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Thrust Angle

alan0043

Active member
#1
Hi Everyone,

I want to understand thrust angle. I am a 70 year old rookie. I like to scratch build. I remember Josh talking about thrust angle in some of his build videos. I think the tiny trainer has thrust angle that goes to the right. I have built a plane and it looks like the front tip of the motor points higher then the the back of the motor. With this kind of problem, what happens to the plane. The plane does not fly to good. If there is an article or thread out there talking about understanding thrust angle, please point me in the right direction. I did a search with not any luck on my end. I understand small washers can help with thrust angle.

I am open to all input,
Al
 

Flitedesign 3d

Well-known member
#2
Hi Everyone,

I want to understand thrust angle. I am a 70 year old rookie. I like to scratch build. I remember Josh talking about thrust angle in some of his build videos. I think the tiny trainer has thrust angle that goes to the right. I have built a plane and it looks like the front tip of the motor points higher then the the back of the motor. With this kind of problem, what happens to the plane. The plane does not fly to good. If there is an article or thread out there talking about understanding thrust angle, please point me in the right direction. I did a search with not any luck on my end. I understand small washers can help with thrust angle.

I am open to all input,
Al
Hey, 1-3 degrees right trust angle is usually put to compensate the propeller tork and 1-2 degrees of down angle is put to compensate the increased lift when the speed of the plane inreases
 

quorneng

Well-known member
#3
alan0043
For a prop that goes round anti clock wise (viewed from the front) the torque of the motor will tend to make the plane bank and turn to the left. Adding a few degrees right thrust to the motor will try to make the plane turn right. Get the angle right at the two cancel each other out with the advantage this will happen at all levels of power.
Any plane that is stable in flight will try to fly at one speed. As power (thrust) is applied the plane will speed up so it tries to return to its natural speed by climbing. By adding down thrust to the motor a small portion of the thrust now tries to pull the nose down to prevent the climb allowing the plane to speed up yet staying more or less level.
For a home design the appropriate amount of side/down angle has to be found by trial and error.
 

Bricks

Well-known member
#4
Once you have it basically trimmed out point the nose straight up and full power pay attention to which way the plane pulls left, right, towards the canopy or away then add washers or some type of spacer to correct, and try again. When she climbs straight up with out any input you pretty much have it.
 

Merv

Well-known member
#6
Getting the thrust angle correct can greatly improve the way a plane flies. Everyone has their own way of doing it, here is my method.

I trim the plane to fly straight and level at full throttle. Then I fly very high, cut the throttle and put the plane into a straight down dive. The goal is to be at to dive 150-200 feet straight down. If the plane quickly pulls out of the dive right side up, you need less down thrust. If the plane. If the plane pulls out bell side up, you need more down thrust.

Why it works, when you trim for straight and level at full throttle, you trim out any errors in thrust or incidents. When you dive without power, you remove the thrust and yet maintain good speed. This will allow you to see what was trimmed out.

When you change the thrust angle or wing incidents your trim will change accordingly. When you get it right the plane will fly well at any speed.