Hingeing

Can someone please explain what the causes of hinging are, particulary in non-flapped ships

Thanks
Adrian

Adrian,

Hinging is usually caused by excessive wing-tip weight.

>Can someone please explain what the causes of hinging are,
>particulary in non-flapped ships
>
>Thanks
>Adrian

Adrian,

Simply stated hinging (the dropping of an outboard wing during maneuvers) is the result of the spanwise location of the Center of gravity being located outboard of what we casually call the center of lift.

When the two "centers" are co-located spanwise the increase in "g-force induced weight" of the airplane in a maneuver is supported at that same location by the increased lift the wing is generating to support the ship during the maneuver. this is like balancing a plate on your finger tip. If you add a dollop or two of mashed potatoes right on the balance point over your finger the plate will stay balanced...it'll just be heavier.

If, on the other hand, you put the potatoes off to the side so you've got more room for the slab of roast beef the plates going to fall off your finger in the direction of the mashed potatoes.

Most of flight dynamics are pretty much this sort of teeter/totter juxtaposition of forces which must be kept in balance to achieve controlled flight...either in a straight line or in controlled maneuvering.

Now, how you come up with that imbalance that results in the "hinging" phenomenom is a more complex issue. Let's take a likely scenario with your unflapped aircraft.

Your plane is most likely a profile ship. It is also likely that as a beginner or intermediate flyer (excuse me if this is too great an assumption--but carry on with the analysis) you may well be more aggressive in the use of "devices" to insure line tension. these might include, for instance, offset rudders, engines and more aft leadout exits from the wingtip and a goodly amount of tip weight. It is also possible that you have chosen to keep the fore and aft CG more forward than a more seasoned stunt pilot might prefer.

All of these trim factors might well result in an aircraft that flies yawed (turned) outward from the center of the circle more than is in you best interest. When such a ship flies around the flight hemisphere the fuselage, angled out as a result of these trim devices, is flying more or less sideways to the airstream. As a result, much of the inner part of the outboard wing may be less efficient in producing lift than it would be if the ship was longitudinally more tangent to the flight path.

You can see that the result is likely to be more lift being generated by the inboard wing. When you couple that with the natural tendency for a profile (with the engine and tank mounted outboard in addition to the tip weight you've added) to be outboard wing heavy you have pretty much put all your mashed potatoes on the edge of the plate. The result can well be the hinge you describe.

There are a lot of other variables that can contribute to what's happening but for now, does any of the above seem to fit your experience with your ship?

Ted Fancher

Ah yes,

The meat and potatoes answer, well, that reminds me that I'm hungry so I guess I'll go to the Glory Days Grill for some good food and a confusing array of TV's all on sporting events!

P.S. I still kind of like my KISS principle answer, even though it's probably not completely accurate.

Fantastic Jim with the KISS answer and thank you Ted for an in depth vegetable analysis! I think there is indeed too much yaw on this plane for several reasons hence the hingeing. All explained wery well - many thanks both
Adrian

>Fantastic Jim with the KISS answer and thank you Ted for an
>in depth vegetable analysis! I think there is indeed too
>much yaw on this plane for several reasons hence the
>hingeing. All explained wery well - many thanks both
>Adrian

You're cauliflo...er, uh...welcome.

Ted

p.s. Let us know if you improve the problem.

>You're cauliflo...er, uh...welcome.
>Ted
>p.s. Let us know if you improve the problem.

Hi Ted
We flew today and this is what happened - improvement - absolutely....

Actually, I must own up - it wasn’t my plane but a very good friend of mine with whom I fly every week. The plane was flying out of the circle (pointing towards France I guess!!!!) – too much yaw by far. Everything looked OK except the rudder which had masses of offset. Mike cut the rudder off and stuck it back on with cyano – just enough offset so it wasn’t pointed the wrong way. He flew it this morning. It was a different plane. No hingeing at all. No nasty yaw. I guess more thrust was available for the right direction – anyway Mike reckons there was a bit more speed and consequently pull. A very happy Bunny indeed.

Many thanks for your help and thoughtful Forum posts - a really good insight into some of the causes of hingeing.

Ted, "simply stated"? Big chuckle.

