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Thread: chipmuck


  1. #26
    cfircav8r's Avatar
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    RE: chipmuck

    No that is not the fix. If you add enough right thrust for a steep climb it will be too much for cruise speed, enough for cruise then not enough for climb. Models fly exactly the same as full sized aircraft. Yes you can get closer to the ragged edge with models and eliminate some quirks but otherwise the aerodynamic principles are the same. For the record F/S aircraft also fix these same issues with right thrust and even a slightly canted vertical stab. The problem is, P-factor is transitory and varying so there is no magic fix, for F/S or models. Pilot input is needed nothing else will fix it. Remember he has a scale aircraft so it will react more like the original, you can design a model that lessens the effects and they tend to be the sport and stunt planes that are not scale replicas or are replicas of high performance aerobatic A/C that have done the design work to lessen the effects. Put a yaw meter in one of your planes and you will find your plane does not hold yaw nearly as well as you believe.
    The three most useless things to a pilot, the sky above you, the runway behind you, and the fuel on the ground.

  2. #27
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    RE: chipmuck

    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.   
    Yes, we're still talking about RC planes, but aerodynamic principles apply equally to both realms. How would RC be any different? Using the flight controls properly works better than adding washers under the motor mount, or a dime or quarter to a wingtip (as was written in MA a while ago).    You'll be fighting that right thrust when it's not needed, too. The pattern guys don't use washers or coins on a wingtip, they use their thumbs.

    Hopefully, I won't catch any washers under my fullscale motor mounts during preflight.  
    I might not be very good, but I'm fun to watch!

  3. #28
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    RE: chipmuck

    cfircav8R and eddieC, Of course the principals are the same however the models have a fraction of the wing loading and a ton more power to weight. That changes the whole ballgame. I have competitivly flown both Pattern and IMAC. In IMAC the rules state that the airplane must be a scale aerobatic airplane with 10% or less deviation from scale outline. We get them to fly very true by careful setup. One has to look at every force that applies to the airplane and make adjustments to work in unison with one another. One of those adjustments is engine thrust line. We do a vertical climb and the goal is a strait upline that extends 150-300 ft depending on airplane size. As the airspeed decays and the prop gets into a higher loading, the airplane will start to yaw left. When one hits the sweet spot of right thrust it helps with the whole flight envelope including take offs. Pattern airpanes do have fewer bad habits as they do not have to resemble a full scale airplane. Both disiplines require that the airplane be set up to fly as true as possible. For me this usually takes 50 or so flights making small adjustments and one adjustment at a time until the airplane flys through a sequence with as little pilot workload as possible. Successful R/C pattern and IMAC pilots do not just " Fly with their thumbs " they do exactly the same as described above. For the record, a Chipmunk is not an aerobatic model, in full scale trim it is a trainer. Yes Art Scholl did an amazing show with his Super Chipmunk however the airplane was not intended nor was it capable of precision aerobatics. So my remaining question for the OP, does your model have any right thrust?
    Of course it's true, I read it on the Internet.

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    RE: chipmuck

    yes my mistake lol guess i should not jump so fast lol.

    still check the gear and the engine for right thrust.
    AMA # 126183
    Fly light, fly fast and fly low.

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    RE: chipmuck

    I have competitivly flown both Pattern and IMAC.  
    Been flying pattern for 20+ years, so am well aware of setup issues, thanks. Also a corporate pilot for 30+ Years.The rules of pattern or IMAC have no real application in a discussion of basics. KISS.  
    My point is, a lot of RCers could benefit from some of the basic principles of both realms. I still see guys stab the power on and have the airplane 'take them for a ride'. We have one guy witha big Cub who goes into the pits 2 or 3 times a year. When he does manage to get airborne, the poor Cub has a right wing low, trying to stop the left turn. No amount of hints or talking does any good to that type, but if the OP is open to learn, then great.
    I might not be very good, but I'm fun to watch!

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    RE: chipmuck

    rye.
    Very normal, had two of these and they were both the same. I don't think engine orientation matters much.
    Nice Chippy by the way.
    Going Ballistic
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    RE: chipmuck


    ORIGINAL: VCScott

    rye.
    Very normal, had two of these and they were both the same. I don't think engine orientation matters much.
    Nice Chippy by the way.
    That nails it. The OP asked whether right rudder on takeoff with a Chipmunk is normal, and the answer is yes. How we got from that to two pages is a puzzle.
    Al Gunn
    Ultra Sport Brotherhood No. 9

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    RE: chipmuck


    ORIGINAL: speedracerntrixie


    ORIGINAL: 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
    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.

