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Old Feb 05, 2010, 02:25 AM
the answer 42 is
Switzerland, AG, Lenzburg
Joined Jan 2006
1,897 Posts
Hey Guys, just in case you are interested, here is a Flying Wings desing Cotest
http://www.rcgroups.com/forums/showt...1#post14265221

EZ
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Old Feb 11, 2010, 07:28 PM
Muslimah
tinuviel's Avatar
Joined Feb 2010
3 Posts
Beginner

Hi

I'm just a beginner modeler. Just wondering if the shape of the airfoil has anything to do with c.g? I'm trying to design a flying wing with a reflex airfoil. Flying it at low Re of about 200000 would give a crazy distribution of cm vs alpha and I don't know how to trim it or find my perfect static margin and c.g.

When I plug my wing parameters into the c.g calculator, i seem to get my c.g located at the % chord corresponding to the % that I chose in the program. Is that really correct for this case?

Thanks
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Old Feb 12, 2010, 09:28 AM
the answer 42 is
Switzerland, AG, Lenzburg
Joined Jan 2006
1,897 Posts
Hey Tun

well to start with your own desings can be exiting but it can be also frustrating, even more when you deal with flying wings. If you are going for a sweep wing (type zagi) then things are bit easier. I have seem that profile affects the real location of your CG, which you will see is always a bit different from what a PC program predicted, those programs only give you an indication where it can be but only by flying your wing you will figure it out. Besides not having stabilizators make the wings more sensitive to CG and control throws.

I fly mainly PLank wings, and I try to start with a forward CG and the move it backwards little by littel till I feel that Im confortable with the wing's flight. Once I build a plank with a friend first his then mine, after succesfully flying his we build mine but we deceided to use a different profile, same wing planform everything was the same, even the CG, in the mainden flight I could barley control my wing, clear sing of a too back CG, after landing and movignt he CG coupple of mm forward every thing went OK.

I dont want to discourage you, but is always good to build many many already proofed desings, and when you have good experience flying you can make imporvements over those desings or go for your own, I learned that in the hard way, with many crashed own desings.

I wish you the best EZ and you can participate on this desing contes

http://www.rcgroups.com/forums/showthread.php?t=1184799
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Old Jan 08, 2011, 12:29 AM
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Last edited by Mictronics; Jul 01, 2012 at 02:43 PM. Reason: Tired of RCG - Quality can be found at FVLAB
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Old Jan 20, 2011, 03:17 PM
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57sailplane's Avatar
United States, NE, Hebron
Joined Nov 2008
997 Posts
is there a bug,

because when i use the wing calculater it no longer shows the wing demisions. just gives the stats..
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Old Jan 21, 2011, 01:14 AM
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Last edited by Mictronics; Jul 01, 2012 at 02:43 PM. Reason: Tired of RCG - Quality can be found at FVLAB
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Old Jan 23, 2011, 10:23 AM View Post
Westrope
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Old Apr 01, 2011, 11:06 PM
Scratch building addict
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United States, CA, Felton
Joined Jan 2005
660 Posts
Has anyone actually used the calculated spot on one of these CG calculators and had it work in real life? Every wing I try them on puts the CG too far back. Sometimes they "almost fly" but are wickedly unstable.
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Old Apr 01, 2011, 11:40 PM
internet gadfly
nmasters's Avatar
Colorado
Joined Aug 2006
2,171 Posts
Quote:
Originally Posted by rotagen View Post
Has anyone actually used the calculated spot on one of these CG calculators and had it work in real life? Every wing I try them on puts the CG too far back. Sometimes they "almost fly" but are wickedly unstable.
Maybe you would like this better
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Old Jun 10, 2011, 07:26 AM
The original Flying Pigs Sqd.
Up&Away's Avatar
Netanya, Israel
Joined Aug 2002
10,026 Posts
I've used this one. It gives a comfortable flight envelope. Usually, for more "intense" flying you can move the CG further back, but the starting point is good.
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Old Jun 14, 2011, 10:10 AM
Registered User
sean.belardo's Avatar
United States, DE, Newark
Joined Mar 2010
67 Posts
Multi Sweep wings

Dear RC groups,

I've been searching for months for an EQUATION and/or a graphical method of finding the MAC and MAC location for a multi-swept wing.

PLEASE HELP, this has been bugging me for the longest time. lol

-Regards,
Sean
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Old Jun 14, 2011, 12:20 PM
internet gadfly
nmasters's Avatar
Colorado
Joined Aug 2006
2,171 Posts
Quote:
Originally Posted by sean.belardo View Post
Dear RC groups,

I've been searching for months for an EQUATION and/or a graphical method of finding the MAC and MAC location for a multi-swept wing.

PLEASE HELP, this has been bugging me for the longest time. lol

-Regards,
Sean
The graphical method for a multi-panel wing involves cutting the wing up into an appropriate number of trapezoids and find the center of each trapezoid then using the MAC of two adjacent trapezoids make an intermediate trapezoid and find the center of that. Repeat as many times as necessary. It can get pretty tedious!

this program handles complex planforms with up to 5 panels

--Norm
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Old Aug 09, 2011, 03:20 AM
Believes in Foamies
DeltaMan's Avatar
Greece/Thessaly/Trikala
Joined Apr 2005
292 Posts
This programm has Literally solved Many of my issues.
Congratulations to the designer and his will to freely share it with us...

I was just wondering if something like a rectangular center section could be incorporated in the Equations, just like the attached picture, which will be as easy as it is now to calculate and view...

Thanks in Advance,
DM
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Old Aug 09, 2011, 11:46 AM
internet gadfly
nmasters's Avatar
Colorado
Joined Aug 2006
2,171 Posts
Quote:
Originally Posted by DeltaMan View Post
I was just wondering if something like a rectangular center section could be incorporated in the Equations, just like the attached picture, which will be as easy as it is now to calculate and view...
Did you look at the link in the message #72?
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Old Aug 22, 2011, 03:50 PM
Suspended Account
Denver, CO
Joined Dec 2004
260 Posts
Thanks for this awesome tool! Maidened my scratchbuilt wing this weekend.

Scratchbuilt Lotek50 Maiden Flight (0 min 52 sec)


Look how well it flies before I mess it up with my thumbs!
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