Elevator SNAPROLL
 

I am flying a 27% Extra 300 with a DA-85 Engine and having the following problem. I am starting to try a littel more extreme manuvers as harrier, the wall etc... but.... alevator is untouchable, as soon as I try a hard elevator manuver, the plane snaprolls to the right violently. As soon as it stalls, the same thing. CG is Centerd

What could I be? Is this normal?
What test could I make, or is it just inexperince and neet to practice to control this behavior?

RE: Elevator SNAPROLL
 

Is that normal?

For most every aerobatic airplane, yes.

They're designed so that the elevator can stall the wing "easily". It's how they do the snap maneuvers so fast and easily.. and do the tumbling ones.

The normal situation with those planes is for you to tune the elevator throw and your flying to give you a plane that's comfortable for you to fly. If you wish it to still do cool snaps, the you'll have to sort out the elevator throw to give you that aerobatic agility and still be comfortable.

You've got an airplane that takes "more skill" to fly. Two skills need developing. To trim the elevator and to fly what that trimming does for you.

RE: Elevator SNAPROLL
 

You want to trim the elevator throw so that you can do loops and such safely and within your ability. You also want max elevator to stall that wing nicely into a snap roll.

Or maybe you don't want the snap-ability.
Then simply move the elevator pushrod out on the elevator horn and in on the servo arm. You may have to do a lot of that before it's comfortable.

RE: Elevator SNAPROLL
 

exactly which airframe is it?

RE: Elevator SNAPROLL
 

Besides the previous advice, try cutting throttle just before initiating those extreme maneuvers.
Big propellers at high rpm resist sudden nose up movements creating a force to the right.

Each snap roll needs:
1) Stalled wings (that is what your strong elevator input does)
2) Yaw around the CG (that is what the rudder does)

If you aren't feeding rudder, where the force that yaws the fuse to the right comes from?

RE: Elevator SNAPROLL
 

I'm far from the world's best aerobatics pilot but my own experience for doing a harrier is that I need to transition more slowly into that post stalled mode. This means you can't just snap the elevator to lift the nose. From normal flying speeds there's too much energy to try to dissapate all at once. Now it is possible to "catch" the model and jam it into a harrier from a dive or such but as noted it'll take a blend of throttling back and then forcing the model into a stall along with a bucket load of skill to catch the model at just the right moment before it rotates too far.

Your post says it's snapping to the right. Is this a 99% consistent thing? If it is then your right and left wings are not true copies of each other. Something is making the right wing stall earlier than the left. It could be a warp or it could be some difference in how the airfoils are shaped or it could be that you're twitching the aileron stick to the right when you jab in the elevator input. You may want to try some hard pullups where you use your finger in a way that ensures there's no possible chance of fudging in any aileron control. If it's still snapping to the right then it's time to examine the model more closely.

From the airfoil standpoint a major factor in airfoil stall behaviour comes from the leading edge shape. I'd suggest make an accurate template of the one side and use this to compare to the other. Differences around the actual airfoil nose of as little as 1/32 inch can have very noticable effect on the stall. More generally on a model of that size differences of 1/16 inch in mid chord can indicate a thickness or camber difference from one side to the other. And on designs like Extras, with their extreme taper ratios, this can be murder.

A roll of "pencil lead" from a fishing supplier can be a good material for forming a template of the overall airfoil section. For around the leading edge some plumber's solder that is around 1/8 diameter produces an easier to check template for the more demanding leading edge shape portion. Use the whole chord template to compare the top and bottom shapes for each wing. A gap at some point would indicate that the airfoil is not truly symetrical. If that indicated camber line is cupped upwards then this would produce an earlier/higher speed stall on that wing compared to the other. Similarly if you find that the airfoil is non symetrical with the camber cupped downwards that wing would experience a delay/lower stall speed.

In addtion to the lead wire template checks fly the model and try to go into an inverted harrier from a negative G push. If there is some camber in one wing or the other then the right panel should now stall AFTER the left so from inverted you should see the it snap to the left instead of the right. If it still snaps to the right then the snap issue is more likely related to a significant difference in the leading edge shapes from one panel to the other.