    Model or full scale, the physics of flight are the same. You can't change the laws of physics:-( No amout of adding right thrust to your engine is going correct for not knowing how to use the rudder.

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    RE: chipmuck


    ORIGINAL: rye

    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
    For every action there is an oppposite and equal reation. The rotation of the propellor is the culprit and throttle/rudder management is the key to the solution.

  10. #35
    David Bathe's Avatar
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    RE: chipmuck

    There is quite a lot of miss guilded info flyin' around here.
    This isn't about Pfactor. It exists but has absolutely no effect on our small models.
    This isnt about Torque. Torque is a twisting, not a yawing effect and has very little (read non) effect on any, even high powered models.
    This is about the spirelling propeller slip stream hitting the left side of the vertical fin causing it to move over, thus creating the left yaw.
    It can't be fixed (unless you use a counter rotating prop/ ducted fan etc), but it can be compensated for. There are two methods.

    1. As mentioned: RIGHT THRUST.
    The wonderful thing about right thrust is that it's proportional... set it for high power... and it's good for middle and low power settings.

    2. Right rudder to throttle mix. 
    Once airborn, find out how much right rudder you need to imput to hold the model in a straight vertical climb using full power, then mix that amount to full throttle, half that amount to mid throttle ect.
    From my experience, even though it's a real easy fix, far simpler than moving an engine around, it isn't as proportional as physical right thrust and will need a mixture curve to get a good feeling across the throttle range.

    That's it and thats that.

    There is one other factor that you should be aware of ... your Chipmunk has it's UC very close to the CG which make it very sensitive to ANY yaw effect on the ground... whether because of to little (or to much) right thrust, over compensated rudder inputs, offset or dragging wheels, a small dump on the runway etc. The only way to correctly set the right thrust is once airborn.

    BTW, somebody mentioned that pattern pilots fly with there thumbs. Not the ones I hung around with!
    They are adding washers, tweeking thrust angles, adding little bits of lead to wing tips etc so the DONT have to fly with thumbs.
    Best Regards: davidbathe.com
    Occasional Aircraft Illustrations.

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    RE: chipmuck

    You can believe whatever you want. But, P-factor is very real on our model aircraft, and is a contributing factor during take off with a tail dragger until the tail is raised, reducing the angle of attack. I used to think that p-factor, torque, etc was a bunch of bunk with our models until I started flying full scale. Talk about an eye opener. The rudder is a wonderful thing if you learn to use it.

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    RE: chipmuck

    So true. Why do you think full scale private aircraft opted for tricycle gear airframes.

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    RE: chipmuck

    HOLYRIGHTRUDDER!

    Hey Rye, how many takeoffs have you been able to practice during this absolute fiasco?!?

    Anyhow, just because I feel like adding my 2 cents. The main contributor, ONTAKEOFF, to the left yawing tendancy is gyroscopic precession. When a rotating object has a force applied to it that force is "felt" 90 degress in the direction of rotation from where the force is applied.

    When the tail of an airplane lifts during takeoff a force applied to the top center of the prop disc as it accelerates forward and also the bottom dead center of the prop disc as it accellerates back. Imagine the prop turning clockwise (as it looks from the cockpit): 90 deg from top center is 3 clock and that is where that force is "felt" creating a left yawing moment. Compensate for this with right rudder, and it does help to apply throttle slowly.If you reduce the acceleration you reducethe force.

    But don't think about all this Jeppesen Pilot Handbook material that everyone is slinging back and forth. Be smooth on your throttle, and this will help a ton. Do not hesitate with the powerjust be smooth, and practice practice, in time you will learn how to lead your rudder. Someone may have asked but what size prop are you running? A smaller diameter will tame the yaw a little and you can warm up that way.

    Joshua Hinrichs
    Director of Sales
    SkyQuest International

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    RE: chipmuck

    hi
    i didnt mean to start this war of words ,i build this plane 10 years ago flew her until a bad landing and tore out the landing gear blocks put her away and she was always a hand full need a lot of rudder to keep her running down the runway straight the old guy who was teahing me how to fly her always took her off for me now 10 years later my two sons are flying with me on large trainers and great planes rv-4s we do add rudder in on take off on all the birds we fly but not as much as the chipmunk needs she flys great once in the air but she needs to have a little more speed on landing as u see in the video she stall just before the landing but a great save by my oldest son i am using a 12x7 ap prop 1 st prop that OS said to use on the OS 61 fx heres a video of her on her 3 flight my son said the same thing i have to learn to use the rudder more as she is more manuverable then the rv-4s we have ,thanks for the help guys,rye

    http://www.youtube.com/watch?v=db1jwA6Er34
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    RE: chipmuck


    ORIGINAL: Top_Gunn

    That nails it. The OP asked whether right rudder on takeoff with a Chipmunk is normal, and the answer is yes. How we got from that to two pages is a puzzle.
    Good grief! NOKIDDING!.. Ithink this one is a little nuts!

