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» Proposals for Model aircraft flying ( CAA registration) April 2019
C of G Empty2019-05-08, 17:49 by Gary M Jones

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Saturday 7/7/18

2018-07-07, 21:07 by Gary M Jones

I was at the field today between 14:00 & 15:00 all on my own , good flying too. There is a dead sheep along the fence line towards the gate from the pits, I saw the farmer so reported this to her. I hope no one had plans for a BBQ Smile .

Farmer …

Comments: 1


C of G

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Post by Guest on 2009-02-11, 23:00

Evening all. Could someone tell me the correct balance point for my Thunder Tiger 40 trainer. I would guess at 20% from the leading edge as a safe start but after all I am a helicoptyer pilot and am not sure about such things Question
Confirmation or alternative positions would be gratefully accepted.


Keep well Very Happy

DaveS

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Post by Guest on 2009-02-11, 23:30

You may find 20% makes the plane a little nose heavy but it will be safe. I'd go for a little further back - between 25% - 33%. If you can locate the position of the main spares in the wing placing the CG on there or a little in front (say up to 1/2 inch) and see how that works out as a % of the wing chord. Another thought, do they provide an on-line manual like some other manufacturers?
Allan

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Post by Guest on 2009-02-11, 23:44

Thanks Alan, I will have a look on line. If I cannot find a manual I will try 25% for starters.

Keep well

DaveS

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Post by Andy Sayle on 2009-02-12, 09:39

I would shoot for about 25% to 30% for a "trainer" wing (parallel chord, clarke Y-ish section). It should be pretty safe up to about 35-40% back from the leading edge, but you might find it a bit of a handful to begin with. It is far safer to start with a forward CG, as the flight will be over-stable, and that is faaaaarrrrrr better than the unstability that results with a CG that is too far aft.

You'll be able to tell if the CG is too far forward by the plane wanting a bootful of UP elevator trim to fly level, and a shedload of down elevator to fly inverted. The plane will tend to reach for the sky and pitch up with increasing airspeed.

A CG that is too far aft usually results in a crash Smile The plane will be unstable in pitch, and any elevator input will result in sharp changes in pitch.

The trick is to find a happy balance between the two, and this is down to personal preference. I like my planes to have a slightly forward CG. Most 3D nuts will prefer a CG that is slightly further back....

HTH
Andy
afro

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Post by Guest on 2009-02-12, 13:01

Thanks Andy Very Happy



DaveS

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Post by George Robson on 2009-02-13, 20:48

The position of the C of G is determined by many factors, tail area, wing sweep, moment arm, wing section etc.
Go to the home page of www.rcmf.co.uk on the left hand side under downloads you will see a reference to a C of G finder. when downloaded this will give a form. Fill in the form with the info. required and it will work out the C of G position.
Hope this helps
George

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