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Old 09-20-2014, 02:59 PM   #1
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Default Balancing foamies

What is the best way to balance a mid wing foamie. I have a sbach342 and I am having a hard time balancing it. any suggestion

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Old 09-20-2014, 03:29 PM   #2
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Domed rubber stops on ends of vertical rods set into a block.

Being mid-wing - you can balance her upright or inverted ... upright if no dihedral and truly mid, or inverted if dihedral and touch lower than mid height.

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Old 09-20-2014, 03:39 PM   #3
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For the maiden flight, balance it 1/4 of the way from the front leading edge on the main wing, it will be a tad nose heavy, but safe, then fly it and move the CG back a little at a time untill you find the sweet spot for your type of flying. new pencils with erasers work well to, set into a 2x6 piece of wood with the erasers pointed up.

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Old 09-20-2014, 11:38 PM   #4
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Originally Posted by CHELLIE View Post
For the maiden flight, balance it 1/4 of the way from the front leading edge on the main wing, it will be a tad nose heavy, but safe, then fly it and move the CG back a little at a time untill you find the sweet spot for your type of flying. new pencils with erasers work well to, set into a 2x6 piece of wood with the erasers pointed up.
I agree with Chellie. IMHO, CG measuring jigs are of limited use. How the plane flies is more important than exactly where the CG is. 1/4 from the LE is good enough for the maiden. Put the plane in an 45 degree upline and flip it to inverted. Keep about 3/4 throttle and center the elevator. If it slowly drops its nose, you've found neutral CG. If it feels like a balloon and wants to raise the nose, you're tail heavy (not likely when you start at 1/4) and if the nose drops quickly you're nose heavy. Experiment until you have only a slight nose drop when inverted.

Some people (typically 3D pilots) like their planes slightly tail heavy. You'd typically see them trim the CG so that it doesn't drop the nose at all when inverted.

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Old 09-20-2014, 11:57 PM   #5
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Presumably the build instructions give a suggested balance point?.. if so i'd just balance it there unless you have reason to think the instructions are wrong. than fine tune as suggested above by flight testing.

As the process of actually balancing (which i believe was the question asked). For small to medium models i just use my finger tips.
On mid wing you probably wont get it to stay in the balanced position for long because it will want to tip one way or the other. But when you find the spot where it balances level for a few moments and then when it does tip is equally likely to tip forward or back, then you have found the balance point. Adjust the battery position until that balance location matches the CG position advised in the instructions. Millimetre precision isn't necessary, if in any doubt err on the side of having it slightly nose heavy, fine tuning comes in the flight test.
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Old 09-20-2014, 11:59 PM   #6
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Battery below the wing while doing the balance check... Then CG will be below the wing and make balancing easier
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Old 09-21-2014, 12:13 AM   #7
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Originally Posted by solentlife View Post
Domed rubber stops on ends of vertical rods set into a block.
Nigel
My cheap balancer is a 2 X 4 with holes 1" deep for unsharpened pencils.

I prefer to leave the erasers flat so the plane will sit still, when the balance point is in the middle of the erasers.

When I find the CG to my liking, I glue 1/2" long pieces of round toothpicks at that point to the bottom of the wing, so I can check it easily at any time. I also outline my battery shape so I get in the right place every time.

I learned these steps, after taking off with a severely tail heavy plane, somehow I got it back with out damage, but that was the tightest snap roll I have ever seen.

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Old 09-21-2014, 09:24 AM   #8
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I do9 have another trick for this ...

My T45's have a tube passed through fuselage for a suspended hook to fit ...







My Prkjet Speed machine has two tubes ... each set into leading edge of wing ...





.....

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Old 09-21-2014, 11:06 AM   #9
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Default How to Balance an RC Airplane

Here is an article on the subject for you.
http://www.rc-airplane-world.com/bal...airplanes.html
It pretty well covers it,and has a few pictures also.
Crash

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