Instructions for building plane without kit?

[bjt4888]

Kyle,

I misunderstood your note regarding wing incidence. Also, to be more specific, I should have stated, do not increase or decrease the wing incidence specifically to change the rate of climb.

There is an optimal wing incidence angle (actually, decalage angle, but your stab incidence is zero, so we can discuss just the wing) for a particular CG that is just less than the amount that causes a stall.

Also, for the airplane that fits this year's rules, your wing incidence angle should be about 2.5 degrees or slightly more. Incidence less than this will cause pitch instability that you probably won't be able to see until you contact the ceiling and the airplane dips dramatically a number of feet before recovery (or, dips all the way to the floor).

If your current wing incidence is slightly more than the 1/4" starting point, let's say it is 9/32", then it is 3.75 degrees. This is a lot, but maybe ok.

Since you are flying at very, very low power by winding to 1,400 turns and 0.30 in oz, this is most likely why the airplane was only climbing to 3/4 ceiling height. If on that flight you had wound to 2,200 turns (with a fresh motor) and backed off to 0.30 in oz the airplane would have climbed quite a bit higher. Wind to 80% or 85% maximum and backoff to launch torque on every flight. This is the only way to see how the airplane really flies so that you can finish trimming.

Once you do this type of winding, you may see that you can move the wing incidence back to 1/4" (which equals 3.33 degrees), or maybe even 3/16".

Good luck and have fun,

Brian T.

[jander14indoor]

Let me reinforce comment on backoff. Good winding practice almost ALWAYS involves winding past target torque and backing off. If you don't, you are not flying with a full tank of gas. About the only time you don't back off is if the ceiling is crazy high.

I've suggested this experiment in previous years, so search the archives for more detail. You are using a torque meter so you can do this quickly.
Make up two or three short motors. Say 4 inch long loop.
Wind the first motor to breaking. Take data on torque vs turns as you wind. Torque value every 10 or 20 turns for example. Record breaking torque. The breaking torque will be pretty consistent for that batch and width/thickness/linear density of motor. No matter the length.
Take a second motor, wind to say 85 or 95% of breaking. Again take torque vs turns data on way up. Now, UNWIND motor taking torque vs turns on the way down until 0 torque.
Plot all that turns on horizontal, torque on vertical. Note how unwind curve drops FAST and is ALWAYS below wind up curve. You fly on UNWIND!
So, pick a launch torque. How many turns to you have to that torque on wind. How many turns if wind pas and come back. I'll bet its hundreds more turns. Lots more fuel in your tank at launch.

Oh, why only use short motors. To save rubber. A longer motor will just hit the same torques as a linear ratio of the length of the motor. An 8 inch motor will need twice the turns of an 8 inch motor to get to same torque. And so on.

Why more than two motors. Wind multiple times and see how motor changes with use. Wind to different peaks and back off to see if you always get to same unwind curve (you mostly will). Etc.

Another couple of side comments.
The return of less torque than you wound into your motor is an example of why perpetual motion machines CAN'T work. You NEVER get back out of something everything you put in. In this case it also has a name, hysteresis. Look up for more on why it happens.
The area under the UNwind curve is the ENERGY or FUEL you have to fly with. You want to maximize that.

Jeff Anderson
Livonia, MI

[Kyle_Guo]

notes from flights on tuesday:
1400 winds, 1min23secs time Climbed in 3 loops, circled at the top for a long time, went down slowly several small stalls (suddenly dropping 6" and continuing flying at the lower altitude, no climbing back)
0.25 in-oz torque, perfect height, was in fear of hitting a light that was lower than the supports by 1 foot or so but just barely missed it. Landed with 20-30 winds left to spare bad.

2000 winds 180 dewinds torque: 0.026 in-oz Circled once, hit ceiling on 2nd spin, on third spin, circle widened so it hit curtains on side. time : 37 seconds

2000 winds 300 dewinds torque 0.024 in-oz circled several times, stalled slightly made one erratic turn, circle gradually widened, hit curtain on side at 7-8 feet time: 1 min 26 sec.

