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Old Mar 23, 2006, 10:22 PM
nooobama
United States, PA, Stroudsburg
Joined May 2004
984 Posts
Help!
Delta wing CG without the Canards??

I'm building the Firebat foamie that has canards on it. Well everyone says that they break off so I'm planning on just loosing them and setting up the ailerons as elverons. I'm sure though this will screw with the CG. Can I just do the old 1/2 the leading edge, 1/2 traling edge and then the 25%? Thanks, Cas
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Old Mar 23, 2006, 10:30 PM
Lift is cheap - Drag sucks
Tom Harper's Avatar
Socorro, NM
Joined Jul 2004
3,513 Posts
The starting point for deltas is just forward of 1/2 the root chord - 25% of the wing area is forward of that line.
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Old Mar 23, 2006, 10:39 PM
nooobama
United States, PA, Stroudsburg
Joined May 2004
984 Posts
What is the root chord? Or how do I get that measurement? Thanks, Cas
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Old Mar 24, 2006, 01:31 AM
Registered User
Crossville, TN
Joined Dec 2004
2,907 Posts
The root chord measurement is from the leading edge to the trailing edge at the half span point.
Another way of stating post#1...
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Last edited by Art Schmitz; Mar 24, 2006 at 01:55 AM.
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Old Mar 24, 2006, 07:36 AM
Lift is cheap - Drag sucks
Tom Harper's Avatar
Socorro, NM
Joined Jul 2004
3,513 Posts
finishman,

The root chord is the width of the wing at the fuselage.
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Old Mar 24, 2006, 09:09 AM
Red Merle ALES
Curtis Suter's Avatar
United States, Mt, Helena
Joined Apr 2002
4,921 Posts
Here's a quick MS Excel program that will give you the 25% location for a wing with up to three chord breaks.

It's called Sailplane Calc.

Curtis
Montana
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Old Mar 27, 2006, 01:42 PM
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uriah's Avatar
Twisp Washington USA
Joined Sep 2005
331 Posts
i got a better idea!!! the canards are there for stabalization and in some cases, flight control... you want them! just build some canards out of a stronger material... even aluminum if you want...
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Old Mar 27, 2006, 02:38 PM
nooobama
United States, PA, Stroudsburg
Joined May 2004
984 Posts
I want speed so I'll try it with them off. I'll find out in about an hour if I got the CG right.
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Old Mar 29, 2006, 09:16 AM
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uriah's Avatar
Twisp Washington USA
Joined Sep 2005
331 Posts
well did ya?
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Old Mar 29, 2006, 09:39 AM
nooobama
United States, PA, Stroudsburg
Joined May 2004
984 Posts
Sorry, I figured no one cared about the 'ol Firebat now that it is so outdated by all the new sexy foamies out there.
Yes it did fly, the CG is a right on but I set up a little in front of it for the first few flights. This plane is made of easy to damage EPS foam and I don't expect it to live a long life. I replaced the ailerons with balsa and the JustGoFly.com 400DF is a little underpowered for this plane but it does about 5 rolls a second and rolls on its own axis. I don't think it would do this if I lefyt the canards on. I may up the powerplant to the 450DF once I get some 20c lipo's. Overall a good plane, looks good and flies well.
Thanks for the help guys, Cas
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Old Mar 29, 2006, 01:45 PM
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uriah's Avatar
Twisp Washington USA
Joined Sep 2005
331 Posts
any pictures?
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Old Mar 29, 2006, 02:00 PM
nooobama
United States, PA, Stroudsburg
Joined May 2004
984 Posts
I have no idea how to post'em here. If you want PM your addy and I'll send some over, Cas
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Old Jul 16, 2006, 02:59 AM
Random Flier
Oxford (UK) and Mtn View CA (USA)
Joined Nov 2002
1,374 Posts
Interesting thread - I just had a spectacular in-air break-up of my Firebat-sans-canards. I was struggling to get the CoG correct (was testing at 2cm in front of the theoretical CoG I'd calculated from some spreadsheet, and it was still barely controllable in the pitch axis, wanting to dive or climb but not fly straight - this was with the servos, LiPo and RX all near the nose!).

[To be fair the crash sequence was nowt to do with CoG, but the canopy ejecting as I struggled to control the plane. This lead to the aft fusalage cover to catch the wind and flip up. This was latched into the top of the motor mount, so it levered off the mount and the motor / ESC / battery ejected. Plane glided beautifully with all that gone... ]
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Old Jul 16, 2006, 10:38 AM
Ascended Master
Sparky Paul's Avatar
Palmdale, CA
Joined Oct 2000
13,203 Posts
Quote:
Originally Posted by isvana
... Plane glided beautifully with all that gone... ]
.
And THAT'S where the c.g. should be!
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Old Jul 17, 2006, 06:06 AM
Random Flier
Oxford (UK) and Mtn View CA (USA)
Joined Nov 2002
1,374 Posts
LOL! Thats what I thought too. Proved I was 1cm too far back and/or had some other problem. I'll mark the CoG and rebuild. Next project is the 3-engine (250 motor) FirebatSC (sans canard)...
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