Wing tip up problem on new airplane.

LAST EDITED ON Feb-22-04 AT 07:43 PM (CDT)
 
I flew the new airplane today. It has a problem that I am not sure how to fix. The airplane wing flies level with the wing parallel to the ground. When I pull up to do a loop the outboard wing comes up about 6" and the lines get very loose. I have to take a step back to keep control of the airplane. After the loop is complete the airplane wing goes back to level or parallel with the ground again. I did not do any ouside manuvers it was not flying good enough to try that. There is no twist in the wing because it flies level. It does not fly with the wing tip up or down. If one of my combat airplanes has twist in the wing it will fly with the wing tip up or down depending on the direction of the twist. I have lots of adjustment on this airplane. First flight it had too much elevator so I changed it on the 2nd and 3rd flight. I did not have a longer control horn with me so I could not fix the problem but I made it better by moving the linkage all the way to the end of the control horn. The outside wing tip still comes up about 6" in a loop. Wings looks straight, flaps look straight and even, stabilizer looks parallel to the wing, elevator looks straight too. Wing tip weight is about 1 oz. Inboard wing is 1" longer than the outboard wing. Outboard wing coming up or inboard wing going down same difference. My fuel tank is too small but I know that when I built it. I can remove the trap door and replace the fuel tank when I get the bugs worked out. The unaflow tank that I built is working great. When the fuel gets low the last 2 laps are wide open the Nobler must be doing 70 mph. A 5 minute flight is long enough until I get all the problems solved. The extra 1.5" length of the fuselage made a big difference is how much leverage the elevator has on turning the airplane. Wing flaps are 20 deg max. up/down. I changed the elevator from 45 deg to 30 deg and it is still to much. Wing tip line adjustment is forward a little too far the airplane pulls hard when it flies but thats fine until I get the wing up problem solved. The 4" long exhaust tubes worked great. I had only a tiny amount of oil on the stabilizer and elevator. I got all the engines to run a 4-2-4 today the OS Max 40LA and the McCoy 35. 4-2-4 it neato. The airplane seems like it is flying too slow then when I pull up the engine goes full speed ahead, cool. The rebuilt McCoy 35 engine on the Flite Streak runs fine and the airplane flies great I got in 6 flights with it. My square loops are nothing close to square. 1st and 2nd 90 deg turn is fine then after that, you just never know whats going to happen next it might be round, triangle, parallagram, trapazoide shaped. The repaired RingMaster flew good on the 1st flight about 10 laps into the 2nd flight the airplane made a strange vibration sound and the engine stopped. I lost the needle valve in flight. I don't have an extra needle valve. Anyone have any ideas on the wing tip up problem on the Nobler?

[photo not recovered: funfly.jpg]

Gary,

The problem can't be diagnosed with any degree of accuracy unless you tell us what happens during ouside manuvers as well.

LAST EDITED ON Feb-22-04 AT 08:03 PM (CDT)
 
Looks to me like it has a low wing, leadouts through the wing, so a vertical CG problem is indicated. If it flies with the wing level in level flight, then there is a warp that counteracts the inboard tip high (caused by the vertical cg being too high for the leadout location). If you fly it inverted, you'll find that the VCG and warp will make the inboard tip fly low...two working together, instead of opposing, as when upright. At the top of an inside loop, the inboard tip is low, and line tension disappears.

Raising the leadouts, dihederal, heavier wheels, mounting the engine inverted would all help...some combination of the above might do it. Try hanging it from the LO's and try heavier wheels, then rotate the engine, if you can. Raise the LO's if you can. Otherwise, chop the wing out of the fuselage and build a new fuselage. You'd still need to do some flap tweeking. Steve

PS: Where's the Nobler? I don't see a Nobler in the picture.

I think you've got it, Steve.

>Looks to me like it has a low wing, leadouts through the
>wing, so a vertical CG problem is indicated. If it flies
>with the wing level in level flight, then there is a warp
>that counteracts the inboard tip high (caused by the
>vertical cg being too high for the leadout location). If you
>fly it inverted, you'll find that the VCG and warp will make
>the inboard tip fly low...two working together, instead of
>opposing, as when upright. At the top of an inside loop, the
>inboard tip is low, and line tension disappears.

