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Old 11-30-2010, 08:57 PM
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r4pt0r
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Ok i want to build one of these [media]http://media.photobucket.com/image/XB-0/JDX_edificios/XB-0Hresvelgr.png[/media] With two 12in puller props in front, made out of FFF and with an approxomite wingspan of 5 to 6 feet. I have no clue where the CG should be on flying wings, is it still 1/3rd back from the leading edge reletive to the trailing edge? i dont want a CG calculator, if someone would just use paint or something and post their best guess as a pic thatd be great
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Old 11-30-2010, 08:59 PM
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[media]http://sky.geocities.jp/ngbsc419/XB-0.gif[/media] heres a working pic
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Old 12-01-2010, 01:42 AM
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CHELLIE
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Pic is not showing up, i just get a blank stare
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Old 12-01-2010, 02:25 AM
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Originally Posted by CHELLIE View Post
Pic is not showing up, i just get a blank stare
Same here, no pixs come-up after slow load'in, bubsteve
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Old 12-01-2010, 02:29 AM
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Attempt #3Click image for larger version

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Old 12-03-2010, 01:54 AM
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the principle is basically the same. If you have worked out CoG for swept wings before this is the same. It may not be optimal, but would give a good starting point. If you haven't i'll post something up when I get home.
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Old 12-03-2010, 03:10 AM
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make a simple profile foam glider model of it, and play with the cg, untill it glides well, and that should get you very very close. when you make the plane, the elevon hinges will have to be 90 degrees to the fuselage center line, if not the angle on the wings elevon hinge will cause erratic flight, I have seen that happen before with swept wings where the hinge angle matched the swept angle of the wing, and caused major flight problems, by wanting the wing to pull right or left and it wont roll for Darn , Hope that helps, Chellie

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Old 12-03-2010, 07:08 AM
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Originally Posted by r4pt0r View Post
i dont want a CG calculator, if someone would just use paint or something and post their best guess as a pic thatd be great
So you don't want to invest 10 minutes of your time on a CG calculator but you are quite happy to accept someone else's guess then quite likely crash and destroy all your hard work

By the way.. No, 1/3 back on a tailless plane is not correct (it's not necessarily correct on a plane with a tail either)

Chellie's idea on the test glider is a good one, the larger you make the glider the more accurate info you will get from it.

Steve
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Old 12-05-2010, 02:27 PM
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Agree , with Chellie that you should built a small scale profile .Toss the profile and add/subtract weight at the nose till you get a good glide. That's what i did when I try a scratch built delta plane the first time.
Scale up and made the actual model slightly nose heavy on the actual model.

The small scale profile form also indicate if the plane form is aerodynamically sound.

All the best

Cheers
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