This is the airfoil I love to hate when we are talking thermal seeking. It is thick, it has a completely flat bottom, it’s easy to build and it sucks. If you use a thick leading edge balsa stock, you can pick up your “QFI-subscription-renewal” Perma grit tool and rise the entry point a bit, and that’s what among others Dave Thornburg call “adding Phillips entry” in his building article on the Bird of Time – well maybe he used plain sandpaper but I believe you know what I mean? You can also build it thinner to lower the drag at high speed - the mean camber will decrease this way. These little tricks should make the plane faster because you lower the camber a bit and reduce the front drag, but it doesn’t at all come close to building the wing with a proper airfoil. The Phillips entry was actually patented in 1891 by Horatiao Phillips and has been used with success on a lot of slow airfoils, because it speeds them up. The Aquila airfoil has been used on multiple designs over the years. Well maybe not exactly this airfoil, but airfoils with totally flat bottom and a curved top. From motorized trainers to beginner gliders over to “new” designs with just another fancy tail to tell it apart from the other gasbags. Another airfoil that looks the same is Spica that was designed by Chuck Anderson in 1978 – he called it a flat bottom trainer airfoil, which sum up my thoughts about this type of airfoil. You can even make your own Aquila-airfoil with a ruler and the spare tire from you wives car. This airfoil is often seen on beginner’s gliders (and motor trainers) and these gliders are called floaters by those who love them and gasbags by someone like me (this is a rewritten expression from The Old Buzzard – credit to those who deserves it). You can though easily make a glider that looks like a gasbag if looks are important to you, but do put in a real airfoil instead, please. Looks can be important - read Dave Thornburgs autobiography: "I have a simple test for a new model: Hold it up to the sun and if you can't see through it, to hell with it". A plane with a real airfoil will still show you the signs of rising air, while giving you the penetrating ability, which the Aquila airfoil doesn’t have. And this is actually the reason that the Aquila airfoil is a good beginners airfoil. When you are learning to fly you can have a hard time controlling just the rudder. But with the Aquila airfoil in the wing, you beginner model will never accelerate wildly when put in an unintended dive. The speed will never rise a lot and that’s good when you are a beginner because you don’t have to concentrate so hard about the horizontal movements (and the soon-to-appear structural problems). But why do you continue to use a beginner’s airfoil when you are actually designing a competition machine? Why spend hours on a new fuselage when you scarify the overall efficiency with a few percentages decrease in building time, with an airfoil that should have had a label on it saying: “Only one glider with this airfoil per pilot per life”?

This is a picture of my last glider with this airfoil: