Electric Wright Stuff B

[bjt4888]

Cc,

It is best to practice in your own gym to determine the trim and voltage settings that fly the height of the competition venue. My teams never attend the open practices at a competition as the potential to damage the airplane is moderately high depending upon the number of teams that are testing.

If you have to practice at the competition venue, get there 10-15 minutes before the start of the practice session. Maybe you can get in a couple flights before others show up. Have the data you intend to test written down so that your are organized and efficient and can finish testing quickly. Finish testing quickly and get your airplane back in the box and protected.

Good luck and have fun.

Brian T

[coachchuckaahs]

I agree with Coach Brian. The open test times, especially only an hour long, can be a real zoo.

At Cornell we had to use this for ELG, as there was no easy way to test in a lower gym. We rented a nearby gym on Thursday night to test WS and get the right rubber for the local altitude (our home gym is at over 5000 feet), but the gym was only 19 feet, where the venue was 38 feet. In WS, you can use half rubber to simulate a full height flight. There is no analog in ELG or EWS, at least nothing I have found yet.

One approach that I think I mentioned before would be to test (at home gym) various charge voltages and carefully record altitude of the flight. Do this with several motor/prop combos, and get a characteristic curve. Then using these curves, you may be able to extrapolate to a higher gym. But this will take substantial testing and data collection to be reliable.

A huge problem with a zoo test session on the morning of is that any damage may not have time to be repaired before competition.

For this reason, we keep our Wright Stuff planes fully assembled so that there will not be any significant trim changes. For AMA competitions where unlimited test flying is possible, we generally tear down the planes for more compact storage, and use measurement to set the wing and stab at the venue. But then we run some low-power flights to verify/adjust trim after assembly.

The rules allow for test flying during the event at the ES's discretion. When I am ES, in a standard gym, I'll allow testing if there are no official flights occurring. However, in some events this is pretty rare, so students should not count on such open times being available.

Coach Chuck

[cctl29]

Thanks to Coach Brian and Coach Chuck. That is very valuable advice. Thank you so much for sharing. We were counting on the practice flights to fly first time in a ceiling height of 8M. We have been struggling with the extra low ceiling and venting issues. Seems that we are heading into un-chartered territory. We might just use the 8min allotted time to do a couple of practice flights. I am thinking first do one official flight (so we get at least a time), and then depending on the 1st, either trim or 2nd flight. How many flights do you usually do in the 8-min window? Considering ours are novice and elementary students, we will probably do much less flights in the window. Thanks in advance.

[bjt4888]

Thanks to Coach Brian and Coach Chuck. That is very valuable advice. Thank you so much for sharing. We were counting on the practice flights to fly first time in a ceiling height of 8M. We have been struggling with the extra low ceiling and venting issues. Seems that we are heading into un-chartered territory. We might just use the 8min allotted time to do a couple of practice flights. I am thinking first do one official flight (so we get at least a time), and then depending on the 1st, either trim or 2nd flight. How many flights do you usually do in the 8-min window? Considering ours are novice and elementary students, we will probably do much less flights in the window. Thanks in advance.

CC,

Step one, be sure to get as much of the 2:00 of preflight period as possible by launching a "practice/trim" flight before 2:00 expires. During this first two minutes of preflight period, my teams have one teammate charging the first official flight (or first serious trim flight) and the other team mate is communicating with the head timer, continuously asking for the preflight period time. When the preflight period time is about 1:30, this second teammate declares a "practice/trim" flight and launches a trim "glide" flight (unpowered). This procedure allows the teammate that is charging the first serious trim or official flight to not fee rushed. With our charging system (a two D-Cell battery pack wired to a multimeter using a two pin dupont connector and with the multimeter/charger attached to the capacitor with mini grabbers - Thanks Coach Chuck) the students cah charge 1.7 volts in about 10 seconds, but it takes about another 30 seconds to minute to bleed off charge to get to exact launch voltage (we replaced the "phone jack/on/off switch" from the kit with an SPDT switch).

Flights of about 1 minute are very easy with the kit we are using (Freedom Flight) with everything stock and no modifications to optimize flight time. Both teammates watch the climb portion of this first flight and discuss whether to use the planned charge voltage on the second flight or to add or subtract from the plan. Also part of the team's discussion is the quality of the launch. We have found during testing that a poor launch (launched a less than flying speed) will lead to about a one foot drop in altitude immediately after launch and a resultant 3 ft reduction in overall climb height. Of course, the students did many practice flights to achieve smooth launches.

