Model Airplane Center of Gravity for Newbies

Model Airplane Center of Gravity for Newbies
In this video I will cover all aspects of Center of Gravity (CG) concerning model aircraft for newbies
Initial discussions will cover the crucial importance of having the correct center of gravity for your RC/free flight model airplane. In short, if the CG is not correctly located, the airplane will likely crash.
Next will be a definition of what the Center of Gravity is, the concept of a range of CG locations and how one can determine if a model is level, nose heavy or tail heavy when balanced at the CG point.
A further discussion of RC model airplane CG ranges follows to include the flight effects of a forward and aft CG, followed by a discussion of how the supersonic Concorde uses CG control via fuel transfer to safely fly supersonic.
The symbol for the center of gravity, or sometimes called a balance point, on RC airplane plans is shown next.
Following is a detailed discussion of how to compute a CG for a straight wing and swept wing. An important point in determining the center of gravity is just the chord of the wings is considered, and the CG has nothing to do with tail/nose moments (distances) or the plane's wingspan.
The importance of locating the CG for ARFs is covered next. Finally, some design considerations for locating the correct CG without the need to add additional weight.
Here is a link to my KZbin Channel:
/ timmckay56
Many thanks in advance for a post of this video on Facebook, it truly helps the channel a lot!
Regards,
Tim
Videos featured:
Foam board F-22:
• F-22 Foam Board RC Air...
Guillows Aeronca:
• Dumas Aeronca C-3 Elec...
E-flite Pitts:
• E-flite Pitts S-1S RTF
Foam board square flyer:
• Square Foam RC Plane -...
Chapters:
00:00 - Intro
00:40 - Center of gravity overview
01:29 - CG definition
03:01 - CG range
08:19 - CG and commercial airliners
10:53 - Computing CG location
15:26 - CG and ARFs
18:34 - Real world airliner CG fails

[@timtheplaneman]

Excellent explanation of CoG Tim - but what about kit built biplanes? Can you just take 20-25% of the distance from the leading edge of foremost wing and the trailing edge of the aft most wing?

[@TimMcKay56]

Tim: Yup, you got it. CG is 20-25% of the total distance back from the leading edge of the top wing to the trailing edge of the bottom wing (assuming a forward stagger). Good luck! Tim

[@dradden1556]

Very good information..Good instruction. You must have been a flight instructor. I'm in the process of building my own . I'm use to having it in the instructions so I didn't know the method of finding cg on a scratch type build. Thank you. I feel confident now that I can do it myself.

[@TimMcKay56]

And thanks for checking in! Tim

[@bradfordtownsend9698]

Bravo, Outstanding: Thank You for sharing your knowledge on this wholesome family friendly hobby. Cheers, Brad

[@TimMcKay56]

Brad: Thank you kindly! Tim

[@willardpearce8218]

Thank you for a great video!

[@TimMcKay56]

👍🏻😊 Tim

[@DaninVA]

Tom, Great video, that most any of us can understand.

[@TimMcKay56]

Dan: I appreciate that! Tim

[@theonlymadmac4771]

Very good explanation! Greetings from Bavaria!

[@TimMcKay56]

Madmac: Thanks for checking in . . . and I always enjoy my time visiting your lovely Bavaria! 😁 Tim

[@aurelioarenas6293]

Thanks for the advice. I just installed motor,esc,receiver to the quick oat, waiting for the battery. The wing cord is 17 cm. Will try to balance at 4.5 cm. Leo.

[@TimMcKay56]

Leo: Very good, thanks for this update. Missed you at the field today, perfect weather! Tim

[@markbonkowski2566]

Hi Tim. Thanks for the excellent informative videos. I have a question regarding calculating CoG, if the wing has ailerons to you include these in the calculations?

[@TimMcKay56]

Mark: Yes, the (strip) ailerons would count as total wing area for CG calculations. Measure from wing leading edge to the trailing edge of the ailerons, CG around 25% back from LE. Tim

[@carlosmanuelgonzalez310]

Great explanation, thank you! I remember a 747 that crashed on takeoff out of Afghanistan. The cargo got loose and the weight moved aft. Horrendous!

