Hi !!.....I purchased this 15 sized ARF, recently off ebay , the box is unmarked and there is no user manual ,could someone help me locate the Cg , the dimensions of the wing are



Span 34 inches

Root Chord 9 inches

Tip chord 5.4 inches



Thanks!!

you cant go far wrong with 33% back fron the LE.

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Agreed, but at the root (where the wing panels join in the center).

This will make the model a tad nose heavy, but flyable. Nose heavy is good. Tail heavy is bad.


Ed Cregger

Make one or two additional measurements as required by the link application and plug them into it and you got exactly where to place the CG.

http://www.geistware.com/rcmodeling/cg_super_calc.htm

Take a look at it.
The first purple box is where you place the measurements. You also have to provide a "safety margin" value. Then click the refresh button (right under the numbers you filled in). It's almost instantaneous. Then look down a block or two below, and you'll see they now have numbers in them. You'll see a value for the CG in percentage of MAC, and also in inches back from the LE at the RootChord.

I'd suggest that you feed in 15% as your first safety margin target. You can also do 10% and then 20% and you'll have the useful range for your CG.

It's dead simple and takes into consideration a bunch more than the usual "rules of thumb".

Half-span of wing and tail.
Root chord and tip chord of wing and tail.
Sweep of wing and tail.
Distance from LE of wing to LE of tail (at roots).
Simple as that.

cheers mate !! looks like 33% percent works all the time , mine came out 32.5% of MAC , will let u guys know about the test flight if all goes well