i hear ( and also read in here) about guys fooling around with moving their C.G. back which makes the plane more responsive to inputs. i was just wondering how this is accomplished. let me say that when i fly a plane for the first time, i try to get the C.G. where it's supposed to be ...i realize this is very important on the first flights with a new model. so....when someone moves the C.G. back....is this done simply by moving the rx and battery aft in the fuse and testing and so on? i wouldnt think adding lead to the tail would be too good of an idea but, who knows. this is what i'm asking. any suggestions? thanks in advance

You move things around as much as you can, in order to avoid adding weight. If you get to the point where you still want to change the CG but can't easily/effectively achieve the desired results, you add the weight as close to the end of the tail as you can--or as far forward, if that's the way the CG is going. Why? Because the longer the length of the moment arm, the less weight you have to add.

Just remember this saying as you start experimenting with moving the CG aft. Overly nose heavy planes fly poorly, overly tail heavy planes fly only once!!! As you start to experiment moving the CG aft do it a very little bit at a time. It's very easy to move it too far aft and lose the plane in flight.

Ken

Move things that you MUST have first. Servo trays can be relocated if necessary, batteries and recievers moved and stacked on top of each other if need be. Remove/add heavy prop nuts. (I don't like those, they're hard on the cranks IMO) On a .40 size plane, don't move the CG more than a 1/4 inch at a time unless you have a garbage bag with you.

Moving the battery or other stuff back is preferred but I have resorted to putting lead weights on the tail. Because the tail is so far away from the plane's CG, it doesn't take much lead, a fraction of an ounce usually.

Move the CG back in small steps and test fly the plane after each "baby step". Stop if you are no longer comfortable flying the plane. Over do this and you have an unstable plane that's going to be a wild rodeo from takeoff to crash. As you move the CG back, the plane will become more responsive to elevator and rudder and will be less stable. It will be easier to stall the plane and will take less push on the elevator to fly inverted. The plane will do snap rolls easier and flat spins will be easier to do and harder to recover from. You will also need less top rudder during knife edge flight.
It doesn't affect aileron roll rate much.

i try not to add dead weight if i can help it.move things around inside to try get what you need if that isnt enough add tale weight as was said here.

Well if you have a radio that allows you to adjust the travel of a aux. servo by means of a rotary knob on the transmitter, you could build a sliding tray for the receiver battery.

Then all you do to adjust the CG in flight is turn the knob on the Tx.

I'd use a servo with metal gears for sure, and mount the servo to the tray to act as as additional moving weight, let the servo move and the lightweight pushrod remain stationary.

Think about it... slide the battery pack way back for the flatest flat spins, and then forward when you have to make an emergency dead stick landing.

Hasn't someone done this yet????

You could be the 1st!!!!

You never did say two very important things in your original post: what type of plane is this (trainer, sport, what?) and how much experience you have with both building and flying. The nature of your post hints that you may not be all that experienced. If that is the case, you may take heed to what RC Ken said above. Be very careful where you put the CG on any aircraft. Slightly nose heavy is always a plus when flying just about anything. Many 3D people put that CG back somewhat, but they usually (usually.... ) have enough experience to handle a plane that is tail heavy. And many of those put a balled up trash bag inside the fuselage. I'm sure you can figure out what that is for.

DS.

Flotation?

hahaha....i've used "the bag" before. no, i'm not going to try throwing a bunch of weight on the tail of my plane just so i can see what happens. that would be mental. and i am indeed a beginner to flying as well. i have six planes of my own ranging from trainers to sporters...ok .....i have a 40 scale cap 232 (many flights...goes very nicely), yak 54 (never been up), a 60 scale cross between a funtana and a 4 star which is a blast by the way, super chipmunk (retired) for now, ... and i'm just wondering what others have to say about tail weight. my planes are balanced pretty much at the mfg's. suggested C.G. and fly pretty nicely as far as i can tell. i know some of these planes seem to like coming in hot and i was wondering if a bit of tail weight would slow them down....along with different pitch props and lower idles...i know there's alot of variables. i will be experimenting with this tail weight this summer and trust me....baby steps are best i know...small adjustments at a time. i've experienced tip stalls with the chipmunk....the cap is extremely snappy....that duraplane with the floats is almost impossible, but it flew...hey, i like that idea of the sliding weight on the flap channel. so...has anyone evr tried this? haha. i can guarantee you i'm not going to do it first. murphy's law is always in the area when i fly..i dont know about you guys. this would be asking for trouble with a sevo control weight adjustment on board...only for me though. i know something would let go. well, thanks for the replies you guys. happy flying .. by the way, this little duraplane 20 is a blast to fly. it's got a 40 size engine with an 11/5 prop. i put inch and a quarter ailerons on the wing and have huge throws on all surfaces. it's an amzing little creature. kind of heavy for what it is. that engine is most of the weight problem but i like the power it delivers.

you should be able to land your plane just a bit above stall speed,moving the cg back will not help to slow it down.

thanks aerowoof....i'll mess around with it this spring and make notes as i fly with each change. it'll be interesting.

BOBREV.. I will tell you this.. If you have the four star on the balance point the you have not seen good flying.. I had one 4*60 and had the ballance almost 1.5 farther to the tail. It was awesome. Knife edge, Flat spins harriers hovers. It would even try to torque roll out but I am not good enough to hold it..

LATER

PS.. Move your weight just a little at the time..

what happenned to the 4* 60?

what happenned to the 4* 60?

sounds pretty sweet powerlines....i'd like to try some of that stuff someday too. but i'm still too green to even attempt it. so, 1.5 is that one and a half inches behind the c.g. mark that the manufaturer gave you? holy crap......thats way back there man. this plane is a great flyer and might be good for harriers. i'll play around with this one this spring.