rye

My Feedback: (10)

hi
i have a C-G chipmuck that i build years ago and havent flown it until now it has a OS-61 siding side ways when i take off i have to give it a lot of left rudder i got the toe set in ,is it because the motor is sideways ? thanks rye

mikegordon10

Don't think so. I think it's cause it's a tail dragger. You can cut down on this tendency by slowly advancing the throttle and not slam it open all at once.

Gray Beard

My Feedback: (-1)

Has nothing to do with it at all. The reason for pulling is called the P-Factor, the way the vortex wind is hitting the rudder. Most people will just call it Torque just to keep it simple. As mike pointed out, if you roll on throttle a bit slower and add some right rudder as needed it isn't any problem at all, it's normal for most planes.

SeamusG

Can the P-factor effect be reduced by changing the pitch of the prop?

speedracerntrixie

My Feedback: (29)

Usually one has to apply right rudder on takeoff and not left. this suggests something with the landing gear is not right.

rye

My Feedback: (10)

sorry i mean right rudder ,brain fart[:@]

tomfiorentino

Hey grey beard...

P factor is asymetrical thrust that is created at high angles of attack; the spiral slipstream is different (that is my understanding anyway. Once the tail lifts in takeoff run (which is very quick) the forces are all aligned so I dont think p factor is the cause at that point anyway because angle of attack of the propeller disk is straight on with the direction of flight.

Did you mean very intitially it is p factor?

idk, I never really thought about it that much; called it torque! But I'm sure it has been kicked around here in the past.

Heck, I haven't flown in so long I think I forgot how! Terrible summer for me..

Tom

Gray Beard

My Feedback: (-1)

If you do a search here you will find a number of threads on P-Factor. According to my books it is the vortex effect from the air flow of the prop hitting the tail feathers. In MAN they have shown it with drawings. But that is just my understanding of it from what I have read. The left drift of a plane is most often mentioned as torque though but how much torque does one of our little engines really have. My two meter pattern planes are long enough that the P-Factor has no effect at all, they will just run out straight every time.
Seamus?? I would think so but I'm no engineer so can't say for sure. Makes sense though doesn't it?

speedracerntrixie

My Feedback: (29)

I'm no expert on P factor either but there are a ton of pattern airplanes out there that have what is called a Canilizer. This is a small wing placed just behind the canopy. What is supposed to happen is the airflow that leaves the prop is doing so in a corkscrew pattern. The canilizer straitens the airflow before it gets to the tail section thus eliminating it's ill effects. I have not flown an airplane with one of these devices so I can't say how well they work if at all. I would like to assume that because so many of them are in use that they do work but pattern being such a trendy nitch I'm not so sure. The fact that most current pattern airplanes are running electric setups with prop sizes in the 20X14 to 21X14 range, the P factor is most likely more pronounced. My pattern airplane has a current electric power setup but being that I like more scale appearing model does not use such a devise. At this point, it's not any lack of performance that keeps me from scoring better, it's lack of practice. Note the pictures, one shows the canilizer. The other is quite funny, it shows a canilizer on an airplane that sports a contra rotating prop setup. Theoretically, that setup is supposed to eliminate the P factor and any side torque.

For the OP. P factor is really not a factor on the airplane and engine setup you are flying. The prop is just not going to generate enough to make a difference. What I think is happening is that you are seeing the effects of torque. How much right thrust do you have? A combination of the proper amount of right thrust and rolling on the throttle gradually on take off should eliminate most need for right rudder. The other thing to check is to measure to see if the airplane is built strait to begin with.

yellerchamp

My Feedback: (42)

I owned one of these for years and yes I had to apply right rudder, also throttle it up slow till the tail is up then a nice long run before lifting it off, this plane always made the best 3 point landing, your plane looks nice good job.........

tomfiorentino

I'm with you on the spiral airflow hitting the vertical fin; not with you on P-factor. As to torque, I think it is just easier to rationalize it from that perspective. If the propeller represented on the right side of the spinner is decending into the forward airstream at high angles of attack it creates more thrust relative to the other half. That asymetry will "torque" the airframe around the vertical axis. I think that is what folks are referring to when they use the word torque. But still, I don't see that happening on take-off roll because the thrust is aligned fine as soon as the tail lifts I guess. Spiral airflow, on the other hand is there at all angles of attack and I would think shows up pretty good at take-off roll when it represents the bulk of the flow over surfaces etc. but then gets increasingly watered down in terms of its ability to effect anything as airspeed increases (ie. and we release that initial rudder input).

Anyway, I could be wrong. I should be more sure of myself before I comment actually. If I get some extra time maybe I'll refresh and read on it. Cancel that. If I get some extra time I'm going flying!

Thanks for your response!

Tom

tomfiorentino

I just read the other couple posts on this.

Spiral airstream vs P-Factor. They are different.

The aerodynamics forum has guys running around that can clarify this stuff in their sleep. But they are probably not looking in this section of RCU....plus I just noticed the title of the thread is "Chipmuck". Too funny when the fingers don't type what the brain for sure knows!

The OP may want to append to a thread on P-factor over in aerodynamics; or start his own.

In the meantime....stay on the rudder!

Tom

eddieC

My Feedback: (2)

Many things cause left-turning tendency, and they all inter-relate.