This was all with the increased incidence, The flights were good on Tuesday but once I tested on Friday, things did not go as well

Notes from Friday:
1500 winds time: 57 seconds torque 0.025
1500 winds time: 53 seconds torque 0.025

This was with increased incidence. There was more frequent stalling and the plane only reached 1/2 gym height no matter what I did. I see that the 1st loop is normal but it just stops climbing after that and stalls until it lands.

[Kyle_Guo]

Does anyone know what is wrong? The plane has been flying ceiling height at this about 3/8 incidence with 1500 winds and 0.26 in-oz torque. On testing on Friday, all the specs were the same, 1500 winds, 0.026 in-oz torque, some incidence, but the plane will not climb. The only thing I can think of is that in a flight prior, I winded to 1600 winds no back off and kept the increased incidence with 0.028 in-oz torque, the plane bumped into the ceiling support, swung, and shot down 7 feet or so and went really quickly into a wall, it slid down slowly due to the propeller still running. One rib in the wing dislocated so I glued it back on with minimal glue. Did this affect how high the plane climbs at the same setting?
Also, included with no climb after 1/2 the gym, the plane drops suddenly for 6 in and continues at the lower height 2-3 times per turn until it lands.
Should I...
- move wing back in effort to remove stall?
- set incidence back to 1/4" and ...
- Wind to 2200 winds, unwind to 0.030 in-oz torque and try the flight?

[jander14indoor]

Most common explanation for sudden changes in performance is something is broken. Since you fixed one thing, are your sure there aren't others? Check EVERYTHING.

Are you sure that the fix got it back to original? Or that you reassembled the way you think?

I don't remember if you are using any clay to balance, is it still there, still in correct place for desired balance?

Jeff Anderson
Livonia, MI

[Kyle_Guo]

One of the diagonal supports for the wing was loose, that was the only thing that was not normal. The gym is currently taken up by a basketball match so I did a 500 wind test run elsewhere. The plane climbed to about 7 feet and the time for the flight was 26 seconds. There was no stalling but I cant really tell with such a short flight.

[Kyle_Guo]

So far, I do not know why the plane is not performing what it should.
notes for today;
1800 winds, 0.040 in-oz, 1 min 19 secs, went up on 2 turns, in middle of 2nd turn, hit top and went down 5 feet, continued circling 3-4 times, started going down with drops of 2-3 feet each time, glided and dropped 2 feet to the ground.
I cant understand why it takes 0.040 in-oz or torque AND almost 1/2" incidence to get the plane even close to what it could do a week ago with 0.030 in-oz and 1500 winds. Nothing is broken, then only thing changed is that one wing spar broke so I had to glue it back on with minimal glue. It was repaired and was exactly as it was before.

[Kyle_Guo]

I set the incidence back to 1/4" and ran the plane on 1800 winds (0.060 in-oz) it circled 3/4 up on the first turn and got stuck the second. I am currently getting it down. My goal is to get the launch torque right (somewhere between 0.030:1500winds and 0.060:1800winds) and then solve my stall issue. Is suddenly dropping a few inches on decent stall? should that be removed by shifting the wing back in even smaller increments like 1/8"? Once I get launch torque and wing position right, Ill shave off ectra weight and try to get more winds in for the same (if not lower) torque.

[Kyle_Guo]

After much testing, breaking, fixing, and head scratching, I feel that I have no more questions about the topic. This topic can now be closed. I appreciate the help I got from the forum (especially Brian T) from knowing nothing about making a plane without instructions to completing a fully flyable plane.Without the generous help of the individuals who replied on the forum, I would definitely been hopeless. At the end, my best time was 1 minute 55 seconds.

[bjt4888]

Kyle,

Congratulations on your excellent tenaciousness and great results! The top engineering schools around the country are awaiting your application (in a few years).

Brian T.