Greetings,
About 12-15 years ago I was flying a Sig Citabria and having great fun. This plane woud do anything that I asked of it.
Now I'm trying to fine-tune another Sig Citabria and she just doesn't want to roll.
The kit calls for 5/8 airelon movement, which is where I have started.
5-8 test flights later, I am still not getting a fast enough roll-rate.
I test-fly then land and crank in more airelon. I am up to almost 1 inch or more of movement but only have a roll-rate of one roll per 5 seconds, not even enough to get out of trouble.
I never had this problem before.

I need advice, help, and info on this problem, please.

One of the very first things that I would check is the linkage geometry to make sure that the moment arm isn't too small at maximum deflection. Many times the servo or servos have plenty of power just off of neutral but run out of steam when the aileron is trying to get to full deflection at higher flying speeds. Try pulling into a vertical position and see if the roll rate increases as the speed bleeds off. If it stays the same or increases then the flight surface is forcing or stalling the servo to a position less than full deflection.
The solution is to either get the linkage in a position of better mechanical when the aileron is at full deflection, or use a higher torque servo.

You also might try some aileron differential. High wing, cambered airfoil airplanes have a tendency to yaw against the ailerons. By introducing differential movement of those ailerons, the extra drag on one side that causes the adverse yaw is cleaned up, and the plane doesn't fight the roll.

I have a similar model that had your problem. It wasn't a Sig but probably came out of the same Chinese factory. From the first differential added, it started responding lots better. I think it got about 2 or 3 increases over time. The changes were done to the rigging so were done in steps.

Thanks for the input.
I have checked and my airelons seem plenty stiff enough..........
I will check into using differential, pretty sure that there is none now, not sure about my older plane.
These Citabria's aren't from a Chnese factory but, rather my Father and I have been building from kits for 20 years.........

I agree with Da Rock, put in some differential (more up than down). It also helps to feed in a lot of rudder, especially on the last half of the roll.

Thanks for the advice.
I am not sure how to incorporate the differential. The airelons are built using bell-cranks.....
I am a bit confused because I didn't have this problem with the original plane, which also had bell-cranks, and probally no differential.

If there is a gap along the aileron hinge-line, you could try sealing the gap with a strip of tape to see if the aileron response improves.

It's really quite easy once you get the idea.

You know that ABSOLUTE TRUTH that's one of the first you hear when you get into R/C? .... the one about "the pushrod should make a right angle with the servo arm"!!!! Or "the pushrod should make a right angle with the horn". You ever wonder what happens if your pushrods don't make that right angle?

Differential happens.

There are a number of ways to describe how to rig your servo arm (or horn) so the angle isn't a right angle, but a picture works better. I'll go look for one. In the meantime, Minnesnowta or BMatts will probably drop one in here. BRB

BTW, bellcranks can even make differential rigging easy. Matter of fact, I think a couple of the early highwing, cambered airfoil trainers with cranks were setup on the plans to give differential. They won't no dummies back then..............

I'm pretty sure that I smell what your cookin Rock.
In fact I have just sat back down after lookin at the Citabria again, lookin to see how to introduce some differential. Unfortunatly, there are no hatches built in for acces to the bellcranks....
Also, as for sealing the hinge line, these are also "Barn-door" airelons*(sp?), making it kinda hard to seal the bottom.....

Thanks again for your time and advice, keep it coming!!!!!!

Edit, I am right now bringing the Citabria out and putting the wing on to better use the advice offered here and to be able to more quickly post results.Will post actual throws, both up and down, shortly.....

Open bay wings provide lots of hatches. Their only drawback is matching the color of the covering material.

I just started drawing up a diagram, but you can easily do all the rigging at the servo arm(s) and not bother with the cranks. Then the diagram won't apply.

It sounds like you've got one aileron servo driving both sides at once. Those are easy to figure out the direction to rig.

Use a round output wheel on the servo. They're great for this. I'd bet they were designed for this, as a matter of fact.

edit.........................
You know, there are so many variations on this rigging............. How about reporting what you've got for a layout in that airplane. Maybe a picture?

I shouldn't have left that as a puzzle.

Open bay wings give you hatches all over the place. You just cut out the covering where you need a hatch. The new hatch cover comes off the roll of UltraKote the color of the cut out covering.

Guys do it all the time. I just put braces into an ARF. The elevator and rudder pushrods were not supported in their length. So I cut out the covering in one side where a lightening hole is, reached in and built a couple of braces, and recovered the hole with covering that matched. It's quick and easy.

