Will someone please help me find the CG and MAC for my delta, I tried doing it on my own, have looked at all the explanations on how to do it, but i am still have a lot of difficulty. The model sizes are as follows"

29' length
48' wingspan
6' tip chord
6' wide where the motor mounts

It would be extremely appreciated if someone to do the math for this. And if it is not too much trouble, show me the formula. Also, the trailing edge is straight, no sweep. Thanks soo much to anyone who helps.

Check this old post:

http://www.rcuniverse.com/forum/fb.asp?m=9265664

someone showed me this calculator that is pretty neat
http://www.geistware.com/rcmodeling/cg_calc.htm#cg

There's online graphical input calculators in the Aerodynamic Resources and Online Tools sticky thread at the top of the thread titles page. You can easily input the numbers into one of those. Once you have your MAC length and location your CG should be located at between 18 and 20% of the MAC.

Also this ' means feet while this " means inches. Unless this is an actual man carrying model I suspect you used the wrong mark....

Shape A or shape B?

Shape B, Thanks!

skater_719,

Study the attached calculation and ask any question if the explanation isn't clear enough.

This will serve you for any future delta wing that you build.

Regards!

Wow, thank you so much, very appreciated. Did you draw that up, or is there a program to figure that stuff out?

You are very welcome, skater_719

Yes, I draw it using AutoCAD.
As you asked, I wanted to show you the process and formula, so you could use them for future projects.

It is not that difficult.
1) Divide the wing shape in simpler shapes.
2) Find the centroid of each shape, over which the MAC runs.
3) Divide each MAC length into four equal parts.
4) Select the 25% closer to the LE for each shape, that is the neutral point (NP) of each shape.
5) Calculate a mean location for the total wing NP from any reference point by computing individual NP locations and areas.
6) Calculate the total wing MAC length.
7) Select the 25% closer to the LE for that total wing MAC, that is the neutral point (NP) of your delta wing.
8) Balance it so the CG is located ahead of that NP.
9) Go flying!

The attached PDF can be read more clearly.
You can download it into your computer by right clicking on the icon / Save target as

Best luck with your project!

If you have MS Excel capable spreadsheet please try downloading "Flying Wing Calc". It'll do all this and much more, very easily. All you need is a ruler in either inches or millimeters and a scale in ounces or grams if you wish to know wing loading.

There are no complex lines to be drawn, no figuring sweep angles, no finding the quarter chord location etc. It's very simple to use.

Please see www.TailwindGliders.com and go to the Articles/Files page.

Curtis Suter
Montana

Just did download the spreadsheet and did verify that the numbers match.

Good calculator.

Thanks, Curtis.

When you finally fly it, you can check to see if the calculations were correct by flying it inverted.
If you have to push lots of forward stick then it's nose heavy.
A little forward stick is a correct.
If it doesn't climb or dive and still flies well then that's it's acceptable but marginal.
If it climbs when inverted then it's tail heavy and will possibly have stability issues.
The model will have less drag if the cg is correct and will generally fly faster as the elevator drag will be reduced. Not sure you would notice on a model but airliners can save substantial amounts of fuel by moving the cg back as far as they can.
Jim