Tail Moment / Watts and thrust

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Mike R. - 13 Jul 2004 03:38 GMT

My first question: I here some "planes have a longer tail moment".
What does this mean???
Second question: I did some calaculations using Diversity Model
Aircraft P-Calc on there web site. I will give the highest and lowest
ratings using the gearbox ( 3.5) and varaius prop sizes ( 9 by 6 to 4
pitch)......Watts in 141 to 110, Watts out 120 to 92. Prop static
thrust 33 to 24 oz. In flight thrust 21 to 19 oz. Prop pitchspeed 50
to 35 mph. The motor I have is a brushless Eflite Park 400, which they
just added to there calaculator. Do these numbers sound about right
for a 15 to 18 oz model( all gear installed ) to fly .???? Am I in
"the ballpark"???

Thanks for any info.
Mike

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Roger - 13 Jul 2004 04:43 GMT

Can't help you weith the electrical stuff--see the threads on LiPo's...
Tail Moment is a function of the length from the Center of Lift to the
tailplane, or horizontal Stabilizer. The longer that moment arm is, the
less force that the stab/elevator has to generate to raise/lower the
nose of the aircraft and the farther the tail has to move to make a
given change in attitude.
This also makes it easier to build a tail-heavy model....
Roger

> My first question: I here some "planes have a longer tail moment".
> What does this mean???
[quoted text clipped - 10 lines]
> Thanks for any info.
> Mike

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The Natural Philosopher - 13 Jul 2004 09:53 GMT

> Second question: I did some calaculations using Diversity Model
> Aircraft P-Calc on there web site. I will give the highest and lowest
[quoted text clipped - 5 lines]
> for a 15 to 18 oz model( all gear installed ) to fly .???? Am I in
> "the ballpark"???

I should think you will be a speck somewhat outside the ballpark in
short order with those sorts of numbers.

WELL enough to fly.

> Thanks for any info.
> Mike

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Model Forum / Radio Controlled / Air Models / July 2004

Tail Moment / Watts and thrust