Howzzat?

RE: Elevator SNAPROLL
 

Hola
Experiment with a little less elevator throw. Your plane is acting very normal. Like a wild horse you have to tame it for what you want.

RE: Elevator SNAPROLL
 

Three things: 1) are you trying to fly normally with 3D rates?
2) have you set your radio so that 3D rates are switched on only for 3D maneuvers?
3) what you describe may also be caused by a CG too far aft. Get on or close to the neutral point and you will have that type of response even with moderate elevator throws.
However, if that is the case, it is seldom the aircraft survives long enough to post for an answer. Simply the
truth.

Set up properly you can make an Extra 300 into a violent aerobat or an advanced trainer. Those are the two extremes. There is NO way you can have both on one aircraft.

P.S. As has already been asked, what airframe, wing area, span and all up weight?

RE: Elevator SNAPROLL
 

Is it safe to assume the lateral balance is OK? If the right wing is heavy that's a problem. As mentioned above, if the engine rpm's are up much over idle then gyroscopic procession of the prop will cause the right wing to drop. If one or both wings are warped (check with an incidence meter) that could explain it. Both elevator halves need to move the exact same travel, in degrees, both up and down. The vertical fin and rudder need to be parallel with the aircraft centerline. I've seen them off from the factory and the plane will drop the wing on the lagging side. The most common thing I've seen with folks complaining of dropping the right wing is they are trying to carry some engine speed when entering the harrier/stalled flight and the gyroscopic procession of the prop causes the right wing to drop quickly. In all fairness it does take lots of practice to enter into and fly harrier/high alpha manuvers.

I have an AeroWorks Extra 260 50cc and there is absolutely nothing I can do to get a wing to drop as in tip stall. You can slow the plane down to just a bit over stall speed and then yank the elevator full up (mine is at 45 deg.) and the plane will pitch up quickly then fall back into a nice elevator with no hint of any wing drop. I can gently slow the plane down and just keep pulling back on the elevator until it gets to stall and then it just elevators (falls) down. Once again not even the slightest hint of dropping a wing. It's a very straight, well built, plane that flies better in high alpha than anything else I've personally flown. I've also flown their 100cc version and it is just as good or maybe better.

RE: Elevator SNAPROLL
 

[sm=thumbs_up.gif][sm=thumbs_up.gif][sm=thumbs_up.gif]

Anything different from a clean jump from hanging form the wings to hanging from the propeller, will result in a 1/4 loop, at best.

RE: Elevator SNAPROLL
 

I'm still curious as to which airframe......

RE: Elevator SNAPROLL
 

Inexperience is apppears to be the real issue -at the moment.
The various hints already given all apply
Before you get even more frustrated, try this:

borrow or buy a good 32 ounce foamy- something with really high power and about 400 squares.
Practice the approaches to the harrier and the wall and any of the other abrupt flailing stuff currently popular.
basically the power is always chopped as elevater is slammed in.

NOW -be ready with rudder -NOT THE AILERONS!
All of the turns and snaps are due to the model yawing as the wing stalls
You can't trim a perfect hands off 3D flail and wail setup
You have to be ready for anything and that anything is usually a low wing and the fix AIN"T in the wing
WHY?
because it's thu flying at the moment so the only working controls are rudder and elevator
practice you will see what I mean.
You will get it
everyone does
The foamie just makes it less painfull if you goof.
One more thing
you have to balance the model back till it is really nuetral (and can be rotated easily in -say an outside loop with very little power
this is about 33% of ANY aerobatic wing setup -

RE: Elevator SNAPROLL
 

For whatever reason my AeroWorks 260 doesn't need to do a clean jump. I can't speak for other peoples planes but it certainly appears some are much more snappy than others. As I said in my original post, MY particular Extra 260 breaks cleanly into an elevator by simply pulling the throttle to idle and then slowly pulling back on the elevator, keeping the planes nose level, until stall is reached at which point it will simply begin to fall. 90% of the time it doesn't drop a wing or any other unexpected manuver other than an occasional wing rock which is the other 10%. It just drops. After the vertical drop begins, a very slight amount of power can be added to bring the nose up just slightly to keep it level.

