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    #61
    Originally posted by Sunstorm
    Mine is slightly up elevon.

    It goes upward when throttling up. When cut power, it sinks. (nose down)

    Let's say I bring it up high, then I point it 45 degree downwards and cut power. It glides down, but over a distance, it would 'auto correct' itself and start to level out over a big distance....(say like about 50 metres in vertical distance or more?)

    I would be grateful for any advice rendered, oh great sensei of rc airplanes.

    I just realised this is a very 'duh' answer previously, but uh, how do we calibrate our settings? Because, the elevon trims for straight and level flight (at least for mine) are not the same for powered and unpowered. I'm kind of clueless here. I would assume the variables are - thrust line, elevon trim and C.G.
    "Always fly with a responsible attitude. You may think that flying low over other people’s heads is proof of your piloting skill; others know better. The real expert does not need to prove himself in such childish ways..." - the Multiplex Build Manual

    Comment


      #62
      Originally posted by Sunstorm
      I just realised this is a very 'duh' answer previously, but uh, how do we calibrate our settings? Because, the elevon trims for straight and level flight (at least for mine) are not the same for powered and unpowered. I'm kind of clueless here. I would assume the variables are - thrust line, elevon trim and C.G.

      Ok, from what I read, if you have uptrim on your elevons, you are slighly nose heavy. That is not a bad thing, people usually trim it that way for wings. So when you fly at say 30km/h, you find that with this trim you set, it flies nicely and level. But when you increase throttle and go faster than 30km.h, you will find that the uptrim at higher speed becomes more effective now and thus put your plane into a upward climb. Some people simply trims for the fastest they can go to fly level and live with it. If you want better consistency than that, you will need to sort out your CG position first such that when you fly inverted, you dun need any elevator input or very little at the very least.

      The other thing is your EDF. If you are using only cable tie to secure it, then there is a tendency for the EDF to pivot around that point that secures to the frame.. So when you are at low speed, the EDF sits in a neutral angle but when you throttle up, the edf will want to push forward and angle itself down due to its pivot point at the frame. What you will want is a proper mounting solution that eithers let the EDF sit on a secure bedding or at least have some of structures to be supported in to the frame. Cable tie and coroplast combination flexes too much and will give you inconsistent angle depending on how much thrust the EDF is generating at the time. So if your EDF is allowed to pivot somewhat to the throttle, then the full power, tend to climb seems like a effect of that.
      Last edited by edmond22; 21-01-2008, 07:50 PM.
      Stop looking for a gyro in my plane, they are all in the head.

      Comment


        #63
        Thanks Ed for the enlightenment. I re-dialed the elevons to fly level at half stick.

        Waiting for Babylon 5 to post pictures of mugi evo ducted fan.
        "Always fly with a responsible attitude. You may think that flying low over other people’s heads is proof of your piloting skill; others know better. The real expert does not need to prove himself in such childish ways..." - the Multiplex Build Manual

        Comment


          #64
          EDF Mugi

          Here is the pic of the EDF Mugi. Maiden last week end.

          Will try to re-adjust the c.g and Elevon and try again this week end


          cheers

          Comment


            #65
            Oh nice. The plywood / or wood supports are a nice touch, as well as the groove in the centre.
            "Always fly with a responsible attitude. You may think that flying low over other people’s heads is proof of your piloting skill; others know better. The real expert does not need to prove himself in such childish ways..." - the Multiplex Build Manual

            Comment


              #66
              Originally posted by Babylon5
              Here is the pic of the EDF Mugi. Maiden last week end.

              Will try to re-adjust the c.g and Elevon and try again this week end


              cheers
              hi Babylon5,
              you might want to shift the entire EDF+motor front by 1".
              Punggol Field Walk - Precision Landing Required!

              Comment


                #67
                Originally posted by P4cm4n2000
                hi Babylon5,
                you might want to shift the entire EDF+motor front by 1".


                Another thing I notice is air is blowing against the lower spine and may have cause the plane to pitch up during max power up.

                I may have to remove the lower spine just behind the EDF exhaust to minimise this effect.



                Thanks for your input.

                Cheers

                Comment


                  #68
                  The C.G should be about an inch or so away from the square panel that you put inside the nose, around the centre of the craft. This is assuming you built the mugi to specifications.
                  "Always fly with a responsible attitude. You may think that flying low over other people’s heads is proof of your piloting skill; others know better. The real expert does not need to prove himself in such childish ways..." - the Multiplex Build Manual

                  Comment


                    #69
                    Originally posted by Babylon5
                    Another thing I notice is air is blowing against the lower spine and may have cause the plane to pitch up during max power up.
                    I may have to remove the lower spine just behind the EDF exhaust to minimise this effect.
                    Thanks for your input.

                    Cheers
                    HI Babylon5,
                    the "spine" behind the EDF no need to remove lah...it has no effect wether max or low exhaust from the EDF, as both are all behind the CG.
                    the "Spine" is too close to the EDF mount, both opposite and equal forces cancels each other. Unless the "Spine" aka Stablizer is behind the CG, and EDF is infront of CG.

                    when the CG is tail heavy or just balanced, at hi-speed the plane will naturally climb, to correct this, its better to put nose heavier a bit,
                    especially when you are going for speed.

                    so theoritically speaking its still the CG affecting the plane causing it to climb at accelerated speed.

                    Anyway..let us know about your experiment of removing the spine..thanks

                    here's photo of Sunstorm's Mugi in action..

                    Punggol Field Walk - Precision Landing Required!

