CG balancing problem
 

Im trying to balance my GSS, problem is I get 2 results. I have one of those blue balancers(cant remember the name,a popular one). If I balance right side up,,I get nose heavy balance, If I balance it upside down I get a serious tail heavy reading. The balancer is completely free of any resistance. Im not trusting any of this. Has anyone had this problem? Or is there a better balancer out there. It seems to work well on my lighter planes. VERY frustrating!

THX a million---TAZZZZ

Thanks Greg, but Im really not interested in any Hi-tech balancer. Just the basics. TAZZZZ

Have it your way then.

I also have one of those blue Aluminum $230.00 BS balancers also that i will never trust again.



http://www.dreamworksrc.com/catalog/...250&height=250

Just the basics' I have no clue as to what a GSS is but assume it is some sort of low wing airplane. typically if you try to balance a low wing right side up there is to much mass above the balance pivot and any balance point derived at like this is suspicious at best.

Here is the bottom line using your finger or any kind of mechanical device there must be more of the airplane mass below the fingers or contact points on the device. This assures positive stability which must be in place or you will never be able to acheve an accurate actual balance point.

John

John,

I think it's a Great Planes Super sportster.

yesssir,,it is a Giant super sportster,,,,so then I should trust with balancing upside down. I just want to be sure before I fly. What confuses me is that the balancer claims that it can be in either position.

thx for the info TAZZZZ

Yes Tazzzz you are welcome and absolutely, that airplane is best checked upside down.

Greg I have been so tempted to Pop for the Xicoy balancer system for some of my stuff it would be such a joy. Not to long ago I bit the bullet and spent the big bucks for the DreamWorks Xicoy electronic retract and brake system for my little Boomerang Nano. What a joy anti lock brakes can be dang even makes this old duffer look good.

John

Why don't you like this balancer?

Chris for me personally it just wasn't worth the $ 230.00 i spent on it.

It ended up being very unstable and awkward for one person to use.

It also didn't give me a very accurate CG setting.

Greg thanks for the info, now I can avoid that balancer.

Here is my homemade balancer with measurement arms. For this plane my target balance point is 3.25". I set the arms at 3.25", set the plane in position and then move the arms out 1/8" so the plane is not touching the arms. In this case the plane was nose heavy. See weight on horizontal stabilizer. I moved the wing forward to balance. Now it is slightly nose heavy. Will check it again before first flight.

You can make a Vanessa rig out of stuff you've probably already got (maybe $10 at Walmart if you don't). Balances any plane, upright or inverted. Dead accurate and easy to use.

The balancer didn't lie. You can balance planes right side up or upside down. It depends on the airplane. High wing right side up low wing upside down. You balance one way you can't double check the other. Kinda like pushing a rope

Hi!
Come on guys! The best and easiest way of balancing a plane is using the your fingers!
Been doing so since I started flying R/C 40 years ago.

http://www.rcuniverse.com/forum/atta...mentid=2107130http://www.rcuniverse.com/forum/atta...mentid=2107131

What you say is technically impossible. There is only one CG location on any object, regardless of it's position. The CG does not move when you balance inverted versus upright, it always stays in the same exact location, a 3 dimensional location.

:)Man I wish I had thought of that what a perfect illustration of trying to balance the wrong way for the wing configuration.

For those who may ask about a mid wing airplane: Easy just try both ways and whichever is the easiest to at least come close to being able to let go.


John

Hi!
come on Jaka! Your claim that the "best and easiest" way is using your fingers. Well now fine however that completely leaves out the individual and the airplane so your claim that there is only one best and easiest method is totally invalid.

For example I will use my self as an example. There is no way I could ever even reach the balance point on both sides with my fingertips from my wheelchair nor is there any way I could ever lift that much weight anyway on my fingertips with some of my airplanes. No sir there are many ways to acheve the goal and its a disservice to diss all methods except what works for oneself.

Threads like this are vary helpful to many and those seeking the various methods that may serve them better than what they were formerly using.

John

Hi!
I understand that there are some people that cannot do what I say but to most of us there is no problem lifting a 0-15kg model airplane with our fingertips.
What I want to point out is that you do not need any fancy gadgets to balance a simple thing as a model plane.
And further more...I get the impression that some people think that balancing is only done once. Which is certainly not the case.
To have a good (perfect) flying plane you have to villing to adjust the Cof G perhaps many times (moving the servo, bttreries ) untill you get the balnce point as you want it.
And the rule of thumb is to get it as far as back you can without having the plane behave badly in any way.

Ya sure, lifting a 33 pound ( I suppose that's what 15kg means) airplane with your arms about as far as you can reach and holding it long enough on two pinkies is as unrealistic as it gets and the rushed results at best are compromised.

If this hobby/sport/passion teaches one anything its: One size never fits all. Now don,t get me wrong I have used and still use fingertips almost on a daily basis when people stick airplanes in my face wanting an opinion. I have used and still own almost all the commercial types as well as just the board with a coupe of nails or whatever except that fancy blue one in this thread.

John

No one size never fits all and its a disservice to diss all other methods except what you do.

