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-   -   I need C/G or MAC on pattern wing...help!!! (https://www.rcuniverse.com/forum/aerodynamics-76/1262173-i-need-c-g-mac-pattern-wing-help.html)

skychief666 11-08-2003 06:53 PM

I need C/G or MAC on pattern wing...help!!!
 
I am using the Compufoil soft ware to compute the MAC and C/G in a wing that is straight in the back and has a tapered leading edge but the numbers I am getting from Comufoil look way to far aft for a 25% c/g...I tried to do the numbers myself but lost the formula...can one of you guru;s help me like real fast...hope to fly it on Sunday.

skychief666 11-08-2003 10:48 PM

RE: I need C/G or MAC on pattern wing...help!!!
 
That's what I was afraid of...to damned hard of a question...stumped ya...huh

Tall Paul 11-08-2003 11:39 PM

RE: I need C/G or MAC on pattern wing...help!!!
 
Yeah, we a bunch a slow guys.... some of us might want to know the root chord, the tip chord, the amount of leading edge sweep, the semi-span.. stuff like that.
Offhand, if the wing truly has a straight trailing edge...
The mac will be at 1/2 the span on one side. The length of the mac will be the root chord plus the tip chord, divided by 2.
The c.g when placed on this chord will appear to be aft of normal for a tapered or straight wing.

skychief666 11-09-2003 01:05 AM

RE: I need C/G or MAC on pattern wing...help!!!
 
Hi Paul...sorry for not spilling the goods along with the question at hand but the Compufoil calculations were right ,it just did not give me a c/g which I should have know because it never asked for it ..all it does ie compute the MAN, aspect ratio,areaans some other stuff. It is left up to the modler to be smart enough to then apply what ever % he/she wants. I guess my next question is once the man chord is known what;t the formula for getting the % of a number such as 11.875? I should know this because it is basic math but as with everything else thst goes when you get old the memory goes too.:eek:

cappio777 11-09-2003 04:15 AM

RE: I need C/G or MAC on pattern wing...help!!!
 
1 Attachment(s)
Here is simple graphical way to calculate the cg on constant chord and single tapered wings.

Tall Paul 11-09-2003 07:44 AM

RE: I need C/G or MAC on pattern wing...help!!!
 

ORIGINAL: skychief666

Hi Paul...sorry for not spilling the goods along with the question at hand but the Compufoil calculations were right ,it just did not give me a c/g which I should have know because it never asked for it ..all it does ie compute the MAN, aspect ratio,areaans some other stuff. It is left up to the modler to be smart enough to then apply what ever % he/she wants. I guess my next question is once the man chord is known what;t the formula for getting the % of a number such as 11.875? I should know this because it is basic math but as with everything else thst goes when you get old the memory goes too.:eek:
.
33% of 11.875 is 11.875x.33=3.919

skychief666 11-09-2003 09:16 AM

RE: I need C/G or MAC on pattern wing...help!!!
 
Thanks Paul...onced again you have saved the day and come up with just the info I was looking for.;)


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