Torque effects - props ?
 

I was wondering if I'd see a noticable difference in the torque effects imparted on the airframe from the engine/prop combo by changing props ? I think it's called P-Factor.

I'm flying a large Decathlon with a Brillelli 46cc gasser and the torque effects on takeoff are very pronounced if I'm not smooth on the throttle. Do you think changing from a 21X8 to a 20X10 would reduce the effect ?

I'm pretty sure going from a 21X8 to a 20X8 would reduce the torque effect but would the higher pitch of the 20X10 create more "resistance" and nullify the change in diameter ?

I'm planning to order some props to try but was hoping for some guidance or predictions before I buy the props -

Thanks in advance,

Eric

RE: Torque effects - props ?
 

Eric, changing props to try to avoid the plane hooking left is a total waste of time and money in my opinion. Use the prop that is best suited for your engine. If your radio has exponential then add a little negative expo to the throttle and rudder channels. When taking off, add just a little throttle and allow the plane to start rolling good before adding a little more throttle all the while steering the plane with the rudder. If you find it very hard to master that technique then install a Futaba GY401 gyro on the rudder channel and use it in the heading hold mode for takeoff only then change to the rate mode.

There is a good thread here about using a rudder gyro on an airplane.
http://www.rcuniverse.com/forum/m_60...tm.htm#6056543

Good luck

RE: Torque effects - props ?
 

The P-factor only is active when the tail is still down and the prop is not perpendicular to the line of motion.
However, the engine torque will try to bank the plane left, and the prop wash will try to yaw the plane left. At higher speeds, these effects are getting smaller relative to the plane's normal stabilizing forces, but they are still there.
Prop sizes do make a difference, and it pays to experiment a bit. Props with much pitch ar the worst offenders.

RE: Torque effects - props ?
 

Then add the influence of the "coupling" distance between the main gear and the tailwheel. This adds or subtracts from Pfactor and torque effects. Better to use the correct propeller for the type of flying and become proficient with the correct application and use of thr rudder. There's no substitue for control competance.

RE: Torque effects - props ?
 

Higher AOA's increase the Yawing affect.

RE: Torque effects - props ?
 

So if your nick name is "Rudder Boy", you probably don't have a problem in this department?

RE: Torque effects - props ?
 

I've been flying giant scale since 1982. I currently have a respectable fleet of gassers including a 1/3 scale Super Decathlon. All tail draggers. Never a problem with takeoff and landings except for the 1/3 scale Bucker Jungmeister. That plane has the LG very far forward. See photo. One has to be extremely careful on takeoffs. Any sleight cross wind is a bear once the tail wheel breaks ground. Weather-vane city.

I completely solved the directional stability problem with a Futaba GY401. Last September at Bomber Field we had an easterly cross wind nearly the whole time that I was there. I think I flew the Jungie 6 or 7 times in AVCS (heading hold) mode on takeoff. Straight as an arrow. All I had to do was lean the ailerons a little into the wind.

RE: Torque effects - props ?
 

Nice plane big bird

RE: Torque effects - props ?
 

Thanks

RE: Torque effects - props ?
 

Truckracer,

I don't think there's any reason to make this hobby or the operation of aircraft so easy that it requires no skill or effort to do. To the contrary, more work in some current areas would develop more skill and more pride. When it becomes so simple that any monkey can do, every monkey will do it. At that point all you will have is a bunch of monkeys.

Development of control skill are a must in this hobby. To become as good as you can takes work and effort. Why get almost good enough to do something? I agree that there are ways to make some things easier, but I insist that some things can't be made too easy. Once all the skill required to perform a task is rduced to zero, what's the benefit of the task? Where's the satisfaction of doing what just anyone can do?

RE: Torque effects - props ?
 

Hi,

On my tail draggers, I found that 40% expo on the rudder allowed a good transition between "wheel on the ground" and the low speed where the tail wheel is off the ground before the plane breaks ground. Also, if the tail is held on the ground until the takeoff roll is at least 25 ft and the plane has some ground speed, the yaw to the left for the remaining portion of the takeoff roll is minimized. Most of my "work stuff" have lifting airfoils on the horz stab and the tail comes off the ground very quickly. This make the whole problem of a straight takeoff roll a bit more difficult because the tail is flying at low ground speed and the rudder is not that effective until you gain some speed.

hope this helps

Elson

RE: Torque effects - props ?
 

Pat,

You must be the author of "Zen and The Art of Flying Models." ;) Work for the sake of work...I agree. And where I fly, the guys with experience support the newbies and everyone enjoys the learning process.

Yet, there are always the guys whose fathers didn't love them enough...when these guys are on the field, you want every input on a gyro or autopilot. It's unchivalrous to gloat over a $2,000+ pile of broken balsa... and snickering at an ugly takeoff will not achieve enlightenment, Grasshopper. Wouldn't you agree? Don't always have to fly with the training wheels just cause they're on board.

Respectfully,

Rick

RE: Torque effects - props ?
 

I too am all with Pat on this one.
The "I did it" feeling, with it's sense of achievement is worth a life time. Or in ZEN terms: "the path is more important than the goal"
Were it not that way, what good is there in achievement and the pride that comes with it?

RE: Torque effects - props ?
 

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