Wright Stuff C

Airco2020
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Re: Wright Stuff C

Post by Airco2020 » January 8th, 2020, 2:13 pm

bjt4888 wrote:
January 8th, 2020, 1:01 pm
Air,

Yes, I agree with Jeff. I didn’t mean to discourage your work on gearboxes. Just want to advise you to get clarification and to consider that one of the most difficult parts of gearbox construction is the housing which aligns the gears and shafts. It’s possible that a premanufactured housing might not meet rules as all the alignment is built in. Definitely submit a FAQ on the official SO website.

Also, even if the premanufactured housing is not allowed, it is definitely possible to make one from carbon plate and using small aluminum tubing for bushings. Just make a jig to align shafts and gears during construction. See examples in issues of this type of construction in Indoor News and Views or in Hip Pocket.

Not sure your current configuration will do long duration as, based upon my calculations from your data, your prop is turning at about 100 revolutions per second. However, you have a good start with an innovative idea. So, maybe a different gear ratio, or different prop, or longer rubber, or Etc.

Great job.

Brian T
Thanks Jeff and Brian for your comments and encouragement. I'll see about posting an FAQ.

How did you get 100 revolutions per second? It does spin really fast!

I was just jacked that I could get it to fly. I think there is a lot of work on prop and rubber to figure out. The current prop I think is too small but it was an easy way to test small props. Somewhere between the trimmed prop from the kit and the current one is probably where I need to be. I built a longer motor stick last night since I only had a 9" stick on the plane in the video. I can also go down in rubber cross section since it didn't have trouble climbing. With those changes I think I should be able to get 1:15 - 1:30 but won't know until I can get back in the gym.

Since gym time is so hard I built a test rig I've been using to try props and rubber. It's a motor stick on an arm that rotates on a bearing. It flies in small fast circles with no wing! I could only use it to compare different prop rubber combos but didn't know if it correlated to flying until I got in the gym. I now know that if I can get over 30 revolutions in the first 20 seconds its enough torque to climb, current setup is 34 revolutions (I'm guessing on 30 a bit I just know right now I have more torque than needed). I also used the same setup as the flight to figure out the cruise speed that keeps the plane mostly level from the video. 13 revolutions in 10 seconds is cruise speed. Current setup went for 1:08 on the test rig and flight was 1:00 so I also think it gives a good idea of total flight time. Now I can test other setups and then see if it translates to the gym or not. Writing this I just realized I now need to put a longer motor stick on the test rig, ugh! Fun to be able to do something at home! Worst part of WS is waiting to go fly!!

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Re: Wright Stuff C

Post by bjt4888 » January 8th, 2020, 3:00 pm

Air,

Since a 2 gram loop of .125” rubber takes about 1,100 turns when wound to about 1.2 in oz and maybe less if this is a first winding; maybe 900 to 1,000. And from 1.2 to 0.6 in oz would be about 50 to 75 backoff turns and assuming landing with a small number of turns remaining; maybe another 50; the turns used for flight would be between 800 and 1,000. As the rubber motor is turning at a 1 to 6 reduction compared to the prop, the prop rotations during flight would be 4,800 to 6,000. Divide these prop rotations by the flight time of about 60 seconds and you get an average prop revolutions per second of 80 to 100.

So, knowing the prop average RPS would allow you to estimate flight time with a longer rubber motor since the maximum turns for the longer rubber motor can be calculated.

Brian T

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Re: Wright Stuff C

Post by CrayolaCrayon » January 8th, 2020, 3:27 pm

A two gram loop of .125 should be taking around 1250 turns on the first wind going up to about 1.9. After 1 or 2 flights, maybe around 1350+

A higher prewind will give you more intial turns, and hopefully you don't have to dewind as much. I've known quite a few to push .125 above 2.0 torque (I've gone to 2.3) before dewinding.

Get the turns in!
Wright Stuff 2nd 2019 Nationals
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Re: Wright Stuff C

Post by lechassin » January 8th, 2020, 3:46 pm

I will be the voice of dissension and caution you from using precious gym time chasing a performance gain that is just not possible. Thinner rubber would achieve the exact same prop torque without friction from extra bearings and gears. You're subtracting energy that would otherwise reach the prop and you're adding mass, with no upside to compensate.

My recommendation would be to first optimize a standard setup and then try to beat that by whatever means you think of, including but not limited to the gearbox.