[@TimMcKay56]

Carlos: You are sadly 100% correct. Video taken by a US vehicle. B-747 pitched full nose up, followed by a horrendous crash. Tim

[@wunkus]

The video thumbnail picture incident happened at the same location as the 747 crash.

[@free-birdrocker8809]

I found about cg on a yacht on a trailer, engine in back, I got up on the trailer and the boat did a wheely. LOL! My buddy told me to put jack stands on the back of the trailer. Yeup Cg is important for the big birdies and the small ones. Weight "x" Arm "=" moment if I remember my flight training from the 80s...

[@TimMcKay56]

Free-Bird: Roger that! Tim

[@LifenSantaBarbara]

I have a question. Since crashing a couple of my foam high wing models (carbon cub s2& Umx timber x) , the cg has changed after repairs substantially. I've added stick on lead wheel weights. Now my planes don't fly as well due to all the excess weight. What can I do to counter this if anything at all???

[@TimMcKay56]

Not much. The smaller models are very sensitive to any extra weight. Tim

[@olgoz1]

Thanks for the video. I'm building a foamboard, straight-wing aircraft, v-tail with flight controller installed and had been planning a 30% c.g. Do you reckon that's too far aft? Is 20% considered a forward-most c.g. and 25% an aft-most for most aircraft? Glad I watched this.. If I could subscribe again I would! :)

[@TimMcKay56]

Olgoz: For our lightweight RC models, the CG range is not super critical. 30% back from wing leading edge should be OK, maybe a bit sensitive in pitch. If you want to play it safe, add a bit of nose weight for initial flights to keep CG at 25% point, then slowly remove weights a shift CG aft. Tim

[@olgoz1]

@@TimMcKay56 Thanks Tim! Will do just that

[@wunkus]

The thumbnail airplane caught my attention, I was there for that incident.

[@TimMcKay56]

Hopefully no one got hurt. Tim

[@wernervandenbosch1609]

Hello Tim, do you have a video on how to find the CG on a biplane with staggered and tapered wings ? I looked through your video's but did not find it ? Many thanks !

[@TimMcKay56]

Werner: Here is my video on swept wing CG kzbin.info/www/bejne/fZa8pnSYj9J3j7M For the stagger on a biplane, just measure 25% back from the top wing leading edge to the bottom wing trailing edge, that should be your CG. Think of the two wings as one big wing. Tim

[@wernervandenbosch1609]

Thanks Tim, so if I understand correctly I take the width of the root from the front of the top wing to the end of the bott wing and do the same for the wingtips and then apply your formula for swept wing using these 2 values and apply the result to the top wing to balance the plane ? Just want to be very sure as this is my first f3a plane, it costs a lot so the math must be perfect. The plane is a Sebart Prometheus F3A biplane (images.app.goo.gl/WWTCdaWmRh8Br8eb8)

[@TimMcKay56]

@@wernervandenbosch1609 Yes, that is correct. And if you wish to be a bit more conservation, consider making the model a bit more nose heavy with the CG as far forward as 20% back from the leading edge. As you get comfortable with the model, you can move the CG back aft a bit, to the 25% back from LE mark. Tim

[@wernervandenbosch1609]

Indeed, nose heavy is more an insurance than a problem. Thanks for your advice, duly appreciated !

[@SubrataDas-nb6fl]

Sir, plz tell me which cg is best for new Rc beginers pilot, 20percent or 25percent . Plz reply sir

[@TimMcKay56]

Subrata: CG at 20% a conservative good start. Tim

[@SubrataDas-nb6fl]

@@TimMcKay56 thank you so much sir

[@altamirofaria5741]

👍🇧🇷🇧🇷🇧🇷

[@TimMcKay56]

👍🏻 Tim

[@SubrataDas-nb6fl]

Sir plz give me vedio how to find out Cg of f22 Rc model plans

[@TimMcKay56]

Subrata: I am not sure how the designer did this, I just used the computed CG. Tim

[@SubrataDas-nb6fl]

@@TimMcKay56 plz tell me how