Page 1 of 1

C of G calculation

Posted: 12 Feb 2020, 12:18
by Nigel Argall
Forgive me, this must have been asked many times before but can anyone direct me to a centre of gravity calculator? I know there are some dodgy ones online. I have a couple of model aerodynamics books but both are unavailable. Thank you!

Re: C of G calculation

Posted: 12 Feb 2020, 12:43
by Cliff Evans

Re: C of G calculation

Posted: 12 Feb 2020, 13:14
by Nigel Argall
Thanks Cliff - that looks a lot easier than the tape measure/pencil/paper/calculator stuff I have used before!

Re: C of G calculation

Posted: 12 Feb 2020, 17:29
by ian davis
Hi Nigel

I used the calc that Cliff references for many years believing it to be fall proof. The results seemed OK over many models.

I discovered https://www.ecalc.ch/cgcal and the differing results between the two calcs was alarming.

There is a problem with the definitions for the neutral point in the Calc that Cliff suggests. I would recommend using ecalc. I've tried and tested it over a large number of gliders with absolute success.

You could always try both and decide for yourself.


Ian ;)

Re: C of G calculation

Posted: 12 Feb 2020, 21:55
by John Vella
Hi Nigel, in practical terms if you find the MAC of your wing and find a point at 28 to 30 % chord at that position and take the perpendicular line from it to the fuselage you will have a safe C of G to start with. Regards John.

Re: C of G calculation

Posted: 12 Feb 2020, 22:53
by Jilles
the rcplanes calculator I use now for a couple of years and it works for me on scale and other models. For the maiden flight you do not have to worry if the COG will be o.k.or not. You can always make changes later but in my case there are hardly any. for the static margin I use a 10% setting on scale gliders.

Re: C of G calculation

Posted: 13 Feb 2020, 08:04
by john greenfield
I give another vote for ecalc

https://www.ecalc.ch/cgcal

I have used it for many models and have always found it reliable even with multi panel wings and canards.

AEB

Re: C of G calculation

Posted: 13 Feb 2020, 10:32
by RobbieB
The CG calc page seems to have been moved to: https://www.ecalc.ch/cgcalc.php