    Kirby C.
    I gotta have more cowbell!

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    RE: chipmuck

    I still have the question of how much right thrust the airplane has. After watching the vid two things come to mind. I did see a bit of drift to the left on downlines and once saw a large drift to the left on an upline. This still leads me to beleive it has little or no right thrust. The fast landing speed is either high wing loading ( The vid does not support this ) or CG too far forward. Your sone does a great job of flying the airplane BTW.


    I know I'm going to get alot of flack on this but most guys just havent flown a really well trimmed model. If they had, there would not be all this conflict of opinions here. I spend hours getting my aerobatic models to fly as well as I can get them. It makes the airplanes easier to fly and that leads to higher scores. If you are one who on a maiden flight pushes the trims until strait and level flight is accomplished at one speed and call it fine or just live with a bad habit figuring that it's just the way the airplane is you need to pay attention and maybe learn something here that will lead to you spending more time getting the airplane to fly better.

    One comment that sticks with me is that this is what a CG Chipmunk does so just learn to use the rudder. To me thats like saying all Car make XXX model XXX pulls to the left on the freeway so just man up and tilt the wheel to the right. We wouldn't accept that answer when it applies to our cars so why would we accept it here? It dumbfounds me that after I explain to people that I have been an R/C pilot for 35 years, have been a sponsored Heli pilot, competed for a spot on a US soaring team, took second place in point standings for the 2006 IMAC southwest region advanced class that when I attempt to help someone trim their airplane to make it easier to fly, it is met with these type of responses.
    Of course it's true, I read it on the Internet.

  17. #42
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    RE: chipmuck


    ORIGINAL: speedracerntrixie

    I still have the question of how much right thrust the airplane has. After watching the vid two things come to mind. I did see a bit of drift to the left on downlines and once saw a large drift to the left on an upline. This still leads me to beleive it has little or no right thrust. The fast landing speed is either high wing loading ( The vid does not support this ) or CG too far forward. Your sone does a great job of flying the airplane BTW. Yes a little right thrust can help, but without knowing how he has it trimmed and what the throttle settings were you won't have any real clue as to the culprit. It could be he has his rudder trimmed incorrectly and is fighting it with aileron trim, or his wing is way out of balance and is fighting it with aileron trim.

    I know I'm going to get alot of flack on this but most guys just havent flown a really well trimmed model. If they had, there would not be all this conflict of opinions here. I spend hours getting my aerobatic models to fly as well as I can get them. It makes the airplanes easier to fly and that leads to higher scores. If you are one who on a maiden flight pushes the trims until strait and level flight is accomplished at one speed and call it fine or just live with a bad habit figuring that it's just the way the airplane is you need to pay attention and maybe learn something here that will lead to you spending more time getting the airplane to fly better. I don't think anyone will argue that you can make a plane fly better by spending time trimming and tweakin, however there are traits to every design that will not go away without a redesign. These traits are usually desirable for the type of plane and if you don't like it your best bet is to get a plane that better suits your preferences. IE: a trainer is designed to self right, this means if you trim it for straight and level it will maintain that airspeed and wings level without inputs. If you loose control and let go the higher airspeed will cause the nose to come up and the dihedral will cause the wings to level. Great for a trainer, but not for a stunt plane. Short of major changes you will not eliminate those traits, but it is a trainer, like it or not.
    One comment that sticks with me is that this is what a CG Chipmunk does so just learn to use the rudder. To me thats like saying all Car make XXX model XXX pulls to the left on the freeway so just man up and tilt the wheel to the right. We wouldn't accept that answer when it applies to our cars so why would we accept it here? It dumbfounds me that after I explain to people that I have been an R/C pilot for 35 years, have been a sponsored Heli pilot, competed for a spot on a US soaring team, took second place in point standings for the 2006 IMAC southwest region advanced class that when I attempt to help someone trim their airplane to make it easier to fly, it is met with these type of responses. Yes you have a lot of experience setting up your planes to perform to your standards, and you were there the whole time testing and tweaking. Yes again right thrust may help, but to say it is the fix is jumping to a big conclusion. I am also curious if there is right thrust but it is too early to say that that is the problem. I would like to see a sticky with your procedures for determining what is wrong and the correct fixes, including ways to determine when you have reached the point of diminishing returns. this would do more for most pilots than throwing out what you think might be the issue without enough real background.
    The three most useless things to a pilot, the sky above you, the runway behind you, and the fuel on the ground.

