CG Tuning
01-30-2012, 10:52 PM
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CG Tuning
I have learned a little about how changing the CG feels.
I had flown a ParkZone Spitfire for the first couple of flights with the nose a little low when setting the balance. (Nose a little heavy)
I added some things but when I checked the CG it was perfectly level. So I thought "great this is going to fly so beautifully"
Was I ever so wrong. It was flyable but took constant adjustments. Every 25ft I was having to do something. But it was a little more windy than I had flown in before so I thought it was just the wind.
Now keep in mind I am self taught to fly and Ihave only flown about2-3 times a year for the last couple of years. So I just didn't have experience at this.
But I did realize that I did screwup the CG balance.
So this weekend I set it up so the nose was heavy like the first flight and it flew like a dream.
But I am not one to leave it alone. I want to know more. So I am asking. Before I make the same type of mistake by making the plane evenly balanced.
What is too much nose weight? If I want to try more weight how much should I ry at a time? 1 ounce? 1/2 ounce? Should I leave it alone?
The plane weights 42oz at its flying weight. It is running a 15 size brushless and a 2100mah battery. It is currently balanced with equipment placement.
I haven't added any weight, so there isn't any to remove. But should I add 1/4 ounce at a time to get a feel? Or will I be able to notice that little of weight?
And what am I looking for when it gets to much nose weight?
I apperciate any help as I do not want to repair it from a crash and I am trying to get out of my I will do it my self habit and ask for help from experienced flyers.
So I look forward to hearing your suggestions.
I had flown a ParkZone Spitfire for the first couple of flights with the nose a little low when setting the balance. (Nose a little heavy)
I added some things but when I checked the CG it was perfectly level. So I thought "great this is going to fly so beautifully"
Was I ever so wrong. It was flyable but took constant adjustments. Every 25ft I was having to do something. But it was a little more windy than I had flown in before so I thought it was just the wind.
Now keep in mind I am self taught to fly and Ihave only flown about2-3 times a year for the last couple of years. So I just didn't have experience at this.
But I did realize that I did screwup the CG balance.
So this weekend I set it up so the nose was heavy like the first flight and it flew like a dream.
But I am not one to leave it alone. I want to know more. So I am asking. Before I make the same type of mistake by making the plane evenly balanced.
What is too much nose weight? If I want to try more weight how much should I ry at a time? 1 ounce? 1/2 ounce? Should I leave it alone?
The plane weights 42oz at its flying weight. It is running a 15 size brushless and a 2100mah battery. It is currently balanced with equipment placement.
I haven't added any weight, so there isn't any to remove. But should I add 1/4 ounce at a time to get a feel? Or will I be able to notice that little of weight?
And what am I looking for when it gets to much nose weight?
I apperciate any help as I do not want to repair it from a crash and I am trying to get out of my I will do it my self habit and ask for help from experienced flyers.
So I look forward to hearing your suggestions.
01-31-2012, 03:35 AM
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RE: CG Tuning
You're looking for a simple answer to a complicated question. I've found that very few modellers ever take the time to truly understand what nose heavy, neutral, or tail heavy really mean. There are many other factors that come into play as well (wing incidence, wing loading, air foil, and engine thrust angle just to mention a few).
There are trim charts you can find online that have a variety of maneuvers you can fly to determine how all those factors are interacting with your plane, and make adjustments, and if you're truly interested in fine tuning your flying characteristics, I would strongly recommend you look those up. For someone that only flys a few times a year, you'll probably just get frustrated, but it might be worth the effort.
For a simple test, make sure you have the plane trimmed to fly level with hands off at 1/2 throttle. Then when you do a banked turn, the nose should probably drop slightly or hold level. If it drops the nose drastically, you're probably a little too nose heavy.
Slightly nose heavy will make the plane "dynamically stable" in flight. Neutrally balanced planes will be much more responsive to elevator input. Tail heavy planes will be "dynamical ly instable" and will fly poorly at best, and will probably crash. What many RC pilots mistakenly call "tail heavy" when setting up planes for 3D flying is actually a neutrally balanced condition.