I'm puzzled by this. If there is a grossly-off vertical CG (and it's probably off by 1" or so, maybe, looking at the picture) covered by a warp in the other direction, why does the roll angle change in the maneuvers?

To the extent described, it sounds like a perfectly classic case of inadequate tip weight (and probably combined with too-far-forward leadouts or excess rudder offset). If the wings are level in level flight to the extent observable, this is perfectly consistent with inadequate tipweight in conjunction with a vertical CG offset. If the vertical CG is off by 1" (in say, 25") it ought to be rolled outboard/right a little over 2 degrees all the time. If its level, it probably needs tipweight added until its rolled 2 degrees when upright. Also, if it has inadequate tipweight, it will hinge torwards you in the maneuvers - just exactly like it did.

I think it would be highly worthwhile to load in enough tipweight until it's flyable, then see what it does on outside maneuvers - certainly before jumping to the conclusion that it needs to be cut up!

A vertical CG error causes a steady-state roll angle - a very small roll angle. If everybody trimmed their airplane for a perfectly constant 2 degree roll angle, most of us would be very happy with the results, I suspect. I've managed to go a lot of years without really ever thinking about it - and it certainly doesn't cause gross hinging! If everything else is right, it will not likely cause an insurmountable trim problem.

Do what Brett says.

Expanding the flight envelope on a new plane is an incremental process. To do it safely, do not do another inside loop until you have made some changes. The plane will behave the same and you might not save it the next time.

Examine your plane carefully and make adjustments before the next flight.

The previous reply stated insufficient information. You might have a combination problem ie two problems masking or enhancing the symptom. ie

Too much tip weight and a wing warp, or

one stiff flap and one flexible flap,Or

too much tip weight and differential flexible flaps, Or

Wing and stab horizontal alignment is not parallel,Or

Engine thrust line is inboard to the arc of the flying circle, (which is caused by improper leadout position or improper wing alignment with respect to the longitudinal axis of the plane.

There are many possibilities as previously stated but you need to isolate, examine and eliminate possible problems to a short list, make changes then do a flight test to slowly explore the behavior but quickly return to safe flight if the symptom persists. If the symptom is gone, continue to expand the flight envelope.

Does the outboard wing drop on outside maneuvers such as a dive? This means the outboard wing is producing more lift than the inboard wing. Suspect the flaps.

I have seen some very flexible flaps on several airplaness to the point where they flex up to 30 degrees from the horn input. This is a useless control surface. If you have one stiff flap and one flexy; wieird things can happen such as you have described.

Someone told me to take your plane, stand about 15 feet away from a mirror point the tail toward the mirror and look at the stab, flap wing alignment and for any warps in all surfaces. You are looking for equal frontal area above and below the flap trailing edge. Anything other than that is a crooked wing requiring the wing to be dewarped or the flaps tweaked. This might tell you something.

Also check your control systems. Holding your flaps fixed with one hand, depress each elevator together and separately. You are looking for rigidity and flexure under flight loads. This might give you some indication of a problem in flight. Then hold the elevators and apply pressure on the flaps and do likewise. Then hold the leadouts rigid in both the up and down position and do the same thing again on the flaps and elevators. Again you are looking for weird stuff like flexing pushrods, flexing elevator or flap horns or flexing flaps or elevators. You might for example have an exceptionally flexible inboard flap as compared to the outboard flap causing differential lift.

So, in summary, you are looking for warps, flexibility, differential flexibility as possible problems.

You did not indicate how the plane behaved inverted.

If you find a problem on ground inspection; correct it before the next flight

Next flight do wiggles up and down observe the wing behavior, observe the line tension. You stated you lost tension on insides and the outboard wing lifted. You might gain additional tension on outsides. Signs of a warp somewhere or unbalanced control loads caused by flexible control inputs. One once of tip weight in upright flight can mask a wing warp causing additional lift on the outboard wing on insides.

I did not discuss tip weight, engine offset, leadout position assuming you are aware of those factors.