I want to assure everyone that I have nothing to do with AeroWorks, and never have, other than owning their products which I paid for. It was bought second hand in a crashed state which I put it back together and it is the plane seen in my avitar. I spent a bunch of money on other planes that had snappy tendencies when trying to learn 3D so I learned the hard way. I finally found out about the 3D foamies, which I thought were a joke at the time, and like Dick Hanson said in his suggestion, I started learning the basics. I had the oppertunity to fly another person's AeroWorks Extra and fell in love with it. I couldn't afford one at the time so when the crashed bird became available I jumped at it. Never looked back.

I know this is a little off subject but I wanted to let the OP know that all planes, even those called 3D by their manufacturers, are NOT created equal. Some have MUCH better manners than others. I've now flown real good stuff by Carden, Wild Hare, AeroWorks and some others but none have been any better than my AW 260 in transition to stalled or "harrier" flight. The right airframe, properly balanced and setup, can make you look much better than you are. I'm still a beginner but at least I've found some stuff that flies good so I can learn instead of crash. Since getting the right equipment I've progressed to the point of being able to do controlled harriers a few feet off the deck and am able to do tail touches on the foamie as well as the big 50cc Extra.

One other thing I have picked up and is something Dick and others mention often, the lighter the wing loading the better they fly.

RE: Elevator SNAPROLL
 

About the only thing that a tail heavy plane with good power can do well is consecutive loops. It's the nose heavy planes and just simply too heavy planes in general that misbehave with too much elevator control.

RE: Elevator SNAPROLL
 

Afraid I'll have to call you on the 'tail heavy' remarks.

Get a Cap or an Extra with the CG slightly back of the neutral point and you will set (with luck) a new world's record for consecutive snaps. But you won't have much left in the way of an airframe.
I happen to own the record from a high altitude of 25 feet !!!!
That was about ten years ago and I am still impressed!!

Trust me, ........ you have no idea how sensitive elevator can get until you've experienced that.

GOD alone can fly such an airplane.

To describe elevator as "on a razors edge" is W-A-Y too blunt.
Pun intended.

RE: Elevator SNAPROLL
 

I disagree completely with anyone who says this is normal or due to inexperience:eek:

NO IT IS NOT NORMAL. If anything, a properly trimmed and aligned airplane should snap LEFT due to slipstream and p-factor. These usually over-rule the right yaw created by the gyroscopics unless you have a very heavy prop.

I suspect u have some rt yaw already built in somewhere. The first thing I'd try after re-checking for proper rigging etc in the tail group and wing is to start adding left rudder trim incrimentally, compensating with rt ail trim to keep the wings level, and repeat your hard pulls. Eventually you should reach a trim condition where it accelerated stalls go staight ahead and snaps one direction ot the other based on your whim, not the airplane's.

I have solved the problem of uncommanded snaps and hard rolling stalls on two models recently using this method.

RE: Elevator SNAPROLL
 

highhorse

I don't believe we suggested it was 'normal'. Simply that you must first define what really is an "untouchable" elevator.

If you take the logged RC aerobatics flying time of the four posters immediately prior to yours you will find that we combine for 167 years experience. One in that group is well published; three are long term expert class while the other is Advanced.
Not exactly newbies to the subject at hand.

You may feel that we don't know what we are talking about but that isn't true.

RE: Elevator SNAPROLL
 

I know what a tail heavy plane is capable of. I've flown AMA Fast Combat for 25 years, you haven't lived until you fly one of those off just a little. In the case of planes that are both tail heavy AND over weight, reference my other remark. A nose heavy plane will fly like it is effectively heavier than a plane that is properly balanced and will stall violently.The same exact plane set up tail heavy can turn so tight you would not believe it. Done it.

