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3D Flying Discuss everything related to "3D" flying including construction, power setups and flying techniques

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Old 02-23-2011, 11:02 PM   #1
drumerdan
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Default Homemade foamy bites the dust... Too much power?

I attempted to design and build a foam board 3d electric. I had a old geared speed 300 to power it and my old receiver and servos to control it. weighed around 14 ounces finished. It had over 600 in^3 wing area.






The build went well, but when came time to fly it my old power system just didn't cut it, turns out the battery wouldn't hold voltage under a load and the speed 300 would have done fine. So I bought a power system that was a bit overkill......

outrunner brushless 2830 1300kv
30 amp speed controller
3S 1000mah LIPO
30+ ounces of thrust and same weight as before.

Anyway under power the plane just pulled up and left hard. I angled the engine down and to the right a few degrees already. This combo made the plane almost uncontrollable and I crashed it.



SO,
now I'm looking a finding a good 3d plane that this motor would be better suited for. I want less wing area and a bit more weight. I'm considering making another foamy and changing a few things.

Any suggestions?
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Old 02-24-2011, 12:19 AM   #2
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Your rudder and elevator look a little small for that much wing area. They may not be giving you enough controll authority.

You generally want the elevators to be about 15% of the total wing area on a bipe and rudder should be at least 10% or larger. In your case, that means you need about 90 sq inches for the elevators and at least 60 sq inches for the rudder.

I think I need a signature.
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Old 02-24-2011, 12:28 AM   #3
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http://www.crashandburnhobby.com/Red...P-S31-p64.html have a look at this

I compress at 60
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Old 02-24-2011, 01:12 AM   #4
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Originally Posted by drumerdan View Post
I attempted to design and build a foam board 3d electric. I had a old geared speed 300 to power it and my old receiver and servos to control it. weighed around 14 ounces finished. It had over 600 in^3 wing area.






The build went well, but when came time to fly it my old power system just didn't cut it, turns out the battery wouldn't hold voltage under a load and the speed 300 would have done fine. So I bought a power system that was a bit overkill......

outrunner brushless 2830 1300kv
30 amp speed controller
3S 1000mah LIPO
30+ ounces of thrust and same weight as before.

Anyway under power the plane just pulled up and left hard. I angled the engine down and to the right a few degrees already. This combo made the plane almost uncontrollable and I crashed it.



SO,
now I'm looking a finding a good 3d plane that this motor would be better suited for. I want less wing area and a bit more weight. I'm considering making another foamy and changing a few things.

Any suggestions?
The power system is perfect, but out of center line with the plane, that IMHO was the biggest problem, and it caused the plane to pull left on the side it was on, the rudder and elevator could stand to be a bit larger like Larry said, Normally you dont need any right or left thrust on a profile plane, just down thrust, about 3 to 5 degrees of down thrust, and I bet the Latteral balance was way off too, to much weight on the left side of the plane, on your next build, put the motor in the middle, put the CG at 25% of the wing cord, or 1/4 of the way back from the front leading edge, also latteral balance the plane, here is how, glue a string under the plane at the CG point on the bottom fuselage, hold the plane up with the string, with everything on the plane, motor, lipo, receiver etc, the wing should be level, if not, add a finishing nail into the wing thats up, it might take a few nails, push them into the wing untill flush, untill the wing is level, now your plane is balanced, and should fly right also check the incedence of the main wing and elevator, it should be at 0-0 incedence or both should be level with one another, use a small bubble gauge/level.

http://www.wattflyer.com/forums/showthread.php?t=39483

http://www.rcplanetalk.com/trim.html

http://www.wattflyer.com/forums/showthread.php?t=23408

http://www.wattflyer.com/forums/showthread.php?t=39733






I may be getting Older, But I Refuse to grow Up I am Having to much Fun to Grow Up LOL
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Old 02-24-2011, 01:21 AM   #5
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Dont give up Drumerdan your almost there it takes a few builds to learn from before you know what to expect, and building from scratch is not easy at all, We are all here to help you Take care and have fun, Chellie

Oh, BTW, Welcome to Wattflyers

I may be getting Older, But I Refuse to grow Up I am Having to much Fun to Grow Up LOL
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Old 02-24-2011, 02:26 PM   #6
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Thanks! Makes sense that you need larger control surfaces with larger wing area. I'm sure its got something to do with center of pressure, kind of like a metacenter for a boat.

The old engine was off center but the brushless was in the center.

I'm going to make bigger elevator and rudder and see how it responds before ditching this plane.

Thanks for the help
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Old 03-12-2011, 03:06 AM   #7
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Time for round two!

What this time? A built up foam board extra 300!
The wing is surprisingly strong and stiff, pretty light too!

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Old 03-12-2011, 01:31 PM   #8
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Nice wing - but what happened with the bipe??

I think I need a signature.
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Old 03-14-2011, 05:54 PM   #9
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that much wing area with that thick of a chord would require a huge tail surface and a longer body to fly like I want. I decided to start fresh.
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