P-factor, also called assymetric disc loading, is most evident during slow-speed, high angle-of-attack flight at high power settings. It's cause is from one side of the propeller disc producing more thrust than the other. In our case with clockwise-turning props (viewed from the cockpit), the right-hand side of the prop has a greater angle-of-attack, so the plane tries to turn left. Also called 'prop-walking' in boats

Gyroscopic precession, sometimes called torque precession, occurs when the prop is moved from its plane of rotation, and the effect occurs 90 degrees from where the force was applied. In a taildragger, as the nose is pitched down to raise the tail, the 'push' is applied at the top of the propeller and the resulting force reacts 90 degrees clockwise (again, from the cockpit) to the right side of the prop disc, causing a yaw to the left. The opposite occurs in nosewheel aircraft; as the nose is raised, there is a bit of right yaw but it's negligible as the other factors counter it.

Spiral slipstream effect is what GB correctly pointed out, the spiral propwash striking the left side of the fin and rudder, also causing a left yaw. The slower the airspeed, the tighter the spiral and the greater the effect. It's present even during cruise flight, and many single-engine full-size aircraft have offset vertical fins to counteract the effect.

Engine torque also has an effect, and it's more pronounced in full-scale aircraft. Quickly increasing the throttle can cause a roll and , in the clockwise example given, a left roll can result. More pronounced at very slow speeds. My Multiplex Funjet rolls left during handlaunch, and I've read that a fullsize Bearcat will roll over on its back if the throttle is suddenly advanced.

P-factor and gyroscopic precession are the biggest culprits for us. Add power slowly at takeoff (3-5 seconds from zero to full).  As the aircraft accelerates, the tail becomes more effective and will help keep it straight. Make slow pitch changes also, for the same reason.

On the more powerful fullsize twins I fly, adding power too rapidly will cause the aircraft to turn left and depart the runway. No amount of brake or right rudder will stop it. Slow, smooth inputs are the answer.

eddieC

My Feedback: (2)

Oh, I thought you meant 'Chipmunk'. 

rgburrill

If P-factor is so important and torque is not why does the same thing happen to dragsters?  Tricycle gear are less susceptible because the nose wheel tends to stops the left movement.  And pattern planes typically have large, flat verticle surfaces that take out the spiralling airflow quite a bit.

Try a full acceleration from stop with a taildragger and you will see it spin around in a circle - and there is NO P-factor until the plane starts moving.  That's torque!

airraptor

My Feedback: (66)

forget the arguing about pfactor. just make sure your gear have the same toe in. use long sticks of 1/4 sq balsa and then look from above the plane to see if one side has to much. Also make sure the wheels are free to rotate. then check to make sure you dont have to much right thrust. it all good and still does it then get better on the rudder or by a gyro lol

oliveDrab

C - h - i - p - m - u - N - k.

lackeyma

My Feedback: (4)

Suggest looking at a thrust line issue.

Jaybird

The rudder is yaw control on the ground and in the air and what you are experiencing is left yaw caused by all the things discussed interacting to some degree. Taildraggers, depending on the design, size, engine, prop, scale shape will experience more left turning tendancies on take-off than a comperable design, size, etc. tricycle gear airplane whether model or full size. Some designs are better at handling all the left turning tendancies and a mimum amount of rudder input is required most of the time where others (like Cub) require vigilant rudder use, but either way, it's a learned skill and no amount of mixing or preset will work precisely on every take-off run.

Another thing to remember is that the rudder doesn't become effective until a certian amount of airflow (spiral or not) is flowing over it. Again, some designs are better than others so you have to figure out what works for you. I lost count of the number of times my 80" Hangar 9 J-3 Cub when roaring off to the left and cartwheeled through the tall grass before I started to get the hang of it. Getting my private pilots licence a few years ago brought a lot of insight into my model flying and the model flying helped with learning to operate full size.

Every take-off and landing is a unique experience where you have to balance speed, power, angle of attack and energy to make it work the way you want and not just be along for the ride.

Jaybird

jmpups

My Feedback: (1)

You don't have any or enough right thrust on the engine. Add a couple of washers on the left side between the engine mount and the firewall. jmpups

airraptor

My Feedback: (66)

YOU GUYS NEED TO READ the OP post.....................

he says he has to add LEFT rudder when taking off. lol you half butt read the post lol

rye

My Feedback: (10)

sorry airraptor i made a mistake as i said before it was right rudder, taking this plane out of moth balls atfer it sat for 10 years we needed to make some changes and we saw that it need more left rudder but we test flew it anyways but it was right rudder on take off not left but we are going to try the washer on the left side of the motor mount so we dont need so much rudder on take off ,when we took off and release the rudder atfer take off the tail would do a little dance [X(] scarey and we are going to change the servo too may have a bad pod will keep u up date on the changes

eddieC

My Feedback: (2)

LOL yerself, read posts #6 and #22 ! 

Physician, heal thyself...

jkpape

The need for right rudder during take-off is primarily from the airflow hitting the vertical stab. Right rudder is also required during take-off in a tricycle aircraft. This assumes that the engine turns clockwise when viewed from the cockpit. P-factor & torque also come into play during take-off. P-factor effects all aspects of flight, but is more pronounced in high angles of attack. I've been flying full scale for 20 something years. A good demonstration of p-factor is go into a climb, then take your feet of the rudder peddles. The nose of the plane will go to the left. Very quickly at that.

P-factor: During a climb, the ascending blade has a lesser angle of attack than the descending blade. RE: the ascending blade is taking a very little bite of air while the descending blade is taking a great big bite.

Joe

speedracerntrixie

My Feedback: (29)

W are still talking about models right? it really burns me when someone well read in full scale theory/practice comes into a thread and puts up info that has little to no use on the REMOTE CONTROLED airplane we are adderssing. For decades it has been common practice to add right thrust to an airplane that has a tendancy to yaw left under power. Call it torque, P factor or spiral slipstream, who cares.............the fix is right thrust.