I am not trying to sound too negative but..... The are bellcranks driven from single servo with just one pushrod soldered together along with a single rod bent into a z-bend, which is connected to a single servo-arm hole.[&o]

Maybe I'll cut this airelon pushrod and make it into two pieces in order to utilize the round servo arms........hmm.

I reset my airelons back to kit specs( I had the airelons moving about an inch and reset to test theory of too much movement stalling the wing), 5/8" up and down with 3/4' for my dual-rates.

Not a problem...............

But you will need to turn that one rod into two.

Your aileron horns point down, right? Most do. If so, we want to increase the pushing and shorten the pulling at the servo.

Is your one hole on the servo arm at 12 o'clock or 6?

If it's at 12, you want the rod from the left to plug into the wheel at 1:30, and the rod from the right connected at 7:30.

Yeah, they'll now reach over center, but they'll also push farther than they'll pull.

What servo are you using for the ailerons? Someone mentioned this but not why. If you're using a lower powered servo than in the old original then it may not have enough torque to push the ailerons to full deflection. You can check the sticky threads here an in the Scratch Building forum for online calculators that tell you how much servo torque is needed to move a given size to a given angle. Punch in the numbers and see what they say. Don't forget to add the two sides up since you're using one servo for both. And finally you want some safety room on the torque value. You want the servo to be about twice as strong as what the calculator says the surfaces require. That way you're not risking having the servo operate near the stall point and you've got some speed allowance for when diving at higher than normal rates.

what are you using to reinforce the push rods?(what tubing are they run in)

If the problem is underpowered servos, check out the use of boost tabs. I used those quite often back in the days when most servos were quite weak compared to todays servos. They were very effective, especially on rudder and elevators. Just do not make them more than 10% of the total surface area and do mass balance the surfaces if you can.

Wow, This is a lot of stuff that could be said much plainer.

Here is how I was taught to make the differential many years ago. Now, this is for a high-wing setup where the servo is UNDER the wing. The linkage arms are in the center and behind the servo, but you'll be able to make it work for your setup once you understand it.

We used a CIRCLE servo arm on a single servo. Consider the FRONT of the wing to be 12 O'Clock, the bottom to be 6 O'Clock. With the ailerons centered with the wing, bring the linkages off of the 2 O'Clock and the 10 O'Clock positions on the circle arm.

When the ailerons are run they will automatically have differential in them, the UP will be more than the DOWN due to the fact that the linkage goes mostly sideways going around the clock from 2 to 10:30 when pulling the aileron DOWN, giving less travel. Going from 2 to 5:30 you get a straight push UP and substantially more travel to the aileron. Thus, you have differential.

If you were running a low wing with the servo on TOP, then you'd use the 4 and 8 O'Clock positions. (That's not your setup, though.)

I just read Da Rock's post, mised it the first time. His is the formula to make your setup work right. I'd go 2 and 8, but 1:30 and 7:30 is certainly close enough to the same thing, you get the idea. Just make sure that the aileron goes DOWN less than it goes UP. Work out that motion before you cut it up.

Hope this helps.

Jim

Did you checked the pushrod stiffness? Maybe it is bending.... try to move the ailerons with servo and push the up aileron with your hand and see the pushrod if it bends or stays.

good luck!

Try using the rudder! Also you can install acute angle bellcranks.

IMO adding rudder is more effective than differantial. That way bothe ailerons have full effectiveness. For rolls its best to mix some rudder so that it is the same amount each time. You should not notice it because it simply puts the yaw back to center when it was yawing towards the down aileron before.

Actually, both ailerons don't have full effectiveness. They cause the yaw because they aren't equally effective, one is creating much more lift and drag (they come together as a combined "gift") than the other. Their imbalance causes the yaw in the first place.

Also, mixing rudder to fight the unwanted yaw adds even more excess drag to the already screwed up airplane. The poor bird had ailerons that can't create clean roll and you're throwing rudder and it's increased drag (it's gotta create lift to work and that combined gift shows up again) just throws gasoline on the fire. You wind up with a doubly inefficient configuration with both the ailerons and the rudder being needed when just a touch of aileron and some elevator could do the job efficiently.

The goal has always been to rig a full scale to be as efficient as possible and to take as little trim as needed. Less surface movement = more efficiency (and a cleaner flight). Differential aileron (when needed) has always resulted in a more efficient roll. Always given less drag for more roll from less stick needed.