I have a stick type model that snaps smartly to the right with just elevator. It is a 60x14"wing, 54" length fuselage, everything set to 0-0, CG set at 3.75". It does well when a limited amount of elevator is used, but go to about 35 degrees and it just snaps only to the right. I have a 3D model that does 3 foot loops, and maintains perfect flight. Any suggestions?

Just too much elevator throw. Cut down the amount of elev. travel. Move the control rod in on the servo or out on the elev. horn. Some planes just can not do three foot loops. Calm down the elev. and I'll bet it will be fine. Just my two cents worth.
John

And the reason it always snaps in the same direction is probably because of wing twist. If it always snaps to the right, the right wing is stalling before the left wing. Since the left wing is still producing lift and the right wing isn't, the plane rolls. And with the tail kicked down the roll is a snap roll.

In addition to reducing the elevator throw you should check for wing twist with an incidence meter. You'll probably find the right wing tip at a more positive incidence than the left wing tip. Twist the wing panel by hand in the other direction until the covering wrinkles and reshrink it top and bottom with your heat gun. Test again. Repeat until both wing tips are at the same incidence as the wing root.

Dave

My Super Air would snap while using an extreme amount of elevator. Decreased the amount of throw and then nice tight loops.

And it could either be wing twist or a difference in the two aileron servos. One might be stronger in it's movement than the other.

But warp or misalignment is probably more apt to be the reason. Got any aileron trim in the plane to get it to fly level? When you look at the wing remember that the ailerons are part of the wing too. If they've been adjusted a bit to keep the plane flying level, there was something out of alignment that needed the ailerons to correct. Now you got two things fighting each other.

BTW, sometimes the tail causes problems like this. If the elevator halves don't work with the same force they can yaw the plane when they're pitching it. A weak connection between the two elelvator halves can give that kind of problem. You got a servo directly driving one side but a connector driving the other. A connector that's worn some slop in either elevator half can be a problem. Too weak a connector can be a problem from day one. I just finished an ARF that came with a halfway fractured metal connector. You could barely see the crack, but after working it with my hands, it broke. Some ARFs come with their connectors installed. You'll have no clue if their connectors were cracked.

A buddy of mine built a beautiful model of a 40s Texaco model. Those were freeflights with one elevator half ground adjustable. So the plans showed one "working" elevator half. So he made his model with one elevator half. When you give it quick, strong elevator movement, it yaws to match. Up gives a yaw one way. Down gives a yaw the other way. Same action you'll see when your elevators aren't working together with the same strength. And when you yaw a wing that's about to stall, it will usually stall the same wing every time. The advancing wing winds up seeing increased AOA due to the yaw. And AOA is what stalls a wing. Or one side of the wing.

could be the rudder too. Put some left rudder trim in, retrim the ailerons if needed and see what happens

It may be some oddities that you've trimmed out as the others have suggested or it may also be that the wing's leading edge or rib shape is not symetrical from side to side. A noticable difference in the leading edge could easily produce such a snap roll.

I'm often amazed at what some folks consider to be an "adequite" leading edge shaping job. I've seem rectangular and square leading edges that are just barely rounded out and I've seen diamon shaped leading edges that are barely dubbed off with sandpaper and are basically still diamond shaped. Both options will leave you with a wing that doesn't stall nicely compared to a proper shaping job.

BMathews I think you win the DR. IQ candy bar. Your comment on the leading edge was spot on. I went and looked at it, and recalled that I used a piece of 3/4 triangle, for the purpose of getting a good snap. It seems I got all I bargained for, and then some. The only question is why always to the right? I would think that the torque of the motor would skew it to the left.. I have this plane trimmed to fly right in all modes. Funny that a few degree too much elevator produces such a vicious snap. Again guys thanks alot.

hello if i read it right a 60X14 wing if this wing is a candy bar type your c\g should be 3.5 for nose heavy which will cause snaps ,try 4.5" this should take care of the snap issue, plus you
should have at least 280 sq" horz stab with elv. need more info about plane to fully correct
problem. but as in post c\g at 3.5" is to nose heavy. anthony@customcraftedrc

I believe that all the above explained is correct.
One more factor to consider:
All references to pilot seat.
Always to the right because there is a force yawing the model constantly to the right.
This could be anything: crossed trim (right rudder fighting ailerons), elevator non-parallel with wing (elevator-rudder twisted to the right), twisted fuselage, engine thrust to the right and down.
When the elevator forces a higher angle of attack of the wing, it reaches a velocity beyon which the lift disappears suddenly.
Leading edge, airfoil, cover, warp, etc. may cause the right half of the wing to reach this critical point (stall) first.
After that moment, you are flying a model that has only a left wing, and a parachute (lots of drag) on the right side. There you have that one force yawing to the right, probably helped by the other.
The model starts rolling to the right and falling nose first, helped by the advanced CG, while the left half keeps flying, helped by the increased air speed.
Test the snap at sufficient height and under power first, and then cutting the power right at the moment of feeding elevator. If there is a marked difference, reduce right and down trust of the engine.
When your wings are heavily loaded, due to elevated weight of the model or/and advanced CG, the stall is reached at higher speeds and lower angles of attack (high speed stall); that is what makes this model perform differently from the 3D you have.
Move the CG as aft as you can, and remove weight from the model.
Good luck!!

Bruce gets the hammer award 'cause he hit the nail squarely on the head.

I've seen so many fine jobs of sanding the leading edge for the first 3 inches or so from either wing tip or center section. But what lies between is barely touched.

Make airfoil templates. Use them while shaping and sanding.