I would raise the leading edge of the wing to correct it.
That will correct the angle of incidence (angle between the line joining the LE and the TE of the airfoil and the datum line (alongside the fuselage)), and will correct the decalage (difference in angle between the wing's incidence and tail's incidence) to the values originally specified by the designer.


Since the AOA is measured between the airstream and the line joining the LE and the TE of the airfoil, and both ailerons were slightly up (reflexed), the airfoil must pitch up to find the "natural AOA" for that speed (and the rest of the airplane followed the nose up attitude).

What type of airfoil do you have? Symmetrical? Flat bottom with curved top? Or curved both top and bottom with less on bottom? Some would call that last one semi-symmetrical, however you and I know that there is no such critter.

If less than symmetrical, I frequently adjust real ailerons (scale models) a bit (2-4°) UP, unless I have a fair amount of washout built in. That procedure saves a lot of heavy warbirds for those that use it.

In most cases of models that drag their tail, they simply are not moving fast enough for the wing area and weight. Actually, a fully symmetrical wing such as a pattern type model must drag a very tiny amount often not noticed by the eye, just to have that positive angle of attack for flight.

This is a Tower Trainer40 Flat bottom airfoil. Idialed in some down thrust and it is much improved but still has a way to go. Imust have gotten the down thrust pretty close since it doesnt ballon nearly as bad when Ispool up that big Irvine 53.

With an engine about to pull the firewall out, [X(] you most likely will never stop it from some ballooning. In jet fightere there is a trim button on the stick, or there was in my day, some years ago. We had thin leather flight gloves. Three flights with some heavy maneuvering formation time and I had to have new gloves. My thumb worked rapidly, and my airplane was "trimmed" at all times from straight and level to maneuvering at 4 rolling Gs or straight 7G maneuvers. Aircraft structural limits were +4.9 rolling, +7.33 straight, and -3

With a strong 53 on a machine that is overpowered with an OS 40LA, I think you just may not be able to stop ballooning with significant top-end-.

The downthrust may reduce the ballooning but the engine and airfoil are fighting against each other so the increase in speed will not really match the extra power input.

A plane flying at full speed with a drooping tail much have an incidence problem on the stab? After all, the fuselage is just holding the wing and stab together, so if the angle of the fuselage is odd then there is something not right in the decalage I would think.

Since the LT25 already had 6* of down thrust, I wouldn't add anymore or change incidence. Your just overpowering a high winged trainer Crash.

Heck with mine I felt I was WAY over powered and I was definitely over propped with an OS FS 30 with a 10x6 on 15%. I couldn't even fly the thing level until I pulled the throttle back to idle going down wind and once going up wind it felt like an on/off switch the way it ballooned or sank everytime I touched the throttle.

Ireinforced the firewall and added glue to the joints Icould get to. The wing loading is rediculously low and it gets bounced around pretty bad in the wind. One of my club mates noticed yesterday how fast it was .

Biff, i'm not sure it has that much down thrust on the motor. i would think 6* would be pretty noticable. when you built yours, did the motor look like it was pointing down pretty good? i'll have to look at mine again, but, it doesn't look like much, if anything if i remember correctly. maybe that's a little of the problem. if i don't have any down thrust at all,... that would keep the motor from "pulling down" the airplane as it's flying??? i know i have to find my radio book, but is it possible to add elevator mixing in with the throttle, instead of playing with the trim switches all the time? would this be a bad idea, and should i just fly it at a "reasonable" speed as intended? it's not flying squirley or anything, i apparently have a screamer for a motor, usually a 10x6(thinking about an 11x6)prop, and running on 10%. i'm at half throttle probably 90% of the time, unless taking off and landing and up-lines. i'm sitting right around 4.25-4.5 lbs flying weight. what's yours weighing in at? maybe i'll just get the tiger 2 and throw that motor combo on there and see if she'll take it.</p>

Look at the drawing. Side veiw of the fuse. Mines still hanging on my wall awaiting my fuse kit from Sig. Hope it gets here today.

I apologize for NOT having read all (some but not all) of the posts so if duplicating suggestions - I apologize.