I get a kick out of anyone using the term BEST with most anything. Good is a better term. I would have loved to see anyone try to CG that Patty 35% Extra I had with there fingers. That one was about 35 pounds. How about last years Prime Cut I built, it was a light weight giant but the sheeting on the wing was so light weight a finger or something like the Great Planes CG machine would break through the wood.
I feel the electronic scales are a lot of over kill for the average builder/pilot but there are so many ways to balance a plane with just cheap home made balancers there is no reason for spending the big bucks. I looked at that nice blue CG machine and shuddered at the price. On a lot of my small models fingers work just fine, on some I have to hang them and use a plumb bob.
This Stick ARF I just assembled and set up CGed perfectly without any lead. I had it sitting on a GP balancer while I moved the gear around and just sat everything on the outside of the plane, marked it then hard mounted the gear.
Whatever works for you is the BEST way.
KISS!!!!!!

I have one of those $230 CG stands and it works as advertised. In addition to that balancer I also have the smaller version. Tried other balancers but they don't compare to quality or durability. Using fingers only apply to a constant cord wing platform.

Durability?? I have had the tower CG machine for 20 years and it's just plastic. Then again I don't throw it across the shop if I'm upset about something.
The CG is the CG and the wing type doesn't care if I'm using fingers or any other type. I have balanced several Bipes with combination wings.
I think I paid 12 or 15 bucks for the tower machine and it works as advertised too. Then again, so did the two pencils in a wood block. Think that one cost me 10 cents to make.

Just a comment hear Hi wing center of mas is blow the wing, low wing the center of mas is above the wing, So whether your using your finger tips or some other rig make no difference, and the center of mas does NOT move but the C of G can have a range, depending on the type of airplane. It is just easer to do with the center of mas below the balance points.

But that is just me

Cheers Bob T

It tells you exactly how to balance the model in the manual. If you don't have a manual, download it from the internet. :rolleyes:

I have tried several ways to balance, and now just strictly use the Vanessa Rig. Just go to the garage, and hang it up. 10 minutes I'm done. Any size. Bi-planes. Whatever it is, the rig can balance. It has been spot on for me.

Where can I get The "Vanessa Rig"?

You make a Vanessa rig out of stuff you've probably got. If not, your hardware store does. Do a search for the details. For small models, your fingers work about as well, but it's handy for the big ones.

Here's a link: http://www.rcuniverse.com/forum/tips...g-rig-how.html

Clearly most guys don't 100% understand CG. For your first flights it is not a super critical setting. Even if you set it to the plans or manual it is most likely not going to be the optimal setting anyway. Use whatever method you wish to make sure you are in the ball park, fly the airplane and determine what changes need to be made based on flight tests. Take note to what elevator trim is needed, landing speed, sink rate when the power is pulled off. For advanced pilots, take note of how much forward stick is needed to hold inverted flight, does,it pull or tuck in knife edge, during a 45 degree inverted up line does it want to climb or dive? These are all good tests to decide where the airplane should have its CG placed for final location. IMO final location can only be determined after test flights. In 20 years I have not had one airplane that didn't have its CG adjusted at least once after flying. This includes several 40% airplanes that initial balance was checked by simply picking up the airplane by the wing tube including the Extra in my profile. After flying it was determined that the RX batteries had to be moved forward 8". Once you understand that CG is not a do or die adjustment and how to adjust according to how the airplane flys you will realize that all the fancy balancing gadgets are not needed.

I use a heavy string taped to the fuse at the C/G with ply to stop hurting the fuse. mount wing on and turn over and hook on something you can take your time and do it right. George

ditto !! :)

What about Bi Planes, such as the GP Super Skybolt, what's the best way to balance, upper wing or lower wing, upside down or right side up?

Put it a small peice of masking tape at the balance point on the bottom center of the top wing, place index and middle finger on the tape spot and lift the airplane.

+1 what he said

I've had some aircraft that if you tried to balance on pencils or finger tips you'll be repairing the holes you just put through the wings.
What works for one doesn't work for another

Not to forget the little bubble level at the datum or level spot. I bought a set of levels at the 99 cent store and removed all the little bubble levels then sanded a flat spot on them so they don't roll. I also mark the CG area shown on the plans with a 1/8 strip of covering so I always know where the starting point is.

He did mention a Super Skybolt that does have two center ribs. The point I'm trying to make is that you really don't need to make this overly complicated. You really only need to get the CG into the safe zone and then go fly. Once you fly the airplane you can determine the optimal CG location. Those of you who set the CG once get the airplane up in the air and push the trim levers to get hands off at a certain throttle setting and call it trimmed are robbing yourselves of an airplane that could be flying much better. IMO it's much better to learn advanced trimming teciniques, your airplanes will fly better, easier and will be around longer.

That's true but not the point, the point is you need not go out and spend a pile of money on a high end CG system. Some people just love the new gimmicks and have pockets that are very deep, most of us are just sport pilots and can get away with just making a system like a Vanessa rig or a couple of cut down dowels stuck in a base. I have a small 3-D Extra ARF from AeroWorks that I used a couple of pencils stuck in a foam block, nothing poked through.
I still have my how to trim instructions from the pattern web site tacked to my wall, I think it is still on the AMA site. I still trim like the instructions say on any precision plane I build, I do it to most of my planes but some I don't take as much time to do. Some planes I have CGed and trimmed for different wind conditions too. I like them a bit more nose heavy when our wind kicks up.
Tex, you CG a bipe right side up using the top wing. What you use to get the CG is up to you.

Sorry GB that is not the point of the original OP either. His confusion was over balancing right side up/down on his device, that was the point and nothing to do with cost.

I will never understand why some posters must turn threads like this into class wars over cost and vilify anyone who may choose not to do as they do.

John

Your right John and I'll try to be a better poster in the future.