bpoates25

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.

chris923

My Feedback: (53)

Where can I get The "Vanessa Rig"?

Top_Gunn

My Feedback: (6)

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

speedracerntrixie

My Feedback: (29)

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.

q-500

My Feedback: (1)

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

Granpooba

My Feedback: (5)

ditto !!

dasintex

My Feedback: (10)

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?

speedracerntrixie

My Feedback: (29)

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.

rt3232

My Feedback: (6)

+1 what he said

jetmech05

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

Gray Beard

My Feedback: (-1)

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.

speedracerntrixie

My Feedback: (29)

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.

Gray Beard

My Feedback: (-1)

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.

JohnBuckner

My Feedback: (1)

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

flycatch

My Feedback: (26)

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

RC_Fanatic

My Feedback: (1)

Is there a chart or writeup somewhere that goes through these trim tests, what to look for, and the best sequence of steps? I've seen a few write-ups but they do not seem consistent, especially in the sequence of the tests. Even as a lowly "sport flyer" I've seen improvements in my planes as I've made some changes but seem to have too much of a piecemeal approach.

Gray Beard

My Feedback: (-1)

Well John, by post #5 the OPs question was answered and got answered a number of times more. I didn't see anything as a class war but if you feel that way, sorry, not my problem. Saving a new pilot a bunch of money is a good thing.
RC, I have the aircraft trim charts from 95 and 08. I quit flying pattern about 05 and I think these charts are either from Model Airplane News or the AMA pattern site. They get published every year and are step by step instructions on aircraft trimming. I still enjoy flying pattern planes but just for the fun of it. CG is step number four in the chart. The instructions are simple, if the plane does this then do this step or look for this. It's really very easy but it takes a lot of time to get a plane just right. Even today I spend at least two days doing nothing but trim and prop testing when I build a new pattern/sport plane.
As soon as I land after the maiden flight I leave the plane turned on and check where the controls are set before I do anything. That gives me an idea of where to start.
I'm pretty sure the trim charts are posted in the AMA pattern section. My scanner is out or I would post them for you.
Speed is still into racing and IMAC flying so he can spend a lot more time to get a plane just right. A plane in good balance and trim is a joy to fly and makes a pilot look good.

p39

My Feedback: (5)

I have used a couple 5 gal buckets and a couple pieces of tristock. I put a small piece of foam on the tip of the tri stocl so it wouldn't dig into the wing tip. I put one side up. Put the other side up and balanced awa6y. Glose enough for government work. Just don't err on the tail heavty side.

JohnBuckner

My Feedback: (1)

For those who balance on simple pivoting device (store bought or homemade) here are some examples of different airplanes that were either checked/balanced right side up or inverted as needed. The device here is the old Sig kit balancer currently discontinued which has ball bering pivots.

Each of the airplanes are stabile enough to be unsupported in the pictures and most cases its easy to see that there is sufficient mass of the airplane below the actual pivot point to allow it to balance without holding.

John

flyoz

My Feedback: (7)

CG is important especially for the maiden fligh. as mentioned "at min it should be in the acceptable zone". but dead on is best.Even a cm out can give a lot of grief in a maiden flight if even 1 surface is out of trim which is enoughg to handle.
Nose heavy a plane flies poorly tail heavy it flies once then bang
a pivot balancer and even fingertips works ok .
I have had the same issue with a low wing plane giving a tail heavy result when the CG was correct with the plane rightway up
So I suggest all low wingers be balanced Upsidedown. The hobbyking CG blancer is a beaut as are any of the other types.

speedracerntrixie

My Feedback: (29)

John, thanks for posting those pictures, they do show a nice way of establishing where the current balance point is and one can easily shift the CG point and verify the new location. Personally I am not hung up on what device to use. If someone wants to spend 300.00 on a custom rig then that's his choice to make. I just don't want to mislead anyone into thinking that an expensive rig is needed. We all seem to agree that CG is something we need to verify before flight but my goal is to let guys know that CG is a trimming tool and can be used to improve the performance and make an airplane easier to fly.

Flyoz, you are correct but my point is how does one know where " Dead on " is? one can set to the exact location as per the plans or manual but is that really the optimum setting? Even after taking a couple trim flights and establishing that a CG change must be made the amount of change is still a best guess and at least for me may require a couple changes until I am happy.

Fanatic, I assume you are flying in Ione? I need to make it up there one weekend as I hear it is a nice site. As Gene has stated the trimming charts are published from time to time. You can do a Google search for Perter Goldsmith's chart as it is one of the most popular. We may want to start a new thread if we really want to dive into trimming but the short version is that step 1 is to measure the airplane to make sure thrust line is set and incidences are set. Verify that the CG is in a safe zone and go fly. If the airplane is straight and the CG is close to optimal you will have little need for elevator trim. Up trim would indicate being nose heavy. If you and your airplane are capable then try a knife edge. Good CG placement will have 99% airplanes tucking very slightly to the landing gear. Tail heavy would be a hard tuck, nose heavy would be a pull to the canopy. CG influences everything right down to landing speed. I have seen many airplanes set up nose heavy then have too much elevator throw dialed in to compensate. This leads to a snap happy airplane that either gets a bad reputation or goes into the ground. I am always willing to start up a trimming thread with someone that has a new airplane and take them through the process step by step. It would be time consuming but I feel it would benefit enough guys here to do. I just havent been able to find a volunteer.

RC_Fanatic

My Feedback: (1)

Gray Beard, thanks for the tip. I did find some useful info on the AMA site.

Speed Racer, yes I do fly at the Ione field. It's a great site if you like short, narrow runways! Dick Belden is, to my mind, one of the key assets of the club. He has helped me a lot, especially when I was trying to get a couple of pattern planes sorted out. I did find some articles and a chart based on Peter's work. That's really what I was looking for. As for using knife-edge flight as a test, I have a hard time sorting out what the plane is doing wrong and what I am doing wrong! But I do enjoy the challenge.

For those who think all you need is to balance it at the point on the plans, I have this example to show that is incorrect. I have two WM T-34's that were set up for a disappointing attempt at pylon racing. They have the same engine, prop, etc and were balanced at the same point on the wing, to within less than a 1/16". They have very different flight characteristics. One flies inverted with little down stick, the other needs a lot. One I can get to knife edge, the other will not.

Interesting how a simple question (with a simple answer) has devolved into this thread!

flyoz

My Feedback: (7)

I think its a veryhelpul thread. All points seem quite valid in context and arent really in conflict

speedracerntrixie

My Feedback: (29)

I found out yesterday that I dont have to work the weekend of an upcoming IMAC contest. I made the decision to enter which means a practice schedule. The contest is the weekend of the 18th so I have decided I need to practice 3 days this week and 4 days next week. I have just been sport flying my airplane for a little over a year now and thought my setup was good. I was quite wrong. At the end of todays practice session the things that got changed were control throws, expo settings, throttle curve and mixture adjustments. Flying the sequen e also showed that the airplane could use a slight CG shift forward. Im currently having a new spinner backplate made from .250 6061 that should cure the CG.The end result os that the airplane is much easier to fly through the.sequence and makes.my goof off flying look even better.

Gray Beard

My Feedback: (-1)

Shawn, you going to fly Vegas this year??? I have gone out and watched some of the local pilots, some of them are pretty good, even in the Vegas breeze.