At 08:57 10 June 2008, Matt Herron Jr. wrote:
Umm...

What happened to the wind tunnel testing that was underway over four
years ago? This is where experimentation that requires such tight
control of parameters and is so sensitive to humidity, turbulence,
etc. should be conducted. If this research looked so promising and
was funded by NASA, they have rather lovely tunnels you could put the
whole Cirrus into if you wished. I would think that performance
questions could be answered in a matter of a month or two. What went
wrong there?

I am the first to consider that new breakthroughs are almost always
met with significant criticism, so I like to fall back on the facts
whenever possible. As a sanity check, lets look at the latest
comparison flight between the Cirrus @ the claimed 33.5:1 glide ratio
and the Dana 1 at 45:1 On one leg that was graphed, the flight lasted
8 minutes with the two aircraft flying side by side at about 51
knots. It looks like the Cirrus kept up quite nicely with the Dana!

But lets take a closer look. At 51 knots, that's about 5164 ft/minute
forward, and for the Dana, about 114 ft/minute sink in still air.
Over the course of the 8 minutes, the Dana should sink 918 ft, and the
Cirrus, 1233 ft, so the expected difference in altitude is about 315
ft after 8 minutes of flying. From the trace, both aircraft only sink
about 100 feet over this time, and are flying through sink and lift
the whole time of strengths up to 4 knots. So one could say that the
variation in altitude contributed by the still air sink rate of the
gliders is only about 25% of the total. The other 75% is due to
flying through rising and sinking air. Given that the gliders were
flying side by side through slightly different air, is it possible
that any performance variations (good or bad) were completely masked
by minor variances in this more dominant variable of moving air
masses? It would take an average difference of only 0.37 knots of
lift/sink over the flight to account for this.

I would like to think it's all true, but so far have little basis
other than hope. Get back in the wind tunnel, or show me a 40 minute
final glide at 7:am in still air.

Matt

Matt,

Notice how the two aircraft match each other bounce for bounce in both
flight legs, especially on the-upwind, cloud-street run. This shows that
the aircraft were close enough to be seeing essentially the same air. In
fact, we did another, shorter out and return but I did not post that one,
because it was clear that the Diana was not matching my "bumps." In
fact it lost altitude to my glider, but it was clear that the Diana was
too far away.

Both flight logs are on the web for you to download. Evidently you looked
at them. But I would just like to make the point to everyone that I am not
making claims here, I am throwing data at you to deal with. It is what it
is!

Thank you, Mark, for making an honest effort to deal with the facts.

JEH