Getting/Balancing CG right

[wickkerr82]

Hi GUys, Hope you guys can clear my doubts.
Heres the doubt: CG Balancing.

the Manual has given a range from for e.g 121i nch to 143 inch.
I normally take the centre CG, which want or how do you go about choosing which CG is the best setup?

After that, do you check your CG with the fuel tank empty or full. i balanced my CG with fuel tank empty and as always i balance it between the range the maual gives me, but when on flying i realise it was nose heavy cos of the fuel. then i added weights to level it off, but i realise that on the fuel finishing the plane wouldbe tail heavy right, although i bever really wait for the fuel to be empty before i land. So can anyone of you guys, point to me the proper way of balancing the CG right from the start. thanks guys.
cheers...
vin

P.S: Oh by the way, i tried shifting the battery but its right to the End so i cant move it back anymore so i've gotta add weights.

[Vahn]

I'm no expert but I always balance without fuel and this seems to be reasonably common way to do it.

In my experience, very few planes will balance perfectly perfectly with and without fuel, even when the gas tank is on the CG.

I also take the center CG when given a large range, but really it's whatever makes the plane fly to your liking.

I have two planes that would "appear" to be nose heavy if you put them on the CG machine or had a friend help lift them with fuel ... but perfectly balanced without fuel and they fly great.

They don't fly nose heavy at all.

I think it's reasonably common that a plane with fuel would be seem to be nose heavy. Unless the manual writer is just flat out wrong about the CG, I'd balance in the middle of the extremes to start without fuel, and then go forward or back ever so slowly/slightly till it flys the way you want.

[wickkerr82]

Thanks Vahn,
Stil confused to if i should reduce the weights or just leave it. its a floater now, im worried if i balance it without fuel or even make it slightly tail heavy without fuel when fuel is present it becomes nose heavy and the landings have to be hot,

[Vahn]

Just my opinion, but when setting up a a new model I try balance the plane at the suggested middle range CG without fuel and without adding weight.

I only add weight if I have to to get the suggested CG.

The bottom line, however, is if you are happy with how it's flying now and you don't feel it is nose heavy or tail heavy then leave it alone and go have fun.

[wickkerr82]

Haha Vahn, words of wisdom which i wil follow. thankks my fren.
cheers

[gary-air]

Check out a CG calculator on the internet,

[MR M]

Always balance without fuel, for the fact that if and when you run your tank dry in flight you will still be within limits. CG moves aft as the flight progresses. I guess you could balnce it twice, full and empty, make sure CG stays within limits during all realms of fight.

[GmanBill]

	Quote: Originally Posted by MR M
	Always balance without fuel, for the fact that if and when you run your tank dry in flight you will still be within limits. CG moves aft as the flight progresses. I guess you could balnce it twice, full and empty, make sure CG stays within limits during all realms of fight.

Mr M is right there also, when you fly the tank out do you want to try to land a extremely tail heavy plane. Also one thing most people do not do is laterally balance there planes often, if all your weight is at the floor of the plane it will pull toward the landing gear in a knife edge and visa versa. If you try to make sure all your weight is down the thrust line in the center of the plane it will take much less input to do your rolling moves and knife edges.

There are still some of us people who are considered professional builders out here, for the most we stay pretty quiet because we already have enough work. What I was taught by the builder who taught me all the tricks he wanted me to know (which were not all of them by far), was you have to talk to you customer extensively and know a bit about how they fly and what they like, it isn't just what the instructions say. You get people who like there planes on the extreme nose heavy side, and then you get someone who wants it to stand on the tail on takeoff like Max (one trick pony Max, but he is really a good guy). You have to know what you like to know how you want your plane set up dry (no fluids, smoke or fuel ) also you have to know a bit more about the airframe (1000's of reviews and build threads on the net) other than what the instructions say. Some manufacturers are giving the CG on the extreme safe side even on the aft placement, some if you put it on the aft placement it is at the lunatic fringe, almost porpoising. There is a lot more than just building a plane, you have to know about the manufacturer and how they do things, there is high quality and them there is that trash can at the field.

[3ddd]

nose heavy will fly,tail heavy will only fly once usually,balance empty and fly full

[MR M]

The reason for a fwd CG limit is elevator authority! You can be so nose heavy you don't have enough elevator to raise and keep the nose up, be ready to switch to high rates or abort your takeoff, an excessively long takeoff roll should tip you off.

[mmcconville]

The convention is to balance with the fuel tank empty. The only way to arrive at the proper CG of a model is through flying it and moving it till the model flies the way you want (relative to CG). I'd strongly recommend starting at the middle to forward CG that is recommended as a starting point then tweak it in as you fly the model. CG is one part of flight trimming.

[GmanBill]

Hey Mike, since no one is buying the 52% edge why don't you just send it to me where I can get it painted and get my servos in it?

[thewrap]

Balance it slightly nose heavy dry so when you have gas it should balance. Landings shouldn't be that bad though. Just keep level and let it come down. That's how I set up my planes when the CG is touchy.