i noticed this pic from another thread

http://image.rcuniverse.com/forum/up...78/Db85335.jpg

the flaps are all hanging down on the planes, how do they get that to happen?

Digital servos and heavy surfaces.

edit: Guess I should explain some more. You know how you can turn a motor even if it has no power to it? Well that's what a servo is, A small, powerful motor and a bunch of gears to give it more torque. When the motor is off, the surfaces have enough weight to move the control arm. For some reason (I don't know why cuz I can't afford digital servos) when digital servos are off, they have less resistance than normal ones.

Know one thing them some high $$$$ planes[8D]

also the ailerons have separate servos so there not connected like most trainers with single servo setups and can sag when the power is off . having a servo for each aileron gives more control authority . that plane in the foreground has a DA 150 which is a 2 cilinder gas engine which means there are probably 2 servos on each surface in the wing and 2 or 3 servos on each of the other surfaces with a pull-pull set up $$$$$$

This has no actual technical point, but I think it also looks cool. I had a SSE with just regular old JR 537 servos. I used to shut the radio down with the ailerons and the elevator down so it looked like the big boys. Looked great sitting on the flight line, and turned a few heads.

It doesn't have to do with digital servos only. It has to do with Coreless servos. You can get coreless analogs which will do the same thing I believe.

When the control surfaces are heavy enough, they will fall when you turn the power off to the servos. Nothing to worry about unless your servos are not heavy enough to properly handle the control surface when powered up. I have many planes with many types of servos that do this, not a problem, nothing to worry about.

how do you make both ailerons go down at once sparky577 ?

One servo on each aileron?

Just guessing.

I had one servo on each aileron, and I had them set up as flaperons. I just flipped the flap switch, and they both would drop.

It is as someone said, due to a coreless servo. The weight of the surface will move the servo arm.

If the surfaces are balanced, they won't fall.

Andy

Balanced surfaces are also a lot less likely to flutter at high speeds. This is why you see control surface counterweights on full scale airplanes.

Yes and on occassion it is effectively done on RC aircraft for the same reasons. Here is one way of doing it on a simple airplane with strip ailerons.

John

John,

I like that balance weight, and the float attach. Got another pic of the plane on the floats? I've had to balance control surfaces on a full scale and it's a pain in the rear. Had to jig up the control surface on it's hinge points, get a weight off the trailing edge, then calculate the weight required and it's location to get the proper size weight and moment arm.

Hoglfyer

Let me guess, Ah ruddavators on a Beech 35 V tail?


John[8D]

Eh, no one has suggested the most likely scenario...

Flaperon mixing with elevator to flap mix dialed in as well.

We have a number of planes larger than this on our field and they do the same thing.

It's not the servos.

Usually several servos are hooked together to act in unison, which in turn prohibits any servo chain from sagging.

Several of the pilots have elevator to flap mixing dialed in and their planes will look exactly the same way when the elevator stick is pushed forward.

If you look in the picture the ailerons are not at full travel as well.

John,

Acutally I had to balance ruddervators on a V-tail for my Airframe practical half of my A&P. I've also done them for a Decathlon and Pitts S2A after recovering the control surfaces. The Decathlon was the ailerons, the Pitts was all 4 ailerons, both elevators and the rudder. Talk about a nightmare!

What plane is that in the pic? The fuselage and wing have Bridi Super Kaos written all over it, but the tail is a bit different.

opjose,

If you head to an IMAC contest, you see on the larger planes the controls droop when the radio is turned off. Just the weight of the surfaces driving the servo's, and the servo's not having any juice to fight back. Just par for the course.

Counter balancing the way John did should stop the drooping issue on the ground, but you'll still need a whole bunch of the high buck servo's on the large craft to overcome the aerodynamic forces for the fast and accurate surface movements required in flight. Aerodynamic balance, on the other hand is an entirely different can of worms.

Hogflyer

Yeah I can't say that I've been to the events to look at this... I'm going by the 33% and larger planes I see on our field.

They usually have several interconnected servos to prevent this, as the pilots are looking for the maximum available torque possible, so the chain of servos stops any drooping.

You got close enough, its a close to stock Killer Kaos the last of the Bridi kitted Kai.

John