I have a Aeroworks 540T Edge. It is rated for a 60 but I found it a little underpowered with a 55 AX. I did some research and found folks had good results with with the Saito 100 on this plane so I went looking. Found a good deal on an O.S.120 surpass II pump and figured I would give it a go. The O.S. is quite a bit heavier than the Saito and the plane has a bad tendacy to roll out when any elevator is applied. It isn't un-controllable and can be countered with a little aileron input. I know or I think this is because of weight so what can I do. Move the CG, weight one wing? I have thought of mixing some aileron with the elevator. I really don't want to do any-thing that will make it worse because right now I can still control it, with some altitude to correct, so first I will ask you guys. What would you do? By the way, I love this engine so I really want to keep her up there.

When you put on the heavier engine, did you re-balance it to get the designed CG location?

There's nothing you can do for an overweight design. And what you're seeing isn't unusual. Check out the ELEVATOR SNAPROLL thread that is currently running for a case of the same problem and comments on things to look for. But in the end if it's overweight there's nothing to be done for it other than learn to fly it in a way that avoids the bad things and promotes the good things. Getting the CG in the right place would be a good first step if it's not there already.

I moved the battery and the throttle servo to get the CG back to where it was supposed to be. I am thinking of moving the CG a little further back to see if it will help. I read somewhere that a little weight in the right wing helps with torque-roll which I do see a little of on take off but it isn't any thing I can't handle as long as I know it is coming. It's the surprise thing that gets you.

Ah, the famous tip weight for takeoff. That's been discussed as well and it would not have a place in this model unless it turns out that it's out of balance laterally and you're just trying to correct it to put the lateral balance back onto the centerline. There's a thread about this article that came out in MA recently as well. It MAY, and I doubt even that, have a place in some trainers or scale models but it sure doesn't belong on any sort of aerobatic model.

I'd start by using something like the Robart incidence gauges to check for warps down to a high degree of accuracy and from there ensure that both ailerons are faired into the airfoil shape and not sticking up or down even slightly. Also check overall rigging of the wing to the fuselage and to the fin for even a hint of misalignment. Diagonal measurements from equal points out on the wing to the fuselage centerline back by the tail should be accurate to within 1/16 to 3/32 inch. And you can't trust the fuselage either. Set up some sort of rig to test the fuselage for straightness and that the fin is accurately mounted with a 1/2 degree of this tested and known good line.

If you read that other thread you'll find that there's a general consensus that radically tapered wings on our models are rather critical to a number of factors. Even small airfoil differences can cause what you're getting. But by far the worst thing is a heavy model and a strong taper ratio. It's just a bad combination that makes the model hyper sensitive to tip stalling. And if there's any sort of misalignment or side to side differences in the wing it'll encourage a stall and snap to one side or the other pretty consistently. About all you can do is try to find any minor differences, especially in the outer 1/2 of the wings, and "fix" them so both wings are identical.

Actually there MAY be something you can do to help this. On some of my gliders I've had good luck with adding turbulators to slightly delay the high drag mush that comes near the stall. They are also supposed to slightly increase the angle where the stall occurs. You MAY find you have some luck with adding turbulator strips on the outer third of the wing on the side that drops away consistently. On the other hand if it drops off either way about equally then try adding turbulators to both sides. Locating them to do the most good is a guessing game but I'd suggest a double thickness of 1/8 automotive trim striping tape at about the 8 to 10% chord point. If it doesn't help move this strip forward a little towards the 5% point.

Just be aware that a key element of this type of model is the ability to stall and snap violently on demand. To avoid it when NOT wanted it's up to the pilot to adjust to the model's needs. The pilots of the full sized airplanes have to do the same thing. Anyhow the big outcome of this is that the model may not snap the same upright as inverted or the same from one side to the other if you end up with the tubulator on the one side only. Adding more strips of different lengths may or may not fine tune the stalling charactarisitics but I just don't really know. At least it's something that's easy to play with and try different things.

It's interesting how so many think a snap with the application of elevator can be counteracted by adding weight to a wingtip. A snap is an aerodynamic happening and not one due to weight. Adding weight to one wingtip only helps if the other wing is heavier before the addition of weight. The common, in-flight way to determine a heavier wing is to do a nice inside loop and watch which way the plane rolls. Then do an outside loop. If the plane rolls right in the inside loop and then rolls left in the outside loop, the right wing is heavier. Weight will help you there.

