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Old 02-27-2021, 11:39 PM
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PiccoLino
 
Join Date: Jan 2007
Location: Modena, ITALY
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Default Power to weight ratio and prop size

In the last years there has been a significant development in increasing the power of both glow engines and electric motors. This has lead to larger and larger prop size consequently. In the same time, especially in F3A planes, the stabilizer and rudder surface got larger too. These factors combined together can cause a tremendous vortex effect on the tail control surfaces of the plane and torque the fuselage to the point of reducing directionality, hence making the the control inputs response less consistent.
So, why does a small wing attached to the canopy solve the problem? Isn't this small wing hit by the same prop vortex that causes the plane behave erratically?
The canalizer is close to the prop (and to the CG) where the prop air flow speed is much higher than it is by the plane tail surfaces. The higher the prop air flow speed the lower the resulting aerodynamic torque effect because the distance between the vortex waves generated by each revolution of the prop blade are farther one the other. Therefore, given these conditions, the canalizer, rather than twisting and shaking, stabilizes the plane because it (the canalizer) travels through the fluid streamlines when they are still relatively straight.