A good rule of thumb to adjust CG is not to look at whether its nose down or nose up on the balancing machine, but rather to determine at what point it balances level. For a small plane like yours, move that CG point 1/8 to 1/4 inch at a time by moving components first, then adding weight. Fly it. Then readjust as necessary.
Remember, nose heavy planes fly poorly. Tail heavy planes fly once.
Brad
There are trim charts you can find online that have a variety of maneuvers you can fly to determine how all those factors are interacting with your plane, and make adjustments, and if you're truly interested in fine tuning your flying characteristics, I would strongly recommend you look those up. For someone that only flys a few times a year, you'll probably just get frustrated, but it might be worth the effort.
For a simple test, make sure you have the plane trimmed to fly level with hands off at 1/2 throttle. Then when you do a banked turn, the nose should probably drop slightly or hold level. If it drops the nose drastically, you're probably a little too nose heavy.
Slightly nose heavy will make the plane "dynamically stable" in flight. Neutrally balanced planes will be much more responsive to elevator input. Tail heavy planes will be "dynamical ly instable" and will fly poorly at best, and will probably crash. What many RC pilots mistakenly call "tail heavy" when setting up planes for 3D flying is actually a neutrally balanced condition.
A good rule of thumb to adjust CG is not to look at whether its nose down or nose up on the balancing machine, but rather to determine at what point it balances level. For a small plane like yours, move that CG point 1/8 to 1/4 inch at a time by moving components first, then adding weight. Fly it. Then readjust as necessary.
Remember, nose heavy planes fly poorly. Tail heavy planes fly once.
Brad
01-31-2012, 05:22 AM
#4
RE: CG Tuning
One of the most interesting and enlightening things I was taught when I was learning was that most new pilots will tend to over-correct the aircraft movement. That is, they will try to make the plane fly perfectly straight. With a trainer, this is usually pretty difficult, if not impossible, especially in the wind.
My instructor told me to trim for straight and level flight, then take my fingers off of the sticks and watch the plane for a few seconds. It will move up, down, sideways all by itself but it will maintain a generally straight line.
The lesson here is that you don't have to adjust and trim every second of the flight time. Once airborne, and at a comfortable altitude, pull back on the throttle a bit at a time until the plane does not tend to climb. This may take a few moments because you are learning what throttle setting is right for that altitude.
Once done, adjust aileron and elevator trims for straight and level. Slight additions of the throttle will cause it to climb while slight reductions of the throttle will cause it to descend. This does not happen immediately. The delay can be a few to several seconds, depending on how much throttle you add or remove. The plane has to speed up or slow down to affect the rate of climb or rate of descent.
So, once you are comfortable with the CG, then do the trim game and see what results. Once you learn this process and do this automatically you will be a much better pilot.
CGr.
My instructor told me to trim for straight and level flight, then take my fingers off of the sticks and watch the plane for a few seconds. It will move up, down, sideways all by itself but it will maintain a generally straight line.
The lesson here is that you don't have to adjust and trim every second of the flight time. Once airborne, and at a comfortable altitude, pull back on the throttle a bit at a time until the plane does not tend to climb. This may take a few moments because you are learning what throttle setting is right for that altitude.
Once done, adjust aileron and elevator trims for straight and level. Slight additions of the throttle will cause it to climb while slight reductions of the throttle will cause it to descend. This does not happen immediately. The delay can be a few to several seconds, depending on how much throttle you add or remove. The plane has to speed up or slow down to affect the rate of climb or rate of descent.
So, once you are comfortable with the CG, then do the trim game and see what results. Once you learn this process and do this automatically you will be a much better pilot.
CGr.
01-31-2012, 05:36 AM
#5
RE: CG Tuning
ORIGINAL: bkdavy
You're looking for a simple answer to a complicated question. I've found that very few modellers ever take the time to truly understand what nose heavy, neutral, or tail heavy really mean. There are many other factors that come into play as well (wing incidence, wing loading, air foil, and engine thrust angle just to mention a few).
