Trimming

[Less_Incidence]

DoctaDave,

I was experiencing similar problems with the FFM kit - even when the A/C was off, it looked like it was being jostled around by air currents. As far as aerodynamic theory, there's a certain, complicated "critical point" relationship between velocity, roll angle, roll speed, and angle of attack. When this critical point is passed, the plane rolls hard toward the inside of the circle and dives in before correcting itself. This was one of the numerous issues I experienced before I made my modifications to the stock FFM kit.

I already detailed my kit mods in the design thread, but I think this roll-diving was caused by trying to make the turn too tight - too much rudder, too much stab tilt, too much left thrust. My new plane has quite a bit of washin on the left wing and also quite a bit of washout on the right to keep it from rolling left too hard, and has a straight tailboom rather than the angled boom specified by the FFM instructions.

For reference, the diameter of the circle my old plane made wasn't more than 8-10 feet; the new one does a good 20' diameter circle, closer to 25' on launch due to the motorstick twisting.

I also made the tailboom drop down quite a bit, so the stab is now about 1 3/4" below the motor stick, but I don't necessarily think that helped the roll-diving, although it did help other things like climb angle.

From what I've heard, every FFM plane is going to have its own quirks and characteristics. What worked for me might not work for you, but if you'd like, give it a shot and see what happens.

[DoctaDave]

I have also modified the FF model a bit. I've already reduced the left thrust, stab tilt, and rudder angle on my plane, because like yours, my plane was flying in tiny circles. right now I'm getting around 20' diameter circles, but I still get a shaky plane.
My plane already has a pretty good climb angle with the stock tailboom, so I don't think I really want to play with that too much for now.
As for rolling to the inside of the circle, that only happens to me during the very beginning of my flight, when theres still a lot of torque in the rubber.

I looked into the dutch roll that Mr. Anderson mentioned, and the description of it seems to match the characteristics of the flight of my plane. I'll try increasing the rudder size and see if it fixes my issues.

[someusername]

I have been having issues with my rubber bands breaking very frequently. they will break after only 5 to 10 flights (about 1300 average winds per flight) and the rubber band is a .094 thickness. I am securing the loop using a square knot and a very small ammount of gorilla super glue to ensure that the knot does not come undone. Is it normal to have motors break this often or am I doing something wrong?

[InfiniCuber]

I have been having issues with my rubber bands breaking very frequently. they will break after only 5 to 10 flights (about 1300 average winds per flight) and the rubber band is a .094 thickness. I am securing the loop using a square knot and a very small ammount of gorilla super glue to ensure that the knot does not come undone. Is it normal to have motors break this often or am I doing something wrong?

From my experience, rubber bands will break relatively often, just perhaps not as often as you are experiencing. Are you using lubricant for your rubber?

[someusername]

I have been having issues with my rubber bands breaking very frequently. they will break after only 5 to 10 flights (about 1300 average winds per flight) and the rubber band is a .094 thickness. I am securing the loop using a square knot and a very small ammount of gorilla super glue to ensure that the knot does not come undone. Is it normal to have motors break this often or am I doing something wrong?

From my experience, rubber bands will break relatively often, just perhaps not as often as you are experiencing. Are you using lubricant for your rubber?

Yea we use armour all as a lubricant and we apply it before every flight.

[InfiniCuber]

I have been having issues with my rubber bands breaking very frequently. they will break after only 5 to 10 flights (about 1300 average winds per flight) and the rubber band is a .094 thickness. I am securing the loop using a square knot and a very small ammount of gorilla super glue to ensure that the knot does not come undone. Is it normal to have motors break this often or am I doing something wrong?

From my experience, rubber bands will break relatively often, just perhaps not as often as you are experiencing. Are you using lubricant for your rubber?

Yea we use armour all as a lubricant and we apply it before every flight.

Alright that's good, sometimes leaving the rubber soaking in it for a bit helps too. I would personally make some test rubber bands, and then test what their breaking point is in regards to torque. Then when winding for a flight, wind only to about 80% of that, and this data should help you not break your rubber.

