limit of trim = limit of travel?

On Tue, 6 May 2008 07:16:07 -0700 (PDT), WingFlaps
wrote:

On May 7, 12:56*am, Stealth Pilot
wrote:
On Mon, 5 May 2008 23:54:37 -0700 (PDT), WingFlaps

wrote:
On May 6, 3:36*pm, Bertie the Bunyip wrote:
WingFlaps wrote :

OK, then if the AOA of the stabilator is constant, and the elevator
angle is constant, why does the lift reduce when the trim tab is
deflected in the opposite direction?

because the elevator angle isnt bloody constant. what is constant is
the stick force which you maintain at the same pressure by
unconsciously moving the stick as you change the trim tab position.

It's as I said, the effect is as
if the _effective_ area is reduced.

no it bloody isnt. the area remains the same the lift force is what
varies and guess what, that's why the tailfeathers have the hinges in
the middle.

You could say that CL is altered
but then it gets more messy as you have to consider different CL's and
areas for each section of the stabilator. It's much simpler to just
subtract the area taken by the trim from the calculation and that will
give a very good first order approximation for longitudinal stability
calculations.

you have basically started out with a faulty understanding and for the
last 100 posts have misinterpreted everything written because you keep
relating the information to the original faulty premise.


Nope. I understand it perfectly. As defined in any good book on
aeronautical design, stabilator effectiveness is _defined_ by the
horizontal tail volume coefficient which is the product of tail moment
and area divided by the wing area and it's mean chord.

From the style of you reply I can see you will have a hard time
understanding this this it really is correct -look it up.

Cheers

no I'm afraid that it is you who do not understand it.
you take a rule of thumb approximation and then try to apply it as a
hard and fast aerodynamic concept.

brother have you got it wrong.
Stealth Pilot