There are trim charts you can find online that have a variety of maneuvers you can fly to determine how all those factors are interacting with your plane, and make adjustments, and if you're truly interested in fine tuning your flying characteristics, I would strongly recommend you look those up. For someone that only flys a few times a year, you'll probably just get frustrated, but it might be worth the effort.
For a simple test, make sure you have the plane trimmed to fly level with hands off at 1/2 throttle. Then when you do a banked turn, the nose should probably drop slightly or hold level. If it drops the nose drastically, you're probably a little too nose heavy.
Slightly nose heavy will make the plane "dynamically stable" in flight. Neutrally balanced planes will be much more responsive to elevator input. Tail heavy planes will be "dynamical ly instable" and will fly poorly at best, and will probably crash. What many RC pilots mistakenly call "tail heavy" when setting up planes for 3D flying is actually a neutrally balanced condition.
A good rule of thumb to adjust CG is not to look at whether its nose down or nose up on the balancing machine, but rather to determine at what point it balances level. For a small plane like yours, move that CG point 1/8 to 1/4 inch at a time by moving components first, then adding weight. Fly it. Then readjust as necessary.
Remember, nose heavy planes fly poorly. Tail heavy planes fly once.
Brad
You're looking for a simple answer to a complicated question. I've found that very few modellers ever take the time to truly understand what nose heavy, neutral, or tail heavy really mean. There are many other factors that come into play as well (wing incidence, wing loading, air foil, and engine thrust angle just to mention a few).
There are trim charts you can find online that have a variety of maneuvers you can fly to determine how all those factors are interacting with your plane, and make adjustments, and if you're truly interested in fine tuning your flying characteristics, I would strongly recommend you look those up. For someone that only flys a few times a year, you'll probably just get frustrated, but it might be worth the effort.
For a simple test, make sure you have the plane trimmed to fly level with hands off at 1/2 throttle. Then when you do a banked turn, the nose should probably drop slightly or hold level. If it drops the nose drastically, you're probably a little too nose heavy.
Slightly nose heavy will make the plane "dynamically stable" in flight. Neutrally balanced planes will be much more responsive to elevator input. Tail heavy planes will be "dynamical ly instable" and will fly poorly at best, and will probably crash. What many RC pilots mistakenly call "tail heavy" when setting up planes for 3D flying is actually a neutrally balanced condition.
A good rule of thumb to adjust CG is not to look at whether its nose down or nose up on the balancing machine, but rather to determine at what point it balances level. For a small plane like yours, move that CG point 1/8 to 1/4 inch at a time by moving components first, then adding weight. Fly it. Then readjust as necessary.
Remember, nose heavy planes fly poorly. Tail heavy planes fly once.
Brad
Wow, someone else here actually gets it!! Great explaination here Brad. I have been trying to get guys to understand CG and overall airplane trimming for a while and for the most part been getting flamed for my efforts.It frustrates the you know what out of me when I try to explain that we can set up our models to have very little pitch trim change with airspeed changes and am told I have no clue LOL I have even been told that by making my airplanes as light as I can that I am wasting my time because heavy airplanes fly better. I could go on for pages.
01-31-2012, 06:51 AM
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RE: CG Tuning
Well said Brad, but I would mention that also once trimmed for level flight, you should check the plane charateristics, with it inverted with hands off. All instructors have told me that inverted flight cg check is the way to go. Although rolling to inverted flight is not something a beginner should be doing right away.
01-31-2012, 07:16 AM
#7
RE: CG Tuning
To also add to what Brad said... BECAUSE, as you move the CG back and the plane becomes more responsive to elevator, some people will think they have the CG back too far bacause it is too sensitive. But first, try reducing the elevator throw. It could be that now that the CG is correct, you just need to turn down the elevator's movement.
01-31-2012, 07:42 AM
#8
RE: CG Tuning
ORIGINAL: MinnFlyer
To also add to what Brad said... BECAUSE, as you move the CG back and the plane becomes more responsive to elevator, some people will think they have the CG back too far bacause it is too sensitive. But first, try reducing the elevator throw. It could be that now that the CG is correct, you just need to turn down the elevator's movement.
