CG for Super Kaos?

balance it on the spar... or slightly forward of it.

While the trailing edge sweep is a little more (in number of degrees) than the leading edge sweep, which would locate the CG further rearward than the root rib would indicate, I still went with the high point of the wing on my Kaos models and then moved it back as needed.

I can't see how it would be that much further back than normal, even with more sweep in the trailing edge.

Please write us a mini review of your model and post it here. TIA

Ed Cregger

Last night I tried the "graphical" method of CG determination. I.E. on a planform view of the wing from the high point of the root rib draw vertical lines equal to the chord dimension. From the high point of the chord draw vertical lines equal to the root dimension. Cross connect the endpoints, and from the intersection draw a line perpendicular to the root rib. This is the CG.

I posted a copy of the drawing over at

In my case this method gives a CG only about 1/2" further back than the center of the spar. It is also exactly where the magazine article showed it. I am currently about 1/2 way between these two points (i.e. at rear edge of the spar). I would think that would be in the safe zone on a 16" wing chord. The plane has a 24 oz. tank which is behind the firewall, as in the original, so I'm definitely going to be nose heavy until the last 2 or 3 OZ. of fuel, even with the CG measured at the center of the spar.

First of all are you sure that is the CG location or the location of the Average Chord? if you add the root chord and the tip chord and divide by 2 that will give you the average chord. Your CG will be the % of that chord. IE 28% of the average chord. Sounds like the back edge of the spar is about where you want to be. Try plugging your dimensions into the calculator at

Doh! I just realized that I got it backwards.

Anyway, the main spar worked fine for my Kaos models.

Ed Cregger

Ya know, I don`t think I`ve ever seen a RC model where the CG isn`t really really close to the main spar.

I have owned several versions of the plane and all balanaced a d flew great with the CG at the spar.

BTW, if the CG is at the 30% point, the ratio of LE to TE taper would be

1:2. That means the LE taper would be half or the TE taper. That keeps the CG at the same distance from the MAC all the way out to the tip.

The difference between the CG point the article recommended and the more conventional "Center-of-Spar" point is 1/2". I actually ran into the man who wrote the original S.K. 90 article ( Dewey Newbold) over on RCU. I would ask him to confirm what CG he used, only the new RCU software still won't let me log in so I can post the question.

I just installed the custom spinner adapter (steel) I had to turn and rechecked the balance. I am now 1/8" behind the spar center. On a 16" chord this should be well inside the safe zone.