Parafoil profile.

Hello Kiters.

Is anyone familiar with experimenting with the rib profile of the Parafoil? My point is, if the profile was to adopt the undercambered shape of a glider high lift wing section, would this make the foil fly at a steeper angle?

Not necessarily Simon. The angle at which a foil will fly depends on the lift to drag ratio, as I'm sure you know. This depends more on the profile shape in general than on whether it's undercambered or not. There are foils of the type you suggest which have good parameters and ones which are not so good. The conventional foils of today of the fat kind also vary widely in their performance. One of the problems of high lift foils is getting them not to exhibit separation of air flow at low angles. This can be disastrous. You may have a foil with tremendous L/D ratio but which will lose all lift at low angles of attack and consequently crash. Momentum can be sufficient to take them past their maximum L/D point far enough to reach close to zero aoa. Lift zilch, bye bye kite. A frisbee for example has a tremendous lift to drag ratio but only at close to zero degrees. The maximum drops very fast on either side to nothing ten degrees off. I have succeeded in producing one design along the lines of the undercambered high lift foils but this is only on paper and it's as yet untried and tested. I suspect that one could use such a design for a four line foil where you could prevent the angle getting too low by use of the 'brake' lines and intend to do this sometime in the future. You could try Martin Hepperle's online airfoil calculation site. You can plug in any foil design you like, calculate on it, change it, play with the aoa and so on. There are programs available for this too.

Here's the index page of MH's site. http://beadec1.ea.bs.dlr.de/Airfoils/index.htm From there you can go to 'Analyse an Airfoil'.

Regards Tel.

Hello Tel,

Thank you very much for your valued posting. The four line arrangement would cure the overflying problem. However, when designing a single line kite that would have to be thoroughly explored first. I will take your advice and visit the foil design site. I hope this will answer some of my questions.

Thank you once again, your help is very much appreciated.

Simon

WWW.221100.CO.UK

I'm sure you know. This depends more There are foils of the type you conventional foils of today of the fat separation of air flow at low angles. which will lose all lift at low take them past their maximum L/D point close to zero degrees. The maximum drops undercambered high lift foils but this is only such a design for a four line foil lines and intend to do this sometime plug in any foil design you like, programs available for this too.

under-camber seems to reduce the pull of the kite, although it definately makes some kite, especially skydiving parachute rather unstable.

Brian BIG AIR SPORTZ