>Ted, "simply stated"? Big chuckle.
Well, shucks, Ty. Simple doesn't always mean "short"!

LAST EDITED ON Dec-04-04 AT 12:31 PM (CST)
 
>Hi Ted
>We flew today and this is what happened - improvement -
>absolutely....
>
>Actually, I must own up - it wasn’t my plane but a very good
>friend of mine with whom I fly every week. The plane was
>flying out of the circle (pointing towards France I
>guess!!!!) – too much yaw by far. Everything looked OK
>except the rudder which had masses of offset. Mike cut the
>rudder off and stuck it back on with cyano – just enough
>offset so it wasn’t pointed the wrong way. He flew it this
>morning. It was a different plane. No hingeing at all. No
>nasty yaw. I guess more thrust was available for the right
>direction – anyway Mike reckons there was a bit more speed
>and consequently pull. A very happy Bunny indeed.
>

Adrian,

That's great. I'm happy the suggestions made a difference. (See, Jim. It isn't always simply too much tip weight. )

You make a great observation about the change in line tension associated with the rudder adjustment. That result doesn't surprise me and I'm glad you mentioned it in your post. I have a tendency to go on and on at too great length on some of this stuff and I purposely tried to stop short on my response.

But, your observation is very important and something that everyone learning to get around the circle in better style could learn from. Here's a few more "too long" comments.

(For those whose eyes glaze over after a couple of paragraphs, here's a Reader's Digest version of what will follow.)

The primary source of line tension for control line flight is almost entirely the result of the weight of the airplane, the speed of the airplane and the length of the lines. Pretty much all we can do is optimize that available tension in a manner best suited to our needs. We can do almost nothing to increase the tension but can throw a lot of it away by inappropriate flight trim.

Stunt airplanes should fly with the fuselage roughly tangent to the circle to slightly yawed out as Igor and others have discussed on those lengthy forums. The slight outward yaw will actually cost us a minimal amount of line tension in level flight but will allow the airplane to be flown at slower speeds and at other than level flight attitudes while still retainin a large portion of the level flight tension.

Any thing that slows the stunter will reduce line tension. Drag is an obvious culprit but so is "mis-vectored" thrust. Any thrust directed out of the circle will reduce forward thrust and the airplane slows. Any yaw out of the circle will produce excess drag (and will simultaneously direct the thrust vector further away from the direction of flight.

Any roll angle toward the pilot will produce a lift vector into the circle and will reduce line tension. Of course, it is also true that a roll away from the pilot will vector lift away and increase line tension. If the roll is the result of a warp you will get assisted tension when flying in the direction (upright/inverted) in which it is rolled away but decreased by the inward roll the oppposite direction.

Adding tip weight to a wing with an existing uniform roll condition (ideally zero) will increase line tension in both directions but, if excessive, will result in other deleterious effects as Jim Pollock mentioned; i.e. hinging.

Finally -- and I do not understand the reason for this -- even at identical speeds and aerodynamic trim conditions, some powertrain systems will produce more line tension than others at the same lap time. I reiterate, I do not understand this and hope that someday someone will come up with a good explanation.

The Long Winded Version

By far the greatest resources we have for line tension is the speed and weight of the airplane we're flying. As we all know, you can get line "tension" from an unpowered bucket of water if we spin it around in a circle fast enough. Simply put, if we want more line tension from a given c/l airplane, the easiest way to get it is to fly faster.

Of course, when we want to fly "precision" aerobatics, flying faster isn't always desireable. What we need to do with our stunters is to find a trim condition that maximizes the line tension produced by a stunt ship at a speed that is comfortable for us to fly precisely. That's a lot different goal than simply making the ship pull as hard as it can in level flight.

The vast, vast majority of that available line tension will be derived from eliminating out of trim conditions that "reduce" tension in difficult parts of the hemisphere. In other words, what we need to do is maximize our ability to retain enough line tension throughout our flight so that tension is adequate at all times to allow the control inputs necessary to do our tricks. It must be accepted that the resulting tension isn't likely to pull your arm off once you leave level flight, by the way. Part of developing advanced stunt flying skills is learning to perceive and deal with "acceptable" line tension rather than assuming the ship will always pull hard.

Let's look at an extreme based on your experience with your friend's ship.