You also did not indicate your line length and was the engine run under normal power nor the lap time of your plane to consider sufficient centrifugal force for normal control operations.

Bob Smiley
A Lancair 360 builder/pilot trying to be a modeler

>I flew the new airplane today. It has a problem that I am
>not sure how to fix. The airplane wing flies level with the
>wing parallel to the ground. When I pull up to do a loop
>the outboard wing comes up about 6" and the lines get very
>loose. I have to take a step back to keep control of the
>airplane. After the loop is complete the airplane wing goes
>back to level or parallel with the ground again.

Add tip weight - a lot, like 3/4 oz.

Sometimes the simplest answer is the best place to start. Go for Brett's suggestion and try again.

Bob Smiley

The inboard wing is heavest because its longer and it has lead outs on that wing. It takes 6 quarters and a nickel = 39 grams = 1.365 ounces to make the wing balance. Is the wing suppose to ballance? Should I put 39 grams of lead in the wing tip?

>The inboard wing is heavest because its longer and it has
>lead outs on that wing. It takes 6 quarters and a nickel =
>39 grams = 1.365 ounces to make the wing balance. Is the
>wing suppose to ballance? Should I put 39 grams of lead in
>the wing tip?
>
>Gary Weaver [email protected]

No, not necessarily. We could get fancy, but I would recommend just going to trial-and-error at this point. Put in enough that is doesn't roll in at you in maneuvers - start with 3/4 oz (i.e., A LOT), but that's just to start. It may be too much (which is OK a this point) or not enough (which isn't OK). Once it's not rolling in at you, you should be able to safely do stunts and then we can try to see what you really have and what direction to go.

Just out of curiosity, how much tip weight to do you have now? When you pick up the airplane by the prop shaft and rudder, does the right wing flop down, or does the left?

I have 2 lead weights in the wing already about 1/4 ounce total.

When I pick the airplane up by the propeller shaft and rudder the left wing goes down very quick I can tell it is heavy. Seems logical it would be heaver because that wing is longer and has the leadouts in it. If I put 6 quarters and a nickel on the right wing for counter balance the wing is level.

I would take Brett's lead .

>I have 2 lead weights in the wing already about 1/4 ounce
>total.
>
>When I pick the airplane up by the propeller shaft and
>rudder the left wing goes down very quick I can tell it is
>heavy. Seems logical it would be heaver because that wing
>is longer and has the leadouts in it. If I put 6 quarters
>and a nickel on the right wing for counter balance the wing
>is level.
>

To first approximation, on well-trimmed airplanes the RIGHT wing drops smartly with no lines attached. Lack of tipweight is most certainly at least one very serious problem you have - there may be others but we'll never know unless you fix the tipweight.

You're further along than you think. If it balances with 38 grams (6 quarters and a nickel - just weighed it), you probably need about 55 grams - maybe an ounce and a half or two ounces more than you currently have. I'm well and truly amazed that the inboard wing is that much heavier, but it is what it is.

Don't worry about the total weight from adding that much. A slightly heavier airplane that is in trim is infinitely better than a slightly lighter airplane that is not in trim. I have a sneaking feeling that 2 ounces will be more than necessary once we get everything else right, but there's nowhere to go if it's trying to chase you.

By the way, for the rest of us - what Gary did (balance the airplane in roll) is a very smart and useful thing to do. All this talk about "N grams of tipweight" really means nothing unless you first balance the airplane laterally. Anything I say about tipweight is *excess* to what it takes to balance the airplane.

>(snip) By the way, for the rest of us - what Gary did (balance
>the airplane in roll) is a very smart and useful thing to
>do. All this talk about "N grams of tipweight" really means
>nothing unless you first balance the airplane laterally.
>Anything I say about tipweight is *excess* to what it takes
>to balance the airplane.
>
> Brett

Totally agreeing with you, Brett. It is sort of like those who say, "My engine flew right out of the box. I didn't have to do anything to it." Yes, but what was your engine? What venturi came with it?...what deck height?...and a number of other questions. What we have learned to do once we have the plane in trim is hold the airplane upside down by the prop and tail wheel and weigh the outboard tip on a gram scale. This way you know exactly how much extra tip weight was needed to get the plane in trim. This can then be a starging point for the next plane of similar design. To say, "Add 'x' amount of weight without knowing how it balances laterally is meaningless. I have a couple of planes where we over did the tip weight box and never had to add anything into it. The weight box itself did the trick.

