I have only been flying for about a year. I have only had smaller, .40, .46, .61 sized two stroke planes. I just bought the seagull 540 .61 or 1.20 sized arf. I have an O.S. 91 FS on it. I'm turning a 14x4 or 15x4 prop.

My problem is that it loves to roll when I give it lots of up elevator input. I have never flown an aerobatic plane that was this big and I don't know if it's just the way an edge flies. Or it's just the way a big plane flies. I had our best pilot at my club fly it and the first time he gave it a lot of elevator he was really surprised by what it did. He said he thought there was definitely something wrong with it.

I have the servos in the tail and couldn't Y-harness them and then reverse one servo, so that both push rods were the same, so I bought a servo reverser, and it's still the same. I have asked other owners of the same plane, in RCU, if they experience this and no one has any problems.

If I want to pull out of a dive I need about 100 feet to do it. I can't do anything close to the ground cause I need such low elevator input to make sure the plane will not turn over. It always turns over the same direction also. I have made the throw distance of the elevator halves, equal, and the center points of both servos, equal. I don't know what else to do.

Could someone please help me. Lots of thanks in advance.

It sounds as though you have too much elevator throw! I have seen this many times!! The first thing I would do is to lower the amount of elevator throw you have! If this doesn't solve the problem then measure BOTH elevator halves to see if they are traveling the same amount. This is most problematic when you have two elevator servos acting independent of one another. Another thing I would do is to check that your CG is correct. This range should be between 25 - 35 % back of the leading edge of the wing. Since you are new to the model and aerobatic aircraft, I would definately move the CG to the forward area of the CG range. NOW!!! One thing you may want to do, if you have a computer radio is to set in a little more exponential in your aileron and elevator controls. If your ailerons are too sensitive and you move the stick with any sidewards travel while pulling or pushing the elevator stick it will cause the plane to roll!!!

If all of these things are okay, now you should check to see if the horizantal tail is parallel with the wing, and thet the vertical tail is perpindicular to the tail. If anything is out of rig, try to correct it. If all of this is okay, well then we are going to need a lot more room to talk about all of the things it could be!

Let us know how it turns out!!!

Reg

Thanks Reg. I have done some of what you advised, and some I have not. I'll be working on it. I appreciate the response.

Another thing to check for is twist in the wings... if there is a little twist it could be trimmed away in level flight and only show up during pulls. If it is not wing twist, or differential elevator, the only thing left is the pilot... Full up elevator SHOULD cause the plane to stall... if you limit elevator travel so that full elevator does not cause a stall you won't have enough throw to do some maneuvers like snap rolls, tumbles, and slow speed manuevers like humpty bumps. To fly an airplane like this you have to learn to limit your thumb travel, not the elevator travel.

Ty

I agree with all the above. It's not that unusual for large amounts of elevator
travel to cause an aerobatic airplane to snap. Extreme travel should only be
used at lower speeds. It seems to be worse on planes with a short tail moment.
I would first try moving the CG forward. Exponential also helps.

tommy s

I agree with the too much elevator throw. I had a H9 Edge that had such a small elevator throw for normal flight, no one believed that it would fly like that. But it was plenty to loop - square corner - snap - spin. Just my 2 cents

It sure sounds like the wing may be warped. But the large elevator throw is what makes the warp show up. The fact that it always rolls the same way indicates that there is a marked difference between the wings. It may be a warp or it may be that a construction error has produces a mismatching airfoil in one wing compared to the other. Check for warps first and shaping differences second.

My Thoughts....

Aerobatic models are by there very nature unstable. If the plane was too stable they would not perform all the aerobatics required during flight. You must learn not to pull too much elevator. As the plane slows the amount of elevator needs to be increased but there is a limit. At a given point the elevator throw will cause the wing to stall. The wing no longer produces lift due to the shape of the wing but instead it keeps the airplane flying by its resistance against the oncoming air. The best think to remember is to keep some speed on the wing until you learn how the plane reacts at slow speeds. Adding expo to the elevator can help this immensly. You need a lot less throw on an aerobatic plane to achieve the same results as say a trainer. What you are seeing is a snap. Most aerobatic planes will do this if too much elevator is applied. As the planes get bigger this phenominon deminished.

