ORIGINAL: Mr67Stang
ORIGINAL: tripower222
Why don't airplanes with high lift wings (like flat bottom trainers) have lifting/airfoil horizontal stabs. I would think ifthelift and tail momentwhere calculated correctly once the elevator is trimmed, the plane would fly level at any airspeed, above stall of course. I would think it would make a more stable plane which is idea behind a trianer.
This discussion really has not addressed the OP's concern or goal heighlighted in the above quote. A trainers tendancy to climb under accelleration or higher air speed. This is a product of the main wing's and horizontal stabalizer's reletive incedence and the engine's thrust angle. I feel it has nothing to do with the airfoil, or lack of airfoil, in the horizontal stab. My Funtana X100 has flat stab tail feathers (epanage SP?) and it does not care what speed I fly it at, it goes where it is pointed.
If you, tripower222, are comfortable with your trainer as it is and want to play with it, Try shimming the back of the wing up a little at a time reducing it's angle of attack reletive to the thrust line a little at a time and see what results that produces.
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</span><span style="font-size: small"><span style="font-family: Times New Roman">If the down thrust on the engine is set correctly the tail will not have to make up the differenceby lifting up or down with changes in throttle and speed. With the correct down thrustthe engine will pull the plane forward and more down as power is applied. Ideallythe horizontal stabilizerprovides neutral lift unless the elevator is deflected to alter the planes path. If one puts a larger than required engine they may also need to increase the down thrust to overcome the tendency to climb.I have seen many folks suffer from constant climb at full throttle because they don't understand this.
Other factors are at play as well. Correct CG, angle of incidence for the tail and wing(s). Model Aviation had a really good article explaining this a few months back.
Also... Don't assume that a built up airfoil is lifting. My old Carl Goldberg Falcon 56 has a built up tail but the airfoil is symetrical. For a slow plane a symetrical airfoil provides less turbulant air over the elevator surfaces resulting in better control. I beleive many of the pattern planeshave a symetricairfoilfor this reason. Built up is generallylighter than a slab as well. </span></span></div>