The Zagi Trick RC manual says, "SANYO RECOMMENDS CHARGING THE KR 1700AE
CELL AT A RATE UP TO 1
AMP....SOME MODELERS REGULARLY CHARGE THEM FOR 40 MINUTES AT 2 AMPS." This is simply not true. Sanyo's recommendation is a fast charge of 2.6 amps. That is the exact same recommendation they give for their "fast charging" (4 mega-ohm) N-1700SCR battery, and their "high capacity" (16 mega-ohm) KR-1500AUL. The KR-1700AU has 17 mega-ohms of resistance. I now feel completely safe charging at a maximum of 2.5C... 4.2 amps... a 25 minute charge. I'm staying shy of the often recommended 3C charge because of the fairly high internal resistance in the battery. When I don't need a speedy charge, I'll keep it at 1C. I'll do this for a while and then gauge (mostly by heat build-up patterns in the battery) how to modify this strategy.
See Sanyo.com or my flying homepage for references.
I went out flying today with the spinner held on tightly with silicon glue. It didn't work. I went through one battery, brought it in, tossed it with a second battery and it only went 50 feet before it started making the spinner's-gonna-fall-off-any-second noise. FYI: the prop gets quieter and the motor spins faster, making a very quiet high pitched whir as it starts to slip. That's the sign for you to prepare for a landing and start watching for the prop because then there's this almost imperceptible clicky-poppy noise when the prop pops off. Now your electric wing is now a glider.
So I took the motor off and tried the Promaxx 7.2 volt motor. I bought this a while ago but never got to try it out. Actually, I'm glad I waited because swapping motors with my new motor mount was a snap... or rather a 'zip', pulling the velcro stays off and resoldering (with my snazzy-and-quick soldering gun). The new motor has a bit less power but it flew a LOT longer than the old motor, maybe 20 minutes per battery WOT the whole time! That's pretty much in keeping with my style so I'm very happy with the new motor. I checked the temperature of the motor after 2 batteries and it was quite a bit cooler than the old motor. My temperature measurement is very scientific: After flying one battery on the old motor, the top of the motor (nearest the prop) was "Ow! I burned myself! [insert finger in mouth]" hot. After flying two batteries on the new motor, the top of the new motor was "Eww. I wouldn't want to leave my finger on there too long!" hot. Using my handy-dandy temper-lee conversion calculator, those temperatures are 400 and 250 Fahrenheit, respectfully.
Now I have a motor I can rip apart for mad experimentation!
I find myself going out between 5 and 7pm most of the time. The mosquitoes can me AWFUL at this time of the day! Today, I tried dousing myself in DEET bug repellent. Even with the repellent, I had to keep constantly walking around or I'd be chewed on by the bugs! I've got marks all over from where those little buggers got me!
Julian gave this to me. It's from several few weeks ago. I suppose I'm a tall fellow by some standards, yes?
Lately, I've been burning up a lot of props. The black plastic press-on spinner has gone loose a couple times. Each time, I have to get out a new Gunther prop-spinner combination. I think what's happening is that my home-made EPP motor mount and motor strap are trapping extra heat in the motor. This heat goes down the axel and melts the spinner. I think this is the case because I noticed a couple spinners where the black plastic looked like it has been deformed by heat. To fix the problem, I'm changing how the strapping sits on the motor to increase airflow a bit and following a recommendation by Kenvil Hobbies and using clear silicon sealant to glue the spinner on. I also scraped up the axel with tin snips to improve it's bite and adhesion. The silicon takes 24 hours to dry so I'm sitting here twiddling my thumbs while it dries. Maybe I'll also scrape out some ridges on the motor mount so more air gets to it.
I took the plane down to my cousin Jason's house and we flew a little on Tuesday. Before the spinner (held in place with CA) melted off, I let him try the controls. Ha. Jaybyrds are a flightless species! But that's ok, we had fun.
Went flying at Great Meadows today. It was pretty crazy... I was trying to get inverted and... well, the battery was a little far forward, which gives better penetration and stability but decreased vertical turning performance... So I flew out away from me, did an inside 1/2 turn back toward me... and then realized that I couldn't pull up. I went right into the roof of the little stand that holds the radio pins. It skidded up and off the peak of the roof and flopped down onto the ground. I'm very happy that no one was over there at the time, but it made me very uncomfortable. I keep telling myself that there never really was any danger in the first place; Heck, I've hit myself in the head with the plane while trying to catch it and neither the plane or my head were damaged in the slightest.
The motor had fallen out of it's home-made mount, the prop had gone missing, and an elevon had broken AGAIN. After calming down and getting around to laughing at the incident, I glued her back together and gave her a toss! She was aerodynamically sound but the motor didn't have nearly as much umph as before. I was worried that the motor was internally damaged. I flew out the battery as Jason, his girlfriend, father and another flyer (sorry I forget your name!) left. I stuck another battery in and the plane was totally fine, with plenty of power. Apparently (and strangely) the battery I had been using (#3) was near empty after only 4 minutes and 1 crash of flying time. Weird.
