Okay, after crashing my Nexstar due to not hooking up my ailerons, I got the radio and engine moved over to a Tower Trainer (SuperStar Select MKII).

I got the thing put together, checked all of my control surfaces everything looks good except for the cg. The CG was way off, with the nose pointing down quite a bit. Because I am using the .46 OS FX which is a little longer and heavier than the .40 I figured it was due to the bigger engine. I added 3 oz of weight on the rear, which caused it to balance, then headed to the field.

In the air the airplane flew nose up, and even cutting the throttle to idle still caused it nose up into a stall. I was able get it back on the ground, but the landing was rough because I had to use massive amounts of forward stick just to get it down low enough. Because I was unable to let it slow down it bounced and then came to a stop.

Obviously the airplane is supposed to decend slowly at idle speeds, but that just wasn't happening.

So the question is, how do I fix this. I balanced at 3.5" from the leading edge, should I remove the weight and try again? What other things can I check?

Thanks,

schu

Balance meaning what? If you mean it balances so that there is no drop in the nose, then that's not good. It should be slightly nose heavy. Nose heavy will not cause problems as will tail heavy. Any tail heavy will cause what you said to happen.

You definitely want to remove some of that weight from the rear and get it back to dropping by the nose when you pick it up at the CG points. It should be set so that when landing, and at minimum throttle, you cannot see the bottom of the wings. It's even good to have to do the approach with a click or two of throttle then go to idle just before touch down.

One more point here. By your post, it sounds like you don't have an instructor helping you (the instructor should have caught the aileron snafu. He/she should also have checked the balance for you to insure that it would fly normally (that is, needing a tad bit.. a click or two.. of up elevator trim for normal straight and level flight at a particular throttle setting (say mid throttle.. the trim will change at a different throttle setting).

If you don't have an instructor, and are not flying on a buddy box at least for the first few flights, you are headed for another disaster.

If, as you say, the plane is balanced properly (SLIGHTLY nose heavy - spinner is about 1/2" - 3/4" lower than center line ), then you need to check a couple of other things.

1. What is the incidence ? It should be 0/0

2. Is the engine thrust set properly ?

From what you have described I don't think it is the engine thrust. I do believe it is the incidence that is wrong.

I would strongly suggest having an experienced person check the incidence. If you, or the person doing the checking, does not have an incidence meter, there are 2 very good ones out there - a Robarts incidence meter and a Great Planes Laser Incidence meter.

I have and use the GP incidence meter. I find it pretty easy to use and it is quite accurate.

I've read through the comments above and I think a lot of your problems result from not having and experience flyer look at your plane. As an instructor I see a lot of stuff come out to the field that shouldn't be flying. It's nothing to be embarrassed about, setting up a plane properly is just something that has to be learned in the hobby. You need to read the instructions for the plane and then balance it where the instructions say the CG should be. Once you have the plane lifted on the CG it should hang level or slightly nose down. There is a saying that I use, "A nose heavy plane flies poorly, a tail heavy plane flies once."

You did balance it with the fuel tank empty right? I just thought I should ask. Because if you balanced it with a full load of fuel, then it would be guaranteed to be tail heavy.

I figured I would get the instructor comments again. Yes I know that an instructor would be a lot easier, but for many reasons I haven't chosen to do it that way, at least for now.

That said, I learned from my aileron mistake and now use a exhaustive checklist, and now that the control surfaces all work I was able to have a successful solo flight despite a very tail heavy airplane that was not flying correctly.

Now I am leaning about setup. Time to make up another checklist. Here is what I have so far:

Center of gravity: Balance the airplane so that the nose is slightly lower than the tail.
Incidence: Should be 0/0.
Engine thrust: Not sure how to check this.

Thanks to those who provided setup feedback. Also, can anyone recommend any good books that cover the setup and balancing of a model before the first flight? I have several magazines and books and have read a bit online, but I haven't found a resource that covers setup in great detail.

Check to make sure your elevator trim is set properly. Get the plane in the air and set your trim levels until the plane flies straight and level with your hands off the controller.

