I have noticed that with my new(er) Tiger 2 that when I perform a reverse half cuban 8, while inverted the plane doesn't want to fall into the half loop like it should when power is cut. It wants to remain at the same attitude and stall instead of the nose falling.

It is NOT tail heavy. I have visible up trim in it for straight-level flight, in knife edge it pitches to the bottom of the plane. Actually its nose heavy. Stall turns are fine with the plane rotating to a nose down position quite easily with no tail slide.

If it is an incidence problem, can it be corrected?

I would say it's incidence especially if inverted flight does not need any down elevator or wants to climb and you know you are nose heavy.

It can be corrected but 'll let someone more familiar with that plane respond as I could be way off here

Straight level inverted flight requires just a touch of down elevator and will climb VERY easily if given too much. In an inverted climb however it you can pretty much take your hand off of the right stick and it will hold its attitude.

This plane is a combination of my last Tiger and new ARF. I used the same wing from the old one but the fuselage and tail is all new. Nothing was changed though and everything was aligned with the current wing so it should have flown very similar to the last one.

If a mod needs to be done to the wing I still have the wing unjoined still in the plastic from the new arf. As for tail mods - ouch, the way the tail goes in on this it would be major surgery.

have you measured the incidence with a meter? if it is slightly off you maybe able to shim the wing to bring it closer. since I have not seen it or know how much it is off it is hard to tell. what is the incidence of the wing and stab to the thrust line of the aircraft?

I have an incidence meter, haven't used it because I really don't know how nor do I know the thrust line Yes, I'm planning on learning! Too bad Goldberg doesn't publish these things.

It’s easy to make a couple of round shims with scissors assuming you can steal something plastic from the kitchen. Suggest making 6 or 8 for experimental purposes. Put one between the bottom of the wing and each wing bolt block. The incidence is changed so fly the airplane and see if you went in the correct direction. If not you had a good time experimenting and didn’t spend any money.

Bill

find the center line marked on the plans that will be your reference point. with the plane sitting stable on a surface adjust the incidence meter while it is on this center line to 0. after this you move the meter onto the wing and it will tell you the deviation from center. you can then compare it with the stab incidence.

I have found the easiest way to measure incidence is to set the plane up so that stab is zero (0) degrees (level) using a small torpedo level. The level is about 10" long and found in any Home Depot, Lowe's or hardware store. With the plane leveled, place the incidence meter on the wing and note the incidence in degrees. Measure both at the fuse and wing tips. Also, remember that if you turn the meter so that it is facing away from the fuse on each wing, the measurements will read opposite. In other words, assume you are reading 1 degree positive on the right wing (and the wing is true), you will read 1 degree negative on the left wing.
To avoid that confusion, I generally face the meter in the same direction on both wings.

One final point, the incidence on the Tiger2 should be zero (0) degrees relative to the stab.

DaveB

I'll check it tonight. I have a GP Laser Incidence Meter. This could very well explain why even though it balanced perfectly (a tad nose heavy) it still took 12 clicks of UP elevator for level flight.

If it's off, its not off by much. Could 1/4-1/2 degree of incidence being off effect flight that much?

That small amount IMO would not have enough effect on flight to be noticed. Do you notice any difference in perfomance with a full tank of fuel vs. a near empty tank? If so, it may point to shifting the balance slightly to improve performance. Just a guess on my part.

DaveB

At first blush incorrect incidence of 1/2 degree and 12 clicks of up does not sound reasonable. Just how far off is the CG?

At every club there will be a few masters at trimming. Although I have flown for a very long time it is still helpful to occasionally have a trim master fly one of my airplanes. Two heads have a better change of catching a problem. Something new is always learned. It is remarkably easy to overlook something simple.

Bill

Yep, I'll agree with BillS on this one. 12 clicks up trim and only 1/2 degree off at the most indicates also to me that you are more nose heavy than you think. Down thrust could also be an issue.

I would now suggest the CG be rechecked and that you are checking it with the tank empty and with the plane inverted. Try to get the CG as close as possible in the middle of the recommended range.

If the amount of trim is still to much then start flying using a good trim chart. It takes allot of time and fuel to work with a trim chart but by the time you are done you will have a great flying plane. It helps to have to people while trimming. One flying and the other taking notes.

Also, are the ailerons set correctly?

