Correct set up of model planesYou ever had the experience that two most identical models at your flying field are flying totaly different? With pilot number one, the plane flies superb and the same one with pilot number two can hardly do a looping? This can be because of maybe one thing: the first model was set up perfect. This can be a difference ou wouldn't believe.
Loys Nachtmann did some instructions which are really very good and very extensively but which will be followed maybe only on competition models. Through the time, I found my own method to set up a model very good with only very less flights. Please note that your model will still maybe not fly perfect, but you should then be very close. 1. BalancingIf your model should fly a loop perfect, it is necessary that it is balanced along the longitudinal axle. If it should be more heavy on one side, the g-force will force the model to spin out of the loop. To test that, you can lift you model while holding it only at the rudder and the spinner. A glider with only one wheel can also stay at the ground and only hold by hand in horizontal position. The model should be balanced, or randomly fall to one side. If this is not true, you should add weight to one side until it becames true.
2. Setting up the rudder travel and the CoGSet up the rudder travel according to the instructions of the model. Take especially care if both ailerons are moving up the same amount.
The center of gravity should set up according to the instructions for the maiden. Therefore you should take a short look in the internet, as it is with the radjet, the CoG can be far away from instructions. |
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3. Find out the CoG and the longitudal dihedral while flying
Now it goes into the air and the first thing we will set up will be the correct CoG and the longitudal dihedral.
Longitudal dihedral? Yes, this means the following: Look at your plane from the side. Think of a line between the beginning and the end of the main wing. Now do the same for the elevator. These two lines will have an angle to each other. This angle is called longitudal dihedral. If both would be parallel, it would be 0°, the more the elevator is standing as you would pull up elevator, the more degree the longitudal dihedral becomes. Normal are values between 0° and 5°.
And how we can set up that in flight? Quite easy:
Trim your model that you are thinking it flies good. Now climb very high, turn of the engine and fly verticaly (!) down and look at your model what it is doing without any steering inputs from you.
The model goes down in the direction from the gears: The CoG is too far behind.
The model goes up very fast, into the direction of the cabin: The CoG is too far in the front.
The model is going down straight, respectively goes up very slowly: Congratulations, perfect!
It is very seldom that the CoG is perfect in the maiden flight, you need to adjust it until it is perfect or ok. Aerobatic and speed models should set up that they are going straight down, beginner gliders and similar will be set up that they are going up quite fast.
CoG finished? Then we come to the next point.
Longitudal dihedral? Yes, this means the following: Look at your plane from the side. Think of a line between the beginning and the end of the main wing. Now do the same for the elevator. These two lines will have an angle to each other. This angle is called longitudal dihedral. If both would be parallel, it would be 0°, the more the elevator is standing as you would pull up elevator, the more degree the longitudal dihedral becomes. Normal are values between 0° and 5°.
And how we can set up that in flight? Quite easy:
Trim your model that you are thinking it flies good. Now climb very high, turn of the engine and fly verticaly (!) down and look at your model what it is doing without any steering inputs from you.
The model goes down in the direction from the gears: The CoG is too far behind.
The model goes up very fast, into the direction of the cabin: The CoG is too far in the front.
The model is going down straight, respectively goes up very slowly: Congratulations, perfect!
It is very seldom that the CoG is perfect in the maiden flight, you need to adjust it until it is perfect or ok. Aerobatic and speed models should set up that they are going straight down, beginner gliders and similar will be set up that they are going up quite fast.
CoG finished? Then we come to the next point.
4. Correction of the longitudal dihedral
During point three, we set up the correct Cog and the correct longitudal dihedral during flight, now you will notice that the elevator rudder is not anymore in one line with the elevator.
According to the model, we have now many ways to correct this, either it needs to get glued in once again or there can be something layed under it. Generaly there is no way to say what is best. Sometimes there is no way to correct it and you need to fly with an elevator rudder that is not completely in line. This should only accepted if there is really no other option, because you are loosing some aerodynamic perfection.