RE: Elevator SNAPROLL
 

Combat models are a different breed of cat
maneuvering is at full power always-unless you are a accomplished "whip power combat pilot"
Years back -I found that my 35 oz profile Nobler could be flown forever -after the engine quit -if a strong steady wind were available to work against.
anyway
the stuff which is popular with many RC guys is the " flail an wail" approach to flying , which started out as the freestyle TOC flopping about cross bred with the lawn dart stuff

The results took flying into a realm of " that's impossible".
As some of the old school boys may have noted, the rules for flight as taught foryears ,are seriously bent.
Too tail heavy?
well on some designs there is no "too tail heavy" rule
a very light model can be flown -under control with the cg at the trailing edge of the wing.
The flightcharacteristics may be horrible but it CAN be done
with a really sharp guy at the sticks -a model can be backed up vertically-for a few lengths-using a reversing pitch prop.
Anyway the 3D "destroy the airframe" approach does include full speed flight with sudden throttle chop and instant 90 degree stop and then hover
Also a fast vertical spin which is cross controlled and just as suddenly braked to a very slow spin
These approaches to entertainment are popular and are part of some new events -indoor electric is one which has some really amazing flyers.
The rules for setting up a nice flying scale model of a Cessna -really don't have much influence on these setups .
Back to my first rule of trimming
If the plane is light enough the cg does not matter
and if it's too heavy it still doesn't matter.

RE: Elevator SNAPROLL
 

I'm with ya Dick. I am trying, after 40 years of flying the old precision way, to learn how my teenage nephew does some of the things he does. Yes, I can now do the airframe killing "wall" into a hover and a few others like a blender. And contrary to my earlier opinion that backing an airplane up was impossible I've witnessed it being done. But for the most part I've got a long way to go before I become any kind of challenge to him in the "Wild" is art department. I have become a believer in your theory of lighter is better in this 3D/DownOnTheDeck, anything goes deal. My experiment into this 3D thingy has also taught me, Not All Airframes are Created Equal. Some manufacturers have their collective act together while others only wish they did. The ones who are doing the wishing, from my point of view, tend to be the old guard (not naming names here).

RE: Elevator SNAPROLL
 

Interesting ain't it
I fly with guys who fly/judge/run BIG contests as well as friends who just assemble ARFS and have others fly em for them
A pretty broad spectrum.
The aerodynamics discussions are also quite varied.
Voodoo aerodynamics as well as "how to trim a Cub"
Something for everyone
One friend flies flybarless choppers thru maneuvers I simply can not follow- at a breakneck speed.
Lately I have been enjoying my old H9 Clipped wing Taylorcraft - just doing touch n go stuff. the little ROTO gasser just sputtering along.
That and a little rip n tearing around with a 6 ounce 3D bipe -makes for a relaxed session.

RE: Elevator SNAPROLL
 

Ok, what the heck 27% airframe can hold a DA-85. 35cc's too much. I am guessing weight is the issue.

RE: Elevator SNAPROLL
 

All my Airplanes have a CG Slightly back of the CG and I NEVER EVER had an airplane even think about doing a snap, I do understand Aerodynamics pretty well and one wing will not stall faster than the other due to a rearward CG unless 1) Engine Torque is acting on it, or I should say Prop Torque 2) you have a heavy wing or The Airfoils don't exactly Match from wing to wing 3) you have a elevator sevro that is pulling faster or has more throw than the other (dual servos for Elevator) and I have seen the exact same servos new out of the box pull harder than the other 4) Laterial Balance is off.. 5)Wing Insidence is off, it is very possible that this has happened, you have to remember where these things are being built, do you think that they take to time to make sure EVERYTHING is right on when they are mass producing them? I can go On on and on, there are so many different factors to a snap that it is almost imposible to sit on RCU and Guess, the way you find the problem is check EVERYTHING one by one and adjust until you find the Sweet spot. As some people on here say, all airplanes are not created equal.

