Hi,

I want to check servos linkages for my Tamjets A-4 skyhawk!
Tamjets already suggest which servos to use in his model, but I am curious to see the result from using this program on the A-4.

For now, just to have a go with the inputs on the program I tried the calculation for the aileron.

Aileron size:
average chord = 7.7 cm (considering the chord from the T.E. till the hypothetical hinge line)
length = 26.5 cm

The aileron has a kind of aerodynamic balancing but I didn't consider it in the computation just to make thinks worst for the servo!

As you can see from the pictures the control horn has its outside hole at 1.5 cm from the surface, that will allow for a control horn height of 2.2 cm (Yc) above the hinge line.
The distance between the hinge line and the servo axis is 7.0 cm (Xs = servo distance forward of hinge line) and looks like the servo axis will be placed quite precisely on the chord line.

Tamjets suggest a 7/16" travel up/dn for the aileron, that equals to 1.11 cm up/dn.
I estimate the maximum speed to be around 180 mph, this will be a EDF powered model not a turbine so I guess this is already anough!
I put the servo rotation @ 45 degrees each side otherwise if I use 50 or 60 degrees the servo arm become very short!


Using this computation here's what the program suggest me.

@ 1.1 cm of travel up/dn as requested by the manufacturer give me a surface movement of only 8 degrees each direction.
The servo arm should be 0.4 cm ??? For sure is correct but is silly
@ 100% travel and speed the servo torque required is 9 oz-in ??? How can it be so low?

In the manual they state to use the further hole in the control horn and the closest on the servo arm, but looks like that will bring too much excursions on the surface!!

Am I doing something wrong?
The only thing I change in comparison to the manufacturer is the style of actuation, they call for an exposed control rod while I am using a partially conceived one by placing the servo arm upside down. Please if somebody have suggestions or see something wrong, tell me!


Thank you
Gianluca