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Author Topic: SO Electric Wright Stuff 2022  (Read 1316 times)
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Little-Acorn
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« Reply #25 on: December 05, 2021, 05:26:28 PM »

About 3/4 of the planes I saw at the tournament, looked like Josh Finn's design (EWS version, I believe he calls it Electron), plus other similar planes with a single vertical fin ahead of the stab. Seems like a very good design. But most of the students didn't know what to do with it. Some were throwing it like a baseball, some were throwing it straight up etc. But there were some who did nice, smooth launches, and they got good results.

This tournament was relatively early in the season, and I pushed my teams hard to get their planes finished a few weeks (or more) before the tournament. So they got in a few weeks of practice in our gym, which helped a lot. For some of the schools we saw yesterday, it seemed to be the first time they'd ever flown their plane. Planes were stalling and falling grotesquely, others nosediving in, etc., which is typical behavior of a first flight of course. Then the real work is supposed to start as students try to work out why it's doing that, what they can do to correct it, etc. etc. you know the drill. At least one team stated frankly that they had bought the kit "at the last minute", thrown it together, and brought it to the tournament.

San Diego Regionals is in February 2022, and I'm sure the great majority of planes that show up there, won't be acting like that. Yesterday's tournament was good practice for my teams, now they have one under their belts and know pretty much what they're dealing with.
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jdpsloflyer
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« Reply #26 on: December 05, 2021, 08:54:35 PM »

Looks like a lot of progress being done here.  

Me not so much.  My school started late (about 1st of November).  EWS did not get started till a couple of weeks ago and I still have students coming and going.  We do not have kits yet, as the school has to order/receive them before I get them for my kids. I did order one WS and one EWS from Josh plus a couple of Motor units for insurance.

I built the kits I received and began my students with trimming for glide and started with 5 sec charge for a test flight. Broke both planes (minor).  Had to solder one capacitor back on (they are fragile)!  I mounted another motor unit to an old 2016 WS plane so we would have something to learn with as well.  I have 6 students and only 2 hours a week to build and practice with them.  Last week I got some old SO balsa that was used to build bridges and we cut LE and TE and ribs to practice building wings from scratch.  Students are 6 and 7 graders who haver never done this. Coaching remotely for 1 1/2 years really dampened things.

After taking firsts, seconds and placing in the top 5 at state for the last five years it's going to be a challenge this year.  We have no gym time reserved yet and are competing with the city basketball teams for it.
« Last Edit: December 05, 2021, 10:17:20 PM by jdpsloflyer » Logged
ceandra
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« Reply #27 on: December 06, 2021, 02:20:30 PM »

jdp:

While difficult to get started, switching to scratch built over kits in the long run will be a huge plus. You can make spare parts, you are never on backorder, etc. etc.

Just be sure to make EVERYTHING fit the rules. Just because a kit was bought does not mean everything fits.

Take a look at the forums, https://scioly.org/forums/viewtopic.php?t=24092, a post I did on observations form ATX invite that I ES'd. In EWS, almost every logbook had errors, making it incomplete (10% penalty). Most were metric units, then missing cover sheet. All but one EWS planes had a switch on the charger, which by rule, and now by several FAQ's, is a construction violation, a tier offense. Build your own charger and you can match the rules! We originally had a switch in the charger wire, but removed it based on the FAQ.

Bottom line, you can be more responsive, more adaptable, and in some cases, more right by scratch building.

We too are having a hard time with gym scheduling. Our second time in the gym was video of flights for National Invite! Have plenty of options (several planes, repair materials, and a plan of action (script) for gym time to maximize effectiveness. If you cannot find a gym, try hotel ballrooms and such. You may have to be creative, going at very early hours and such, but use the "its for the children" and "STEM education" lines to get preferential treatment. You may even be able to find a STEM-related business with a large conference or warehouse facility. Perhaps try your local airport, in the general aviation area, for hanger space. You don't need super high (20') to get some testing done!


