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Old Mar 01, 2004, 04:40 PM
Tech freak
Sundsvall Midlanda, Sweden
Joined Aug 2002
502 Posts
Will this one fly? And where should CG be?

Hi

I`m wondering if my new little plane will fly.
Very bad design perhaps, but it`s cool I think.

Any suggestions?

Wheaz
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Old Mar 01, 2004, 04:41 PM
Tech freak
Sundsvall Midlanda, Sweden
Joined Aug 2002
502 Posts
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Old Mar 01, 2004, 04:59 PM
Fly it like you stole it..
Tram's Avatar
Florence, Al
Joined Oct 2000
29,310 Posts
I'll be intested to see it fly!

Is it EDF?
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Old Mar 01, 2004, 05:15 PM
Tech freak
Sundsvall Midlanda, Sweden
Joined Aug 2002
502 Posts
No, if you look close you can see the little mega 16/7/12 in the nose.
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Old Mar 01, 2004, 06:06 PM
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Abomination's Avatar
Dallas Downtown, Texas, United States
Joined Jan 2004
168 Posts
The basic rule for stable flight is the center of gravity must be in front of the center of lift.

Here is what I would do - To find the center of lift, go halfway down the span of one wing and make a dot. Then measure the length of the wing - called the cord. Find 1/4 of that length.... hold on, let me draw a picture. Its pretty bad, but it might make sense to you.

EDIT - CG should say CL, but you get the idea....
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Last edited by Abomination; Mar 01, 2004 at 07:29 PM.
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Old Mar 02, 2004, 02:16 AM
Tech freak
Sundsvall Midlanda, Sweden
Joined Aug 2002
502 Posts
Thanks Abo, but lets say the cg is just half of an inch infront of the cl. will it be stable anyway?

How do I know that the cl is at half the span and 1/4 of the cord?
Is it always like that? Sounds strange....

Wheaz
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Old Mar 02, 2004, 10:55 AM
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Abomination's Avatar
Dallas Downtown, Texas, United States
Joined Jan 2004
168 Posts
when you lift the airplane from the point you found, it can tip a little forward. If it tips a lot in one direction you are in trouble - if it tips backwards - trouble. The center of lift changes during flight - its a function of several variables. Saying it is at the 1/4 chord is just an estimate. This point is where the 'resultant force' of the pressure on the wing lifting the aircraft is and this changes during flight. It is to say, if the pressure on the wing was replaced with one force at one point, it would be (approximately) where you found it. I encourage you to get a physics book or aerodynamics book and check it out.

You should take any information you get on this site with a grain of salt. I have seen some stuff that is inaccurate. This is what I think is correct, I didnt look in a book or search the internet. Im an engineer - aerospace/mechanical - and I think this is correct - but I have been wrong before... let me do some research on the web. There might be something wierd that changes the approximate center of lift on a forward swept wing, but I doubt it, I am pretty confident I did it right.

http://perso.wanadoo.fr/scherrer/mat...glish/mce.html

this should tell you exactly where it is, I didnt play with the software, but it looks good.

This is good reading on stability, CG, CL, etc...

http://www.zenithair.com/kit-data/ht-90-4.html

another good read

http://www.modelaircraft.org/templates/ama/700_7.asp

... I am finding lots of good stuff. Do a google search on stability, center of lift, center of gravity etc... good luck.
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Last edited by Abomination; Mar 02, 2004 at 01:31 PM.
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Old Mar 02, 2004, 11:02 AM
Formerly of mcba fame
Matthew Allen's Avatar
Luxembourg
Joined Apr 2001
3,007 Posts
Don't know about flying, but it looks cool

Reminds me strongly of a ship from that old game Terminal Velocity.

Matthew
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Old Mar 02, 2004, 12:33 PM
Fiberglass dont bounce???
RandyK1's Avatar
Zion, Il.
Joined Sep 2002
2,408 Posts
Thats a sweet lookin plane, it looks FAST!!! Did you make it out of spair parts?? It looks like a high quality kit. You did a great job. I hope it flys as good as it looks. Good luck ...R...
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Old Mar 02, 2004, 03:52 PM
Tech freak
Sundsvall Midlanda, Sweden
Joined Aug 2002
502 Posts
Thank`s Abo, I am more confident with the cg now. Although I am a bit sceptic to the negative wing angle.
It is an experiment so IF it would crash I have learned something.

The plane is ready for flight now, but today was WAY too windy.

Wheaz
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Old Mar 03, 2004, 10:41 AM
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Dallas Downtown, Texas, United States
Joined Jan 2004
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There is a program on this website that does a nice job of finding the CL and CG

http://www.mh-aerotools.de/airfoils/index.htm
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Old Mar 03, 2004, 07:25 PM
dingbaticuselmaximus
Georgia
Joined Jun 2003
124 Posts
Does the wing have anhedral( negative dihedral ) or is it just the forward sweep of the wings when viewed head on? Couldn't find anhedral in my Funk and Wagnalls so I'm not sure it is a real word. How about it Abomimation? Is it a real word?

David
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Old Mar 03, 2004, 07:36 PM
Tech freak
Sundsvall Midlanda, Sweden
Joined Aug 2002
502 Posts
Yes, the wing has "anhedral"

Pretty much too...
With wheels in the pods an 8 inch prop would go free from the ground. Right now the wheels are left out due to snow start.
Able to use 7.5x4 folder now. Span is just over 40 inch.

Wheaz
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Old Mar 03, 2004, 07:40 PM
Fly it like you stole it..
Tram's Avatar
Florence, Al
Joined Oct 2000
29,310 Posts
Has it flown yet?
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Old Mar 03, 2004, 08:22 PM
dingbaticuselmaximus
Georgia
Joined Jun 2003
124 Posts
Best of luck. It is one wicked looking plane!!

-David
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