>
>>(snip) By the way, for the rest of us - what Gary did (balance
>>the airplane in roll) is a very smart and useful thing to
>>do. All this talk about "N grams of tipweight" really means
>>nothing unless you first balance the airplane laterally.
>>Anything I say about tipweight is *excess* to what it takes
>>to balance the airplane.
>>
>> Brett
>
>Totally agreeing with you, Brett. It is sort of like those
>who say, "My engine flew right out of the box. I didn't
>have to do anything to it." Yes, but what was your engine?
>What venturi came with it?...what deck height?...and a
>number of other questions

But at least you expect engines built on CNC machines to be at least awfully close to each other. The airplanes are obviously not that way and depend VERY WILDLY on the builder and the materials. That's why it takes so much longer for expert builders to build an airplane than a sport flier. Once you have a lot of experience, you know all the places where it can go wrong, and spend a lot of extra time to get it right.

My next questions is, what is the best way to build a weight box for the wing tip. This will be the best thing to do sence I will have to experement with changing the weight until I get it right.

Gary, In a previous post you said

"I use .045 copper plated steel welding wire for lead outs."

This may have something to do with the heavy inboard wing.

You can make a tip weight box out of 1/8" plywood, several ways to configure it depending on the airplane and how much height is available in the tip, if the tip is thin put it on the inside of the last rib up next to the spar. The tip weight box Brodak sells has a blind nut in the bottom with a long screw that holds the cover on.

Gary:
Before you build an internal box, consider using exposed tip weights, but not the sticky-tape kind. I made a base of plywood in the shape of a triangle gusset inboard of the tip, between the spar and outboard rib, epoxied a T-nut into it, epoxied it flush with the lower covering surface and monokoted over it. Don't worry about the heavy epoxy since you need the weight anyway. I used SIG weights with the hole in the center and a 4-40 bolt and let 'em hang in the breeze. Used a drop of white glue over the bolt head as a locking feature, too. If anybody notices, and I doubt they will, say it's a tip skid. And, since it'll hang below the vertical balance point, it might help you with that, too. I had a Veco Chief that wanted to wander into the center and it's exciting flying that way! Have fun.

Rollin Keszler

Rollin, that may get you "in the ball park" but I much prefer the weight box where you can use steel shot or some such and vary the amount of tip weight by degrees. Put in some cotton or wad up a piece of paper towerl to wad it in tight. And don't use lead shot. It will turn to powder as the little shots vibrate against one another.

With a new plane that I know very little about, I follow a quote from a Paul Walker article (Impact I believe) that says to put enough tip weight that the outboard tip just falls when the plane is upside down on the table. Not crashing down, but gentle. This has worked, so far, to get "in the ballpark" for the first flights, at least.
Bill <><

LAST EDITED ON Feb-23-04 AT 10:38 PM (CDT)
 
I just finished making a lead weight for my Nobler and glued it on with epoxy. I removed the 2 small weights in the wing tip and replaced them with one 40 gram weight. I will probably need another 10 to 20 grams in the weight box. The 40 gram weight will get me close to the ball park. I will make a weight box tomorrow for steel BB's at work then do some test flights. I have lots of steel BB's for the BB guns.

LAST EDITED ON Feb-23-04 AT 08:06 PM (CDT)
 
Well, Folks, in Gary's last post, he's said he's going to do a bunch of things that others have specifically said to avoid...taped on tipweight...a weight box with lead shot in it...I think maybe Howard has the right idea. It doesn't matter what anybody suggests, Gary's in his own timezone. Too bad. I hope nobody gets hurt in the forthcoming accidents. Steve

I just agreed with you and Brett. Looks like the light tip would have more effect than the high CG, though.