Coach Chuck

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jdpsloflyer
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« Reply #28 on: December 06, 2021, 04:56:15 PM »

Coach Chuck,

I appreciate your perspective and advice. 

SO at the school I coach meets one day a week for 2 hours.  Some of my students have more than one event in the time slot EWS is scheduled. Given that, I have found scratch building with kids who have never done it is difficult.  In past years where some students are returning for their second or third year, I have been able to help them build from scratch.  I have always demonstrated the skills needed to do that. With first year students, and the limited time I have with them I decided using purchased kits was an easier way to go. 

For a couple of years I had them design, draft and cut out gliders and WS planes.  I even produced glider kits myself for them to build.  When the kids were designing, cutting and building, they rarely finished one that would fly due to time constraints.  Consequently, I have gone the kit route and encouraged those who want to build their own which I help advise them with.

I looked at the FAQ's on charger rules etc.  We will have to modify our chargers by removing the switch.  Since the plug switch is directly soldered to the capacitor, we will have to figure out a way to either use the plug as is or put a "switch" in line on the plane.

If "we" were to design and build the motor/switch/capacitor system, would a description of that be required in the log as opposed to a manufactured part?
I've had to repair 2 motor systems from my kits by soldering the wires back on the capacitor/plug assembly.  With my skill and the size of the wire/leads i do not think a normal student could do it.

I have reviewed the Youtube videos on building/flying these planes.  It was much better when instructions were included in the kits.  I feel that the videos are a good supplement to the diagrams and explanations that were included in past kits, a video does not have the same information the instructions did and I have not been successful in getting the students to watch them on their own. I guess that is a plus for coaches helping students design/build from scratch their own planes.

Pre-covid I usually had ~10 to 15 students at a time.  For Helicopters last year I had 2 and they took 1st and 2nd at state.  One of my teams placed 6th at nationals in 2016 or 2017, (I can't remember which).

Jerry

P.S. I timed your 2019 team at SO Nat's, my Glider team placed 10th.
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ceandra
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« Reply #29 on: December 06, 2021, 05:43:09 PM »

Jerry:

You would have the option of "kitting" a plane yourself (Coach-designed, or use Bill's excellent Finney design), with pre-cut parts. Just no gluing or covering by Coach! Note that prior years the FAQ's have clarified that the design could come from any source, this year the rules themselves indicate that. While there is more satisfaction in the kids building 100% from scratch, as Jeff Anderson emphasizes in his video, this is NOT a design event, but rather a flight optimization event.

As far as the documentation, the rules are rather nebulous on "description". Is a label enough, or do you describe how the capacitor works? I would keep it simple. I see no real difference in the documentation for the electrical parts whether it is kit-supplied or coach-supplied. I would label key parts (Cap, motor, prop, switch, charge jack), and describe them very simply/

The one exception to this is if a computer-aided machine (3-D printer, CNC router, laser cutter etc.) is used to make parts. If the kids do this, there is extra documentation as to what software and hardware was used, and who did the design, where if supplied in a kit, that extra info is not used. (See FAQ)

To clarify on the switch, a switch MAY be incorporated on the plane, but not on the charger. We built a momentary switch (normally closed) out of music wile and brass (small), so the kid holds that to keep the motor off, and upon release the motor runs. A slip of paper maintains "off" while charging and handling. With a commercial unit with a barrel-style connector and integrated switch, I would put another connector at the charger, plug that in to charge, unplug to stop charge, leaving the pigtail plugged into the plane until ready to launch (switch function).

Note: It is HIGHLY LIKELY that many ES's will not even notice that switches are not allowed in the charger. Even at Region and State levels, we have run into ES's that do not know the basics of the rules, let alone these details.

Since we built a switch on the plane, our charger has two "mini grabber" type leads, which they clip to the capacitor to charge. These work 100% better than the alligator clips they originally tried, and are readily available at Amazon. The charge leads also have banana plugs on a "Y" lead, which they can plug into a stock voltmeter to monitor charge levels. Alternatively, the voltmeter can connect to the Cap with a second set of mini grabber leads.