That's been our general approach this year: we have three planes on rotation, two ready for competition and a third that tries to beat the other two. As soon as the third plane succeeds, we modify the other two to match and repeat the whole process. The design can evolve at no risk to any gains we already have.

Since you mention limited gym time, I'll offer another bit of advice that has worked well for us, knowing that upon me will descend the wrath of the forum's gurus: make one log that you can show at meets and then put away the pen and paper. Video each flight with relevant commentary on the setup (the numbers you'd put on the paper log). Old videos become obsolete as the design improves and we just delete them. It's much faster than logging on paper plus, and this is huge, we can repeatedly review each video akin to what pro athletes do. Watching a flight is way better than reading an inevitably incomplete description. If you're by yourself, you can set up a tripod and just hit play before you launch.

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Re: Wright Stuff C

Post by bjt4888 » January 8th, 2020, 3:53 pm

CrayolaCrayon wrote:
January 8th, 2020, 3:27 pm
A two gram loop of .125 should be taking around 1250 turns on the first wind going up to about 1.9. After 1 or 2 flights, maybe around 1350+

A higher prewind will give you more intial turns, and hopefully you don't have to dewind as much. I've known quite a few to push .125 above 2.0 torque (I've gone to 2.3) before dewinding.

Get the turns in!
Crayola,

Agree that 1.9 is usually max for this loop. I was basing my RPS calculation on 1.2 as this was the torque data given by Aircoco. Yes, duration would be better if wound to 1.9 inoz max torque even after the additional backoff needed.

Brian T

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Re: Wright Stuff C

Post by Airco2020 » January 8th, 2020, 4:48 pm

lechassin wrote:
January 8th, 2020, 3:46 pm
I will be the voice of dissension and caution you from using precious gym time chasing a performance gain that is just not possible. Thinner rubber would achieve the exact same prop torque without friction from extra bearings and gears. You're subtracting energy that would otherwise reach the prop and you're adding mass, with no upside to compensate.

My recommendation would be to first optimize a standard setup and then try to beat that by whatever means you think of, including but not limited to the gearbox.

That's been our general approach this year: we have three planes on rotation, two ready for competition and a third that tries to beat the other two. As soon as the third plane succeeds, we modify the other two to match and repeat the whole process. The design can evolve at no risk to any gains we already have.

Since you mention limited gym time, I'll offer another bit of advice that has worked well for us, knowing that upon me will descend the wrath of the forum's gurus: make one log that you can show at meets and then put away the pen and paper. Video each flight with relevant commentary on the setup (the numbers you'd put on the paper log). Old videos become obsolete as the design improves and we just delete them. It's much faster than logging on paper plus, and this is huge, we can repeatedly review each video akin to what pro athletes do. Watching a flight is way better than reading an inevitably incomplete description. If you're by yourself, you can set up a tripod and just hit play before you launch.
I got the same advice at home about "chasing the holy Grail". I know you can't get something for nothing.

It seems there are a lot of constraints this year. A lot of people are adding ballast which doesn't help. At some point your motor stick is limited and then your motor is limited. I keep thinking there are more turns available with the box somewhere....

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Re: Wright Stuff C

Post by Airco2020 » January 8th, 2020, 5:36 pm

jander14indoor wrote:
January 8th, 2020, 10:24 am
Why would a great long flight get you banned, that IS the purpose of the event afterall!

Again, NOT official, only one person's opinion.

Before you ASSUME it is not legal, I'd recommend you request a FAQ or clarification from the NSO website, www.soinc.org
It might be considered OK under general rule 1: Actions and items (e.g., tools, notes, resources, supplies, electronics) are permitted, unless they are explicitly excluded in the rules, are unsafe, or violate the spirit of the problem. (straight from the rule book, page C1)
I don't see where it is explicitly excluded in the relevant construction paragraphs. Para 3.e lists things that "may" be part of the prop, excludes only one mechanism type, pitch change.
Doesn't seem unsafe to me, unless someone wants to claim it is because of the high prop speed.
Spirit, always subject to interpretation (personally I hate that clause, though I have used it ONCE in 20 years of event supervision). While I might not say it is against the spirit, someone else may. That's where an official position from NSO would be useful, and the only way to get that is an FAQ or clarification.

Thanks,

Jeff Anderson
Livonia, MI
FAQ submitted. Thanks for the help.