My LT-40 (kit build) was powered with an Evolution 52 NX. Straight-n-level at 1/2 throttle. At full throttle, oh maybe a 45 - 60 degree up-line.  I replaced the Evo with an OS 46 FX to reduce the power. Not as aggressive but still a "hard" up line. Since this LT-40 now has a bolt on wing (2 1/4x20 nylon bolts at the trailing edge) I added a good old zinc washer (maybe 1/8") under the wing for each bolt to alter the wing incidence. The plane flies straight-n-level at all but wide-open throttle. With an APC 11x5 prop and shims it will perform nearly all of the basic patterns - yea, full throttle up line is still iffy at best. Remove  the shims and replace the prop with a Zinger 11x6 it behaves like a docile trainer that has plenty of increase in altitude with the throttle for "training night".

Hope this helps ...

Hi!
As we have said earlier! You better ad some down trust!!! That's the thing you have to do to have your trainer fly good at all throttle settings! Mixing is no good!

WRONG! The wing will fly at an angle-of-attack that it is forced into by the stab., if the pilot places the elevator in a position to do so. If the weight and airspeed are producing the proper lift for straight flight then lift equals gravity. A dragging tail will always be applying force against the wing to make it move somewhwere else.

Just go watch a jet airliner on final approach. The angle of the fuselage will be high, yet the airplane is on a descending path towards the runway, due to the high AOA (angle of attack) of the wing required for the relative slow speed. The elevator of the machine may appear to be inline with the stab, but that is because the stab, in most machines is a slab, and trims to an AOA that holds the wing in the high AOA. No big secret.

There again starts another great conversation. There is no such thing as "Stall Speed" a concept often used which does not exist.
Think about that one for a while. [sm=confused.gif]

L (lift) equals the Coeficient of lift (angle-of-attack) times 1/2 (air-mass density times Velocity squared times wing area). Hasn't failed yet in subsonic/transsonic convergent airflow.

Well it cannot keep that angle of attack at full speed and level flight, that was my point...

At any given full, or otherwise, speed while maintaining level flight, for any given wing area, for any given airfoil and for any given air-mass-density, there is only one angle-of-attack that satisfies that specific level flight, which is held in position by the force of whatever stabilizing element that the specific aircraft utilizes.
Any variation of any factor disturbs such previously established level flight therefore some item has to be changed to resume the perfect balance.

Excactly, and that is why a plane cannot simply drop its tail at full speed and maintain level flight.

.........unless the angles of incidence for the wing and/or tail are incorrectly set, forcing the fuse to take an incorrect attitude for the point at which the wing and the tail find their antagonist balance for that airspeed.

In the simplest way to put it, the wing is what flies, and everything else attached to it just follows.

<span style="font-family: Comic Sans MS">no... the wing keeps the craft aloft from the lift generated by thrust, the tail flies it. any change in airflow over the tail surfaces changes the attitude of the craft. changes in the incidence of the wing has nothing to do with the attitude of the craft. changes in the incidence of the wing improves or hinders theefficiency of the craft.the wing generates lift, the tail directs trajectory. as previously stated, look at a real plane coming in for a landing, or scale for that matter, when they are decending or in a flare just before touch down.high AOA and decending. the entire craft is in a high AOA due to the lack of thrust able to generate enough lift to support the weight, to over-come gravity. the tail is what keeps it in this attitude.

an indifference in the wing incidence and the tail incidenceWILL cause the tail to fight the wing. this in-difference is what gives you a more or less efficient flight path??? can't figure out how to explain it. that's why on full size "real planes", the horizontal stab has a trim function. the entire stab changes it's incidence to improveefficiency of flight.

arguments on downthrust, i'm stilltrying to figure out how that ties into the incidence of the wing OR tail OR theAOA. seems to me the down-thrust would pull the craft down as it accelerated, thrust fighting the lift... but lift maintaining the altitude... things that make you go "hummmm".

did i justsolve my own problem?

