SUNDAY, DECEMBER 17, 2017

Differences Between Reflex & Classic Paragliders

In reflex-airfoil paragliders releasing trimmers and activating speed system results in shifting pilot’s weight towards leading edge, so that A and B risers carry almost all of the weight, while C and D risers get relieved.

The opposite happens in classic paragliders – with increasing airspeed load on the A and B risers decreases, while more weight is carried by C and D risers. In some extreme cases full acceleration on a classic paraglider can lead to total unloading of the A risers, with subsequent frontal collapse (frontstall).

The important quesiton is, how to discern a reflex paraglider from a classic one? Currently there is quite a number of paraglider available claiming to be partially or semi-reflex, and no one knows for sure what does it exactly mean.

Sometimes such names are a mere marketing tricks, aimed to use established position of fully reflexed designs. However, there is a way to prove if there is a reflex attitude present or not.

In 2006 an idea was born within Dudek Paragliders concerning effective measurement of variable loads occuring at individual risers.The idea was brought to life by a Swiss test center Air Turquoise (http://www.para-test.com), while detailed technical solutions were prepared by École Polytechnique Fédérale de Lausanne.

The project included sample flights on a reflex and classic profile paraglider. The reflex paragliders were represented by Dudek Action (its characteristics well proven by its long presence on the market) and as a classic sample we used a Sky Paragliders Atis (thanks to the company for the measurement reports). The results are accessible below.

It is worth noting that in case of classic profile no measurement was done for the max speed configuration (released trimmers + full speed bar), where even more unloading of A and B rows would be observed.

Here is the reflex report:

Reflex 1

Here is the Classic paraglider report:

Classic 1

Diagram of forces occuring at classic profile Sky Paragliders 2

The diagrams confirm that in accordance with theory there is a distinct increase in load of A and B risers while accelerating a reflex profile paraglider.

Similar tests have been performed for the Nucleon and Synthesis paragliders which we will talk about in the next post.