You observed that the airplane had excessive rudder offset in an attempt to produce "line tension" and keep it from flying "into" the circle. Reducing the offset not only solved your "hinging" problem but improved the overall line tension in flight. The increased line tension wasn't an intuitive outcome. But it was real. How come?

Let's see what is accomplished by "offsets" by taking them to an extreme. If we were to attach the control lines to the tail of the airplane we will have achieved the Ultimate Offset on all the devices normally thought of as means to produce line tension.

The engine will be offset 90 degrees to the desired flight path; all of its thrust will be vectored away from the center of the circle. The control lines will be in the ultimate offset condition, aligning the airplane such that the entire thrust of the engine will be directed away from the circle center. (forget the rudder, it's just going to confuse us in this silly scenario)

What have we achieved? We have aligned all the force intended to make the ship fly directly away from the circle center. The result will be "zero" airspeed (the airplane won't even roll, let alone fly) and the only source of line tension will be the static thrust of the engine...a couple of pounds more or less.

And remember, static thrust is not indicative of inflight thrust where at constant velocity flight thrust is equal only to the drag of the airplane. This is a difiicult concept to get one's head around. When you hold the airplane on the ground what you feel from the engine is static thrust. This is a pretty good measure of how fast the ship is going to accelerate once you let go of it but has very little to do with how fast the ship will ultimately go. In fact, for a given engine, it is close to correct to say that the harder it pulls on the ground the slower will be the ultimate airspeed when thrust equals drag. This is the low gear concept where you could compare the pulling power from start of a automobile starting from zero in high and or low gear. It will ultimately go faster in the high gear but will be very slow to accelerate. In the low gear it will accelerate quickly but peak out at a relatively low speed.

As we stated before, it is ultimately the speed of the vehicle that produces our line tension.

Getting back to our stunt ship tethered to the pilot through its tail...

Of course, doing any tricks is out of the question because at zero airspeed the wing produces zero lift. Give the elevators full up and nothing will happen because the tail is on the ground, the wing's not producing any lift to speak of and, besides, the airplane can't go anywhere so any pitch axis tricks are out of the question.

Not a good way to fly stunt, I think we can all agree.

Now, let's gradually bring our leadouts from out of the tail forward toward the inboard wingtip and evaluate what happens at intermediate positions. Let's look at the leadouts at a point 45 degrees aft of directly out the wingtip.

We now have a real hermaprodite situation. The airplane will (as discussed in other threads) now be flying with the CG lined up pretty much with the leadout guide (some aero modifications will result from the lift produced by the fuse and the rudder, let's ignore them or consider them to be minor annoyances for now). The result will be a flight path roughly at 45 Degrees to the fuselage.

Flying at this angle the fuse (especially a flat profile) will be producing enormous drag thus sucking up large amounts of thrust and decreasing the airspeed of the airplane. Both these conditions will reduce line tension greatly. In addition (as Adrian's friend discovered) the airflow over the outboard wing will be anything but smooth and the lift it is capable of producing will be reduced commensurately). Not good!

The engine thrust is now vectored outward 45 degrees. Sounds like a good deal but really isn't. A huge part of the thrust is being absorbed in the same manner as when pointed directly away from the pilot and does nothing to produce the thrust necessary for flight. We have wasted a lot of thrust and vectored what's left dramatically from the directions necessary to produce airspeed which is necessary for the airplane to perform its aerobatic functions.

Just for fun, it is worth noting the use of large offsets in other c/l disciplines. Note how the modern navy carrier ship uses this exact concept -- far aft leadouts and the huge thrust offset that results -- during their "low speed" flight regime largely carried out with the engine at very high thrust. At the very low speeds which result, the line tension is clearly an issue. Very careful and skillful pilot technique is required to keep the airplane flying forward and under control inasmuch as the primary source of line tension is now solely the vectored thrust. Note also that the low speed carrier ship uses not only yaw but also large amounts of outboard roll (right aileron, if you will). Remember how we mentioned tension could be generated by vectoring the lift of the wing away from the pilot? These guys do it in Costco bulk quantities.