To also add to what Brad said... BECAUSE, as you move the CG back and the plane becomes more responsive to elevator, some people will think they have the CG back too far bacause it is too sensitive. But first, try reducing the elevator throw. It could be that now that the CG is correct, you just need to turn down the elevator's movement.
yes yes yes.......LOL It's always a combination of things.
01-31-2012, 07:44 AM
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RE: CG Tuning
ORIGINAL: MinnFlyer
To also add to what Brad said... BECAUSE, as you move the CG back and the plane becomes more responsive to elevator, some people will think they have the CG back too far bacause it is too sensitive. But first, try reducing the elevator throw. It could be that now that the CG is correct, you just need to turn down the elevator's movement.
To also add to what Brad said... BECAUSE, as you move the CG back and the plane becomes more responsive to elevator, some people will think they have the CG back too far bacause it is too sensitive. But first, try reducing the elevator throw. It could be that now that the CG is correct, you just need to turn down the elevator's movement.
I see alot of people move the CG back and then complain it just doesn't fly as good as it did. I will usually help them and take some of the throw out
of the elevator and they are much happier.
01-31-2012, 08:11 AM
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RE: CG Tuning
ORIGINAL: billd76
Well said Brad, but I would mention that also once trimmed for level flight, you should check the plane charateristics, with it inverted with hands off. All instructors have told me that inverted flight cg check is the way to go. Although rolling to inverted flight is not something a beginner should be doing right away.
Well said Brad, but I would mention that also once trimmed for level flight, you should check the plane charateristics, with it inverted with hands off. All instructors have told me that inverted flight cg check is the way to go. Although rolling to inverted flight is not something a beginner should be doing right away.
01-31-2012, 08:48 AM
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RE: CG Tuning
While all the above discussions are right for a more advance design, it is the wrong setup for a pure trainer trimmed out for a beginner. For a trainer to have the "self-righting" stability, it must be nose heavy to become speed sensitive. Set up with the balance well forward, it takes a certain amount of decalage to fly at any set speed. When the airplane is trimmed out to fly level at one power setting and speed, any change in speed from a climb or dive will result in the airplane attempting to come back to level flight if the controls are simply neutralized. It's the one feature that tends to annoy the pilot as he progresses, (or his instructor), and also requires a change in elevator trim if the power level is changed. Somewhat surprisingly it is also how full scale general aviation aircraft are configured.
As a student progresses, this stability can also be removed from his trainer by changes in the aircraft setup, by reducing the wing incidence and down thrust, while also moving back the CG. Learning what goes on with these slight airframe adjustments will serve your students well in the future, and extend the capabilities of their first airplane.
As a side note, if the basic trainer is trimmed out at about half to 2/3rd, power for level flight, then fly the airplane using nothing but rudder and throttle control. If the wing incidence and down thrust are correct, you should be able to do take-offs and landings with only the throttle and rudder, never touching the right stick. Mild acrobatic flight is also possible (loops and rolls) too.
As a student progresses, this stability can also be removed from his trainer by changes in the aircraft setup, by reducing the wing incidence and down thrust, while also moving back the CG. Learning what goes on with these slight airframe adjustments will serve your students well in the future, and extend the capabilities of their first airplane.
As a side note, if the basic trainer is trimmed out at about half to 2/3rd, power for level flight, then fly the airplane using nothing but rudder and throttle control. If the wing incidence and down thrust are correct, you should be able to do take-offs and landings with only the throttle and rudder, never touching the right stick. Mild acrobatic flight is also possible (loops and rolls) too.
02-01-2012, 07:42 AM
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RE: CG Tuning
Hi!
Been teaching people to fly now for 36 years and I trim my pylon racers, aerobtic and scale planes the same way I trim the high winged trainers.
Moving the the C of G as far rearward as possible and at the same time having the smallest possible elevator trow...and of course! trimming is always done att full speed! Not at 2/3 rd throttle or anything like that!! -Why! Because then you know that when you hit the stick the plane will always go straight and not take off (up,down,sideways) in strange way, taking the pilot by suprise! Suprises aren't good for newbies!