[jander14indoor]

Where are your motors breaking? How and where do you store your motors? How hard are you winding, is it close to breaking?

The motors don't last forever.

What is a reasonable life.
Winding hard (>95%)with well kept motors, a couple of flights is considered good.
Winding 80% with well kept motors, 5 flights is on the low end, 10 reasonable, 15 plus not too rare.
Not well kept, you might not get one wind to the torque you expect.

Things that shorten life.
Winding HARD(90% plus of max torque, more is worse on life). Of course if you want to win you'll need to wind hard in competition and at least sometimes in practice.
Not keeping them clean, try not to drop them on the floor for example.
Storage temperature, heat is bad.
UV Light, these things don't like the sun.
Some chemicals. Particularly some plastic bags off gas nasty chemicals. Archival quality bags or paper envelops are best. Ozone is bad and common around electric motors. Some places in your house may have an excess of Ozone.
Anything hard or sharp while winding. I don't like glued knots myself for that reason. I use the double overhand knots as I find them easy to adjust and I've never had one slip. But I know some people are successful with them.


Regards,
Jeff Anderson
Livonia, MI

[someusername]

Where are your motors breaking? How and where do you store your motors? How hard are you winding, is it close to breaking?

The motors don't last forever.

What is a reasonable life.
Winding hard (>95%)with well kept motors, a couple of flights is considered good.
Winding 80% with well kept motors, 5 flights is on the low end, 10 reasonable, 15 plus not too rare.
Not well kept, you might not get one wind to the torque you expect.

Things that shorten life.
Winding HARD(90% plus of max torque, more is worse on life). Of course if you want to win you'll need to wind hard in competition and at least sometimes in practice.
Not keeping them clean, try not to drop them on the floor for example.
Storage temperature, heat is bad.
UV Light, these things don't like the sun.
Some chemicals. Particularly some plastic bags off gas nasty chemicals. Archival quality bags or paper envelops are best. Ozone is bad and common around electric motors. Some places in your house may have an excess of Ozone.
Anything hard or sharp while winding. I don't like glued knots myself for that reason. I use the double overhand knots as I find them easy to adjust and I've never had one slip. But I know some people are successful with them.


Regards,
Jeff Anderson
Livonia, MI

Thanks for the information, I think the most likely thing may be winding too hard, but 1500 on a .094 seems low to me, but I also haven't looked into the breaking point of it either like Infinicuber mentioned. As far as overhand knots go, I'm not a fan of using them because the shape they make tends to get caught on my motor stick, which gets annoying at times.

[jander14indoor]

Put the knot at the rear hook and you won't have any problem with catching on the motor stick.

Are you winding to torque or turns? Torque is more accurate and consistent.
If you are winding to torque, look back at my posts where I discuss how to test motors and interpret the results. You really should know what the breaking torque of your motors is.

To avoid breaking when winding competition motors, inspect them carefully along the length. Look for knicks and cuts in the edges, don't use or depend on motors with such damage.
Oh, and you should break-in competition motors. Look around this sites archives for additional discussion, but a motor stores energy best after being stretched slowly to a significant portion of its capacity once. You may have noticed you get the best flights out of motors on the second or third flight if you don't break your motors in. If winding hard, you'll see a lot of fall off or breakage beyond the third flight or so.

Jeff Anderson
Livonia, MI

[fifty_missions]

.094 Rubber-

This is a pretty large cross section and at this loop size (to meet the 2 gram rule) makes for a motor than does tend to break after 1300+ winds. Be very consistent with following your procedures with your motors and treat them like human muscles. They get very tired when you max the winds. Rotate the motors between high torque flights and mark your bag or envelope for each "high torque" flight. Let the motors relax a good ten minutes or more before putting them through more stress. This procedure and those as described by Jeff Anderson should help prolong the life of your motors.

Good Luck,
50 Missions