Next, note the large amounts of offsets on fast combat ships particularly leadout sweep. But, you say, these ships go like blazes. Yup, they do. Part of the reason (other than a monster power loading) is the lack of a fuselage; they are pretty much flat plates from any view other than straight down on the planform. The drag condition on a combat ship is very little different regardless of the angle of yaw. Combat ships are impacted solely by the vectored thrust issue we've discussed. The thrust available is so great that the losses are comparatively insignificant. It is nonetheless true that the combat ships would fly even faster if they were trimmed for yaw and thrust so both were essentially tangent to the flight circle.

I believe the primary reason for the large leadout sweep is to insure control authority anywhere in the hemisphere regardless of wind condition AND to allow them to continue to fly with significant parts of the outboard wing blown away as a result of trying to parallel park with another ship at 120MPH.

This last was a severe case of the issues facing Adrian's friend. In his case the yaw appears to have been the result of excessive rudder offset but it is likely, if we were to be able to work "hands on" with the airplane, we'd find some less than optimum trim conditions in tems of leadout position, tip weight, etc. I don't say this to denigrate the individual. This is simply the result of several decades of exposure to airplanes whose flight characterizations resembled Adrian's description.

Finally lets move those leadouts forward to the "correct" position which is going to turn out to be just a little bit aft of where the ship balances at the wingtips. Again, the precise location will differ based on weight, speed, line length and diameter, etc. For all practical purposes it is going to be about an inch aft on your 40 to 45 inch span Ringmasters and Twisters, etc., up to about an inch and a quarter or a tiny bit more on your 60 inch span, tuned pipe, .65 belchfire special. Not a huge range, huh?

With the leadouts properly positioned almost all of the thrust vector is straight ahead, acting only to overcome drag. This is the most efficient relationship for utilizing the thrust for flight purposes. A tiny bit of the thrust will still be vectored away from the circle depending on the ideal body angle and any engine offset. But any such offset from the dynamics of the circle vice the airplane or from the use of washers under the engine's front mounting bolts are tiny, tiny, tiny. They will, as will locating the leadouts a tiny bit aft of that required for a perfectly tangent condition of the fuse, provide the needed fudge factor to account for the fact that speed is going to vary as will line tension due to aircraft location on the hemisphere.

Once again, the amounts of offset necessary for this fudge factor is extremely small. You will almost always be better off to err on the side of too little offset rather than too much. This is simply because your primary source of tension is the airplane speed. You're never going to lose all the tension from that primary source as long as the airspeed stays at a reasonable level. Once again, you can throw away tension a lot easier than you can manufacture it.

With the fuse now tangent (or nearly so...with a bow to Igor) the drag it produces is reduced to the minimum possible. plus it doesn't disturb the airflow over the outboard wing. Both big positives.

Finally, any aircraft aerdynamic trim condition which causes yaw issues similar to those we've discussed resulting from leadout location will cause similar problems plus a whole lot more. Excessive rudder offset (generally speaking anything sigificantly greater than zero), or grotesque amounts of engine offset, will produce these same problems, plus some of their own by forcing the aircraft yaw into a position contrary to that which the physical forces between the aircraft's center of gravity and its point of tether would naturally cause.

The existence of fuselages and, especially, rudders complicates the ultimate yaw trim issue enormously as can easily be seen in reading the other threads on this fascinating topic. For the level of trim we're discussing on behalf of Adrian's friend such complictation is counterproductive. What Igor and Brett and others are spending thousands of bits and bytes on is for the most part important to the handful of us who feel the last one or two percent of trim perfection are at least as important as the previous 98 or 99%.

OK, that's pretty much the long version of why tension increases with reduced offsets, etc. Hope one explanation or the other was of some value.

Ted,
Thanks for the detailed post concerning these important issues. It's been copied and placed in my folder. I have a question. When you refer to grotesque amounts of engine offset what values are you refering to? 1 degree?, 2 degrees?, 3 degrees? etc. In my limited experience I have noted that my set ups include some positive stab incidence of +1/2 degree, some downthrust of about 1/10 to 1/4 degree, and some engine offset of 1 or 1 1/2 degrees, LO placement as per Soules program, and just a little rudder offset. I have to admit that the rudder offset is very minimal and in experimenting, adding rudder offset does produce a noticable yaw in hard corners.

Again thanks for sharing and you and Shareen have a happy Holiday Season.

