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Author Topic: C.G. of Delta Wings  (Read 5033 times)
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AlpineSeeker
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« on: July 18, 2008, 12:26:42 AM »

Hello All,
 
I am new to this site and would like to post a question. I would like to build (and hopefully fly....lol) and delta wing RC aircraft that I would like to build and was wondering how to find the proper Center of Gravity on a Delta Wing aircraft? On a regular wing I have heard 30% behind the leading edge? but have not heard anything about Delta configurations. Any help would be greatly appreciated.

Take Care.
Ross
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Mike Taylor
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« Reply #1 on: July 18, 2008, 01:10:08 AM »

Flying wings and deltas balance a little further forward than convention models. 22% to 25% work well in most cases. A MAC and CG calculator is here: http://www.palosrc.com/instructors/cg.htm
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JetPlaneFlyer
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« Reply #2 on: July 18, 2008, 02:26:38 AM »

I think Mike may be talking about 22-25 MAC (Mean Aerodynamic Chord) rather than root chord.
I've made a few deltas and (assuming they are a true triangular planform Delta) the CG comes out at about 40-45 % for tailless, and for a tailed Delta 45-50%, maybe further back if the tail was very large.

The CG calculator Mike linked to actually confirms this.
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Mike Taylor
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« Reply #3 on: July 18, 2008, 06:40:22 PM »

Yep, sorry - that's 25% MAC.

My edf30 F-102 measures 12" WS, ~11 1/2" root chord, and the CG is 5 1/2" back from the LE at the root.
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AlpineSeeker
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« Reply #4 on: July 18, 2008, 07:23:52 PM »

Hello again,

Thank you both for the good input, I will use the calculator and see what I need to set it at. I was wondering if using a
canard configuration would affect the calculation as would a tailed configuration? Any ideas?

Thanks again and have a great weekend.
Ross
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Mike Taylor
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« Reply #5 on: July 19, 2008, 03:51:42 AM »

Perhaps this will help: http://adamone.rchomepage.com/cg2_canard.htm
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JetPlaneFlyer
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« Reply #6 on: July 19, 2008, 04:03:54 AM »

Hello again,
Thank you both for the good input, I will use the calculator
and see what I need to set it at. I was wondering if using a
canard configuration would affect the calculation as would a
tailed configuration? Any ideas? Thanks again and have a great weekend.

With a Canard the optimum CG will move forward, with a rear mounted stabiliser it moves backward. There is a CG calculator for conventional 'tailed' aircraft here: http://adamone.rchomepage.com/cg_calc.htm. these also work for tailless, simply put tiny values in for the tail area and moment arm Wink
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AlpineSeeker
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« Reply #7 on: July 19, 2008, 10:16:43 PM »

Hello there,

Once again you two have come thru, Thanks so much. Where do you guys
find all these cool sites?.....lol. I just knew that I should have paid more
attention in geometry class........lol. Have a great weekend!

Take Care.
Ross Wink
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