What's the difference between the Monarch D airfoil and the Chrysalis'?

From : Don Stackhouse

Adam, I can't answer this one directly because there is no SINGLE airfoil for the wing of either model, nor should there be. The section requirements vary along the span, and with changes in flight condition. For certain flight conditions the freestream airflow is not even uniform over the entire model. For optimum performance, different airfoils are required for different parts of the wing, even for so-called "uniform" or "constant lift coefficient" planforms such as the ellipse. For example, in level flight the Reynolds number near the tip of the Chrysalis wing is less than half the Reynolds number at the root. In a turn, the Reynolds number at one tip can be considerably different from the other tip's, not to mention the lift coefficients and angles of attack! We therefore vary the airfoils, chord and twist along the wing to match the local requirements.

The only reason we even publicly give names to any of the airfoils we use is because most of the sailplane flying public out there seems to have some sort of compulsive "need" to know what "airfoil" (note the use of the singular) is on the wing of their model. As ludicrous as it may sound, there's a common misconception out there that you can actually predict the performance and behavior of a model just by knowing the name of the cross section of the wing! I know, I'm exaggerating to make a point, but this has to be one of my personal #1 pet peeves. Try as I might, I haven't had a whole lot of success in stamping out this myth, but I keep trying anyway.

When you see an airfoil name in the specs for one of our models, what you're actually seeing is the name of a family of airfoils. For example, the specs may list the airfoil as "Clampett". What this might mean is that we have "Uncle Jed" at the root, "Cousin Jethro" and "Granny" at different places along the mid-span where they are most suited, and sweet, friendly Elly-May at the tip. While these are all related, I would hope that no one would mistake Uncle Jed for Elly-May! ( If you do, I strongly urge you to seek counseling IMMEDIATELY! )

The Chrysalis actually has one of the most complex wings in our collection (aerodynamically speaking), with several different families of airfoils along the span, and non-linear blending in between them. That's even before we start talking about the adjustments to the individual rib shapes for covering sag!

One of the families in one portion of the Chrysalis wing we call the DS6082. This is a proprietary family of sections we designed for good stall characteristics and a wide speed range at low Reynolds numbers, without using flaps. This has turned out to be a very versatile family, with cousins we've used in a number of applications, including various regions of the Monarch 'D's wing, all or part of our slope combat and 1/2A sport foamie prototypes, and even in one particular portion of our new "Reaper" hand-launch flying wing. This does not mean that any of these models have any of the same airfoils as any of the others, it just means that their airfoils' general proportions and aerodynamic behavior are loosely related.

I would advise that you not try to read anything more into it than that. Just be satisfied in the knowledge that we put a great deal of thought into each wing design, and we carefully fit each individual airfoil to the spectrum of conditions where it operates.

It's important to have good airfoils, but it's even more important to have airfoils that are naturally good at the job you've asked them to do.

Don Stackhouse @ DJ Aerotech