live matter. Wing runners and Safe-Splat designers are involving with the A-frame in new ways. We attach and embed things in the A-frame. We stay the A-frame by struts, cables, or a combination of such, or just leave the A-frame without obvious staying...cantilevered. Dimensions vary, materials vary, cost varies, etc. Fuel is sometimes stored in A-frame compartments. Consideration of have the A-frame as an ultra-capacitor has been mentioned in the literature. In 1800s, it was clear that hung trapeze was understood by glider patentees (Beeson, for one).
Starting this thread which may become robust:
Did Rogallo invent the triangle control frame for hang gliders?
No, the triangle control frame or A-frame for hang gliders was invented mechanically for foot launch hang gliders in at least the early year of 1908 in Breslau in a hang glider in an organized gliding-club setting--cable-stayed and with pilot hung from keel behind the control frame, just as many of us know today; further use was in many places including the Spratt before the 1950s; and a firm use was in a kite-glider for homebuilders by Igor Bensen...well published in the first half of 1950s; Mike Burns SkiPlane used the A-frame in 1962 for the NASA-inspired flex-wing kite-glider (as he referred to it); then Bensen-influenced-kite-tinkerer-John Dickenson and the following two Bills used the ancient A-frame on Rogallo-NASA-influenced flex-wing kites. The first decade of 1900s had a first issue of FLIGHT; in that issue was a featuring of the triangle A-frame for aviation. The Pilcher hang glider had a firm A-frame. JD and the two Bills chose the ancient A-frame for their waterski kite-gliders. ~JpF
There was no triangle bar Rogallo at Otto Meet of May 23, 1971. The first triangle bar Rogallo at a So. California meet was Kilbourne's at the Montgomery meet in August of 1971 (ref: Matt Colver).
Kilbourne's Kilbo-Kite plans referenced for the wing: NASA; Self-Soar Association put those plans into 23 countries to help explode and expand the HG renaissance; such did spawn DIY makers and manufacturing centers. We added free the Seagull III plans to the world within an issue of Low & Slow. These two plans also featured the ancient A-frame cable-stayed. Seagull Aircraft sold a single formed tube for the A-frame. Belly bars, speed bars, etc. followed.
In the play, recall all one might know about triangles. Consider the null triangle, the degenerate triangle, the triangle using an infinitely remote zenithal vertex point netting parallel uprights, the tensional A-frame of Tony Prentice in 1960 kite-hang-glider of rigid frame, the Worth triangles beneath flex-wings, the inverted triangle, the X options, the double options to cinch payloads, the wheeled base, the ski-based triangle, ...
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