These are MY INTERPRETATIONS of the rules, and should not be taken as official. Refer to the rules and FAQ's for official interpretations, or submit new FAQ if questions.

Coach Chuck

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jdpsloflyer
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« Reply #30 on: December 07, 2021, 07:14:44 PM »




To clarify on the switch, a switch MAY be incorporated on the plane, but not on the charger. We built a momentary switch (normally closed) out of music wile and brass (small), so the kid holds that to keep the motor off, and upon release the motor runs. A slip of paper maintains "off" while charging and handling. With a commercial unit with a barrel-style connector and integrated switch, I would put another connector at the charger, plug that in to charge, unplug to stop charge, leaving the pigtail plugged into the plane until ready to launch (switch function).


Good idea to put a contact switch on the plane. I removed the switch from my charger today.  I plan on modifying one (positive or negative) wire on the motor assembly with a copper foil and a pin soldered to the cut wire and glued to the fuselage and bent to contact the foil on launch.  The plug at the capacitor already acts as a charging jack, the foil and pin switch would isolate the motor during charging and turn it on at launch. 

I have some copper foil from an early hobby of making leaded glass terrariums years ago.

jdp
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Little-Acorn
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« Reply #31 on: December 07, 2021, 08:07:11 PM »

In my earlier designs for EWS, I had the motor connected to the capacitor by soldering one lead and using a slide-on connector (from an old Arduino kit) to connect the other. Then I would use mini grab hooks on the battery, to connect the battery (after disconnecting the slide connector) to the capacitor and charge it. When charged, I'd then disconnect the grab hooks, and leave the slide connector also unconnected, until the student was ready to launch the plane. He'd then slide the connector onto the free lead of the capacitor, and launch immediately.

Since then I've modified the installation slightly, soldering a tiny SPDT slide switch to the positive lead of the capacitor and the other switch terminal to a tiny connector. I'd then solder a black wire from the other (negative) lead of the capacitor to the other pin of the connector. Then I'd solder the two terminals of the connecter receptacle to the motor. (The connector is just in case the motor needs replacing.)

The students can charge the capacitor either on the judge's bench, or at the launch point. Then disconnect and stow the battery, walk out to the launch point, align the plane at its launch angle, flip the switch and launch.

Total weight is the same as having a magnetic switch on the plane, but more versatile. For a major contest, we might remove the tiny connector and have nothing but the switch between the capacitor and motor, lowering the weight.
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ceandra
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« Reply #32 on: December 07, 2021, 08:38:45 PM »

We found that any extra equipment adds weight. We want to be right at the 9.5g launch weight, it makes a huge difference. So we stripped off all connectors, but we keep the momentary-off switch so that the motor does not run until the plane is released.

We even took all insulation off the wires, as that was considerable weight, The wires can be tack-glued to the top and bottom of the MS, there is no way they will touch each other.

We have only about 60mg of ballast on this current model. We hope to save a bit of weight on the next one to have about 200mg ballast for more flexibility in CG location.

Coach Chuck
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jdpsloflyer
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« Reply #33 on: December 08, 2021, 01:17:28 PM »

I wish that my public school kids had more time to spend with me than (I assume) home schooled kids do with their coaches.  My school and parents have limited time bc there are so many other school and extra curricular activities to do.

We tested my J&H (balsa) plane last night. got from 44 to 55 sec in cat1 gym with one stick in the rafters.  Broke the plane getting it down. Each student took turns  launching a flight.  The plane was charged with a switched charger (illegal) and they had to pull the plug which cost them a few seconds and some erratic launches.

I am going to work on a on-board contact switch this week on my plane. hope it works.  The planes are overweight so we will have to work on that later when they build.  We will weigh everything before assembly and save where we can.

