|Discussion About Flaps and Variable Camber for Hang Gliders|
The Sensor's flaps reduce the stall speed 4 mph as measured on Mark West's test vehicle from 23 to 19 MPH correct airspeed.
The use of flaps have been in aviation for a long time, they expand the flight envelope of the aircraft and make it higher performance by adding control over the shape of the airfoil. When you're able to very the camber of a wing you can have in effect a smaller wing because you can change its airfoil for different flight requirements. Instead of having one wing size and shape that is generally larger to cover the minimum slow flight requirement, you can have a smaller wing that fulfills the high speed requirement and make up the lift for slow speeds by adding camber. Different flap designs produce different amounts of lift. Simple flaps may add only 10% lift, where more advanced configurations may add upwards of 50% or more to the lift of the wing.
In hang gliding less or simpler is generally better. To create a significant change or effect in performance with little increased weight and complexity is a very good thing. To add lift only when you want it and get away with a smaller wing is the way to improve the overall performance. The in-flight VG was the first step in articulating a hang gliders wing shape. With that came an unwanted side effect. The VG produced in VG full loose a twisted and more flexible wing for takeoff, landing and flying in gaggles or next to the hill. The side effect was a higher stall speed and a worse sink rate than in tighter VG settings. Increased twist decreases lift and raises the stall speed, reduced twist increases lift and lowers the stall speed. This is why hang glider pilots throughout the 80s and even today fly their VG gliders generally as tight as they can handle it. Hang glider pilots even tend to land with a little VG on just to reduce their stall speed. Also, hang gliders can have a crisper stall with the VG a little tighter than full loose and that's another reason why pilots have landed with the VG a little tighter than full loose. The Sensor's flaps however reduce the stall speed a measured 4 mph, eliminating the need to launch, thermal or land with any VG on at all. It is important to understand that flying with flaps means you have to be speed conscious. That is to say with flaps down or in VG loose if you want to go up you have to fly slow. Where as, with flaps down in VG loose if you want to come down you should fly fast.
The Sensor's flaps are unique in the industry as there is no other glider yet available on the market except for rigid wings. Flaps on a hang glider are both a performance and a safety device; the performance is obvious, the safety aspect is as important as some of the safety refinements in the beginning of hang gliding. Flaps will make a marginal launch in no wind safer with full control and on landing they reduce your mass energy closing velocity and touchdown speed significantly. The real joy is thermaling with flaps because they improve your minimum sink rate or climb rate as much as 10 to 20 feet per minute. Isn't this why we love to hang glide?