  18. #43
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    RE: chipmuck


    ORIGINAL: cfircav8r


    ORIGINAL: speedracerntrixie

    I still have the question of how much right thrust the airplane has. After watching the vid two things come to mind. I did see a bit of drift to the left on downlines and once saw a large drift to the left on an upline. This still leads me to beleive it has little or no right thrust. The fast landing speed is either high wing loading ( The vid does not support this ) or CG too far forward. Your sone does a great job of flying the airplane BTW. Yes a little right thrust can help, but without knowing how he has it trimmed and what the throttle settings were you won't have any real clue as to the culprit. It could be he has his rudder trimmed incorrectly and is fighting it with aileron trim, or his wing is way out of balance and is fighting it with aileron trim.

    I know I'm going to get alot of flack on this but most guys just havent flown a really well trimmed model. If they had, there would not be all this conflict of opinions here. I spend hours getting my aerobatic models to fly as well as I can get them. It makes the airplanes easier to fly and that leads to higher scores. If you are one who on a maiden flight pushes the trims until strait and level flight is accomplished at one speed and call it fine or just live with a bad habit figuring that it's just the way the airplane is you need to pay attention and maybe learn something here that will lead to you spending more time getting the airplane to fly better. I don't think anyone will argue that you can make a plane fly better by spending time trimming and tweakin, however there are traits to every design that will not go away without a redesign. These traits are usually desirable for the type of plane and if you don't like it your best bet is to get a plane that better suits your preferences. IE: a trainer is designed to self right, this means if you trim it for straight and level it will maintain that airspeed and wings level without inputs. If you loose control and let go the higher airspeed will cause the nose to come up and the dihedral will cause the wings to level. Great for a trainer, but not for a stunt plane. Short of major changes you will not eliminate those traits, but it is a trainer, like it or not.
    One comment that sticks with me is that this is what a CG Chipmunk does so just learn to use the rudder. To me thats like saying all Car make XXX model XXX pulls to the left on the freeway so just man up and tilt the wheel to the right. We wouldn't accept that answer when it applies to our cars so why would we accept it here? It dumbfounds me that after I explain to people that I have been an R/C pilot for 35 years, have been a sponsored Heli pilot, competed for a spot on a US soaring team, took second place in point standings for the 2006 IMAC southwest region advanced class that when I attempt to help someone trim their airplane to make it easier to fly, it is met with these type of responses. Yes you have a lot of experience setting up your planes to perform to your standards, and you were there the whole time testing and tweaking. Yes again right thrust may help, but to say it is the fix is jumping to a big conclusion. I am also curious if there is right thrust but it is too early to say that that is the problem. I would like to see a sticky with your procedures for determining what is wrong and the correct fixes, including ways to determine when you have reached the point of diminishing returns. this would do more for most pilots than throwing out what you think might be the issue without enough real background.

    Points well taken however I beleive the same can be said for the guys who start throwing full scale theory out there to explain what a model is doing. I have seen this happen multiple times and it usually ends up with the OP leaving his thread and not returning. You are correct that not all airplanes can be " Tweaked " to fly strait and true. This will mostly effect scale designs. Your idea of a stickey is a good one but I think it would be way too long. I am just about finished with a 33% Laser 200. How about I document the maiden flight and then chronicle the trimming process? I think that would cover some real world situations and fixes. Granted this would take some time but would also allow some discussion on each change as it happens. I think sharing the settings on the bench before she takes to the air would be useful as well. I may even be able to post some videos as well. Your thoughts?

    Of course it's true, I read it on the Internet.

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    RE: chipmuck


    ORIGINAL: jkpape

    You can believe whatever you want. But, P-factor is very real on our model aircraft, and is a contributing factor during take off with a tail dragger until the tail is raised, reducing the angle of attack. I used to think that p-factor, torque, etc was a bunch of bunk with our models until I started flying full scale. Talk about an eye opener. The rudder is a wonderful thing if you learn to use it.

    then why does it still happed on tricylce geared planes??????
    AMA # 126183
    Fly light, fly fast and fly low.

