Chris,
Great research.
In my small tailed 320, increased flap reflex experimentation did
not result in increased top end speed. The nose up pitch was
increased, requiring increased nose down trim - probably resulting in
greater empennage drag negating any reduction in drag from the
greater reflex. Of course, we would have to discuss the angle of
incidence of the small tail and its relationship to the elevator correcting
for nose down pitching ( my incidence was at -.9 degrees).
By moving weights forward and aft in the same flight, forward CG
was better for maximizing speed - unlike some aircraft that see max speed
when the CG is at the neutral point, probably a consequence of more standard
wing/tail design that saw drag from wing/horizontal +/- lift factors more
balanced and minimized.
For me, the biggest gain in speed came from adding $140 worth of gap
seals to both sides of all control surface and the flaps
(remember Greenameyer made his flaps part of the wing in his very fast
Reno Legacy - he didn't need no stink'n flaps). I believe that I lost no
speed when I removed the upper seals from the flaps last year. The seals
were curved Mylar seals often obtainable for gliders. The gain was
from 6 to 8 KIAS, depending. Controls were more responsive and the
wee rudder was effective about 5 KIAS sooner.
I didn't follow up on a cockpit controlled diffuser for managing cooing
drag as I saw about 7" H2O upper to lower cowl at about 135 KIAS (climb
speed), but 13" at 200 KIAS and such pressure was not necessary as the engine
ran cool there.
I found the small tail had enough control - I only wanted my little
engine to pull everything along as quickly as possible.
Scott Krueger
In a message dated 9/13/2013 7:32:54 A.M. Central Daylight Time,
chris_zavatson@yahoo.com writes:
N91CZ has been a flying laboratory for most of this year. Below
are links to three reports that may be of interest to the Lancair community,
in particular 320/360 flyers.
The first takes a look at the effect flap position has on
total aircraft drag using the NLF(1)-0215. The numbers are
quite impressive in terms of drag coefficients. In the end, it
looks like we could benefit from a little more reflex beyond -7
degrees.
The second report looks at the neutral point differences and static
margins of the small and large tail 320/360 models. A large portion of
the document is a tutorial of sorts on longitudinal stability. It
deals only with static stability, but is a good lead-in to the third
report.
The third report looks at the stability of the 360 MKII in much greater
detail. It include dynamic stability in both cruise and landing
configurations, as well as, stick force gradients and elevator effectiveness
all the way down to stall speed.
Chris Zavatson
N91CZ
360std
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