Standard Cirrus and Deturbulator Project

1. The Standard Cirrus was not chosen for Deturbulator experiments. It
was what we had to work with. *That's all. *Turns out, the stability
of top surface reattachment point worked to our benefit.*

2. Since going my own way with this work, I have dismantled the parts
of the original configuration that Dick Johnson tested in 2006,
measuring performance at each step. Now, I know the contributions of
the individual parts.*

Turns out that the rear-facing steps near the leading edge, achieved
by wrapping the LE with 2" wide tape (.0027" thick) was playing the
major roll in the changes we measured. *The deturbulator panels play a
relatively minor roll, important but not the whole show by a long
shot.*

The top surface step produces very large performance variations with
extreme sensitivity to airspeed. *These are repeatable but not
consistent. I believe this can be tamed by moving the top surface step
a little bit aft where the pressure gradient is less steep. *This
should reduce the performance extremes and make the polar more normal,
though still lumpy.*

The good news is that the lower surface step alone appears to be offer
a much superior alternative to traditional zig-zag turbulators.*

A measurement two weeks ago indicated 15% improvement and a normal
polar. *All airspeeds from stall to 85 kts show improvement. Above 85
kts, performance was normal. *More measurements are needed, but, given
the history of measurements that led to this point, I am confident
that further measurements will confirm and smooth the data.*

And here's the best part, it only takes a strip of 1/2" wide .003"
thick (this dimension is critical) tape located 45 degrees under the
leading edge. *In that position, the forward edge of the tape is
harmless. Get it too high and you will pay a high price.*

The installation takes less than an hour and you can rip it off in ten
minutes.*

Yeah, that's right. *A dead simple, essentially free, easy mod that
offers 15%. *

I expect similar results for all gliders with Wortmann airfoils. Don't
know how it will work on modern airfoils, but would not be surprised
to see it work at least as well.*

Disclaimer: *I am not recommending that You modify your glider, just
reporting results on my glider that is registered experimental for R&D
specifically for this kind of research.*

For more information and pictures of this mod, go to*http://
deturbulator.org/Progress-03192011-15Cheap.asp .

3. You can follow this work at*http://deturbulator.org . *Join the
Google Group for announcements.*

4. You can learn everything you ever wanted to know, but were afraid
to ask, about Standard Cirrus gliders at*http://standardcirrus.org .
Join the Yahoo group to interact with 450 Std. Cirrus owners and
pilots around the world.*

Happy soaring,
Jim Hendrix