Wright Stuff C

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DatSciolyBoi
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Re: Wright Stuff C

Postby DatSciolyBoi » October 8th, 2019, 11:26 am

*That feeling when you realize they forgot to ban electric steering mechanisms by only placing a ban on means of propelling the plane*
You might check the description of the event, I think you'll find 'free flight' rules out any external controls. Pretty much any active controls too.

Jeff Anderson
Livonia, MI
oof yeah you're right :?
Chaparral Middle School -> Troy High School
Background in: Wright Stuff, Bottle Rocket, Mission Possible, Wind Power, Experimental Design, Elastic Launched Glider, Fossils, Mystery Architecture
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lechassin
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Re: Wright Stuff C

Postby lechassin » October 11th, 2019, 7:59 pm

Here's our first attempt at a stop action video (I plan to keep my day job):
https://www.youtube.com/watch?v=uBAMoaZyWhQ
We now have two contest planes ready to go that are identical in every way except for a slight difference in the amount and placement of ballast due to slight differences in wood density.

One of the two planes I built was up to 8.2 grams due to repeated modification and has been discarded. We're using the second one I built as a test bed for props and for new ideas, the latest of which is a quick release mechanism to move the wings side to side and move the rudder in 10 seconds, yet have everything sit precisely every time, while staying at 8.0 grams. We haven't determined how much lateral wing adjustment is best yet, but the technique seems to work and appears durable.

Here is the process of switching the rudder and wings without rushing, in 16 seconds:
https://www.youtube.com/watch?v=TSLT4MT ... e=youtu.be

The wing in the video uses 1/16" leading and trailing edges instead of 3/32 to reduce turbulent flow a little, denser wood and still adequate strength. We might reduce incidence some but the resulting aft CG prolongs recovery from a hit, so 4mm decalage (all of it in the wing incidence) seems to be as far as we can take that for now.

We are working on slowing the prop down while keeping the tip pitch just below 30 degrees. The blade design we're gravitating to reminds me of a box fan, which isn't too surprising. Very large blades do slow the prop down 10% but the resulting prop is 50% heavier. That inevitably pushes us over the 8.0 gram threshold, so we can't try it yet.

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xiangyu
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Re: Wright Stuff C

Postby xiangyu » October 13th, 2019, 6:50 am

Here's our first attempt at a stop action video (I plan to keep my day job):
https://www.youtube.com/watch?v=uBAMoaZyWhQ
We now have two contest planes ready to go that are identical in every way except for a slight difference in the amount and placement of ballast due to slight differences in wood density.

One of the two planes I built was up to 8.2 grams due to repeated modification and has been discarded. We're using the second one I built as a test bed for props and for new ideas, the latest of which is a quick release mechanism to move the wings side to side and move the rudder in 10 seconds, yet have everything sit precisely every time, while staying at 8.0 grams. We haven't determined how much lateral wing adjustment is best yet, but the technique seems to work and appears durable.

Here is the process of switching the rudder and wings without rushing, in 16 seconds:
https://www.youtube.com/watch?v=TSLT4MT ... e=youtu.be

The wing in the video uses 1/16" leading and trailing edges instead of 3/32 to reduce turbulent flow a little, denser wood and still adequate strength. We might reduce incidence some but the resulting aft CG prolongs recovery from a hit, so 4mm decalage (all of it in the wing incidence) seems to be as far as we can take that for now.

We are working on slowing the prop down while keeping the tip pitch just below 30 degrees. The blade design we're gravitating to reminds me of a box fan, which isn't too surprising. Very large blades do slow the prop down 10% but the resulting prop is 50% heavier. That inevitably pushes us over the 8.0 gram threshold, so we can't try it yet.
That's pretty cool. Thanks for sharing!

I'm doing my first test flights today with my team with the freedom flight kits. I'll share results afterward. :)
2020 Events: Wright Stuff, Gravity Vehicle. Machines, Circuit Lab, Boomilever, Ping-Pong Parachute, WIDI

Inv.1/Inv.2/Reg
WS:
WIDI:
Boom:
Circuit:

Medal Count: 2
East Grand Rapids High School, Michigan

lechassin
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Re: Wright Stuff C

Postby lechassin » October 13th, 2019, 12:35 pm

I'd love to see video of your flights. We're using that in addition to flight data to analyse behavior on repeated viewings.

Today we made good progress using the planes with wings fixed permanently at 4mm incidence. Flights are consistently between 1'25" and 1'30" with only a rudder change, from the time the motor is just broken in until the motor is worn out and breaks. Initial climb to the right is still too violent but the plane stays nicely on course every single time so we accepted that pending tests next week with the moveable wing design.