                    Comment


                      #70
                      Did you guys try to fly upside down and determine your if your CG is optimal?

                      Do that and perhaps learn something about your setup. My bet is that either your thrust angle is off or your CG is not optimal. I am betting you will need a lot of push elevator to fly level inverted.
                      Stop looking for a gyro in my plane, they are all in the head.

                      Comment


                        #71
                        I have done the above and finally concluded that it's because of thrustline issues, but did a bit of tweaks like repositioning the battery.
                        "Always fly with a responsible attitude. You may think that flying low over other people’s heads is proof of your piloting skill; others know better. The real expert does not need to prove himself in such childish ways..." - the Multiplex Build Manual

                        Comment


                          #72
                          Originally posted by P4cm4n2000


                          HI Babylon5,
                          the "spine" behind the EDF no need to remove lah...it has no effect wether max or low exhaust from the EDF, as both are all behind the CG.
                          the "Spine" is too close to the EDF mount, both opposite and equal forces cancels each other. Unless the "Spine" aka Stablizer is behind the CG, and EDF is infront of CG.

                          when the CG is tail heavy or just balanced, at hi-speed the plane will naturally climb, to correct this, its better to put nose heavier a bit,
                          especially when you are going for speed.

                          so theoritically speaking its still the CG affecting the plane causing it to climb at accelerated speed.

                          Anyway..let us know about your experiment of removing the spine..thanks

                          here's photo of Sunstorm's Mugi in action..
                          Hi, after removing the spine by cutting out a u shape just behind the EDF exhaust, the climb up is not so severed at full power. Nonetheless it still climb out at max power.
                          With motor cut off and heading against the wind , there is a nose heavy attitude. The C.G is 220mm behind the apex.


                          I suspect the EDF thrust line is not optimun. Have adjusted the thrust line and will try out next weekend.

                          Nice Sunstorm Mugi.

                          Keep up the good work

                          Cheer

                          Comment


                            #73
                            Hey Babylon5, you tried flying invert already or not? Check CG flying sideway or upside down and see what the plane does.

                            Up down Thrustline check is done by neutralising your elevator, fly fast level and pull into a vertical climb(orientate yourself so you can be sure it is pointing upward), see if your plane pitches up or down.

                            CG whether optimal is very easy to check. If you have a lot of elevator reflex, this is a sign of nose heaviness already. When flying slow, that reflex position is enough to hold a level flight but when you go full throttle and achieve max speed with your model, that same amount of reflex is going to get more effective and put your model into a climb.

                            So please do these checks and tell us what you see the model doing in the air. The methods you are using now not going to tell you much. My AJ is neutral CG (3D plane) and when landing with no throttle, I may pull as much as 45 deg elevator as the point of touchdown to be level, but that doesn't mean my plane is nose heavy. That is just because I am stalling the bugger and am pushing the envelope of its glide characteristics.
                            Stop looking for a gyro in my plane, they are all in the head.

                            Comment


                              #74
                              Anyway this is what I did;

                              Adjusted position of battery - backward by 2 cm.

                              Result: Craft can now do loops. It can now loop easily. Previously I had to dive in order to enter a loop. It is odd as my C.G now is at the point where I marked as the AC. So now it can do tricks like fly level, turn invert, do a 180 turn, fly upside inverted (up stick though) and then do another 180.

                              It is much more responsive.

                              Elevon trims - level at mid throttle, slight upwards on max throttle.

                              However, there is the following factors that I have to query;

                              1) camber of the Mugi wing; it's not even, it curves upward from front to back very gently. If it's not symmetrical then how to fly inverted without pulling elevator? Is it even possible?

                              2) thrustline, my thrustline is not even, it points slightly down.

                              But thanks Edmund for pushing us to greater 'heights' in flying, har har! Never be contented with just mediocre performance.
                              "Always fly with a responsible attitude. You may think that flying low over other people’s heads is proof of your piloting skill; others know better. The real expert does not need to prove himself in such childish ways..." - the Multiplex Build Manual

                              Comment


                                #75
                                Originally posted by Sunstorm
                                Anyway this is what I did;

                                Adjusted position of battery - backward by 2 cm.

                                Result: Craft can now do loops. It can now loop easily. Previously I had to dive in order to enter a loop. It is odd as my C.G now is at the point where I marked as the AC. So now it can do tricks like fly level, turn invert, do a 180 turn, fly upside inverted (up stick though) and then do another 180.

                                It is much more responsive.

                                Elevon trims - level at mid throttle, slight upwards on max throttle.

                                However, there is the following factors that I have to query;

                                1) camber of the Mugi wing; it's not even, it curves upward from front to back very gently. If it's not symmetrical then how to fly inverted without pulling elevator? Is it even possible?

                                2) thrustline, my thrustline is not even, it points slightly down.

                                But thanks Edmund for pushing us to greater 'heights' in flying, har har! Never be contented with just mediocre performance.
                                ah, That is the part of semi symmetrical wings. You can still adjust to the point where you need little "push" elevator to fly inverted. My Mugi still need some pushing to fly level but models like my F20 EDF doesn't need much at all, just a touch. The reason for achieving little or no push for inverted flying is so that you know your AOA is optimal. This is more crucial for pattern and speedy planes where speed or precision is a concern. The other simple method of check CG is rolling. If your AOA and CG is optimal, rolls will be very axial with less tendency to corkscrew.

                                No need to thank me, just helping to lessen frustrations in setting up planes. You get more fun now than before right?
                                Stop looking for a gyro in my plane, they are all in the head.

                                Comment

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