If you have an airplane that snaps very easily upon the application of elevator, then you have a "snappy" airplane or one that's too heavy. To reduce snapping, you can make the wing thicker with a more-blunt leading edge...especially if you can change the airfoil towards the tip to have a thicker section. Unfortunately, that's not easily done...you have to build a new wing. The idea of a turbulator strip may help, but it would also reduce the aerobatic capabilities of the model.

We once had a kit of an Extra that had a very specific limitation on the elevator travel. That was good for all flying, and exceeding it made the airplane very prone to snapping....there ARE limits to everything, and going beyond them can cause difficulties.

Depends on your expectations for your models. What is unacceptable to you?
The Saito should be able to manhandle 9 pounds pretty good, so if you think you can build a new wing with more area and stay within the weight budget, you should end up a happy camper.....

there is a thread here as referenced above regarding elevator deflection,in the threat it gives deflection of 12 degrees up and 12 degrees down, anyway we have several in our club with extras, 2 of them are aeroworks as well, after setting the elevators to these numbers, no more snapping, or rolling out of loops, there are no shortcuts to properly trimming out a aircraft, nor for not reading the manual, this is a discipline...

For those who may care The elevator throw can be as high as you uwant to make it
There is no magic setting to avoid unwanted responses
How can that be?
Yoiu just have to match throw with speed
the faster the model is travelling - the less any high throw can be tolerated
also the lighter the model - the more the elevator can be deflected
correct elevator throw is like "the best airfoil"
there ain't one answer. Same goes for a 40 lb 42% or a 5 ounce indoor setup

Amen!

Have you checked the simple things first? Such as equal throw of elevators. Also try putting the elevators under load using rubber bands to simulate flight load and then check deflections.

Must set your CG correctly. It sounds like a relatively small model and it would be particularly sensitive to CG accuracy when overweight. Wing loading may be so high that up elevator input may be stalling your wing when CG is too far forward. Usually shows up at slower speeds but high speed stalls are also possible with a CG that is too far fore. What's the weight of your edge? What's the wing area?

MattK

Well I will find out today. I have made some changes that will allow me to move the CG by sliding the battery. On the balance jig I have it moves the CG two inches both foward and back. I did a latteral balance and found the right wing to be heavy and corrected that. I re-read the article on wing-tip weight and,as someone on this thread had said, pertains to take off and usually war-birds and trainers. I don't think it would help me as take-offs and landings are fine. Take offs have a slight lean but I will learn that and landings are so easy and sweet I think my wife can land it and she don't fly. I did notice that slow, wide loops are no9t affected by the "roll-out" so limiting the amount of elevator may be the only solution. As for the balance, my dad and mentor, said that a little nose heavy is a lot easier to handle than tail heavy so that is the reason for the slide deal I made on the CG. I want to tak the chance to tell all of you how much it helps to have a place like this to go to when I feel a little lost or confused on a issue. Which seems to happen a lot lately! You all make this hobby alot more fun. Gotta go and get ready. We, HRRC," Hampton Roads Remote Control", have a Toys For Tots fly in today and I want to get there early to make these trials befor the kids get there. Wish me luck and thanks for the help. James

Assuming that you have the CG right, you can compensate for overweight by adding engine power, although an overweight airplane will still be more of a handful no matter how powerful its engine. My calculations indicate that 10% overweight dictates 25% more power, not 10%, in order to get recovery from incipient stall with the same altitude loss. The accurate rule appears to be that available power must be proportional to weight to the 2.5 power.

A good example is the relatively low powered early Spitfire fighters that weighed about half as much as the later versions. Pilots rated the earliest models much friendlier to fly than the much higher powered later versions, even though power:weight ratio of the late models was higher.

If weight is doubled, I think that power must be increased by a factor of up to 5.65, in order to retain the ability to recover from a dangerously low airspeed situation, with the same altitude loss.

It's not a question of power to weight. At some point when the wing loading goes up the handling goes from pleasent to cut throat. That's why the Spitfire pilots hated the later higher powered planes more and why nice models become not so nice when overweight regardless of fiting a bigger engine to them in an attempt to compensate.