</span>

This amazing website shows some animations that will explain these things better than I can:

http://www.geistware.com/rcmodeling/...mics/index.htm

The horizontal thrust force keeps the wing going thru the air.
The downthust adds to the weight that the wing has to sustain in the air while it subtracts from the horizontal force.

The airfoil shape of the wing transforms that movement into a force pointing up or lift.

Everything else (including the engine that generates the thrust) hangs from the wing or falls to the ground.

Have you ever seen a wing detaching from a model airplane in flight?
It cannot keep flying, it flips and rotates in the way down. Why?
Because a wing alone is non-stable.

The wing needs something far away from it that keeps it in a more or less horizontal position, so it can do its staff: transforming thrust into lift.
That something far way that keeps the wing in the position it needs to be is the stabilizer, which can be aft (tail), forward (canard) or built-in as reflex for a flying wing.

We change the lift (up or down) of that stabilizer at will (elevator up or down inputs).
Then, we induce a rotation in pitch around the CG.
The nose of the fuse points up or down and the AOA increase or decreases.

When the AOA increases, under our command, the wing transforms that thrust into more lift, at the expense of reducing the velocity of flight, and the plane goes up in a loop.
The opposite happens when we feed down elevator, the plane loops down and accelerates.
We can hear that engine changing rpm’s in both cases, because the wing is asking for more (when going up) or less (when going down) thrust and torque.

As High Plains says, a lot of the problem is a CG that is too far forwards.
You are flying with some "up trim" in to compensate for the nose heavy airplane. As you open the throttle or fly faster the "up trim" becomes more effective and you climb.
Every airplane exhibits this to some extent. My turbine Hawk climbed during high speed passes and moving the cg back cured it. I also had to give it a little more down trim to compensate for the CG move
Your model is a trainer and is designed like this to get you out of trouble if you lose it.
Cg is the biggest factor in this problem.
I have had flat bottomed winged airframes that had no zoom climb.
Changing the wing incidence actually means you are changing the body angle as the wing always flies at the same angle for any given weight and speed.

On the topic of down thrust, we do that mainly to reduce speed sensitivity, most noticeably when making sudden speed changes. If there were no thrust angle, the nose on a high wing plane would rise when you gun the throttle and drop when you cut it, assuming the plane was trimmed straight at mid-throttle. Yes, the wing and engine are fighting each other at full throttle, but that little bit of efficiency is a small price to pay for a well-mannered airplane.

Full scale planes do this, and the way they fix it is with trim and training. Trim for the airspeed you want throttle for the altitude. If you gun or chop the throttle, learn to compensate until you can re-trim. I adjust elevator trim for the different phases of flight with my models. Trim for takeoff, cruise, and landing.

Downthrust is a trick to eliminate or reduce nose up reactions each time the thrust force increases via throttle control.

The idea is to make the thrust line get close or coincide with the location of the CG and the center of drag in the airplane.

This pitch sensitivity to thrust changes is good for trainers and bad for aerobatics.

My LT-40 has a pretty severe climb slope under full throttle. I raised the trailing edge of the wing with some positive results BUTI better understand the issues and will be testing the addition of down thrust. The TE shim will be removed and washers behind the engine mount will be added. The LT starts with 6 degrees and 1 #6 washer adds 2 more degrees.

Do Iwant to ask the question? Em, yea. How do you determine the center of drag? Some guys at the field think the center of drag is San Franciso so Ihad to explain that I was talking about the airplane's drag.

Thanks for the info.

lol!

Hi, SeamusG

Any new amazing project of yours with Ultracote to share with us?

The center of drag is where the center of lift is (lift cannot exist without associated drag).

For practical thrust line determination, the CG can be used, since the horizontal distance between the CG and C of L is small (the pitch stability marging).

The wing's C of L moves along the airfoil with changes in AOA.
The closest we can get is by considering the total C of L of the wing, fuse and tail, which is named neutral point (NP).
Vertically, it should be very close to the line that joints both 1/4 chord points of wing and stab (the geometrical center of the lateral projection of the fuse has some effect on it).
Horizontally, it can be calculated here:

http://www.geistware.com/rcmodeling/cg_super_calc.htm