I bet your elevator trim is pulled all the way back on your controller, and thats causing you to not have any down elevator until you put it in with the stick.

All surfaces where checked to be in range and neutrual before taking off, and all the trims where checked. These things are on my checklist.

Also, the up elevator needed to land was far more than what the trim would let me set.

thanks for the suggestion though....

schu

By eye, viewing from the side, can you see if the engine shaft line is slightly angled down or up? If its slightly up, unbolt the engine mount and stick a washer or two on the two top screws of the engine mount to act as shims to get the engine shaft to be at a downward angle. You dont want a lot, maybe 1 to 2 degrees down. Anymore and you will have problems.

Does the plane have servos on each aileron or is it one servo for both ailerons? If its 2 do you have flaperons activated? Long shot, but worth asking...

Crude, but you can try it.....I cant guarentee itll work though.....

Make a couple simple little shims and put them under the leading edge of the eing before you bolt it down. Not a lot, but enough to give you a slightly higher front wing edge. If it works, you probably have an incidence problem.

I'm looking at the book and there are no incidence measurements given nor is there a way to adjust them. Since this is a ARF trainer, do I really need to get a incidence meter and start measureing everything out?

Also, how far down should the nose be when I go to check the CG. Without the weight it was pointing down 30*, so it was quite nose heavy. Do I want it pointing a little down or a lot down.

Thanks,
schu

Another thing I found was that the instructions say to position the engine so that the distance between the firewall and the back side of the spinner is 3 3/4", but with the engine all the way back, the closest I could get it was 3 7/8. So basically the prop is 1/8" to far forward. How much difference would that make on CG and engine thrust?

jwalsh1,

Thanks for your comments. I only have 1 aileron servo, and I don't have a computer radio so there are no flaperons. I noted that the elevators where nice and level before I took off.

The wing, stab, and engine are all pointing slightly down in relation to the bottom of the airframe.

Here is a picture, but I doubt you can see it that well:

I am not sure you have correctly defined CG. It should state in the instructions where the cg is to be located, usually on the spar or somewhere about 25% of the mean chord width, and measured with no fuel onboard. Slightly nose down says nothing unless the cg point is referenced. Getting competent help on first flights cuts the probability of your first effort happening down to near zero. Even having help set it up, inspect it and fly it once is the cheapest insurance for future flights you can buy.

Well thrust angle would be the same, but it would cause a more nose heavy condition. an 1/8" difference isnt going to cause your problem, especially on a trainer. I could be wrong, but I think the problem is more obvious than this.

I would start trouble shooting by taking that tail weight out. Make sure theres no fuel, and get a benchmark CG observation. The nose wil be in the same place as before, very nose down attitude. I would then move your battery back to some new location and remeasure. If its still severely nose down, move the reciever back. If none of this helps, then add weight, a little at a time, until the plane balances out with the nose pointing slightly down. To describe with words and without tools, if the plane is nose down but will not slip off your fingers when your fingers are at the CG point, then you are at the planes' designed balance. The manual should tell you where the balance points are, make sure you measure them from the correct reference point and make sure you make all balance measurements from these points. I make marks using small bits of covering right close to the fusealage on the bottoms of the wings so I know where to position the plane when checking for balance every time.

The goal is to get the plane to balance without using weights. Weights are a last ditch effort. Im thinking now that you may have added too much weight and are using a too far forward CG point because the plane shoul nose down in a stall, not nose up unless its REALLY tail heavy. If it was balances out on the ground with the weights but still nosed up in the air, thats tells me something is amiss in the locations you are using to check CG. Just make sure its correct and go from there.

Ok, the manual says that the CG needs to be 3.5" behind the leading edge. With the weight removed I can't hold it there without it slipping off my fingers because it is too nose heavy. if I move my fingers 1" forward then it will balance with the nose about 3" down from the tail.

I'll reposition my radio and see if I can make up some of this, but in the end I am pretty sure I'll need weight. It isn't just a little nose down it's WAY heavier on the front than rear.

