One or Two Aileron Servos
 

Is there any advantage to having two aileron servos
if you are NOT using a computer radio?
Thanks,
KW_Counter

RE: One or Two Aileron Servos
 

Well, sometimes you can get more torque out of the system, or you can also get a more direct coupling between the surfaces and the servo. The latter happens because most single servo setups use a torque rod or some sort of bellcrank mechanism to actuate the ailerons, but most dual servo setups are mounted outboard on the wings and have a simple pushrod out to the torque arms. I prefer them, but I also have a computer radio and don't need to hook up a Y-cable.
Curtis

RE: One or Two Aileron Servos
 

You can engage the middle of the aileron, instead of the inside portion. I use wing mounted servos in most of my 40+ sized planes adn my 25 sized combat planes, even with a y-harness for this reason. I just converted a 4*40 to wing mounted servos.

There is nothing wrong with a single servo system, I just feel that the dual servo is more powerful and precise.

The downsides are additional weight and current draw.

Jack

RE: One or Two Aileron Servos
 

Here's one, from experience with the Global Hobby "Tequila Sunrise 40" ARF. It's a nice looking plane, aerobatic and all that, but putting it together was a surprise.

When I went to put the wing in place, I found the standard aileron servo would interfere with the elevator & rudder servos. In order to eliminate the interference, I had to (1) buy a low profile servo for the ailerons, and (2) use a short servo arm. Of course, I didn't spot this up front, so there was a delay and some fiddling around while I got the servo and figured out the short servo arm requirement.

So, in that case, it would have been a good idea to design the wing with two servos rather than one in the center. In other cases, where the available room in the fuselage is minimal, the same may apply.

Best wishes,
Dave Olson

RE: One or Two Aileron Servos
 

For most planes up to .60 size one aileron servo will work fine (unless the plane is designed for dual servos). A couple of exceptions are when you need dual servos: my Alpha 60 had aileron flutter due to soft ailerons so I converted it to dual servos to eliminate the flutter, or if you want to convert to flapperons.

It is a fair amount of work to cut into a built-up wing and build up additional structure for dual servos if it wasn't designed for them in the first place.

Hogflyer

RE: One or Two Aileron Servos
 

Dual as in two servos per aileron, or dual as in one servo per aileron?

Most planes smaller than 80" wingspan typically have one servo per aileron.

My small .15 to .30 size planes also have one per aileron.

The few exceptions are a .40 biplane, and a couple that use linkages to drive both ailerons.
I prefer one servo per aileron on the smaller planes.

RE: One or Two Aileron Servos
 

Another advantage of 2 servos is the posibility of saving the plane if one of them fails in flight. Actually happened to me.
The linkage on on of the ailerons came off in flight, I had no problem flying with only the one aileron working.

RE: One or Two Aileron Servos
 

surprised that noone asked the OP....

which airframe?

RE: One or Two Aileron Servos
 

Hey All,
Thanks for your replies - great info!

Missileman,
I had one side of a single servo come off once - interesting flying.
No problems, used the rudder.

Exeter,
Why would the airframe make a difference?

KW_Counter

RE: One or Two Aileron Servos
 

Because if you're putting together a trainer it won't make a difference.

If you're putting together a 3D plane with huge ailerons it will make a big difference.

RE: One or Two Aileron Servos
 

two is better than one , because there is less slop , and you can put the servo closer to the a ron or the flap horn, for a more positive
control on the wing

RE: One or Two Aileron Servos
 

Barracuda,
Please back up your statement with facts.
Thanks,
KW_Counter

RE: One or Two Aileron Servos
 

It's actually rather obvious. The load on the ailerons of a 3D model is often considerable. It's actually common for some of them to experience blow-back when the servo(s) are not up to the load no matter how many. Look at the number of servos on most IMAC birds. Those big models often have multiple servos in each wing and more than one on the elevators and they're often rather huge servos to boot. Bottom line, there are a number of models that have 2-3 servos per aileron. So two per wing isn't even a limit. And we've not even discussed the aileron style, strip, barndoor, whatever. Nor what percentage of the wing area is present in the ailerons. Yeah, there are lots of planes that'd suck with just one aileron servo. What airplane is the one in question?

Trainers are usually 40-60 size and are designed to provide stable, rather sedate flight with no demand to execute quick, hard maneuvers. They're not powered to go fast and the flight envelope doesn't put the ailerons under appreciable load. You will see trainers with two aileron servos but it's obvious from the numbers that use one, that one is all that's needed. So the the airplane in question a trainer?

Is the airplane in question even a 40 or larger model? If it's a park flyer the wing might not even be large enough for two.

So there is a huge range to the loads that the huge range of ailerons we have will see. Yes, there are trainers with one servo, but can you think of any 3D birds that have just one? So there's the "proof".

RE: One or Two Aileron Servos
 

Take a look back through modeling history - pattern planes flying with piped .61's flew on one aileron servo. Those servos had about 1/2 the speed and 1/2 the power of today's standard sport servo, and many of those 7 lb - 9 lb planes flew well over 100 mph. For a primary or secondary trainer (since the question was posted in the Beginners Forum) a single aileron servo is all that is needed.

Hogflyer

RE: One or Two Aileron Servos
 

Rock,
Very good reply. Lots of info one can digest and understand.
Yes, I understand if you are flying a large plane or one with large
control surfaces you need more servos.

Essentially the question is if I convert a single aileron servo wing
to a two servo wing do I gain anything?
I wasn't very clear on that in my first post - for a reason.
From what I have picked up here - none to very little gain.
Maybe a slight more positive action from pushing in the middle of the aileron
rather than the end.
Thanks for the replies,
KW_Counter

RE: One or Two Aileron Servos
 

It depends upon the plane, which is why you are asked this.

How about telling us what plane ( and size ) you are talking about?

RE: One or Two Aileron Servos
 

As I said, you might gain something if the control surface load is large. (large surfaces, high speed, larger airplane etc)

You also might gain a reduction in control surface flutter with a more direct connection.

If you intenionall ask vauge questions then you're going to get vauge answers. If you ask a specific question, then you're going to get more direct, helpful answers.

RE: One or Two Aileron Servos
 

it does really depend on the plane , on some you cant use two . its probably not going to make a difference on a fairly light sport plane or a trainer.

RE: One or Two Aileron Servos
 

Would I only use one servo in my Edge? Hell no! Would I use one servo in a mini stick - yes, why not. This is the reason people are asking which plane this is since it is going to influence the question at hand.