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Old 09-27-2014, 10:21 PM
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Old dog, New tricks
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how tail heavy?

Im flying a aeroworks 50cc yak 54. Im having a issue with balance when doing hovering/harrier maneuvers. On a 45 degree rolled inverted, it falls gently and requires little down elev on level inverted flight. But when hovering and harriers, it will not stabilize. it tumbles like a pro but fails to flatten out in a flat spin....


Im running a EME 55 with a 23x8 zoar. It will punch out vertical easily. Does this sound like the model is still nose heavy or am I way off?
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Old 09-29-2014, 10:44 AM
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Nobody? Do i need to rephrase the question?
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Old 09-29-2014, 11:08 AM
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For 3d, I tend to prefer a perfect inverted 45. If the plane falls very gradually to the nose it's probably still fine for 3d. If it is a quick deviation then it's too nose heavy. Inverted flight shoyld only require a *tiny* bit of down. Also, run the plane through the entire trim process before moving to much stuff around. Incorrect thrust angle can throw everything off.

Fwiw, it's easier if you have someone with 3d experience help you at the field.
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Old 09-29-2014, 11:20 AM
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I also trim my 3D planes for a sustained inverted 45. Depending on the plane/airfoil you may even want to go to a slight climb from an inverted 45. That would probably help with the flat spin issue. I actually fly my WWRC 30cc YAK profile balanced to climb from level inverted, but that's just me. The YAK's airfoil allows this while not being overly sensitive in pitch. Spins flat like a Frisbee!

A "side benefit" of this set up is that the plane flares automatically on landings!
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Old 09-29-2014, 01:28 PM
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Obviously, heavier tail stays better in harrier and hover. But makes the plane hard to land on gusty days. Harrier landing is the solution.
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Old 09-29-2014, 02:25 PM
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Thanks guys.. i re trimmed yesterday and took more weight out of the nose but it still falls gradually in the 45 up line. Also took throws down to low on flat spins and it is flattening out better. As far as thrust goes, what's a good starting point? Right now I have 4 degrees right but no down or up thrust.......
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Old 09-29-2014, 03:27 PM
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I usually don't add more than 3 degrees of right thrust. Also, you can generally double check up/down thrust (assuming symmetrical airfoils and 0/0 wing stab incidence) by making a full throttle level pass and quickly cutting the throttle. The plane should continue level for a short time. An immediate pitch change would indicate that you are fighting up or down thrust from the engine.
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Old 09-29-2014, 06:35 PM
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Here is how I check thrust. In level flight, full power trimmed for hands off. Pull power. If the plane pitches up, you have too much down thrust. Pitches down, too much up thrust. Then, go vertical. If it goes left, more right thrust is needed. If it goes right, less right thrust.
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Old 10-04-2014, 09:08 AM
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checked up/ down thrust this morning..... its showing it has 1.5 degrees down thrust. set to 0? It does tend to "balloon" often when power is chopped at slow speeds....
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Old 10-04-2014, 10:05 AM
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The tail might drop at low speed due to a tailheavy condition. If it balooned at speed, then you would have too much down thrust.
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Old 10-04-2014, 10:25 AM
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Check out the goldsmith trimming chart. I know it is intended for imac style flying. If you are willing to spend the time to balance and set up your plane to fly neutral then toss in some 3d throws you may be surprised by the results. He has a good article explaining how each change effects the others. Even just going through it once makes a huge difference.
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Old 10-04-2014, 02:30 PM
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2nd the Goldsmith Trimming article from AMA magazine.
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Old 10-04-2014, 08:41 PM
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Thanks guys, I forgot what it was called.....
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Old 10-05-2014, 10:16 AM
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Good reading!!!!
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Old 03-14-2016, 06:26 PM
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