On May 8, 6:22 am, nospam wrote:

For those who were wondering about tab effect, or indeed elevator effect
on total tail lift the following may help;
Each item can be considered separately.
There will be a basic tail camber lift component which in many cases is
zero.
Then find the tailplane AOA and from the lift curve slope find tail Cl -
put that into the normal lift equation.
At that particular tailplane AOA, select the elevator AOA and again find
the Cl from the lift curve.
Then do the same for the tab.
Add the 3 solutions to get total tail lift.
Do this for the complete range of angle of attack for each component and
you will know the total range (and direction) of tail lift.
Cheers

Sorry, but each item can't be considered separately, any more
than an aileron can be designed or its effect determined without the
wing ahead of it. Removing the elevator from the stab, physically,
would make the stab almost useless, especially if it has an airfoil
shape and/or has aerodynamic balance. Working out numbers for an
elevator without considering the stab's effect on the camber and AOA
for the whole assembly is also useless. The air doesn't decide what
bits it will react to or ignore; it only sees an airfoil of some sort,
having at any given instant a particular camber and AOA, and the tab
is part of that assembly, whether deflected or not. The tab doesn't
contribute much, if any, to tail downforce, but does affect elevator
float position, and that elevator position sure does affect downforce.
Airplanes are not the sum of their parts. I wish it was that
simple.

Dan