  20. #45
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    RE: chipmuck

    Not all trikes suffer from a yaw during rollout, during climb out they are all the same. All four forces work together to cause the yaw, but some aircraft have characterisics that reduce some of the effects. Some tailwheel aircraft also don't yaw on takeoff.
    The three most useless things to a pilot, the sky above you, the runway behind you, and the fuel on the ground.

  21. #46
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    RE: chipmuck

    There is quite a lot of miss guilded info flyin' around here.
    This isn't about Pfactor. It exists but has absolutely no effect on our small models.
    This isnt about Torque. Torque is a twisting, not a yawing effect and has very little (read non) effect on any, even high powered models.
    This is about the spirelling propeller slip stream hitting the left side of the vertical fin causing it to move over, thus creating the left yaw.  
    There is no 'one answer', sorry. I suggest you do a search on the 'Aerodynamics'forum.

     The factors causing left-turning tendency all exist, and are worse on some types than others depending on design criteria. Being aware and ready to counteract it is most of the battle.

    I agree poor rye has enough info, his head must be swimming.  [8D]
    I might not be very good, but I'm fun to watch!

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    RE: chipmuck

    You all have too much time on your hands if you can argue on such details...When I came back after being gone for 10 years I thought I was having problems and whether it was P-factor, Torque or DT (dumb thumb), it took some time to get my take offs to look right. Then I noticed the tail wheel was loose and it was wandering...So just offer your advice and let the poor guy decide what he wants to try for himself. Time spent arguing is time not flying the way I look at it...

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    RE: chipmuck

    For those of you who would like to learn something about the aerodynamic forces acting on all aircraft, model & full scale. See the link that I have attached. Especially read pages 4-26 & 4-27. If you can grasp/understand this, it will make trimming out your aircraft much easier/faster.

    http://www.faa.gov/library/manuals/a...apter%2004.pdf

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    RE: chipmuck


    ORIGINAL: jkpape

    For those of you who would like to learn something about the aerodynamic forces acting on all aircraft, model & full scale. See the link that I have attached. Especially read pages 4-26 & 4-27. If you can grasp/understand this, it will make trimming out your aircraft much easier/faster.

    http://www.faa.gov/library/manuals/a...apter%2004.pdf

    I'm not argueing that our models don't have the same forces applying to them, I am simply stating that for the most part the forces are too small to be significant. There ars simply too many differences between the two other then size to apply full scale logic 100%. Take the following examples and by all means I am not a full scale pilot so correct me if my figures are too far off. For comparison lets look at a 35% Extra 300 VS a full scale Extra 300.

    35% Extra wet weight 30 lbs

    Full Scale 2,000 lbs

    35% Extra max RPM 6,5000

    Full Scale 2,700

    35% Extra power to weight 1.75 to 1

    Full Scale .8 to 1 average 1 to 1 at best

    35% Extra wing loading 1.5 lbs per sq ft

    Full Scale 17 lbs per sq ft


    You can see where I am getting at. it's not really comparing apples to apples. A good example is that if I have no yaw on a full throttle level pass then when I come in at a high AOA slow pass then the Pfactor should have me yawing to the left. I assure you this does not happen. On all of my aerobatic airplanes to date, once set up correctly there is no yaw differences that I am able to see regardless of AOA. I'm just not seeing why people want to apply full scale principal to our models at 100% value? Can anyone explain to me why the above specs would not make any difference?

    Of course it's true, I read it on the Internet.

  25. #50

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    RE: chipmuck

    I'm sorry that you don't get it. P-factor does not exist in straight & level flight. It only exists during maneuvers involving high angles of attack, like climbing. For those of you who don't know what angle of attack is/means, here's the def: Angle of Attack is most frequently defined as the angle between the cord line of the wing, and the relative wind. Generally, it is sufficient to say that the angle of attack is simply the angular difference between where the wing is headed and where it is going. (per FAA's Flight training Handbook). The FAA's Flight training handbook is really good and is written such that an 8th grader can understand it. It can be downloaded from their web site free.

    If torque reaction from the engine & propeller, corkscrewing effect of the slipstream, gyroscopic action of the propeller, and asymmetric loading of the propeller (P-factor) was not an issue with our models, there would be no need to do any trimming to them if they were built straight & true. Like it or not, all the trimming that you say you do to your aircraft is to counter the effect of those 4 items.

    FYI: I've been building & flying model airplanes for 45 years of my 50 years on this earth. Also, I've been flying full scale for almost 25 years. I'm also an aircraft mechanic. My real job is a mechanical engineer.


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