According to the model, we have now many ways to correct this, either it needs to get glued in once again or there can be something layed under it. Generaly there is no way to say what is best. Sometimes there is no way to correct it and you need to fly with an elevator rudder that is not completely in line. This should only accepted if there is really no other option, because you are loosing some aerodynamic perfection.
5. Checking the balance in flight
In point one we already checked the balance of the model while it is on the ground, now we have to do that again in the air. For that you are just flying straight, turn around and fly the same distance once again upside down.
The model should stay normal and inverted in the horizontal position and not slowly turn out.
If the same wing side is going down all the time, then this one is still too heavy.
The model should stay normal and inverted in the horizontal position and not slowly turn out.
If the same wing side is going down all the time, then this one is still too heavy.
6. Set up the side and down thrust of the engine
You should have noticed already that the engine is showing a little bit down and to the right. This is necessary to have a straight flying model because the rotating propeller is generating some force to the whole plane.
To check the side thrust, you are flying straight away from you and then go into a vertical climb. if the model goes to the right, the side thrust is too much, if the model goes to the left, the side thrust is too less. Check this more times so that you can be sure that it is not moving because you are not flying perfect.
The down thrust will be checked nearly the same way, the only difference is, that when you are going vertical, you will rotate the model with the ailerons 90° so that you will see the plane from the side. If it goes up, the down thrust is too less, if it goes down, the down thrust is too much.
There are some points to notice:
Hotliner, Pylons and Speeder normaly don't have any side or down thrust. if it should still be necessary, a mixer throttle -> elevator will be used. 3D models normaly have too less down thrust, because otherwise you would need much elevator to keep them into torquing.
Generaly, a wrong down or side thrust can always be corrected with mixer, but this does have some disadvantages like that it only works according to flight speed etc. Beside that, it is just wrong. so ifthere is the possibility to change that mechanical, you should always do that.
To check the side thrust, you are flying straight away from you and then go into a vertical climb. if the model goes to the right, the side thrust is too much, if the model goes to the left, the side thrust is too less. Check this more times so that you can be sure that it is not moving because you are not flying perfect.
The down thrust will be checked nearly the same way, the only difference is, that when you are going vertical, you will rotate the model with the ailerons 90° so that you will see the plane from the side. If it goes up, the down thrust is too less, if it goes down, the down thrust is too much.
There are some points to notice:
Hotliner, Pylons and Speeder normaly don't have any side or down thrust. if it should still be necessary, a mixer throttle -> elevator will be used. 3D models normaly have too less down thrust, because otherwise you would need much elevator to keep them into torquing.
Generaly, a wrong down or side thrust can always be corrected with mixer, but this does have some disadvantages like that it only works according to flight speed etc. Beside that, it is just wrong. so ifthere is the possibility to change that mechanical, you should always do that.
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7. Aileron differentialYou maybe found the point "aileron differential" in your transmitter but you don't know what to do with that? Ok, it's way simple ;). You should have noticed already that there are models which are rolling in a perfect straight line and that there are models which can hardly do a roll? The trick is only the aileron differential. This one does nothing else, then reducing the rudder way of the down side of the ailerons. how much differs from model to model, but a value between 10% and 30% should be normal.
The easiest way to check, is to fly with the model with full throttle straight up and steer full side aileron in one direction. Go up with the differential until the rolling looks good. if you have there a good value, you can try to fine tune it in horizontal flight. There it should not loose much height and the roll should just look smooth. This looks a little bit unprecise, but be sure, you will see the difference. Sometimes this point needs a lot of time and trial and error. You finished!Congratulations, if you've worked through all seven points you should get a model which is flying very good and neutral. of course you will find by time your own way and your own preferences. But as long as you don't know what and especially WHY you are doing that or that thing, stay with my list and you will get a good flying and fun model!
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