lmopar69

Hey guys, SSG Stahr here. Im building a "pusher jet" over here out of some foam I found. It has a speed 400, 5x5 prop, 9 cell AA NiMH, HS-81s and a 555 reciever.

What I really need to know, is how do I figure out where the CG should be? Even a guestimate is better than nothing! Help if you can, please!

SSG Stahr, Laine C
Mosul,Iraq

PhilLin

If you can take a plan view photo from directly above, as square as possible, I can do a graphic determination using CAD for you; although I have not proven the outcome from my method on a tailless model. So it would be interesting to know your outcome. You may already know, tailless aircraft needs a reflex trailing edge airfoil to counter the normal nose down moment. It can be achieved also by cranking in some up trim on your elevons. Nice looking effort so far. Cheers,

Phil Lin

P.S.: Please include a reference dimension, such as the root chord at the wing fuse intersection, if you want some specific units instead of percentage measurements from this method.

lmopar69

Im on it... give me a few minutes, and you will have it

Laine

Jemo

My Feedback: (5)

You can figure it from here


http://www.palosrc.com/instructors/cg.htm

lmopar69

Hope this helps some. Thank you.

Laine

lmopar69

Thanks Jemo, checking it out now. I have all night to work on this thing, I would like to get my electronics put in. You guys are great, thanks for the help

Laine

lmopar69

I went to that site. Thats a pretty cool deal. The only problem is, I dont know what to put in for %MAC. I dont really understand that. So, I went to the MAC page and it says to put in the CG, well, I cant, so now what? lol Ahhh! I can confuse myself pretty well!

lmopar69

http://www.rcgroups.com/forums/showt...&page=17&pp=15

Got some really good advice from Dan Savage and Vanning at rc groups. Theres a link to the thread.

Thanks guys
Laine

Jemo

My Feedback: (5)

%MAC 25 to 33

lmopar69

Cool, thanks for the help, what does that mean though? lol

Jemo

My Feedback: (5)

Mean Aerodynamic Cord

NickC5FE

My Feedback: (31)

It means the cg range in percent of mean aerodynamic chord. Its the range you have inside tolerances to fly (on cg, forward cg, aft cg) progressively. Nick

lmopar69

makes sense, thanks guys

afterburner

My Feedback: (18)

Laine,
It seems that you got your answer on the CG and I hope the maiden flight goes well. When I saw the title of your post and where you are, I could'nt resist posting in this thread. I just want to thank you and all the men and women in uniform for what you are doing over there. It is appreciated.


Marty

lmopar69

Thanks Afterburner, much appreciated.

I took the "jet" out yesterday.... not pretty, I wouldnt even call what it did "flying" Oh well, I will fix it back up and study the video and see what the problem is. Here are the pics before and after...