Great reading Ted, now if I can get the old man to just listen to the coach, maybe it will. By the way the "Doctor" folded the wing finally for the second time. Guess I was over powering it. It is now in the hands of an up and coming flyer that is learning the pattern. Thanks to Ted, Shareen and all of the stunt fraternity, DOC

>Ted,
>Thanks for the detailed post concerning these important
>issues. It's been copied and placed in my folder. I have a
>question. When you refer to grotesque amounts of engine
>offset what values are you refering to? 1 degree?, 2
>degrees?, 3 degrees? etc. In my limited experience I have
>noted that my set ups include some positive stab incidence
>of +1/2 degree, some downthrust of about 1/10 to 1/4 degree,
>and some engine offset of 1 or 1 1/2 degrees, LO placement
>as per Soules program, and just a little rudder offset. I
>have to admit that the rudder offset is very minimal and in
>experimenting, adding rudder offset does produce a noticable
>yaw in hard corners.
>
>Again thanks for sharing and you and Shareen have a happy
>Holiday Season.

Hi Crist,

I certainly wouldn't cite any of your numbers as grotesque. Certainly within the realm of ordinary and acceptable. Glad you noted the effect of rudder offset, though.

This is the part that gets tricky because if you do have rudder offset you can find a leadout location that will reasonably accomadate it. This is one of the many things I'm still learning from hanging around with Brett. His discussions of roll coupling, etc. (although phenomena I'm reasonably familiar with from my full scale activities)and so forth are tremendously illuminating. The work he did, for instance, on the Bob Hazle Medic was really eye opening.

I wouldn't pretend to "quantify" what grotesque would be. I have routinely built .35 size ships with an average of two degrees engine offset for many years. I think that perhaps with the very light weight of most of these there might be some merit to doing so but I wouldn't pretend to say for certain it is necessary.

Frankly, my very first stunt mentor, Bob Emmett, a now retired Boeing engineer was the first to tell me way back when I was a teenager that offsets weren't necessary.

The positive incidence in tails is a very interesting phenomena and, again, once I've experienced as far back as my earliest stunters.

In many cases something of that sort has been necessary to obtain equal turns inside and outside and David is far from the first to utilize it in one form or another. Remember that Al Rabe talks about positive incidence in his semi-scales as well.

I remember noting that my best flying Veco ships (mostly Chiefs) all had a little bit of down flap when the elevators were neutral. I hasten to add that this came about because I did my aligning in those days with a wet forefinger held up in the air. Generally what looked like neutral flap was usually a bit down. True neutral always looked a bit "up". Thus came a number of ships with some down flap.

Looked at backwards, you have probably noted, that is the same thing as some down elevator with neutral flaps. Which is, in turn, the same thing as a little positive incidence in the stab Ta da! the worm turns full circle again.

This clearly has something to do with downwash off the wing. Can't for the life of me figure why it doesn't backfire with negative G stuff though.

I've used some built in downthrust on the last several ships I've built as well. Some after the fact down thrust on the original Trivial Pursuit showed great promise so I built the Great Expectation/Final Edition and the Special Edition with an 1/8 of downthrust over the 12" long motor mount assembly. Never did the math but it's got to be on the order of between 1/4 and 1/2 degree.

I caution again that all of this fine tuning is pretty esoteric stuff and not something the intermediate or new advanced flyer should be spending a lot of time worrying about.

>I caution again that all of this fine tuning is pretty
>esoteric stuff and not something the intermediate or new
>advanced flyer should be spending a lot of time worrying
>about.

Agreed. And there's a couple of huge problems with suggesting slight tweaks to people. Mostly, we are talking (in regards to positive incidence, but downthrust, too) about *tiny* changes in alignments that correct specific issues. Many modelers over-generalize these ideas, and also overdo them. "If a little's good a lot's better" has led people down some pretty crazy paths over the years.

But certainly things like deleting the typical kit-specified, usually grossly excessive, rudder offset will make a huge difference in the end result that anyone can tell. AT LEAST, make it adjustable.

Friend Ted. I'd like to know how you find so much time to write these long essays. I'm also retired, but I have less time now than when I was punching a time-clock at Lockheed.

