I think I've messed something up here. Correct me if I'm wrong.
I recently modded my UMX J-3 Cub with a UMX Mustang motor. (I was sick of breaking prop shafts and this is a common mod.)
Most people use a Mustang prop, but I went with a 3-bladed Corsair prop mainly to avoid the prop clearance issues that come with the big ol' Mustang prop. Others have posted that they run the Corsair props.
But ... the prop spins clockwise when viewed from the front. This means - doesn't it? - that the plane will want to respond by rolling to the right.
However, the motor is mounted so that it is angled to the right (and down). In my case, though, this is exacerbating, rather than compensating for, the torque roll. Am I right?
Cuz this thing is a pill. It really, really, really wants to roll hard to the right on launch/take-off.
I want to check my thinking before I cut a bunch of foam out of the motor mount area and screw the plane up forever.
Looks like a reverse prop to me as well. I have used them with no issues but my motor mounts have always been straight so had no issues. Your motor mount is angled to reduce the affect of torque roll with a normal prop. So yes you are compounding the problem. Just buy another $5 prop to fix all issues.
And a bit of advice, couple actually. Don't always believe the rule of thumb.
Not all props have the numbers on the front. The one used on the Parkzone Corsair, the park size, not the micro, is one that can bite you. Properly installed the numbers are on the back of the blade.
Ask me how I know.
#2 don't confuse torque roll with P factor.
Prop P factor is the forces (on a normal rotation prop) that makes the prop pull to the left and up. That's what your down and right angles on the motor are used to compensate for.
Torque is the force used to turn the prop, bigger the prop, the more torque it takes to turn it. And in turn, the more the airframe has to counter it.
You'll see torque roll as a type of condition, where the torque of spinning the prop is used/fought to make the plane roll on the prop axis. Do a roll to the right and it's easier as the torque is helping roll the plane over. Try it going left and you have to over come the torque to roll.
Prop P factor (again normal set up)is always trying to pull the nose up and to the left.
Torque is trying to twist the airframe to the right/clockwise, when viewed from the rear.
When I die, I want to go like my Grandfather did, in his sleep...... Not screaming like the passengers in his plane.
If we are getting technical then it's not actually P-factor that's responsible for most of the yaw experienced due to the prop rotation. P-factor is not a cause at all of nose up pitching, that's a different issue altogether and related to stability, trim and other factors.
Most of the left yaw you might experience and the main reason for right thrust is helical prop wash creating a sidewaws force on the vertical stabiliser. P-factor is only an issue where there is a large difference between the line of the prop axis and the direction of travel, like in high alpha flight or on a taildragger during the take off run. In normal level flight P-factor isn't an issue.
This is an attempt to answer the frequent question "Why is my airctaft turning left all the time?".
This occurs only in aircraft with propellers at the front of the aircraft. And yes, it does occur in real life. Four distinct phenomena cause the effect, all causing the aircraft to turn in the same direction. They are:
A propeller pushes air not just horizontally to the back, but more in a twisting helix around the fuselage (clockwise as seen from the cockpit). As the air whirls around the fuselage it pushes against the left side of the vertical tail (assuming it is located above the propeller's axis), causing the plane to yaw to the left. The prop wash effect is at its greatest when the airflow is flowing more around the fuselage than along it, i.e., at high power and low airspeed, which is the situation when starting the takeoff run.
Propeller torque effect
Torque effect is the influence of engine torque on aircraft movement and control. It is generally exhibited as a left turning tendency in piston single engine propeller driven aircraft.
According to Newton's law, "for every action there is an equal and opposite reaction," such that the propeller, if turning clockwise (when viewed from the cockpit), imparts a tendency for the aircraft to rotate counterclockwise. Since most single engine aircraft have propellers rotating clockwise, they rotate to the left, pushing the left wing down.
Typically, the pilot is expected to counter this force through the control inputs. To counter the aircraft roll left, the pilot applies right aileron.
It is important to understand that torque is a movement about the roll axis. Aileron controls roll. Prop torque is not countered by moving the rudder or by setting rudder trim. It is countered by moving or trimming the aileron.
This correction induces adverse yaw, which is corrected by moving or trimming the rudder (right rudder).
On aircraft with contrarotating propellers (propellers that rotate in opposite directions) the torque from the two propellers cancel each other out, so that no compensation is needed.
Further Reading: Propeller Torque Factor
P-factor is the term for asymmetric propeller loading, causes the airplane to yaw to the left when at high angles of attack.
The descending right side of the propeller (as seen from the rear) has a higher angle of attack than the upward-moving blade on the left side and provides more thrust. This occurs only when the propeller is not meeting the oncoming airflow head-on, for example when an aircraft is moving down the runway at a nose-high attitude (i.e. at a high angle of attack), as is the case with tail-draggers. Aircraft with tricycle landing gear maintain a level attitude on the takeoff roll run, so there is little P-factor during takeoff roll until lift off. In all cases, though, the effect is weaker than prop wash.
According to What You Need to Know About Aerodyanics... by Franklin Gutierrez.
This is the tendency of a spinning object to precess or move about its axis when disturbed by a force. The engine and propeller act as a big gyroscope. However, gyroscopic precession is likely to be minimal in a typical aircraft.
Gyroscopic precession is frequently confused with p-factor.