Helium bubbles used to show bird aerodynamics

Martin Gregorie wrote on 3/19/2020 8:11 AM:
On Thu, 19 Mar 2020 06:23:40 -0700, jjdk737 wrote:

Are these lifting tails creating upward lift during low speed flight,
close to stall speed?

Or... are they only providing upward forces at high speed during the
climb, transitioning to a downward force during slow speed flight after
powerloss?


So yes, all three types glided with the tailplane providing lift. All
free flight competition models are better thought of as tandem wing
aircraft with both wings providing lift. That was more obvious in the old
days, when very large tailplanes, up to 35-50% of the wing area, with
short moment arms, 3-3.5 times wing chord, were used. Now tailplanes are
around 20% of the wing area and the moment arms are about 5 times the
wing chord. All free flight models are trimmed to fly at minimum sink
trim and to, hopefully, stay in the thermal you launch them into.

I flew hand-launch, towed, and power FF in the early '60s. After a detour to race
sports cars, I ended up sitting in gliders instead building them.

How do you determine the tail is lifting in gliding flight? And wouldn't be more
efficient to have the larger wing provide all the lift, and just use the tailplane
to provide stability?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1