>Friend Ted. I'd like to know how you find so much time to
>write these long essays. I'm also retired, but I have less
>time now than when I was punching a time-clock at Lockheed.
>
>Floyd

HI Floyd,

Merry Christmas.

Oh, I don't know. I did the column for Model Aviation a decade or so ago and writing this stuff as a sort of flow of consciousness just seemed to start to happen. It only took a half hour or so.

I think my approach to this stuff is a little more user friendly to the average guy (like myself) than is the technically more accurate but difficult to comprehend math and graphics from the real wizards like Brett, Howard, Igor and Wild Bill. I like to use examples and extremes which pretty much anyone can associate with to illustrate principles...teeter totters, merry-go-rounds, control lines out the tail post, stuff like that.

I frankly think principles are a whole lot more valuable to us average toy airplane types than are facts down to the third decimal. After all, we're working in balsa and sandpaper rather than steel, carbon, aluminum and C and C driven lasers and mills.

Plus, even more important, actual living bodies don't inhabit our creations.

Ted

by the way, I'm only partly retired. Still got the part time astronaut gig at NASA to get me out of Shareen's hair a couple three times a week.

Friend Ted. Good for you, old pal. I got straight "A"s in English back in college, but I certainly admire anyone who is able to pontificate at such length on the subject of "hinging". Sorry, but I still don't understand it. Maybe my lack of a proper education prohibits me from responding the subject at length.. I feel very inadequate at this time.

Floyd-

Question Please.
Do you compare CG with no fuel and CG with fuel?
Not to start somthing ,but I am curious about this as there must
be a Move ment of CG with 5 to 6oz of fuel at the front of the plane.
Is this considered negleable or is it worth considering?

Thanks:9

>Question Please.
>Do you compare CG with no fuel and CG with fuel?
>Not to start somthing ,but I am curious about this as there
>must be a movement of CG with 5 to 6oz of fuel at the front
>of the plane.
>Is this considered negleable or is it worth considering?
>
> Thanks:9

Normally you check the CG with the tank empty. When you fuel the plane it becomes a bit more nose heavy, which is OK (and, yes, you can feel it). But when you look at the pattern, it works in your favor. When do they judge level flight (upright and inverted)? At the beginning of the flight when the plane is the most stable. It is towards the end of the pattern that the more intricate maneuvers are being flown when the plane becomes slightly more maneuverable.

So, even though there is a (slight) difference of feel as the CG moves rearward, it becomes something that you use to your advantage and learn to compensate for. This is also a good reason why you should always practice your maneuvers in the order that they will be flown. If you go out and immediately do a couple of hour glass maneuvers, for instance, the plane will resond differently than when it has burned off most of the fuel which is the time that you normally perform this maneuver.

Ron B.
F4Fguy

Ted:

Magnificent!!! NOW:

Can anyone think of a rules proposal which make it mandatory for all flyers (competition or otherwise) to swear they have read and understood these basic tenets before applying their intuitive adjustments to a basically good airplane.

>Ron B.
>F4Fguy
>
>Ted:
>
>Magnificent!!! NOW:
>
>Can anyone think of a rules proposal which make it mandatory
>for all flyers (competition or otherwise) to swear they have
>read and understood these basic tenets before
>applying their intuitive adjustments to a basically good
>airplane.
>
>Ron B.

Ron,

No.

Merry Christmas

Ted

Just got to thinking while perusing the replies.

There is (or at least used to be) a truly great resource for a real life study of the effects of speed to tension on a tethered vehicle.

Do they still allow old fashioned merry-go-rounds in playgrounds any more? I can see where somebody "could" get hurt playing on one so it is possible that they are simply relics from the past.

At any rate.

That playground gadget provides a perfect example of what's happening with a control liner and will provide graphic evidence of the reality of the vehicle's speed as the primary source of tension. Whe a merry-go-round is spinning and you are sitting on the edge hanging onto a hand hold the faster it spins the harder you've got to grip to keep from being thrown off and forward of it. Spin it fast enough and you could hang on with your hands and your body would lift off and hang outward, defying gravity (at least as we think of gravity).