Alittle more about one wing stalling before the other, IF both wings have the same exact Airfoil and Weigh Exactly the Same, length is the same width is the same, they would stall at the same speed and same Angle of Attack (this is taking out the Torque factor)

A tail heavy CG would have no effect of that, I can get a Nose Heavy Airplane with more throw than a tail-heavy Airplane to throw the tail around faster than a tail-heavy airplane.

Wyatt

RE: Elevator SNAPROLL
 

That isn't what I said at all !

You need to look up 'neutral point' and to do a considerable amount of reading.
This isn't a characteristic of RC aircraft but of ALL such aircraft.

Go on-line, full scale aerodynamics ..............longitudinal stability (pitch), factors affecting,

Your stated values are shall we say a 'bit' unique.
Your last paragraph is, ........ well you evaluate it after you've spent a few hours reading and "playing" with some of the on-line visual displays which you will find offered as aids to your understanding of the concept.
You'll find it quite helpful.

RE: Elevator SNAPROLL
 

Well goodie for u.

1) I took NO issue with your comments regarding CG and thought they were spot on.

2) I'm no rookie myself, and have no interest in your collective resume's (yawn).

3) Re-read "Da Rock's" first post above and you will see that he, in response to the thread originator's question, unequivocally stated that the uncommanded right snaps are "normal".

4) They aren't.

RE: Elevator SNAPROLL
 

I know what Neutral point is... its the Point at which all Aerodynamic forces are equal And If you want me too, I can get out my Airframe Book from school and give you the Equation for it if you really want me too... I will be the bigger man here and admit I did misread your post and I Apoligize for that. With saying this My Statment is still correct... I was trying to help the guy with his problem, he stated that his CG is centered, If he says it is centered then why are talking about it ??? a Tail-Heavy CG would still not cause a plane to Favor one wing, if it does it would cause the left wing to dip not the right!, That is the whole point I am trying to get across, I do not wish to argue anymore, so I think I will take my ball and go home!

RE: Elevator SNAPROLL
 

Welllll............... actually what da Rock was trying to say was that it's normal for tapered wing models like the OP was asking about to snap very easy naturally and especially if the elevator had too much throw. It's quite normal for this forum to have relatively new modelers to our hobby wind up here wondering what's "wrong" with an Edge, Cap, Yak, Sukhoi, etc they just finished. It's usually the first tapered wing, non-trainer type they've flown. They're usually very sure the behavior that surprised them shouldn't be happening. And I must admit to feeling that the opening post was a repeat of that situation.

Sorry that I didn't use lots more words to qualify my response within that first sentence. I planned to lay it all out in the sentences that followed, but must not have.

But I will stand by my guarantee.
I have always guaranteed that if you're not entirely satisfied, there will be no additional charge. ;)

RE: Elevator SNAPROLL
 

The right hand snap is fairly normal
Why?
The single biggest reason is that the mode 2 flyer ,typically adds right aileron as they add elevator
This becomes automatic -and if the UP is pulled hard -the condition is exacerbated.
Don't believe it ?
I don't care .

RE: Elevator SNAPROLL
 

"Don't believe it ?
I don't care . "

I bow to superior logic.
With that 'ditty' you've established a new superlative. :D

RE: Elevator SNAPROLL
 

Re-read the original post please.

The poor guy quite plainly said that it's also breaking to the right during stalls. He didn't spec what type of stall, but it does narrow the problem down all the same to something NOT "normal". That was his question, whether this was "normal".

And rather than finding an answer to the man's question, I've read several posters re-defining the question to fit their apparently favorite canned answer. To wit: "You are stupid, we are smart. You are a newb with bad thumbs, we are vastly more experienced (167 years!!) and have golden thumbs. You should quake before the very might of our published experience and be grateful for the wisdom of our brow-beating. If you didn't SUCK, then the airplane would be flying just fine"

U think I'm off base in that analysis? Perhaps I am. But if you carefully re-read what is actually written above, one post at a time, then perhaps you could forgive my mis-interpretation.

