Author Topic: Interesting method to quickly find CG of any airplane.  (Read 492 times)

Offline Maxray

Interesting method to quickly find CG of any airplane.
« on: December 20, 2018, 12:34:05 AM »
Method to quickly find CG of any plane:

Nice video. For R/C but seems makes sense for any aircraft. Tricycle, tail dragger, straight or swept wings.....
It would be interesting to check this method against the regular 3 point formulas..

EAA member
USUA  member
AMA member
Spread Eagle U/L to XL builder

Offline stevejahr

Re: Interesting method to quickly find CG of any airplane.
« Reply #1 on: December 27, 2018, 01:45:17 PM »
If you only need to get sorta close to the true CG then his method is workable. But if it is your butt on the line you probably want something a wee bit more precise than that.

On models I used something like shown in this link:
Shows a hanging method

Or for the modern generation that prefers video (this is the *exact* setup/procedure I used):



I could see this being scalable up to an ultralight and probably more precise than using multiple scales. At least to establish a baseline for W&B. Once you have the baseline you can add in stuff like fuel and pilot to verify the envelope.

Offline Beeson

Re: Interesting method to quickly find CG of any airplane.
« Reply #2 on: January 14, 2019, 07:46:39 AM »
That's interesting indeed. And it makes sense. I wish I had a quick way to test this out right now.

Offline Maxray

Re: Interesting method to quickly find CG of any airplane.
« Reply #3 on: January 20, 2019, 01:50:47 AM »
If you only need to get sorta close to the true CG then his method is workable. But if it is your butt on the line you probably want something a wee bit more precise than that.

On models I used something like shown in this link:
Shows a hanging method

Or for the modern generation that prefers video (this is the *exact* setup/procedure I used):



I could see this being scalable up to an ultralight and probably more precise than using multiple scales. At least to establish a baseline for W&B. Once you have the baseline you can add in stuff like fuel and pilot to verify the envelope.

That's a really good old school method that us old timers have used on on R/C models. It works. However, in the real world,
I would prefer to not gamble and load my Eagle's wing roots on such small contact points. I can just now imagine hearing the ropes or cable ripping through leading edge ply! Doh!

No thanks, As an experienced full scale airplane builder who has put his butt on the line, I will continue to use the tried and true 3 scale method and Leonard's knowledge for locating the true CG and adjust afterward.
Still, the Demon driver video is interesting for quickly estimating or eyeballing a CG though...
EAA member
USUA  member
AMA member
Spread Eagle U/L to XL builder