Now consider that these forces you feel are being generated by a rate of rotation of somewhere around four to six seconds a revolution, very similar to the rotation of our stunters. It is easy to recognize that it requires a significant effort of some sort to come "into" either the middle of the merry-go-round or for the airplane to come into the circle. On the merry-go-round we would do it through brute strength literally pulling ourselves toward the pivot. Our airplanes can "only" do so by applying aerdynamic forces such that the tethered environment no longer applies to them. In other words they want to turn left faster than the tether would force them to do.

Just another way of visualizing the fact that the airplanes "want" to stay out on the lines unless we do something foolish to make them "not" want to. Anything we do that reduces the rate of revolution reduces the primary forces that keep the airplane on the end of the lines.

Great post Ted - informative and understandable. I've got another question coming up about drag and thrust........LOL

Merry Christmas from the 'other' side of the pond

>Great post Ted - informative and understandable. I've got
>another question coming up about drag and thrust........LOL
>
>Merry Christmas from the 'other' side of the pond
>
>Adrian

Hey, Adrian. What pond are you the other side of? You're not just across the lagoon from me, are you?

The same to you.

Hingeing can also be caused by too much rudder offset. I had a Twister that was horrible, I broke off the rudder and reglued it with a lot less offset and it cured it.
Bill

>Hingeing can also be caused by too much rudder offset. I
>had a Twister that was horrible, I broke off the rudder and
>reglued it with a lot less offset and it cured it.
>Bill

Hmmm, Bill.

I thought we just covered that one?

First, great posts!

I have never been able to understand the trim process for adding/removing tip weight. At the extreme, I understand the tip weight can cause the hinging being discussed on this thread. How do you know you have the proper amount of tip weight?

The rudder/engine offset I’ve figure out totally…..I don’t build in any. Once I started removing the rudder offset and the outward engine thrust, everything started flying a 100% better. I now have less line tension in level flight, but more consistent tension throughout the maneuvers. However, I would like to try a slight amount of down thrust in my next ship.

LAST EDITED ON Dec-08-04 AT 08:18 AM (CST)
 
>First, great posts!
>
>I have never been able to understand the trim process for
>adding/removing tip weight. At the extreme, I understand the
>tip weight can cause the hinging being discussed on this
>thread. How do you know you have the proper amount of tip
>weight?

If everything else is right, you add tip weight until the tip starts dropping in the hard corner. Then you back it off. Everything is interrelated, but if you have the rest right, that is the first ting you look at.

Just remember, if you move something else (leadouts, rudder, etc.) you may have to adjust tip weight again. (It is not as simple as "add tip weight equal to half the line weight". Nope, doesn't work that way.)

>The rudder/engine offset I’ve figure out totally…..I don’t
>build in any. Once I started removing the rudder offset and
>the outward engine thrust, everything started flying a 100%
>better. I now have less line tension in level flight, but
>more consistent tension throughout the maneuvers. However, I
>would like to try a slight amount of down thrust in my next
>ship.
>
>John

OK, now I am going to add the next question: Some (and I say "some") will all a little (very little) incidence to the stabilizer. This all depends upon design. With some it may work. With others it won't. (And this isn't something new. Check the Still Stuka plan. Ironically I took it out of mine and it flew just fine.)

But down thrust, now, might cause problems if the engine thrust changes during flight (and the engine thrust does change during flight.) You might want to put a little wedge under the engine, see what it does, and then decide if it is a good idea or not. Otherwise we might nick name your next plane the "Elmer Fudd". (Oh, a hunting we will go, a hunting we will go...)

Leadouts are far aft in combat planes because they are light and have fat lines. Modern F2Ds are an exception, and I don't know why.

If you trim a combat plane with the leadouts in the "correct" position, from Wild Bill's calculations it will tend to hinge a bit from the leadouts being too far back at full speed. Moving the leadouts forward, ala' F2D makes the plane roll in slightly in maneuvers. It tends to make the plane more stable in direction changes because when you switch control input the plane is already slightly banked in a direction to keep it tight on the lines. If the plane is hingeing, when you switch directions the plane is banked the wrong way and it comes in.

Another point in F2D, if the plane rolls in slightly in maneuvers it evens out the tips speeds. The inboard tip is flys geometrically slower. It gets worse in a tight loop. Banking the plane in helps it avoid tip stalling.