You'll have reduced the moment of inertia. Folks generally think that will make it fly better.
I watched Viper fly at least 5 times this past weekend and since I launched for you every time, I watched each flight closely and I was really impressed. That plane is special!!!
But battery and motor and now 5 inches apart? You said it was lower when they are close together.
Is it easier to lever 6.5 ounces or 16? That's to the extreme as the battery is still there but closer to the fulcrum.
Please remember this is not a debate its a experiment you will need to try so you can see what I feel.
Motor at a distance "x1" from CG with weight "m1"
Battery at distance "x2" from CG with weight "m2"
Tail weight at distance "x3" from CG with weight "m3"
m1*x12 + m2*x22 + m3*x32 + MiM
Motor at a distance "x1" from CG with weight "m1" - same as before
Move the battery a distance "x4" from its original spot - battery now at (x2-x4) from CG
Move tail weight a distance "x5" from its original spot - tail weight now at (x3-x5)
m1*x12 + m2*(x2-x4)2 + m3*(x3-x5)2 + MiM
I think it is easy to see that the moment of inertia of the second experiment will be less than that of the first. And that agrees with everything you have been saying! All else being equal, the model with the lower moment of inertia will turn more quickly and will STOP turning more quickly as well. Your empirical, real-world testing is simply supported by the physics of the situation! SHAZAAM!Imagine that
I also think you confirmed Ted's experiments with the super light plane he had years ago. If he would have added the same weight that he added to the cg to the nose and tail (balanced at the same point) the plane would not have flown as well as it did with the weight at the cg. I am not going to get into the lighter is always better argument with you. I believe that there is an appropriate weight for every design, I know this because I have had a plane that was too light and so has my dad. I don't think it is possible to build an electric too light, like you said there is 27 oz of fixed weight...
Derek
Be sure to tell Ron the next time you see him that a 48 ounces Tucker will fly better than a 38 ounce Tucker. I am sure he will tell you what he thinks. I am not saying that particular plane didn't fly better but you have to think maybe something else was wrong with it. At least I do. No mater how many you build or how careful you are a mistake in alignment can sneak in and you not catch it. Quote Bill Werwage from the Man and his Museum tape.
Moment of inertia (the barbell effect, the resistance to starting and stopping a turn) of each piece of mass about the CG is its mass multiplied by its distance from the CG, then multiplied again by its distance from the CG. So distance from the CG is a big deal.
Brett you have tried to interject some hypothetical scenario of a plane that does not exist mine does and this is what has been done to my airplane. So any formula you come up with is just that. I can feel the difference in the way it flies with the concentrated weight shifted closer to the CG while remaining the same CG as before.
This is for electrics as it will be easy to do and remain the same weight. Pick a airplane of any type full body. Build the tail as light as you possibly can. (sand it out inside) Finish it light. Put the battery up close to the motor so the moment of inertia is low. (whatever that means) Now take solder and wrap the tail wheel until you get it to balance not plan balance, but trim balance. Note the feel of how the plane flies. Should do nice rounds and groove well, if you did your job right and built it straight and light it should turn well. Remember note the feel!
Now take the weight (solder) off the tail wheel set it aside. Move the battery back and add the same weight you took off to the nose and make sure it balances in the exact same spot. It remains the same weight. Note the feel.
What I find interesting is that sparky never smiles in his photos. "Why so serious" LOL
Derek
No Dean, the reason for that longer nose was not CG problem. Reason was aerodynamic :- )))) I was even prepared to move battery over the wing to save that tail ballast. Fortunately I found that I can move CG more forward (compared with older model) so I did not have problem with tail weight. I even used heavier Scorpion motor to move CG even more forward (+20gramms), but then I changed back to AXI and CG comes OK.
Igor,
So you were trying to get the propellor farther away from the wing?
Dean
No, it is not because of distance, however it could be important to make some investigation around. If the AoA in corner is ~8 degrees, the the long nose can keep prop exactly on tangent point, so the yaw comming from P factor can be minimized ... or used to cancel precession? :- ))) I do not know, worth to think about it little :! n~ VD~
The reason for longer nose is only to better balance side area, nothing else. My previouse model had too short nose designed for heavy IC motor, so I elongated it little bit knowing that I have elecro motor and battery position is not fixed to motor position. Probably I will do it even longer by 10mm on next model.
If the AOA in a corner is 8 degrees, then the AOA of the descending blade is increased by 8 degrees in relation to the relative wind and the AOA of the ascending blade is decreased 8 degrees. This results in a difference in AOA between the two blades of 16 degrees, and an associated thrust differential resulting in yaw due to P-factor. The length of the nose moment should have no effect on this phenomenon. It is strictly a factor of the difference between the chord line and the relative wind, I.e., AOA.
Igor, if I'm not mistaken, precession is a torque on the airframe. It doesn't matter where it is applied, it will take the same amount of a reverse torque to correct.Exactly
The idea of extending the nose to put the prop on a tangent to the loop would put the prop more squarely to the airstream. That would tend to minimize the difference between AOA of the prop blades and minimize P effect, at least on a two bladed prop.So short nose will make Peffect stronger and since prop is at positive AoA then its moment yaws fuselage IN. So it looks that longer nose works just opposite we need. So what a shame ... I must use Rabe rudder also on next model :-)))
The AoA is not the same on all parts of fuselage, we are on circular path in corner, and the tangent point (means 0 AoA) is somewhere on nose. That is why we need so large elevator to keep such small angle as 8 degrees necessary for corner.
Look pic, you can see that tail is at approximately at 15 degrees if model goes tangent to path on LE of wing. In that case motor will be at approximately half of that angle but NEGATIVE angle ... means -8 degrees, so plus some AoA for corner and you see that little longer nose will move prop to 0 AoA (means tangent) position.