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Old 01-08-2009 | 02:45 PM
  #27  
Joe Counter
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From: Lawrenceville, GA
Default RE: clark Y, zero lift angle?

Actually, after you made the incidence changes, your wings had the same "lift", but the trim angle of the horizontal stabilizer/elevator was different. People tend to confuse the fact that a model that needs down elevator for level flight does not mean it has "too much lift". No such thing.

[quote]

Bax,
I think that in trying to keep readers from being confused you took exception with my use of the term "too much lift" a little too hastily. Of course lift always equals aircraft weight in stabilized flight[sm=49_49.gif]. However, with excessive positive wing incidence and elevator trim set to anything near neutral an unstable condition exists: more lift than gravity, the very state that allows an aircraft to pitch upwards and climb. I do not consider it technically incorrect to describe this as a state of "too much lift". It creates an uncommanded and unintended pitch up from an undesired excess of...lift!

You are absolutely correct to point out that it is a matter of trim, and that (stabilized) flight could be maintained in such a situation by trimming the elevators such that wing incidence relative to the airflow (not the fuse datum) is reduced, returning a "stabilized" state of level flight with no pitch-up. However, the tail would be following the front of the fuse at a considerably higher altitude. Works, but looks pretty goofy and creates lots of drag.

Hope this is not too esoteric. I think we both are on the same page but saying it in a different way.