One other item you may want to address is your prop size. I would run a little bigger prop on a .91 FS. If it is an .91 Surpass II I would run a 15X6 APC Prop. The 14X4 prop you have on there now is a little too small. I run that same prop on my OS .70 Surpass II. If you have a tach or someone at your club does I would recommend checking it. Look for about 10,000 RPM with a 15X6. Any more RPM and you risk damaging your motor.

You can also check the wing incidence by first checking the root then moving the gauge to the tip and they should be the same. This given the idea that the wing does not have washout built into it.

Good Luck, Phil (Mesa, AZ)

Check your ailerons and raise both of them about 1/8" above the neutral position. You may have both of them drooped slightly causing a wash-in effect which could result in premature stalling.

Hi,

I don't know if this has anything to do with it but have you
balanced your plane side to side? Perhaps if one wing tip
was say .... a lot heavier it could cause a tendency to roll out
a bit.

JK

"Aerobatic models are by there very nature unstable."

Let's not use that statement. Aerobatic models are nicely stable else we couldn't fly them. Rather say.......

Aerobatic models are by their very nature very responsive to control movements. Or something similiar.

Thanks for all the help from everyone. I have done much of what has been advised up to this point.

I have not, lowered the throw on the elevator, just because at this point my low rates would be at something like 25% for me not to roll out at full elevator, so I have saved trying that until last.

I also have not tried to raise the elevator as Ed suggested. This has me very curious. Ed could be on to something here.

I have tried to balance side to side and everything seems ok.

I will look for warps in the wing again and I will put on a bigger prop.

When the rain stops here, I'll try flying her again. I do appreciate everyone's help and I will keep everyone posted. Thanks again.

Well, I think I found it. One of the elevator halves seems to be warped. I called Horizon and they said I just had too much throw on my elevator input and said the warp wouldn't change much, they said they won't fix it, so I guess I have to fix it myself or fly it the way it is. I'm not much of a builder so I'm not sure what I'll do. Thanks again for everybody's input.

Down, there is something that might be rather easy to do to fix it! If you have a heating iron for iron on covering, you may be able to shrink the covering to correct any warping! Just find the area that is warped, and heat the opposite side, in this case top or bottom, to get the warping out. Now if the warp is more than heating the covering may fix, then you will have to resort to something a little more drastic. This fix, remove all of the covering from the tail area involved and slowly apply warm water to the warped area until it is soaked through. You want to make the area "bendable." then using 2 straight and flat surfaces and clamp them to the wet part making sure that you are seating them EXACTLY STRAIGHT, FLAT, AND INLINE with where the part needs to be. This envolves a lot of measuring before you start! Now leave the plane alone for 24 - 72 ... closer to 72... hours without being moved, nudged, or even thought about hard! This gives the part time to dry again and hopefully in the correct way to correct the warp. Hope this helps!

Reg

I said to raise both ailerons very slightly.

Without noticing it, you may have both ailerons slightly down. This can have the effect of adding wash-in at the tip, especially on a tapered wing plane, causing it to stall faster.

If your plane continues to tip stall on up elevator, you can add stall strips to the inboard section of your wing. Glue some 1/4 triangle to the leading edge in next to the fuselage. This will cause the root section to stall first. You will have a slightly faster landing speed.

In a perfect world, all ARFS would be absolutely perfect and free from warps.
They also would not be prone to being tailheavy and too high in wing loading.
Many EDGE models in smaller sizes suffer these problems.
I have built and flown two of the better ones -- the D Patrick and the H9.
in both cases - it is extremely easy to make them tail heavy .
When tail heavy, these models pitch extremely easily and snap rolls are easily induced.
ANY control input (deliberate or accidental)which causes even the slightest yaw during the elevator input, will make this situation even more pronounced.
An Edge - built straight and light and with no "funny" trim problems -is a good plane.
Aerobatic models when setup correctly are extremely easy to fly.

