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Old 05-18-2003 | 10:03 PM
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From: Bainbridge, Ohio
Default What goes up?

If a plane tends to go vertical immediately on takeoff, needs a whole lot of down elevator to settle into a managable climb, and the CG is right, am I correct in assuming that there might be too much positive incidence in the wing?
Everything seems to be lined up pretty well. The wing (corro) does have a bit of concavity in the bottom, and yields tons (well, not really, but you know what I mean) of lift.
There is about 3 deg. down thrust at the engine.
Should I try angling the wing saddle down a couple of degrees? What else am I missing here?
Old 05-19-2003 | 03:24 AM
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Default What goes up?

TailDragon, first set it up for 0-0-0 on the wing incidence tail incidence and engine incidence. Make sure your C/G is in the range or 25% to 33% of the MAC. If your nose moments and tail moments are all with in range then it should fly great. I suspect the down thrust is causing you problems if you don't have a positive incidence in the undercambered wing. Hope this helps.
Old 05-19-2003 | 03:58 AM
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Default Re: What goes up?

Originally posted by TailDraggin
If a plane tends to go vertical immediately on takeoff, needs a whole lot of down elevator to settle into a managable climb, and the CG is right, am I correct in assuming that there might be too much positive incidence in the wing?
Everything seems to be lined up pretty well. The wing (corro) does have a bit of concavity in the bottom, and yields tons (well, not really, but you know what I mean) of lift.
There is about 3 deg. down thrust at the engine.
Should I try angling the wing saddle down a couple of degrees? What else am I missing here?
You state the wing is under-cambered. High lift and high drag wing.
Although most plans relate *incidence* to the drawer's centerline and relate stab incidence, wing incidence, down thrust, etc. etc. the airplane only sees the stab as NEUTRAL with all references to the stab's chord-line.
The wing incidence should be determined between the wing's chord line (between the center of the wing's leading edge radius) and the trailing edge ctr.
If it's positive, then you have positive wing incidence. If you measure the thrust line reference the stab chord-line then you will know true down-thrust.
Depending on the power available, you may well need more than 3* down-thrust. I have use up to 14* in some "Old-Timer" models (converted from old-time gas FF).

Reference the "CG is right", I think a CG on that type wing (Given a flat or symmetrical stab) should be NOT aft of 28%.

BTDT


HC

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