Aeronautical Engineering Help needed

David Lednicer wrote:

To get long range, you want to fly at a speed slower than maximum, near
or at the best L/D point.

snip

Hold it right there, pilgrim. Your premise, which forms the basis for
your entire post, fails the practicality test. When people talk about
the cruise range for aircraft such as a Long EZ or an RV-4, they are
not talking about lumbering along "near or at L/D max" (about 70 kt in
both the Long EZ and the RV-4). Rather, they are talking about the
range at cruise speeds (65% and 75% power at altitude). In a like
manor, the cruise range for piston powered aircraft is typically
specified at 65% and 75% power at altitude, not throttled way back to
max L/D speeds. In truth, the actual cruise range for the Long EZ and
RV-4 are practically identical given the same engine and same fuel
load. That's the difference between reality and an argument based
upon an inappropriate premise and CFD "analysis". The previous
poster's comment that "if you want good range don't choose a canard"
remains laughably absurd in both theory and practice, and his
subsequent post reveals his considerable grudge ax -- no surprise
there.

As for the Voyager, it didn't lumber along "near or at L/D max"
either. The average speed was 122 mph. I find your claim that a
non-canard Voyager would have had better range quite suspect. One
simply can not make such a determination by punching in a few what-if
scenarios into a CFD program, especially for such a highly specialized
aircraft. For example, the Voyager's canard forms a structural box
with the booms and the main wing. Remove the canard and you would
have to add significant structural weight elsewhere to obtain the same
airframe strength.

If a non-canard "Voyager" would indeed have greater range then I will
believe it when I hear it from Burt Rutan himself. I expect that any
realized range difference, one way or the other, would be quite small.
Yes, the new Rutan designed GlobalFlyer will not be a canard
configuration. That design choice, however, could be based solely on
the wishes Fossett/Branson rather than on technical considerations.
The authoritative answer to these questions will come in time but
certainly not here in Usenet (unless Burt himself decides to chime in
as in the old days).

David O -- http://www.AirplaneZone.com