How to Measure CG

[lperagallo]

In another topic I had mentioned my Heli pitching up in forward flight. It was suggested that I check the CG. It suggested to balance the heli by holding up the machine by the blade grips with the blades vertical to the floor. Then level the tail and nose and see which way the heli drops. Mine drops towards the tail. If I lift the heli by the flybar with the skids in their normal position the heli balances fine. I also seem to remember the Gary Travis set up video saying to use the flybar to balance the heli.

What is the 'correct' way to check the CG? :dontknow

[Stott1]

Use the flybar to balance your heli.

[Brady Longmore]

yes, grab it by the flybar. Use a table. As you lift the heli from the table make a mental note if the skids leave the surface evenly, or if one end or the other tends to want to come up first. Do the same while lowering the heli back to the table. The skids should be touching down flat and even.

[flyinfool]

The lifting by the flybar method works if you are;
1. Sure that the table is level.
2. Sure that the skids are still perpendicular to main shaft (Skids do sag and take a permanent tail low set after a while causing you to balance for a tail heavy condition).
3. Willing to accept that close is good enough.

If you want to be as accurate as possible, hold it by the grips with the blades vertical.
Holding by the grips eliminates several variables that can cause error.

Try it both ways to prove it to yourself.
Lift it by the flybar and put a small weight on the nose or tail and see if you can see the change, then try it from the grips and see if the same small weight makes more or less of a difference.

That's my story and I am sticking to it.

[Greg Alderman]

lperagallo...I balance mine using the grip method...I believe it is much more accurate than just hooking your fingers or whatever around the flybar or grip when heli is sitting on table...

[spork]

The difference is that, when held by the flybar the C.G. will be well below the pivot point. When holding by the blade grips with the blades vertical the C.G. will be dead on the pivot point (when it's correct).

Sooo... In the first case you'll generally only see the heli go a bit nose high or nose low (once the C.G. is beneath the pivot point it stops pitching any further). In the second case any imbalance at all will cause it to go nose straight up or nose straight down (assuming it's balanced left-to-right).

Like others said, both methods work. It's just easier to see small imbalances with one.

Personally I just pick mine up by the flybar, and if it's anywhere close I go fly. But once you've seen me fly you might opt for a better method.