Taping on the tip weight does sound imprudent.

>I just agreed with you and Brett. Looks like the light tip
>would have more effect than the high CG, though.
>
>Taping on the tip weight does sound imprudent.

Sorry, Howard. I thought you were just agreeing to avoid making any more suggestions for Gary to ignore. Steve

PS: I MAY be a bit cranky today. I had another vehicle clip the end of my rear bumper on the way home. Scuffed the end of the bumper up a bit worse than it was already, and put a serious crease down the whole length of his Chevy Cavalier. But he looked back, and kept going. I chased him down, and got him stopped (not at gunpoint, but that was next option available), and police. I don't know the miles I "chased" (at the speed limit) him, but from 116th & 256th (over nearly to PW's house) over to 245th & Benson. A couple of miles, I'd guess. I hope it costs him his license and insurance.

Hi

It could be a combination of things though I think Brett has the most likely cause pegged. This seems to be a good place to start a process of elimination. Check the CG in the spanwise direction.
It has to be outboard of the geometric centre of the wing. The outboard tip is traveling faster than the inboard tip so generates more lift. The centre of lift is therefore a little outboard of the wings geometric centre. The CG must be aligned with the centre of lift, at least in the spanwise direction. If this is not done, lift through the centre of lift and weight/enertia through the CG form a moment couple that will roll the plane. In level flight, the roll is not very noticable because line tension opposes it easily. In a manouver, lift and enertia are vastly increased while line tension is not so the roll increases dramatically. That exactly fits the symptoms you describe.

I can calculate the spanwise CG offset necessary to align with centre of lift. Just e-mail me the span and flight circle radius: [email protected]

Then you can at least check if you have enough tip weight. That will either confirm or eliminate this as the cause of your problem.

On another forum a long time ago, far far away, many of us argued with him about flaps, remember, and still he comes up with them hooked up wrong. Why do you still bother? Another time zone? More like another time dimension.

>On another forum a long time ago, far far away, many of us
>argued with him about flaps, remember, and still he comes up
>with them hooked up wrong. Why do you still bother?

Ah yes, I remember it well. But he was polite.

He had an easy-to-diagnose problem that could be solved quickly and provide a good example.

>>On another forum a long time ago, far far away, many of us
>>argued with him about flaps, remember, and still he comes up
>>with them hooked up wrong. Why do you still bother?
>
> Ah yes, I remember it well. But he was polite.
>
>He had an easy-to-diagnose problem that could be solved
>quickly and provide a good example.
>
> Brett

Yes, unlike the issue with the effect (or not) of stock mufflers on things like 25FPs.

I am the type of person that, "Questions all the answers and Answers all the questions."

When someone tells me, "When the flaps go down the elevator must go up. That is the way we do it. We have always done it that way." I have to ask the question, "WHY."

You never learn much in life if you don't experement and do it yourself to see what happens. I want to do it the right way and the wrong way on purpose just to see what happens.

How narrow minded can a person get just to play follow the leader and except the fact that someone said do it like that and never ask why.

Asking questions until you understand is good. And in your case, doing the experiment didn't hurt anything. However, you also apparently didn't have the cg where it should be, either, so some of your conclusions weren't what they should be. However,

I don't shoot dope, I don't drink and drive (I don't even drink--well, alcohol stuff). I never smoked, and I don't play in busy streets. What would have happened if in trying the experiment you had crashed? Some things can be learned without trying. And, after all these years, one would think that this would be the correct way to hook up the flaps. Certainly you weren't the first to try it "backwards" "just to see".

Good for you, Gary. One of the cool things about these airplanes is that we can try anything we want, and usually nobody and not much stuff gets hurt. They don't let me experiment nearly as much with the airplanes at work as I do with the ones at home.

>Good for you, Gary. One of the cool things about these
>airplanes is that we can try anything we want, and usually
>nobody and not much stuff gets hurt. They don't let me
>experiment nearly as much with the airplanes at work as I do
>with the ones at home.

Sometimes an experiment like this will help us to understand the dynamics of what is happening and why. And then from there we may be able to "go where no man has gone before" (I never understood why they said that at the beginning of every Star Trek episode and then wherever they went they met someone who got there before them.)