Thanks for the correction, Ed. I know what you meant, I just typed elevator instead of alieron. I also think the model is pretty heavy. It weighs about 8.5 lbs. Some people have worked really hard to get them to about 7. Those probably fly much better than mine. All this advice is great. I appreciate it very much. Like I said before, the weather has not let me try out the changes to the plane. Hopefully, this afternoon. Thanks again.

does the same thing cut down on the elevator it will solve all you're problems and fly great
Hope your elevator is stronger than mine. It broke in two halves in the air. but neat my friend dan almost landed that plane beat all i had ever seen. brought it home with no elevator halves.
But i fixed that problem went to a hobby town and got some bass wood. I traced the same pattern, cut it out and put it on. flew the next day. good luck. I run a os 91 fs
the fearles pilot has crashed 3 times and still flying. hadn't crashed in a while since i turned down the elevator throw and up on the rest.



if we didn't crash em this wouldn't be a hobby.


brett

I agree with what has already been said.
I tend to suspect a slight warp in a wing, very hard to see; well worth buying or making an incidence meter.
Grasping at straws here but I have another possibility.
Is the rudder connected by a pushrod to a horn on the left side?
When you pull 'g' a heavy sagging pushrod could be applying a little left rudder which would cause the problem you describe.
I nearly always use closed loop on rudder which avoids that problem.
Alasdair

alasdair thank you very much i checked my rudder and come to find out that it has well more than an inch worth of slop.
Thanks for bringing that up




brett

if we didn't crash em it wouldn't be a hobby

what is a heavy sagging pushrod? And what is closed loop? I have never heard of these terms. This is the first .60-.90 sized airplane I have owned, besides an Ultra Stick .60. I'm not sure I have set this plane up correctly. I have used only standard futaba servos and the hardware this ARF came with. Is there something I might do to counteract the rudder problem? Thanks.

DownSideUp,
A pushrod is (usually) a balsa rod, 3/8" square to 1/2" square balsa on that size of plane. It has a short , 2" to 4", piece of wire on each end with a clevis threaded on for connecting to the servo at one end and the rudder horn at the other end.
Sometimes on ARF they use a piece of 3/8 dowel rod for convenience, and that is heavier than balsa.
If you can imagine, when you pull 5 'g' in a loop or turn the pushrod weighs 5 times as much. Try sticking you fingers or a stick inside the model and push down on the middle of the pushrod. Does the rudder move? If it moves to the left that could be the cause of the left flick out of high 'g' manoeuvres.

I always use a closed loop on rudder. I put a control horn on each side of the rudder, back to back symmetrical. To each I attach a piece of light steel wire coated with nylon (fishing shops sell it as 'trace' wire, and many hobby suppliers sell it as well now). Hobby shops sell the connectors, often with some wire.
Both wires are led into the fuselage (often crossing over) and they go to either side of the rudder servo arm. So left rudder command pulls one wire and right rudder command pulls the other. It is also called a pull-pull system.
You adjust the wires firm, but not tight, and it is very positive, light, and cannot be affected by pulling 'g'.
Does that help?
Alasdair

Sorry. I haven't replied, but I've had surpass problems and the plane's been out of commission, plus it's raining here. I got a chance at it yesterday. I think the biggest problem is the amount of elevator throw I had built into the plane. But I also think a "pull-pull" system would help as well. Thank you Alasdair for explaining the whole pull-pull system to me. I know it as pull-pull but not as the other term you used before. I think that would be a good idea and it would take some weight out of the tail, which I think accounts for some of the problem as well. The plane balances out as per the instructions, but the way it snaps, flat spins, and flies inverted I tend to think it is quite tail heavy. Thank you everyone for your all of your help and I'll keep everyone updated.

what kind of surpass problems have you been having. My surpass has been poping and cracking ever since i got it. Ichecked the valves with the filler gadge and everything checked fine. Do I have it too rich or am i running too big of a prop in it?



brett

If we didn't crash em it wouldn't be a hobby.

it is snapping because your wing is stalled. once the wing is stalled, it is useless, and any little diference will cause it to snap. the reason is it is too heavy. when the plane is too heavy, the inertia from the moving plane is so much that the wing's surface isn't large enough to handle it and it will stop flying. the only real solution is to loose weight.