RE: Elevator SNAPROLL
 

I guess for some ,this sounds harsh
But Imeant what I said - and to es'plain to those who misunderstood me -
I simply meant that it is a fact.
It is a fact that what we unconsciously do when flying , does NOT register as an error on our part
The tendenceny to pull right with up is as common as fleas on a dog.- We
"learn it"
Why?
one, it tends to overcome any prop forces which pull to the left AND cause some rotation at the sam time -and so we imprint that correction and do it automatically.
Two, unless one has a really good tray setup, a pure elevator input takes some careful hand training.
A thumbs only flyer has a better chance of moving the stick in a straight line
Anyone can learn to do it but the natural hand movement -using thumb and forefinger is to pull toward the palm.
accomplished musicaians on strings/woodwinds etc., ran into the same thing- learing to make unnatural finger movements .
Dave Brown -who was a past president of AMA- flew holding in a tiny bit of up elevator so that down lines and inverted sections of maneuvers required less "correction."
I tried it -but it did not work for me.
Neither does Mode 1
Actually, mode 4 (ail and throttle on the left)works for me -but not as well as mode 2.


Learned responses are both good and bad.

RE: Elevator SNAPROLL
 

I've got a .40 size Giles 202 that will snap to the right when you pull full up elevator. Is this normal. I've been told that they are designed to do that.

RE: Elevator SNAPROLL
 

You can ignore further helpful info of that type-

RE: Elevator SNAPROLL
 

kq, any model that has a highly tapered wing with a high enough wingloading will be prone to that when least expected or at the worst times...all the first planes I ever designed were very good at snapping until I finally got a clue.
If the wingloading is right, the tendency is dampered, even eliminated. My goal for a good handling model is to be able to use the elevator at will to make the model go up and down, not to make it stall to one side or the other. A good model in my opinion needs both rudder and elevator commanded to generate a snap at flying speeds.
Some "built in" tendencies that full scale planes have don't scale down very well or lend themselves well to good handling models.
There are a lot of great examples of 3D models of the full scale aerobats that have bumped the wing area way up past "scale" and are more forgiving than your average trainer. These planes will fly circles around their more scale like counterparts and avoid involvement in those messy garbage bag rituals better, too.

RE: Elevator SNAPROLL
 

Thanks Combat,
 The wingspan on this Giles is 49.5 and the wing loading is to the higher side. When test flying the model I almost lost it twice due to this snap at low altitude. I did not know that would occur. I have learned to not get into a situation that calls for full elevator.

RE: Elevator SNAPROLL
 

pigg hit on the stuff dick Hanson has been preaching for a long time. Wing loading, wing loading, wing loading. The heavier the wing loading the nastier the snap tendency.

RE: Elevator SNAPROLL
 

Ok, light is always better, the lightest model is the best.

However, what do you believe is a god compromise for regular mortals, like Santiagotor (OP) and kq4ra, who own a heavy model, and still want to have some fun with them instead of trying to sell them out or permanently hang them from a room ceiling?

Is the old CL trick of mixing elevator with flaps or flaperons a crazy idea that may help to palliate nasty snaps that are persistent in these RC models?[sm=idea.gif]

RE: Elevator SNAPROLL
 

Probably with such a big motor on the plane, it is trimmed to the left to stay level, and when the power is pulled back or it looses airspeed, the trim balance is gone. Latency in the radio mixes can be a problem too

RE: Elevator SNAPROLL
 

I'm ok with the plane as long as I know what to expect. It's the surprises that catch you off guard.

RE: Elevator SNAPROLL
 

It works like gangbusters in C/L but there's a difference and a caveat.

Coupled flaps are going to work safer than using coupled ailerons as flaperons. The flaperons can be a help, but aren't as safe a choice. There's also a good bet they'll have just as nasty a snap when you push the plane too hard. Since there is a tried and true proceedure already, why not try that first. Learn to fly the plane the way it needs to be flown. And consider trimming the amount of elevator deflection if that seems necessary.

The biggest problem we have with this edge/sukhoi/etc "suddenly snapping for no reason" problem is education. Way too many modelers have noone around them who know to warn them that a tapered wing aerobatic plane needs to be flown with the consideration tapered wing aerobatic planes need.