I, too, try to learn why things happen and then see if I can make them work better. ("Tim, the tool man, Taylor" was always my hero--until he messed it up) To "question all answers" (and I don't think Gary really intends to do this) can lead to a very dangerous situation--like when your mother says, "Don't put your hand on a hot stove" or when someone says "Make sure the rudder doesn't point in". Some answers can be accepted by reason or faith (that person knows what they are talking about) without having to question them.

>With a new plane that I know very little about, I follow a
>quote from a Paul Walker article (Impact I believe) that
>says to put enough tip weight that the outboard tip just
>falls when the plane is upside down on the table. Not
>crashing down, but gentle. This has worked, so far, to get
>"in the ballpark" for the first flights, at least.
>Bill <><
>
>Just an Old Advanced flyer.

With all due respect to Paul, that answer is only good for certain planforms. Paul's planes all have a modest amount of assymetry ... longer inboard wing. I don't really know exactly how much but some. Equal span wings would be an entirely different matter, requiring significantly more weight. Greater amounts of assymetry would require less. It is entirely possible with enough assymetry to actually get to a point where (balancing on the fuse centerline) the inboard wing will be heavier.

This is really nothing more than realizing that we aren't really making one wing longer or shorter. In reality we have a single wing and the question is where we choose to mount the fuselage on that wing. Mount the fuse far enough outboard of the geometric centerline of the wing and it does exactly the same thing as adding tip weight to the same airplane with the fuse centered.

The ultimate aim of tip weight and wing assymetry and so forth is to balance the lateral (spanwise) center of lift to the lateral center of gravity. this doesn't necessarily mean co-located but will pretty much always be close. This adjustment is due, of course, to the fact that the further out the wing the greater the speed in our circular flight and, therefore, the greater the lift. Ergo, the lift produced isn't concentrated at the geometric center of the wing the way it would be on an untethered machine.

Now there will be other considerations that we haven't addressed. Most notably the eventual location of the thrust line relative to the center of gravity. For good take off performance (tight lines) the thrust line should be at least directed through the center of gravity and ideally slightly inboard. The greater we make wing assymetry the further out the thrust line moves and we start to aggravate take off tension (anybody flown an All American with no engine offset?!!!). Thus, like everything in the stunt world we must work around appropriate compromises to achieve a synergystic outcome.

How's that for psychobabble doubletalk!

Hi Ted,
No argument from me on your comments. I didn't get into "which" planes I was talking about. Usually it is a modern ship where I just have the plans, or drawings, and like I said, for these types, it usually gets close enough so that I ain't running like a scalded dog to keep the plane in the air! LOL!!
It's a testament to your post that my Argus ('58-'59 version), and my Ares, to name two, do not have wing tip weight. After asking the foremost authority, IMHO, about these types of I beamers, he said he never added any WT weight when building, just some clay in special occasions. I tried it and yep, they trim out pretty good in most occasions without the weight.
It is a matter of design parameters, no?
Thanks for your input,
Bill <><

Thus, like everything in the stunt world we
>must work around appropriate compromises to achieve a
>synergystic outcome.
>
>How's that for psychobabble doubletalk!

Well, you managed to get "synergistic" in, but you didn't work "paradigm" into the discussion. You have a way to go before you manage full use of non-sequiter buzzwords.

Brett "Using a team approach with personal empowerment of individual contributers to achieve a synergistic paradigm" Buck

>
> Brett "Using a team approach with personal empowerment
>of individual contributers to achieve a synergistic
>paradigm" Buck

I can only bow to the master.

Is this value-added?

>Is this value-added?

I left that out on purpose because it could represent actual content.

Brett "I'll follow ISO 9000 Command Media from now on" Buck

LAST EDITED ON Feb-28-04 AT 07:21 PM (CDT)
 
45 grams of wing tip weight fixed the problem. It flies great.

And you did what? to fix it???

>45 grams of wing tip weight fixed the problem. It flies
>great.
>

Glad to hear it, and happy to help.