You could email Carl Goldberg and ask what the incidences and thrust angles should be. That way you would be working with facts instead of assumptions.
[email protected]
or better yet
http://www.carlgoldbergproducts.com/tiger2.htm
wing and tail are 0 degrees and engine should be 2 degrees right and 0 down.
CG is 3-1/2 to 4-3/8 from leading edge of wing.

The ailerons are fine and the roll rate is perfect for me. Doesn't seem to be any adverse yaw either.

If it's nose heavy would it want to stall in a 45 degree inverted climb when chopping the throttle? Wouldn't it require quite a bit of down elevator for inverted flight? Right now it requires almost none.

Now, I got 2 incidence readings last night and I'm wondering about my meter. The very first time I checked it, it showed 2 degrees negative on the main wing. Now, I wanted to keep checking to make sure things were correct. Subsequent readings were in the 1/2 range.

I will check it again tonight because I really don't think its the CG. My instructor from when I was training flew it as well and he thought the CG was fine.

The plane is certainly flyable as is - just not to my liking



Downthrust:
This was one of the fuselages with the firewall glued in backwards. I wonder if it the thrust line of the firewall is off. I drilled out the hole for the throttle pushrod myself (like others have said to do on here when this happens).

First, keep in mind that engine thrust line, wing incidence, stab incidence and balance point are all related. A change in one will act like and/or effect the other.

I’m not sure what other planes you have flown, but be aware that more aerobatic models require almost no down elevator when inverted. Compared to a trainer, it will feel very different. The ideal setup for most is just a breath of down elevator to maintain inverted flight.

You mention two problems. Climb while inverted at neutral elevator at idle, and pitch to belly at knife edge.

A climb while inverted (at idle) can be caused by being tail heavy, not enough down thrust, and too much wing/stab incidence.

A pitch to belly at KE (assuming high throttle) could be caused by tail heavy, too much down thrust, and too much wing stab incidence.

You are carrying up elevator for trim, which would explain the too much stab incidence. The question is then why that much? Something else if off requiring you to carry up elevator trim.

Pitching issues like what you mentioned can take awhile to isolate. My suggestion would be to use a trim chart, such as can be found on the NSCRA web site at http://www.nsrca.org/trimA.htm

What I would first check is CG. Be 100% sure it is where it should be. You may need to tweak the CG later, but recheck it is as per the plans.

Next check that the wing & stab are both at the same incidence. Be sure to check this with the elevator retrimmed to level with the stab. My guess is you may find a problem with the stab. Do your best to verify they are at 0 compared to the datum of the plane, but this may be difficult to judge.

Then check thrust. At WOT in level flight, chop throttle to idle. The plane should slowly arc down as it slows. If it climbs, you have too much down thrust. If it sharply arcs down, you have too much up thrust.

Next, put plane into a straight down dive at idle. Be sure you are high enough to get into a 5+ second dive. It should continue straight down. If it pulls out, you don’t have enough wing or stab incidence. If it tucks, you have too much.

You may have to go thru several trials & changes until you isolate and solve the issue. It is not uncommon to require 20 or more flights to setup aerobatic trim on a model.

Hi John,
Thanks for the information. This is my second of the Tiger 2 model - the first I started flying back at the end of March with too many flights on it to count.
Due to some strange glitching the first crashed. Instead of rebuilding I purchase a new one but kept the same wing from the first which had zero damage to it. I am not making a transition from a high wing trainer.

I know how the last one flew and I am comparing the flight characterstics of this one to the first. It didn't need much elevator inverted but it still did not behave like this one. Also, the stall in an inverted 45 degree climb was not apparent in the first model. It would start a nice half loop when chopping the throttle.

I will check the CG again in the exact middle of the CG range and balance it there. It is currently balanced toward the rear of the CG however so was the original model with no ill characteristics.

Ok, you had one before, so you understand how they should fly by comparing the current to the previous one. Is any thing different between the two? Engine? Prop? Where you put gear? Did you change throws or expo on the radio setup?

The reason to check the CG again is becasue of the relation between CG, incidence and thrust. There isn't much point in chasing thrust and incidence if your CG isn't in a reasonable location. If the CG is close (probably +/- 1/4" on that plane), then move on to the next check, incidence. Then the flight tests. Cheers.