Been teaching people to fly now for 36 years and I trim my pylon racers, aerobtic and scale planes the same way I trim the high winged trainers.
Moving the the C of G as far rearward as possible and at the same time having the smallest possible elevator trow...and of course! trimming is always done att full speed! Not at 2/3 rd throttle or anything like that!! -Why! Because then you know that when you hit the stick the plane will always go straight and not take off (up,down,sideways) in strange way, taking the pilot by suprise! Suprises aren't good for newbies!
02-01-2012, 07:52 AM
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RE: CG Tuning
bkdavy- thanks for the info. I will read through what I find and I will run the test. I have noticed the nose does drop in my turns.
That kind of brings up something different. I do not use my rudder if I can avoid it. Right now it is more than I can think about when trying fly and cordinate it in a turn. I have been testing the effects it has in level flight. I am guessing I need to use it more than I do.
So I have added it on my Mix switch, I have added it with the ailieons to help keep the nose up. I will now do some of the other test with the mix turned off. It has been windy when I have been flying so I haven't had much luck figuring out if it is the wind or trim.
Windy to me is 10-15mph wind with little gust. For my comfort level the wind is just low enough right now.
I haven't flown much in the past. But I have quit the car/truck racing and will have more time to fly.
I have been out more so far this year than I have in 2 years together. I am looking forward to flying each weekend possible.
Thanks for the input so far.
That kind of brings up something different. I do not use my rudder if I can avoid it. Right now it is more than I can think about when trying fly and cordinate it in a turn. I have been testing the effects it has in level flight. I am guessing I need to use it more than I do.
So I have added it on my Mix switch, I have added it with the ailieons to help keep the nose up. I will now do some of the other test with the mix turned off. It has been windy when I have been flying so I haven't had much luck figuring out if it is the wind or trim.
Windy to me is 10-15mph wind with little gust. For my comfort level the wind is just low enough right now.
I haven't flown much in the past. But I have quit the car/truck racing and will have more time to fly.
I have been out more so far this year than I have in 2 years together. I am looking forward to flying each weekend possible.
Thanks for the input so far.
02-01-2012, 09:52 AM
#15
RE: CG Tuning
ORIGINAL: Handiman
I do not use my rudder if I can avoid it. Right now it is more than I can think about when trying fly and cordinate it in a turn.
I do not use my rudder if I can avoid it. Right now it is more than I can think about when trying fly and cordinate it in a turn.
http://masportaviator.com/2004/02/27/using-the-rudder/
02-02-2012, 03:31 AM
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RE: CG Tuning
Personally, I don't like to mix rudder with anything, and can't see any reason to mix rudder with the ailerons. The aileron position is not constant during a turn in order to hold a particular bank angle. If the aileron angle isn't constant, then you're rudder is going to be changing. The amount of rudder needed to hold the nose will be dependent on so many other factors, that trying to mix it to only one surface is a waste of time. Learn to use the left stick by practicing. Forget mixing while you're learning.
The easiest way to remember rudder in the turn is to move the left stick opposite the right stick. If you bank left, use right rudder, and vice-versa. But thats just a generalization.
Remember, the small parkzone planes are not built for precision flying, so don't overthink it. Just fly it like you stole it and have fun.
Brad
The easiest way to remember rudder in the turn is to move the left stick opposite the right stick. If you bank left, use right rudder, and vice-versa. But thats just a generalization.
Remember, the small parkzone planes are not built for precision flying, so don't overthink it. Just fly it like you stole it and have fun.
Brad
02-02-2012, 05:40 PM
#20
RE: CG Tuning
Rudder is not to keep the nose from dropping (unless of course you are flying knife edge) it is to maintain coordinated flight. As you roll into a turn, depending on wing design and aileron throw, the nose usually will yaw opposite of the direction of the roll so rudder in the direction of the roll is needed to compensate. The nose drops as you initiate the turn due to the fact that some of the lift to maintain level flight is now being used to turn the aircraft so you need to add a little elevator. This obviously changes when flying stunts such as four point rolls, knife edge, inverted etc...
