What is the airfoil of the 2 meter Chrysallis? Is it undercambered?

From : Don Stackhouse

Uh-oh. That's a touchy question with me.

You see, the airfoil(s) used in a wing only have meaning when considered within the context of the rest of the wing.

Furthermore, the job that a tip section has to do is quite different than that of a root section, or something around mid-span. Therefore, the airfoil that best suits the needs of one part of the wing is usually not the best choice for other parts of the wing.

When I design a wing, I'll do a rough study of what airfoils can realistically achieve in that general range of Reynolds numbers, just to get a gut feel for what's reasonable, then I proceed with the wing planform and twist analysis at a variety of flight conditions (thermalling, best L/D, penetrating, launching, etc.), including the effects on lift distribution and lift coefficients along the wing during turns. Once all of this is optimized, I then develop different airfoils for different portions of the wing based on each portion's unique requirements, but also considering the interactions between the various sections along the span.

Most of the different airfoils along the spans of the Chrysalis series come from the DS 6082 family (by staying within the same family of sections I can be reasonably sure they will interact well with each other), with non-linear blending in between. The DS 6082 series is a family of proprietary airfoils I developed. Don't try to read any geometrical information from that airfoil family name, the designation has nothing to do with the shape or the aerodynamic properties. And, sorry, but no, we don't give out the coordinates. To do so would be literally taking food from our own children's mouths.

Between the various baseline sections along the span, I use non-linear blending in between for a smooth transition from one baseline section to the next.

Furthermore, on the Chrysalis we decided that since beginners frequently have trouble with applying leading edge sheeting without getting warps and bubbles in it, we would not use a D-tube structure, and the only sheeted areas would be the rib bays immediately adjacent to dihedral joints. In order to provide an accurate wing shape in spite of covering sag, we bulged the segments of the ribs outward by various specific amounts in several different segments of each rib, so the covering in the relatively flat areas between the ribs would be lifted up to very close to the correct airfoil shape. The vast majority of the wing is therefore very close to the intended airfoil shapes, despite the covering sag.

So, not the answer I'm sure you were hoping for, but I'll wager you learned more from it. I will say that no, the sections on the Chrysalis are not undercambered. However, that doesn't mean it can't "float" well in light air. It just means that in addition to being able to float with the best of them in light air, it can also go fast if it needs to.

Don Stackhouse
DJ Aerotech