Hi Tom:

I am having a problem with the CG setup on my Edge 540 with the G62. This caught me really off guard since the airplane was designed around the G62.

The following are the numbers from my CG software. The same used on the big airplanes.

Total Wgt: 18.75 pounds
Distance from datum line to MG axels:18 inches with Wgt LG 145.0 oz=2610.0 moment.
" " " " " Wgt RG 130.0 OZ =2340 moment
Distance from Datum to Tail wheel: 71.0 inches and a Wgt of 22 OZ =1551 moment.

At these numbers the CG is 21 inches from datum and recommended to start is 25 inches from datum.
It will take 26 oz's in the tail to move the cg to 25 inches. I have no idea why the LG is so much heavier.

My 8 oz RCVR battery is located right behind the trailing edge of the wing along with my 4 oz ign battery. I do have two standard servo's in the front part of the fuse 4 inches behind the muffler for throttle and choke. Four servo's in the tail.

I sure hate to add that much wgt to the tail. Wing tube tight very tight.

Looking for ideas and would like to from other people using the G62.

Thanks
Tom W

Radar, I have put 11 flights on mine and had to ground my plane to fix the muffler.
I wanted to ask you if you are using standoffs? You may have your engine out too far.
I have my rudder and aileron servos in the tail and my receiver battery on the rudder tray. My CG is at 4.75 inches.

Hi Tom,

Sorry, not an answer to your question, just an observation and a question for you!

1. What CG software are you referring to, I'd like to check it out! I was going to do my own using MS Excel, but I don't want to reinvent the wheel.....

2. I'm a few days away from checking the CG on my G62 powered Edge, and I'm only planning 3 servos in the tail. Yikes! [:@]

Thanks!

John

I have no idea what you are talking about. Balance it 4 1/2" to 5" behind the leading Edge and it will fly fine.

TF

Tom that was a very poor answer. Of course I can balance the airplane by putting over a pound of wgt in the tail. I expected better from you Tom!

Tom W.

Why don't you just tell us where it balances in relation to the leading edge of the wing like everyone else and the manual does. Typing a bunch of formulas and big words does not convey the message.

Joe

I don't understand what you are doing. With a G62 the plane will be nose heavy with a pull-pull rudder setup unless you hung some other weight in the tail. I know this for a fact, I've been building these for months. There's no way it needs a pound of weight added to the front. Have you actually assembled it and balanced it?

Apparently you are using some type of software program which predicts different results, what I am saying is just forget that and use real-world results.

If it is tail heavy I suggest you check and see if there is something lodged in the tail that would change the balance.

TF

I reread your post and I'm beginning to understand what you are describing. PLease just try balancing the plane using the normal method, pick it up at the tips about 5" back from the LE.

Normally with a pull-pull it should be just a bit nose heavy. The last one I built with a G62 had rudder servos in the tail and was slightly tail heavy.

There's no way it will need 26 oz. in the tail. With that long tail an ounce will move the CG 1/4" or a little more. 2 servos changes the CG a full inch.

The landing gear is so close to the balance point that it makes almost no difference, same is true for the wing tube.

TF

Hi Miles:

No standoffs used. I am using the cup that you see on most G62's. When are you going to be at the field with your Edge.

Thanks

Big words! I don't use big words: The airplanes balances at 2 inches from the leading edge. I hope I didn't use too many big words.

Tom W

Tom I don't know what you mean by the real world. I balanced your G202 1/3 scale using this same procedure and it worked perfect. The CG software does not care if the airplane is a 500,000 lb jet or a 19 lb airplane. It works the same. I added nothing to the airplane except what is required to fly. This airplane is very nose heavy in the real world and I have been in this model business for more years than I like to think about.

Tom W

Hi EZFLYR:

The software I am using came from one of my flying buddies that flies a B767 for Delta. If he says it is ok I will send you a copy. If not you can send me the numbers and I will run it for you and see how your CG is turning out. It is sure beats trying to balance a large RC airplane.

Tom

Is that 2" figure via the software or via actual testing of the balance by picking it up?

TF

I agree that this method for figuring the CG should be perfect. However, when you plug numbers into any formula (spreadsheet,etc) and get numbers that are very different from what you expect, it is time to evaluate from a "real world" perspective. If you check the balance of the plane at its tips and the result is closer to 5", then there is a problem with your formula/meaurements. The batteries in the scale could be bad, the plane might not have been level, the datum line measurements may be wrong, a sudden gust of gravity, whatever.

Checking the CG with your fingers is a reasonable first step prior to performing surgery on your plane or adding 26 oz of lead. If it confirms the CG, you have only lost about 10 min to assemble the plane. If it is markedly different, you may have saved yourself alot of trouble.

Leonard

What you are saying makes a lot of sense. I am going to borrow another scale and recheck some things. Thanks for your input.

Tom, I have 11 flights on my Edge and have taken the engine out to get the muffler worked on. I am sending it off tomorrow and hope to get it back soon. The plane flies great. There is a lot I need to get accustomed to so I will not be doing anything but dialing it in over the next couple of months. Once I get that done, I should be putting some serious time into flying that plane. I really like it.

Radar,
Here are some pix of my plane built. The engine, mount, muffler, and battery weigh 4lbs 4 oz. The standoffs may weigh another 3-4 oz. The total weight of the plane is 16lbs 8 oz dry. The CG is at the very back of the range 5" from leading edge. It requires absoluley no down elevator when inverted and raises the nose slightly as it slows to land. I am going to try and move the reciever battery forwar some to move the CG forward about a 1/4". I dont see how your plane can be so nose heavy. My rudder servo is way forward. If yours is in the tail your CG should be close.

Joe

I really like the pictures of your airplane setup. I see you used the BME50. I have a 50 but elected to use the G62 because it needed a home. I am thinking you are right and I have something wrong with my calcalations on my CG. I have a friend that will come over tomorrow and we will check the CG by holding up the model by the wing at the 5 inch mark. Thanks for your input and I will let you know how it turns out.

Thanks
Tom

JBrannon

Joe,
Can you tell me exactly what you have in the plane. Servos, battery size, etc., etc.

What do you think of the power with the BME at over 16 lbs.

Hey there Radar-RCU,

I understand what you are doing with the weight and balance numbers, to get 26 oz's in the tail though I think you have mixed up your moments some how.

PS: I am an aircraft engineer and while lifting the model by it's wing tip works. It's a little tougher with a 60, 000 lb jet:0)

I have used this method a few times to calulate modifications to the airplane. Works out to the letter if you do the math corrrectly.

Take Care for now,

Riverdancer

you guys were balancing by first weighing the load on each main and the tail wheel as referrence?
As long as you like doing a little work -here is an easier setup:

Weigh completed wing assy and find exact cg of THAT ass'y
transfer that point to the fuselage. (a dot of ink)
set wing ass'y aside.
Make a couple of weights that you can hang to the fuselage- which represent exactly the weight of the wing ass'y.
affix the wing weight to fuselage at the point marked --I sling it in two bagggies, hung over the fuselage and secure with a piece of tape.
Then,build and move stuff as necessary to get balance close to this point (c/g).
A wing ass'y is typically only 3-5 lbs on a model this size -but is awkward to use during balance tests.
using this setup -I can easily check c/g as I go.
This procedure won't work well on a full scale B36 -but then again - these are models.