Now i can understand, but is that has some major effect on the plane's behaviour when landing? Plus that it will be hard for doing aerobatics since excessive force must be applied to the horns for the same move that a longer adjust on a horn could do it.

Yes it has a major affect when landing. Though you have the "force" backwards see below...



On my Giant UCD, when I followed the directions, the first "step" of the servo caused the elevator to deflect about 1/4" or more.

That is a LOT of elevator movement, and would cause the nose to pitch up, when I want far less movement up.

Once I set things up for maximum mechanical advantage, the first "step" causes the elevator to barely move 1/16th", which gives me better control.

To compensate for the lower resulting movement of the elevator to it's very extremes, I set my TX to permit 150% movement of the servo.

In other words the servo now travels further to obtain the same movement from the tail as before....

So I have finer control of the surfaces.


Note: A SHORTER horn produces LESS stress and torque on the SERVO too, so it is better for aerobatics and 3D.


The servos fight blow back better as well.

The horn acts as a "lever" so the longer the lever is, the more force the control surface can put on the SERVO.

When you go for maximum mechanical advantage, you shorten the control horns, and lengthen the control linkages on the surfaces ( within reason)

That way there is a lot of torque on the control surface, not on the servo.



So what's the drawback?

The surfaces take a longer to move from one extreme to another since the servo must turn more... however with most servos you would never notice this anyway... and if you did, you could merely use a higher speed servo. Unless you were engaged in competitive or pattern flying, this should not be an issue.

That's true of a flat bottomed wing or one with a positive angle of attack/incedence built in (and flaps act to increas a wings' angle of attack). A symmetrical wing just flies slower with less throttle . . . up to the point of stalling and usually rolling to one side. Unfortunately, models don't have a stall alarm, red airspeed zone on the instrument face or a published landing speed and a way to judge same from your position on the ground.

Even with a symmetrical I line up and fly her in to six feet elevation or so and then cut the throttle with a touch of flair. Biplanes are especially prone to disaster if you try and land them by dropping throttle to bring them in slow from any elevation.

When we are talking about the horn, i mean that plastic thing that in on the wings which are connected to the servo arm via a linkage rod, right? Just to be sure Thanks for the help buddy.

dont force the plane down let it come down by itself with no throttle but keep the engine running incase you have to go around again

That's the problem. In fact there is some throttle which i can't slow it down because the engine is going to stop. I insist that it might be the prop problem. Don't worry. I will soon tell you what's wrong (in July perhamps I have a lot of business that and the next month)

Yes, you want the horn on the servos on the UCD you have to have the linkage closer "in" to the horn affixing screw, than what the manuals say.

Move the linkages IN two holes on the servo horns.

Leave the control surface horn as recommended, and adjust the throws by increasing servo travel.

Ok, i understand, i'll try that