It should be pretty easy to get a couple of practice flights and a couple of official flights finished in 10 minutes if the students have their procedures down pat and if your team uses a 2 D-Cell charger and voltmeter setup. My students discovered that, with the Freedom Flight kits trimmed and configured as high thrust pushers the difference between 1.70 volts would produce pretty consistent 20 ft flying height and 1.71 volts would produce 22 ft flying height. As I was pretty busy coaching my four high school Wright Stuff teams, we focused the middle school on repeating and thoroughly learning procedures of charging, launching and managing the 10 minute preflight and flight period. Learning to manage the preflight and flight period can be practiced in a classroom without flying the airplanes. My teams did numerous repetitions of this "mock competition" with me acting as the judge (including me judging incorrectly so that they could practice respectfully correcting me and referring to the rules).

Brian T.

[jander14indoor]

Ref partial motor Wright Stuff (rubber) flying translation to EWS (capacitor) flying. This thought just struck me, not sure if it is correct, but...
...wouldn't a capacitor with half the capacitance charged to similar times as the full motor be equivalent to a half rubber motor? I mean it is capable of half the energy storage just like a half rubber motor. And for the same charge state should give the same output, right? Or does it need half the charge time? Hmm, now I have to break out my old electronics texts and look up capacitor charge/discharge characteristics with time and voltage.

Jeff Anderson
Livonia, MI

[bjt4888]

Ref partial motor Wright Stuff (rubber) flying translation to EWS (capacitor) flying. This thought just struck me, not sure if it is correct, but...
...wouldn't a capacitor with half the capacitance charged to similar times as the full motor be equivalent to a half rubber motor? I mean it is capable of half the energy storage just like a half rubber motor. And for the same charge state should give the same output, right? Or does it need half the charge time? Hmm, now I have to break out my old electronics texts and look up capacitor charge/discharge characteristics with time and voltage.

Jeff Anderson
Livonia, MI

Jeff,

Here are a few data points from one of my students whose EWS airplane was flying pretty consistently (although, power system not optimized): 1.3 volts - 4.5 meters, 1.6 volts - 5.5 meters, 1.7 volts - 6.0 meters.

This is launch voltage charge on the capacitor as measured with their multimeter and climb height for that flight. Sort of appears to be linear in this portion of the voltage range, doesn’t it? (.28 or .29 volts per meter). I don’t think that this relationship holds generally though. Once we were flying 22 ft high, it only took another .02 to.05 volts to get to 24 ft.

They had a lot more data than this, but this was from an early log that I happened to take a picture of.

Brian

[cctl29]

Thank you Coach Brian for sharing your meticulously planned procedures using the 10-min event window. It is very revealing even though we will have to practice it next time. We finished our state tournament this past Saturday. Our EWS was disappointing to say the least with both flights hit the overhead obstructions (all kind of) multiple times and aloft time was greatly cut short. One thing I noticed this time was that besides it was fast climbing, the angle of attack was very high (I believe it was probably always too high but for some reason I had never thought about it before.). How is fast climbing related to high AOA? Would reducing the wing incidence or moving the CG backward (adding clay to the nose) address high AOA? Another lesson we learned is that we should have used a voltmeter, as Coach Brian suggested earlier. We were too scared of damaging the airplane to add any extra components. Counting like a quasi-metronome is just not reliable.

The journey is the destination. We have had lots of fun working on this event, and I have learned so much on flight from this forum than I had ever imagined. With our event season over, we wonder how we can continue the journey. With Gym time hard to find, and indoor air currents practically impossible to regulate, I wonder if there are any outdoor models (kit or plan) that we novices can try. It seems to be a great project for the late-spring/early-summer months. Any recommendation is greatly appreciated. Thanks in advance.

[bjt4888]

Thank you Coach Brian for sharing your meticulously planned procedures using the 10-min event window. It is very revealing even though we will have to practice it next time. We finished our state tournament this past Saturday. Our EWS was disappointing to say the least with both flights hit the overhead obstructions (all kind of) multiple times and aloft time was greatly cut short. One thing I noticed this time was that besides it was fast climbing, the angle of attack was very high (I believe it was probably always too high but for some reason I had never thought about it before.). How is fast climbing related to high AOA? Would reducing the wing incidence or moving the CG backward (adding clay to the nose) address high AOA? Another lesson we learned is that we should have used a voltmeter, as Coach Brian suggested earlier. We were too scared of damaging the airplane to add any extra components. Counting like a quasi-metronome is just not reliable.

