Hello!
I have fabricated an electric RC Hovercraft. Now, I want to calculate the CG of the same. Can anyone tell me the procedure to calculate the CG of the Hovercraft?

Perhaps you could try CG directly below the lift thrust line...

Hi,

From my experience, CG should not match the down thrust motor center. If so, you cant control your hovercraft. It will keep rotating opposite to down thrust motor direction. So how far you keep the CG away from down thrust motor, you will get good control. Keep the down thrust motor in the front and CG in middle. This will hold good.

But this case is not applicable if you use duct fan.

@saikat sir,
I can see that you are watching this thread and itching to input...

Hi Mr. KK Iyer,

Initially I have kept CG at the lift thrust line. But I could not control my model. Its keep spinning. Hence I decided to keep the thrust line far away from CG. This model had good control over previous one. I have attached model images of both types.

@samayaraj,
That model looks great!
The big fins/rudders in the slipstream must also be helping to prevent rotation.
Regards

Dear mr. KK Iyer,

I tried even a bigger rudder. But all went in vain. Control was too worse. So I found out the reason and decided to keep lift thrust line away from cg.

@Samayaraj can u post the videos?

Hi,

Please see the video in below link

https://www.youtube.com/watch?v=1kGrJ0Y-OKM&feature=youtu.be