right thrust only matters if the nose is up. Do a full power vertical climb as close to vertical as you can and let go of the sticks and see which way it yaws. If it goes right, it is too much. also check to see if it pitches up or down when you do this. You may even need up or down thrust.
A plane designed for symmetrical flying should have
(i) No thrust offset of any sort (ii) Thrust as near to CG and Cof drag as possible (iii) No dihedral (iv) Fully symmetrical wing section (v) As much fin and rudder below teh cenbter line as above (vi) plenty of fuselage side area for knife edge. and a fair bit in front of the CG as well as aft. (vii) Ailerons in the prop wash.
That way it will fly in almost any attitude. Side thrust is normally used with dihedral to counteract torque rolling via yaw. Its a bastrad way to do it. If teh ailerons are in teh wash, just couple a tad of right stick to teh throttle. That should work even in 'hover'
Sorry for the double posts. Honest, when I checked, it was not here at
8 AM this morning.
I agree with the Natural Philosopher, however the plane's designer calls for 1/8" of offset on the motor mount for right thrust. I had built just about all my planes with zero, zero in the wing, tail section and motor.
The plane is quite a zesty craft with verticals you'd not believe. I just wanted to get it right again. So if I'm to follow your commentary, I should shim the motor to align straight with the center line of the fuse?
Right thrust does more than just compensate for nose-up flight. It helps counter the left-turning tendency caused by the rotating slipstream off the prop, most noticeable in the takeoff roll. There are four forces that the prop imparts to the airplane, besides the obvious thrust. The first is the rotating slipstream, which, in an airplane that has a clockwise-turning prop (as seen from the cockpit), strikes the fin on the left side and swings tail right, nose left. The second is the higher angle of attack of the downgoing blade, if the airplane is in slow flight or a climb, or in a taildragger before the tail comes up on takeoff. This is on the right side, and pulls the nose left. Third, The torque reaction puts more weight on the left wheel on takeoff, creating a bit more friction and pulling nose left, and in flight may cause a left-banking tendency. Fourth, the gyroscopic precession of the prop will swing the nose of a taildragger left as the tail comes up on takeoff. Note that all reactions are to the left, and if the prop turns the other way, they all pull the nose right. Right thrust makes the airplane easier to fly. Down thrust makes the airplane easier to fly. An experienced pilot doesn't need either of them any more than an experienced cyclist needs training wheels. They create some drag and hurt overall performance. Some full-scale manufacturers use them, and others don't.
Thanks for the thorough explanation about right thrust, Dan. The four points that you made have made the need for right thrust understandable. So, if I'm a more experienced pilot, I would not need right thrust.
A Mr. Winzer is succinct in his answer to my two questions in my original post. Herewith: His post on 10-29-03; answer to question #1--NO answer to question #2--NO
His answer has me thinking, from the cockpit point of view, the prop is still rotating clockwise so it doesn't change anything whether right side up or upside down.
I didn't, because frankly that statement makes no sense anyway.
IF you have dihedral, then anything that introduces a yaw, will end up rolling the model.
Right thrust works to counteract power dependent rolloing moments via dihedral. Right thrust works upise down - as does rudder, because when upside dwon teh wings have ANHEDRAL if you like. To get an invrted rudder only model to turn left, you do indeed use LEFT rudder, which doesn't turn the plane INTO the desired bank, it turns it OUT, but the (anhedral) rolls the plane in the OPPOSITE direction to the yaw, and if you then take the rudder off, and apply some 'down' elevator, you can turn your plane to the left...a most unnatural looking manouver to be sure, but thtas how it works..
If you have no dihedral, then right thrust is going to simply make your model yaw, and not actually turn it right.
IF you have sweepback, and no dihedral, then the effect is to always roll in the direction of the yaw. So under these circumstances the right thrust will roll the model to the right , right way up, and to the left, when inverted. Its no surprise then that pattern models have no right thrust and slightly sweptback wings, typically. This makes them behave the same way either way up, and any propwash/torque effects are taken care of by aileron trim, and, with teh ailerons inboard near the propwash, the work under low airspeed conditions as well.
Sidethrust IMHO is an ugly way to get a scale model or trainer to track straight when you haven't got a computer mixer. On a neutrally stable aerobatoic model it shouldn't be necessary.
Now, there is an aerobatic low-wing homebuilt aircraft known as the Jurca Scirocco that has NO dihedral. The designer felt that dihedral was not always necessary for stability. This airplane will roll in the proper direction when rudder is applied, even without dihedral, partly because the fuselage blanks a bit of the inside wing as a skid begins. Many high-wing airplanes have no dihedral either, and behave perfectly normally, banking when yaw is introduced. The Bede BD-4 is one. All of the Cessna high-wingers have only a degree or so, and still bank with yaw. There are other factors that will make a wingtip rise if the wing is yawed a bit. I believe a minimizing of the tip vortex on the leading tip has something to do with it. Our first RC was a powered two-axis sailplane, with plenty of dihedral. It banked normally using rudder whether right side up or upside down, though it was difficult to keep it inverted. In full-scale training, you will learn that the turn is accomplished using bank angle, to change the lift vector from vertical to toward the centre of the turn. The rudder is used ONLY to eliminate the adverse yaw created in most airplanes as the downgoing aileron on the outside wing creates more drag than the upgoing aileron and pulls the nose a bit away from the desired turn direction. Rudder is a coordinating device, not a turning device. Using rudder to turn creates a skid, which at low speeds can result in an uncoordinated stall and a spin.