<div></div><div>So I think I have the CG thing down, I understand what needs to be done and how to do it. I usually just balance the plane by eye; if it looks level then I am good. I do not use a level, but I will look at the horizontal stabilizer and line it up agents a level object. I am assuming that a plane is balanced when the horizontal stabilizer is level. So my question is, would it be better to error on the side of nose heavy instead of tail heavy. I know that a plane will be more sensitive if the CG is further back (tail heavy). So fare my plane is flying good, a little nose heavy.</div><div></div><div>TB</div>

It's always best to err on the side of nose heavy

I just used a Sig Pro Balancer for the first time. Plane balanced level. Flew it and it was very tail heavy==what a hand full. Apparently I don't know how to use it. Guess I will go back to the old fingers and evil eye. At this point not very happy with the balancer. Just my 2c

Hi!
Balance by eye...???
Do you mean measuring out the Cof G (25-30% of the wing cord, on a straight tapered wing) and then holding with your index fingers under the wing???

Goirish, The Sig balancer is fine and I have one along with some others. If your airplane flew badly after using the balancer it is not the balancers fault it is the fault of the decison you made on where to balance at or some directions that are sometimes wrong.

TonyBuilder, yes to balance at a specific point your airplane will set relatively level and not neccessarily level with the stabilizer Thats another varible dependant on the design tail decaledge) Also Tony as pointed out by MinnFlyer you are correct that erroring on the nose heavy side (nose angled down slightly) is preferrable for test flights.

Do understand though that if the fuselage is not level and at a nose down angle that you are not actually balanced at that point. Instead the airplane is actually now balanced at some unknown point forward. The point is being careful to not get carried away with this nose down angle and thats easy to do with small angles making a big differance.

John

I used the balance point that was listed on the plans. It is a Clamato with a 70 4 stroke. It was balanced upside down as it is a low wing plane. The pivot point was put on the CG mark. The part of the balancer that sticks out the front was about 1" lower than the leading edge. I could put another plane on the balancer for you and take a picture if that would help. I know that I am doing something wrong. I was feeling really good as I had it balanced level.

<div>No I use a GP balancer, but I just look at the plane, and if it looks balanced, then I go with it.</div>

JohnBuckner, so the stabilizer is not the level point, is it the plane as a whole?

I will keep the nose just slightly down for now. I know that you can move the CG back for beter performance.

TB

Just remember that the "Recommended" CG is just that - a recommendation. Start slightly nose heavy just to be sure that you're not tail heavy. Then fly it and adjust from there.

For the record, I just balance with fingertips and eyeballs. Once the plane has flown, I'll shift or add weights in small increments until the plane flies as I want it to.

I never re-balance it unless it flies well and I am going to make a major change, like switch to a different engine or something else that might change the point where it currently balances.

Goirish I do know what you are talking about and that is caused by the rounded airfoil shape on the top side of the wing which does not allow the measuring device to stick straight out in front of the leading edge when resting on the pads. It is a varible that will occur among a variety of airplanes.

The Great Planes balancer corrects for this by allowing the rules to pivot at the pad getting the stops in front of the leading edge. The Sig balancer will not do this due to the design of the slides and pad.

What I would do and have done with a few low wing airplanes is not ballance upside down but uprite instead. Yes it will be less stable that way but manny low wings can be balanced with care an in many cases allowing rules to be in a better position due to a slightly less curved surface on the bottom of many airfoils.

All the balancers and balance methods do have a variety of problems with no perfect one size fits all. I do use both the GP and Sig balancers along with just my fingers. Thats a favorite of mine on my controlline stuff since on those the symetric airfoils with the desired CG so far forward that they don,t balance well on any table top balancer because of the problem you experianced. For those I always simply make my decison as to where I want the CG, measure it on the table and drop a dap of epoxy on the wings at that point making checking the balance instant on your finger tips.

For larger stuff the popular hanging methods and one called sometimes the vanessa are useful but those are difficult for me setting up in my wheelchair so usually for my largest stuff around 26 pounds I usually just have two wing walkers sit the airplane in my fingers in my wheelchair and its easy to find the CG.

Actually hardly a day goes by without someone walking up and sitting an airplane on my fingers and wanting an opinion. Its surprizing how quickly you will learn to estimate Mac and developing ideas on what percentages of that Mac to use for many kinds of airplanes and no computers needed.

I hope that maybe that will help you to enjoy your new tool a little more.


John

Yes a visulized centerline of the fuse is correct for balance purposes.

Yes, "slightly down" is fine. I always commuicate CG info without that fudge factor knowing its going to be fudged on even more down the line and measure with fuse level however simply because there is no way practical way to communicate that fudge factor with 'slightly' meaning very different things to different people.

John

Nose heavy planes may fly poorly but tail heavy planes fly once.

Gordon Banks-RC Report

I'll tell you I had all I could do to keep that puppy in the air. It jumped off the runway almost vertical. Added all the down trim and still had the stick forward. On lap and put that sucker on the ground. Then I went to the little boys room and ...................well you get the idea.......[sm=drowning.gif][sm=drowning.gif][sm=drowning.gif][sm=tongue_smile.gif]

Yes indeed and I feel your pain, dealing with an airplane CG that is to far aft is not a pleasure
unfortunately that is all to often and many will fight to the death to not deal with it. A common situation I see is some folks with quality arf's that have instructions describing how to mark the target CG on the airplane and then balancing it at that point will instead mark the point as instructed but stop there. At the field when i pick up it of course bangs the tail down and they will swear that they balanced it just like the instructions said. At this point many will still get mad if I want it fixed first.

John

The advice to start nose heavy is very standard in the hobby, but it's important to note that it's just a starting point. The best flying planes have their CG's set right and then their throws set (sometimes much lower than recommended) to give the response the pilot wants. Tuning the CG is the first thing I do on a new model, starting a touch forward and then moving back a little at a time until it feels right in the air.