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Re: Wright Stuff C

Post by builderguy135 » January 8th, 2020, 6:06 pm

What event is replacing Wright Stuff next year?

HLGs please
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Re: Wright Stuff C

Post by nobodynobody » January 8th, 2020, 6:14 pm

Hi! I have been doing wright stuff and I seem to have hit a wall and don't know how to advance. I have the freedom flights biplane kit and can consistently get 1 minute on both sides :shock: So these are the observations I'm making:

I tested with .072" of rubber and it seemed to be to most consistent and "easy" to get. I first tried 2g of rubber and it ran out of winds really early. I tried with 3g and the same thing happened. At 4g however, it descended while there were many winds left. I think this is because it wasn't being stretched out enough by the motorstick and didn't have much power left at that point. I extended the motor stick thinking I can fit more winds in and found the sweet spot to be around 3.8g of rubber. I haven't gotten a test where it didn't hit the wall(my teseting spaces are small) and I estimate it should get around 1:10 on both sides at competitions

I also tried out the .065". It was getting about 50 seconds both sides because it would not have enough power to stay up anymore. This time I used a little bit less of rubber. I'm hoping I could really use this because it spins significatly slower than the .072" and I think it has much more potential.

The main problem I think I have(I could be wrong) is just how the plane behaves very differently at different times. At the beginning the initial blast of air makes the plane shoot straight up for about 5 seconds, ~15 seconds of climbing, ~30 seconds of staying at the same altitude, then a 10 second very rapid descent. I've been kinda juggling all of these at once hoping that nothing will ruin the flight.

I'm hoping to improve my times with the .065" rubber. I'm testing again tomorrow and I'm thinking about how I could improve this. My incidence is pretty high at the moment(3.75mm) so would decreasing the incidence and moving the wing forward allow for lower power climbing? As with the initial blast of air, how much would dewinding do to it? What is the difference between winding less and dewinding? What should I be doing to improve the times?

Sidenote: I wanna just mention how great this forum is. Everybody here is helping each other and being very open even though you are competitors, and this just wants to motivate me to work on wright stuff! I want to thank everyone for posting here, as I would not be where I am right now!
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Re: Wright Stuff C

Post by CrayolaCrayon » January 8th, 2020, 6:24 pm

nobodynobody wrote:
January 8th, 2020, 6:14 pm
Hi! I have been doing wright stuff and I seem to have hit a wall and don't know how to advance. I have the freedom flights biplane kit and can consistently get 1 minute on both sides :shock: So these are the observations I'm making:

I tested with .072" of rubber and it seemed to be to most consistent and "easy" to get. I first tried 2g of rubber and it ran out of winds really early. I tried with 3g and the same thing happened. At 4g however, it descended while there were many winds left. I think this is because it wasn't being stretched out enough by the motorstick and didn't have much power left at that point. I extended the motor stick thinking I can fit more winds in and found the sweet spot to be around 3.8g of rubber. I haven't gotten a test where it didn't hit the wall(my teseting spaces are small) and I estimate it should get around 1:10 on both sides at competitions

I also tried out the .065". It was getting about 50 seconds both sides because it would not have enough power to stay up anymore. This time I used a little bit less of rubber. I'm hoping I could really use this because it spins significatly slower than the .072" and I think it has much more potential.

The main problem I think I have(I could be wrong) is just how the plane behaves very differently at different times. At the beginning the initial blast of air makes the plane shoot straight up for about 5 seconds, ~15 seconds of climbing, ~30 seconds of staying at the same altitude, then a 10 second very rapid descent. I've been kinda juggling all of these at once hoping that nothing will ruin the flight.

I'm hoping to improve my times with the .065" rubber. I'm testing again tomorrow and I'm thinking about how I could improve this. My incidence is pretty high at the moment(3.75mm) so would decreasing the incidence and moving the wing forward allow for lower power climbing? As with the initial blast of air, how much would dewinding do to it? What is the difference between winding less and dewinding? What should I be doing to improve the times?

Sidenote: I wanna just mention how great this forum is. Everybody here is helping each other and being very open even though you are competitors, and this just wants to motivate me to work on wright stuff! I want to thank everyone for posting here, as I would not be where I am right now!


Try some longer .065 loops. About 2g to start with .065 should put you over 1:00. You get the most time gains from correct trim and getting the most turns out of the rubber.
Wright Stuff 2nd 2019 Nationals
USA F1D Team 2020 Image
1391 Turns

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