I went over Chuck's review of where mistakes were made at his invitational with my teams.  It was very educational for them comparing errors to the rules and how important they were.  We also worked on what parameters we would use on the log to track performance to factors on the log and what they correlated to.

jdp
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ceandra
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« Reply #34 on: December 08, 2021, 01:49:31 PM »

Jerry:

Ha ha. For home schoolers, life is an extracurricular activity! My kids do band, orchestra, guitar ensemble, cross country, mountain biking, and countless other activities. The older ones take courses at the local community college. Getting time to build or fly is near impossible! We have had two build sessions (one for C division), and two flying sessions so far the entire year.

But, these kids are top notch, and learn quickly, so they make the most of the sessions. My high schoolers are also F1D flyers (as in one mid-schooler), so they are pretty much on their own at flying sessions, while I focus on the mid schoolers.

On the switch, we originally did just thin (0.015 I think) music wire, but found the contact resistance was high. We added a short sleeve of 0.062" OD brass tubing on each side of the contact and that worked much better. After initial build we were at 12.5g. We removed the entire electrical circuit, cut down, and got it just under 9.5g. Wires and connectors are heavy!

As far as log, here is what we include:

Motor
Propeller (number)
Propeller diameter
Propeller pitch (this can be changed with a heat gun)
CG location
LE and TE height above MS, wing
LE and TE height below TB, stab
Charge duration (s)
Peak charge voltage (voltage after charge)
Charge runoff time (usually 0 because we monitor charge voltage)
Voltage at launch
Duration
Altitude
Voltage remaining after flight
First lap altitude
Notes

Some of these are redundant on the charge, we did not know what would work best before getting going. Or primary motor, after about 10 different props, barely reaches 20 feet with a shoulder launch. This is fine in our gym, but we need more climb for Regionals. Our second motor has too much thrust, flies too fast on full charge, and with a small prop runs down in less than a minute. We are well over a minute on the first motor at 17-18 feet. More motors coming, which will give us various torque curves to tailor to different gym heights. Then these charge parameters will eb more beneficial.

It is hard to get necessary specs on the motors! So we end up buying a lot of cheap motors and testing.

Chuck
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jdpsloflyer
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« Reply #35 on: December 08, 2021, 03:13:11 PM »

Chuck,

I stand humbled and corrected for my assumptions.  Being only a WFF (wet finger flyer), please forgive me.

You have quite an impressive set of students and the parameters they are tracking as well. Not to mention a coach with years of experience.

My students decided to use the three required parameters plus wing/stabilizer decelage as measured by wing/stab incidences like yours, CG and comments (if that counts).  For the others, we either do not have the equipment or expertise (me) for them.  Our motor systems are as supplied by J&H and (later) Guru eng.  Hopefully Lasercutplanes will have an entry as well. I did not research and buy capacitors, props and motors.  I did ask for an electronics soldering iron for Christmas (hahaha).

I did round up some kits from my stash of 2016, 2019 and 2021 Wright stuff rubber planes we can cut down to specs and use to build and fly until new kits come in. The school bought some kits, however the logistics are too slow to get them so I purchased some as well to receive earlier.  Going through the bureaucracy is a hassle.

I have not figured out how to build a switch onboard, let alone how it will work.  I guess I will sacrifice one of my units for prototyping purposes. 

Jerry
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ceandra
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« Reply #36 on: December 08, 2021, 04:17:25 PM »

Jerry:

I'm relatively new, I started coaching in 2016 with no indoor experience. This group was instrumental in success!

Attached is a (lousy) photo of our switch. I'll see if I can get a better one next time the planes are out.

A wire (0.020? or 0.015, I forget) is tied to the MS, and bent so that it springs to contact the MS. On the end you see the piece of 1/16" brass tubing as a contact, and the capacitor wire is soldered to that (inside). Near the end with the brass tubing, the wire bends 90 degrees into the page (into the MS), then bends 180 degrees back, and 90 again to make the end in line with the rest. This gives a "top hat" that goes through the MS, and becomes a button the students can press to open the switch. A second brass tubing has the wire to the motor soldered inside, and is CA glued to the MS in a vertical orientation, making the second contact of the switch.

What I did not recognize when we made this is that two of my 3 students on EWS are left handed!

