RC-Captain

I notice on the electric planes I fly, the motor for some reason is not set perfectly straight but is set a certain degree to the right . Can anybody tell me the reason why the motor is installed this way? Please keep in mind I only fly electric planes . Thanks in advance for all replies.

Airborne 2007

From what I get, the one side of the prop generates more thrust, so I think that angle is to counterbalance that difference. Go ahead and correct me if im wrong.

-John

phantomphixer

Hi,
Just joined this website and came across this first thing. Don't know why more people have not jumped in on this as there must be a dozen explanations. I can tell you that in my earlier F/F days this was a more or less exact science(some voodoo involved).
Motors were always set with some down and right thrust. The down thrust was to keep the climb under control and still maintain level flight in the glide mode. Of course if a lifting stab was used then a bit of voodoo was needed. Mostly gentle trial and error. As for right thrust, The prop wash against the left side of the vertical stab combined with the torque of the motor will produce a left turn tendancy. The 2 or 3 degrees right thrust cancels this nicely. My slow high wing planes have down and right thrust but my faster stunt types have no down thrust and only about 1 degree of right. This works for me but is not the answer to all planes. Hope this helps just a little. If this is wrong, it is what we were taught in the "old days".

David

Matt Kirsch

My Feedback: (21)

It is fairly common for planes to have down and right thrust. As stated before, the reason for this is to counteract most planes' tendencies to yaw to the left and climb under power.

There are multiple reasons behind why most planes yaw to the left and climb under power. First is what's called "P Factor." P factor is caused by the fact that planes generally fly around slightly tail-low. Thus, the downward-moving blade of the prop has a higher angle of attack than the upward-moving blade, and produces more thrust. Since the downward-moving blade is usually on the right hand side of the plane, the additional thrust tends to push the plane to the left.

Second is motor/engine torque. From the pilot's seat, the prop normally rotates clockwise. Every action has an equal and opposite reaction, so the clockwise-turning prop tends to make the plane roll counterclockwise, or to the left.

Third is lift. The faster the plane moves, the more lift is created. When lift exceeds the weight of the airplane, the airplane tends to climb.

The plane tends to balloon up and to the left due to a combination of P Factor, lift and torque. Angling the engine down and right counteracts these forces and make the plane fly "truer" at all throttle levels.

RC-Captain

Thanks for all of the speedy replies. I now understand why motors are mounted in this manner . Just one more question please . I noticed a big difference from flying the Carl goldberg Lightnin' Bug with a 9x5.5 prop verses a master airscrew 9x5 prop. The thrust and ROG with the 9*5.5 prop was incredible compared to the 9x5 . Correct me if Im wrong , the 5.5 and 5 on these props represent the so callled THROW of the prop ? so the question is, If the throw is greater , will the prop deliver more thrust and power with noticeably results ?


P.S. or did I already blow my load with this geared motor I received with the plane ?

Matt Kirsch

My Feedback: (21)

The second number indicates the pitch, in inches, of the prop. Pitch is how far forward the propeller will move per revolution if it were turned through a block of Jello. That is, a 5.5" pitch means the propeller will move 5.5" per revolution.

To a point, increasing pitch will increase thrust. Like a wing, though, if your pitch, or angle-of-attack, gets too high, the propeller will stall and produce significantly less thrust. At that point, pitch more controls the maximum potential speed of the airplane than thrust.

.5" of pitch should not make a significant difference in performance. What is probably going in here is that the 9x5.5 propeller was designed with a much more efficient airfoil than the 9x5 Master Paintstick, er, Airscrew