So just to be clear, what I'm looking for is for the plane to point a little nose down but balance when I hold it up 3.5" from the leading edge where the manual says the CG should be.

Thanks,

schu

Thats correct. When you lift the plane using your fingers on each CG point (on the bottom of the wing), the plane should be slightly nose down BUT balanced.

I had also thought...what are you using for the elevator push rod? Could it be flexing instead of throwing the surface when the plane is flying and air is flowing over the surface? Do you have elevator control or is it mushy at best?

My wife is heading into town today so I'm having her pick up the GP incidence meter and CG machine. Later tonight I'll be able to take a good look at the setup with my new tools.

I had elevator control but it was touchy. Since the plane wanted to nose up all the time, I had to up elevator to get it pointed at the ground which worked, but the second I let off on the elevator it quickly went back to nose up.

I'll take a picture of the plane on the CG machine and post the thrust and incidence before I fly again. Thanks for all your help!!! It is greatly appreciated.

akschu,
Ok, I've went back from the beginning of this thread and re-read your problems. From what I read your problems sounds like the motor you put on the plane is making the plane too nose heavy. First of, Minnflyer had written and excellent how-to on balancing your plane. you can find it at

[link]http://www.rcuniverse.com/magazine/article_display.cfm?article_id=84[/link]

Read over the how-to and it should answer your questions about how you should balance. I seriously doubt that the incidence has anything to do with your problem, so I wouldn't mess with that right now. I'm pretty sure that the you just need to get your balance correct. If the instructions say that you need to balance at 3-1/2" back from the leading edge then you need to move weight back until it balance AT THAT POINT. Move your receiver and battery as far back as you can. If that still won't bring the balance to where it should be then you are going to have to add weight to the back of the plane. Minnflyer's how-to addresses this too. I wouldn't worry about having to add weight and making the plane too heavy, the motor you have on there has plenty of power to pull the extra weight. After you add weight to the rear of the plane it needs to balance so that the plane is level, or just below level. By "just below level" I mean no more than 1° or 2° toward the nose. The 30° you mentioned is way too nose heavy. Also, as mentioned above, make sure that the fuel tank is empty when you balance it.

I have the exact same plane with the exact same engine. Depending on how far forward or back you mount the engine will determine the balance of the plane. With that said, I set up my plane according to the directions, and I had to add about 3/4 oz to the tail. After the silicone was added it probably came out to about one whole oz. To do this I cut open the covering in the aft most portion of the fus and added the weight using RTV silicone to the inside of the plane. (I don't like adding weight to the outside of the plane)

When I set up my trims I put the plane on the kitchen table. Next I took a straight edge and made sure that every single control surface was level (don't just eyeball it). The ailerons are level when they are flat with the bottom of the wing (according to the directions) To set the throws I put the ruler on the table in the vertical position and I move the aileron back and forth to make sure it moves equally in both directions and that the throws are correct.

When I took out to fly the first time, of course I needed to adjust the trim, but it was flyable and the trim was VERY close to dead center.

My two cents.

This plane has the velcro in it for thr radio gear right? I wouldn't move the radio gear, because that velcro very easily saves your airplane and i have seen it happen.
A friend of mine has a cub and theres wasn't strapped down, they did a loop and they were in that loop for about 15-20 full loops till it augered the ground.

The reciver pack came undone in the high g's. So just put some weight in a little at a time. and nose should be slightly down, yet hardly noticeable

Chad,
Yes, he should try to move the receiver and battery first. This is a common practice in balancing planes. Weight should be added ONLY after you can't shift the weight of the plane any other way. Of course it should be secured after it is moved to a new location. Adding weight before trying to move anything is just poor construction practices.

Move your gear first, then add weight if needed.

Ken, Thanks for clearing that up for me. Will help me laot in my four star.

Any luck balancing?

The nearest decent hobby store is 60 miles south so I'm still waiting for my wife to return from town. I probably won't fly until this weekend. I want to make sure that the plane is right.

Hopefully this next time the plane will be enjoyable to fly instead of a complete handful.

adstott,

What prop did you use? I have an 11-6 on mine now....