We put a scrap of paper between the contacts while charging and moving to the launch area. When they first squeeze the switch, the paper drops out. Then when they release, the motor runs.

The J&H motor should do fine, Josh tested many motors to arrive at that one. We have a variety of props form Amazon and from Micron Wings, as well as a growing selection of motors, so tracking which motor and which prop is important, especially if we have changed pitch on a prop!

Coach Chuck
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jdpsloflyer
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« Reply #37 on: December 11, 2021, 02:21:52 PM »

Chuck,

A picture of my first attempt at a fuselage contact switch.  The simplest idea is to use the charge socket that isolates the capacitor and use a paper strip between the pin and copper film contact switch to isolate the motor.

Took me a few tries to get one that works.

Jdp
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« Reply #38 on: January 08, 2022, 07:32:39 PM »

Finally got around to helping the middle schoolers build their EWS. Two are Freedom Flight kits with small modifications. Two are Chuck Markos' Double Whammy rescaled for this year's rules.

The Freedom Flight kits are nice and quite robust and came in at about 3.7-3.8 grams for the airframe. Power modules added about 5.0 grams and a little clay ballast to bring the total to 9.5 grams. The Double Whammy airplanes I assembled the power systems for and as I used 7x20 motors (instead of the 6x15 in the Freedom Flight kit), the airframes of these airplanes needed to be about 3.0-3.2 grams to keep the overall weight to about 9.8 grams. So, a little overweight, but not bad as the 7x20 motors are about 0.8 grams heavier than the 6x15's.

The Double Whammy's are deliberately simpler; flat airfoil and all balsa, to make construction simple for the younger students on the "B Team". Also simpler to budget my time as I am coaching four HS teams (four students each team) too. A 10.5 gram demo version of the Double Whammy flies 55 seconds and I'm hoping that the lighter weight versions the students built will fly over one minute. Also hoping that the Freedom Flight kits fly considerably longer. The motor that comes with the FF kits is quite a bit more powerful than the 7x20 that I found for the Double Whammy's.

I stay positive with the students as they'll have fun with their airplanes, but I don't like this event. There is minimal "accessible" data that the students can record compared to rubber WS. Electric data that is accessible includes: changing out propellers for different diameters and pitches, charge time, charge voltage, hold time before launch and climb height. So, six data elements. Other changes can be made, like capacitor changes and testing and motor changes. But these tests involve rebuilding, or building additional, power systems and this is not such an accessible process as soldering or crimping is involved (can't be quickly handled during a test flying session).

For Rubber WS, I count nine accessible variables in the rubber winding alone: rubber stretch, turn count at full stretch, torque at full stretch, max turns, max torque, backoff turns, launch torque, rubber density, rubber length and rubber vintage. Then, as the rubber WS propeller can reasonably be self-constructed, there are a number of variables for the prop, including: propeller type, blade material, blade flaring stiffness, blade planform, pitch and pitch distribution. Then also as the propeller specs work in concert with the motor density and length, every propeller change means a new series of test of different motors.

Just my thoughts.

Brian T.
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Little-Acorn
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« Reply #39 on: January 14, 2022, 02:03:21 PM »

So far so good. Coach's plane did a 1 min 31 sec flight in our Middle School gym last night. And even its companion, a canard with swept and tapered wings, did pretty well at 58 seconds.

They still have problems - the first one is a little tricky to put very slight adjustments into, and still shows affinity for the girders in the ceiling, as well as nearby basketball backboards, even when retracted. The second plane (canard) has tapered wings... meaning, its wing area is significantly less than the usual rectangular or trapezoidal wings. That promotes higher speeds and somewhat greater current draw - not good in an endurance contest. It also still has a slight stalling problem that reduces aerodynamic efficiency, have to work on CG position and stabilizer angles.

But my students are working on their planes, and their flight times are increasing satisfactorily. A great bunch to work with!

Rectangular-wing plane: https://youtu.be/b873S9EcnSc

Swept-wing canard plane: https://youtu.be/EAvZ5mnFh3c
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