We were able to get four flights in a row, two by me and two by Luke, using contest rules. We used the same motor and same-ish winds and torque, around 3600 turns.
Me, 1'28" right and 1'27" left:
https://www.youtube.com/watch?v=a-kf8k2 ... e=youtu.be
Luke, 1'30" right with one ceiling hit and 1'25" left:
https://www.youtube.com/watch?v=rgVqyn2 ... e=youtu.be

The first launch is well within that 3 minute initial period in the rules and both launches are well within the 8 second period. Only the rudder was changed between flights. We were very happy with the consistent turns, the few knots remaining at the end of each flight, the consistent times within 5 seconds going both ways, and the nice recovery from the one ceiling hit. Hopefully the moveable wing version will climb more gently to the right.

We did play around with other props, rudder settings and motor lengths after the videos and while none of those later flights was less than 1'15", none were over 1'25", so I think today's videos are where we're at until new ideas pan out. The big things we plan to try next Sunday are the adjustable wings which will hopefully reign in the initial climb to the right, and the larger bladed prop to extend the motor run.

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Re: Wright Stuff C

Postby xiangyu » October 13th, 2019, 1:20 pm

I just came back from the gym. Overall it was okay. When we got there the fans were on blowing pretty hard and we tried to fly the plane but it didn't work out great (the fan is one of those that's attached to the ceiling and blows straight down - We consistently got around 50s - a minute in that condition). We flew for about an hour in that condition and then decided to look for another place with less current. (My school has 2 gyms so...) The other gym was better and we did a couple of flights (See details below) but then sports practice started and we had to leave, but I think we're off to a good start and we'll test again next Sunday.

Details of flight in "the good gym";

Time: 1 minute 8 seconds
Wing incidence: 5 mm
Rubber width: 1/16 inch
Rubber Weight (without the 2 black rings): 2.54 g
Winds Forward: 3000
Winds Backwards: 345
Torque: 0.16
Winds Left after Flight = ~ 300 (not exactly sure since the plane hit one of my teammates and released a bunch of winds before we recovered it)
Main problem - Steep decline at last second (perhaps due to rubber running out?)
Gym Height - ~30 ft

See counter-clockwise video here (we didn't have time to try out turning clockwise): https://youtu.be/ISIuRUXOGik

Let me know if you see something that I should change. I think the main problem is that we ran out of winds causing the final steep dive so we will probably add another 300-600 winds next time.

Xiangyu
2020 Events: Wright Stuff, Gravity Vehicle. Machines, Circuit Lab, Boomilever, Ping-Pong Parachute, WIDI

Inv.1/Inv.2/Reg
WS:
WIDI:
Boom:
Circuit:

Medal Count: 2
East Grand Rapids High School, Michigan

lechassin
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Re: Wright Stuff C

Postby lechassin » October 13th, 2019, 4:37 pm

The steep dive may have been from the sudden movement of your team mate ducking. We noticed that too so now we anticipate getting hit and move away slowly ahead of time. I'm curious to see if you're using up most of your knots in 1'08". You can see we use all of our knots in 1'30" running three blades.

The main thing that surprised me in your video is how well the plane does with one wing! Apparently the decrease in drag of your design offsets at least some of the increased wing loading. Your times are equal to our first-day times and it'll be interesting to see how much more you can get.

We're getting 3750 turns into a fully broken-in 2.9 gram motor and we break them in about 10 flights, so I'm curious to see how many more winds you can reliably get into a 2.5 gram motor. I wonder at 3600 turns you might be close to 100%.

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Re: Wright Stuff C

Postby bjt4888 » October 13th, 2019, 6:25 pm

Xiangyu,

If you can supply the rubber motor loop length we can calculate the motor density per inch and determine the maximum number of turns it can handle.

The typical solutions to all turns getting used before landing is: thinner rubber, longer rubber, more propeller pitch or different propeller design (flaring, for example). This list is in the order that we usually test.

Brian T

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Re: Wright Stuff C

Postby bjt4888 » October 13th, 2019, 6:30 pm

Sorry, didn’t see the end of your data set mentioned that you have turns remaining of about 300.

Still would suggest the same set of items to test in that order. Rapid descent indicates motor remaining torque is very low. A thinner motor will result in more turns remaining, but possibly longer time period of usable torque.

Still would like to know rubber loop length (measured before use).

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Re: Wright Stuff C

Postby bjt4888 » October 13th, 2019, 6:55 pm

If, for example, your loop length is about 30.5” (.0415 g/in), and your stretch 5x relaxed length to wind (after break in, properly lubed) an 85% breaking turns number would be 4,100. Probably need more back off (the large number of backoff turns needed is another indicator of needed changes (thinner rubber, more pitch or flaring prop).

Brian T

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Re: Wright Stuff C

Postby bjt4888 » October 13th, 2019, 7:05 pm

Also, it appears that the airplane is stalling at the end of the flight. Iis difficult to tell for sure as the video cuts off just as the biggest stall appears to be happening. Stall can be fixes by adding nose weight or sliding the wing saddle back a little. The airplanes this year are very sensitive to center of gravity changes, so sliding back about 1/8” could be all it needs. Keep sliding the wing back in small increments on successive flights to see if this helps.


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