The journey is the destination. We have had lots of fun working on this event, and I have learned so much on flight from this forum than I had ever imagined. With our event season over, we wonder how we can continue the journey. With Gym time hard to find, and indoor air currents practically impossible to regulate, I wonder if there are any outdoor models (kit or plan) that we novices can try. It seems to be a great project for the late-spring/early-summer months. Any recommendation is greatly appreciated. Thanks in advance.

cC,

Too bad about the ceiling hits. Fast climb rate would probably best be adjusted by using a smaller diameter, smaller blade area or lower pitch propeller. The inner wing panel washin amount also has a big effect on climb rate. Our airplanes used only a couple of millimeters of washin and I think that some designs can be flown with zero washin. Sometimes you can trim rudder amount and washin amount to deliberately cause the airplane to roll and not climb at all during the early high-powered portion of the flight and then have the roll decrease and a gentle climb occur during the low powered portion of the flight. Decalage angle can also be reduced (along with moving the CG back) to reduce the climb rate somewhat, but I would generally try this last after power and washin adjustment. The main benefit of less decalage is to reduce drag. Depending upon all of your other design parameters, decalage reduction (with CG further back) may or may not improve duration though.

Brian T

[bjt4888]

Thank you Coach Brian for sharing your meticulously planned procedures using the 10-min event window. It is very revealing even though we will have to practice it next time. We finished our state tournament this past Saturday. Our EWS was disappointing to say the least with both flights hit the overhead obstructions (all kind of) multiple times and aloft time was greatly cut short. One thing I noticed this time was that besides it was fast climbing, the angle of attack was very high (I believe it was probably always too high but for some reason I had never thought about it before.). How is fast climbing related to high AOA? Would reducing the wing incidence or moving the CG backward (adding clay to the nose) address high AOA? Another lesson we learned is that we should have used a voltmeter, as Coach Brian suggested earlier. We were too scared of damaging the airplane to add any extra components. Counting like a quasi-metronome is just not reliable.

The journey is the destination. We have had lots of fun working on this event, and I have learned so much on flight from this forum than I had ever imagined. With our event season over, we wonder how we can continue the journey. With Gym time hard to find, and indoor air currents practically impossible to regulate, I wonder if there are any outdoor models (kit or plan) that we novices can try. It seems to be a great project for the late-spring/early-summer months. Any recommendation is greatly appreciated. Thanks in advance.

CC,

As for you question about outdoor models, here is a short and not so great video of one of my Science Olympiad students flying AMA Catapult Launch Glider in a playground sized field. To keep the airplanes on the field, the wind needs to be close to zero and flying should be early in the morning or late in the evening (almost sundown) to avoid rising thermal air currents. The airplane show flying is a simplified version of the Stan Buddenbohm "Littl Sweep". It has a basic "flat plate" 1/16" thick sheet wing with a small amount of airfoil sanded in. It weighs about 6 grams. It's not trimmed very well and stalls quite a bit after the climb to glide transition. After a little work trimming, and switching to launching and gliding "right/right", we got it to fly closer to 45 seconds on this field.

https://youtu.be/4QYIE5zMB44

Another fun class of outdoor airplanes for rubber band power is P-30. See a very instruction thread here (with videos included). There are also electric motor powered classes of these types of airplanes. AMA and NFFS members compete with these airplanes all around the country.

https://www.hippocketaeronautics.com/hp ... board=80.0

Here's the NFFS youtube channel with more video of catapult gliders and other classes of outdoor free flight airplanes.

https://www.youtube.com/c/NationalFreeF ... ety/videos

These outdoor airplanes make great projects to learn more about airplane trimming that can help advance skills for Science Olympiad, and they are fun to fly.

Brian T

[coachchuckaahs]

In addition to the outdoor flying in Free Flight, keep in mind that there is a LOT of AMA Indoor competition. All of my students have progressed to Limited Penny Plane, P-18, F1M, and F1D, and compete well against adults. Many contests also will accommodate SO planes, even though not an official AMA class.

Gyms are always an issue, but can be had. Also look at other venues that do not have hoops, they may have better mid-week availability such as early to mid morning. Look at things like wedding venues, hotel ballrooms, etc. Also look for modern (climate-controlled) hangers at the local airport (private hangers).

If interested in AMA indoor flying, let me know and I can point you to good plans and/or kits.

Upcoming we have Eagar AZ April 8-10, AMA Nationals in Eagar May 24-28, and Johnson City TN, July 1-3. There are local events around the country as well. At Nationals, we hope to do a seminar series and have SO flying as well, similar to last year in Pontiac.

Coach Chuck