Finishing up a kit and wanted to double check the CG that is given in the manuel.... When calculating CG do I include the measurements of the control surfaces as well??? It seems that you would... just wanted to double check....

BTW long time lurker... First time poster... Love flying community here and the wealth of information that I have learned so far..

Yes, go by the instructions below....sorry

http://www.geistware.com/rcmodeling/cg_super_calc.htm

See the simple picture of the planform in the example? That outline is what you measure. It includes all the sufraces.

And that application is just about the simplest and best way to apply the CG formulas that've been used by aeronautical engineers since close to day one.

Rock.. this all assumes a person knows what all the terms mean and can directly apply those to the forumuas. It seems easy enough, but to many beginners, it is way overwhelming.

The manuals usually give a pretty solid method of determining the CG range and it comes in close enough for most modelers, both for ARF's and kits. Just make sure that you read the instuctions and that they are clear to you. For instance, "from the leading edge 3 inches from the fuselage" may be one instruction, and on another, it may say "2 inches from the leading edge at the tip of the wing". Follow what the manual says and it will be close enough for the maiden flight.

After that, you can slightly adjust it rearward or forward according to your flight style, but be very careful with setting the CG to far back. Remember the addage "nose heavy planes fly badly but tail heavy planes fly once".

And, for planes with the engine up front, adjust the CG with an empty fuel tank. For rear mounted engines (pushers), do it with a full tank.

CGr.

Thanks guys... thats what I thought... It is a CMP plane and most of us know how screwed up their manuel can be. I just wanted to double check things...

I have heard it said to start at one third the wing cord which will get you pretty close.
If you take a trainer to the field your instructor will automatically check the CG on the main spar. Seems to be a common point.
What airplane did you get? maybe you can get a more specific answer.

Very good move!

Err on the side of being a bit nose heavy to start with. You can always move the C.G. back in increments.

Not at all.

If you look at the picture that's right on the front page of that webpage, it is pretty clear that all it demands of anyone is they can read a yardstick.

The application may look complicated at first, but it's actually quite simple. And if you're a beginner who doesn't know any of the terms, it'll teach you those aeronautical terms that seem so daunting.

All you actually need to do is fill in those blank boxes that are in that ugly light purple box. There are just 9 measurement you do with a yardstick.

Let's do the first one.
The big blue arrows point out the first measurement we need. The left blue arrow is pointing at the 'A' in the line, "Root Chord (A,AA)". The line includes two blank boxes. The first box is where we're going to fill in the measurement for the 'A'. If you look to the right and find the 'A' in the picture of the airplane, it's easy to see what to measure and where to measure. And obviously, you've just found out what and where the root chord of the wing is.

OK, the 'AA' is the root chord of the horizontal stabilizer. etc etc for just 9 easy to do measurements.

Each of the 9 measurements you need to do is shown on the picture of the airplane with a letter code like the 'A'. Just fill in the blanks. Find what to measure for each empty box by the code to the left of that box. Match the code from the left of the box by finding the code in the picture of the plane.

Simple. And you learn what some terms stand for.

Now all you have to do is run the application with a couple of different "Desired Static Margin" inputs. That's the bottom box in the light purple area. If you wanted the CG location for a "twitchy" aft CG location, you'd fillin the box with the number 5. If you wanted the airplane to have a "VERY safe forward CG" you'd plug in the value, 20. And the airplane would probably fly "mushy". So....... You've measured 9 things and plugged the measurements into the boxes and filled in a Desired Static Margin value. Just click the bar directly under the DSM input box and the application is so fast it looks like nothing happened. But if you scroll down the page, you'll see numbers have appeared in the blocks below the light purple block. Look in them and you'll find the location for the CG for your airplane if you want it to give the Desired Static Margin. That term too scientific for you? Then don't say it out loud in public.

BTW, run the application with a 10% and then a 15% and record the two CG locations, and you've got an extremely dependable CG range for that model.

Hope this helps reduce the mystery.

Thanks a ton Rock!!! I will try and get this done over the next few days... I am wondering what this calculator will show the cg to be compared with the plans that came with the plane...