Hey Jason, if you're reading this.... (and even if you're not, nya) the plane is -totally- fine! The motor wasn't damaged as I thought. Wee!
My last flight of the night ROCKED. I'm sad that everyone else missed it! It was full of zooping and zipping, cartwheeling turns, powerful leaps, graceful slooping, connectedness, and a gorgeous sunset! I love to fly!
Oh and one last thing... It was a bit windy today. I flew 1 battery at the Allamuchy field and was having a pretty sucky time. The wind was rolling off the trees and tossing the plane around a bit. I could hold on without too much trouble but it wasn't very fun. At Great Meadows, the distant trees smoothed out the wind and flying in the 10mph winds was fun. What a difference!
from The Sussex Air Show
Simba F5B electric hotliner. This thing is so frigging fast! And maneuverable too! 10 2400 mah zapped cells power a brushless motor. The motor draws around 100 amps, leaving the batteries too hot to touch for several minutes. The pilot says he only gets around 50 flights on a battery pack before they're toast.
To launch: Hold upright. Turn motor on. Let go.... straight up as high as you like. It went about 100-120 after a dive on the flats and loops like.... It's hard to describe... It goes into the loops so fast and barely loses any speed even though the motor is off when in the loop.
SIModels biplane. There were larger planes out there but this one had the most stability and commanded the most attention of any plane in the air. That thing is at home in the air like a Lazy-Boy! The engine purred wonderfully. The plane costs what you think it does, in the $5,000 range. Powerful, smooth, commanding, beautiful.
This Lazy Ace is for sale by Chuck Howarth (I've saved his phone number). I'm very tempted! I think it was $750 complete minus receiver and transmitter.
Going to the Sussex model air show tomorrow. Yip!
I have to fly battery #2 13 times more than #1 before I can charge #1 and #2 together. Ugh.
Hey, I've flown over 10 hours! 64 flights * approx 10 minutes per flight = 10.6 hours!
I replaced one battery in my transmitter battery pack. For as long as I've had it, the transmitter was only good for just barely 1 1/2 hrs of flying time per charge. I finally tested it and found that one cell was completely shorted out, 0 volts. I think that it's always been like this but I never looked into it. The new battery is a Radio Shack 700mah AA cell. The other batteries are 600mah cells. I hope it works alright.
I fixed the motor mount and flew on Saturday :-)
I created an EPP foam motor mount. You can't see in the image but where the front of the motor touches the foam (in the photo, very close to where the blue wire is soldered to the motor) I buried a quarter in the foam to distribute the force of the motor sliding forward during a sudden stop.
I found a coroplast sign on the street that no one was using [grin]... (one of those awful "Lose 50 lbs in 10 days, Guaranteed!!!" signs). I cut a long rectangle of it and put it on the bottom of the plane as a reinforcing plate. I then sliced holes down through the wing to insert "GB Grip Strip" velcro strapping from Home Depot. This strapping now holds the motor in place! As well, I put strapping in front because, cool as it looks, I want to stop the battery from it's habit of flying loose and cutting into the ground like a throwing dagger tossed high in the air during my inverted stints.
A couple times now, the battery has come loose! Just this weekend it happened too... before we put the battery strapping on. Julian and I had finished putting the motor mount on, and I wanted to FLY immediately. So I gave it a toss. I was showing off my new inverted skills over the strip when.... the engine cut out suddenly, the battery flipped 200 feet with a thud (Julian was looking away at the time but he tells me that he felt the thud!) and the plane wafted down like a giant sheet of construction paper let go from a building-top. Yea, time for better velcro on the battery!
I am now officially a die-hard. It drizzled on us a couple times when we were out flying. We kept watching the sky, wondering when we'd get the brunt of it. I went up and was having a blast when... It felt almost like I was getting tunnel vision. I was losing my peripheral vision due to a sinister darkness that was sneaking up on me from behind! The air suddenly smelled different. The leaves on the trees flipped over. It was time! The rain hadn't started but I called out, "That's it! Here comes the rain!" As I was landing and packing up, the rain started.... and then in earnest! It poured! Four of us hid in the RAMAC shack. Julian luckily had the combination to the lock, there was also a Russian man named Gen and .... oh dear, I forget the last guy's name. We sat around talking about Gen's diesel powered control line plane. He last flied a control line when he was 15... an old diesel :-). His new plane had a new engine on it... but it was the exact same model engine :-). Diesel engines are more efficient but they can be a REAL pain to start. While it rained, he worked on getting it started for an hour or so. The smell of the fuel was wild! It's 1/3 ether, 1/3 kerosene, 1/3 mineral oil. The ether gives it this cool, fruity, clean smell... maybe like a doctor's office... After a few minutes in the shack with him starting the engine, (the door and windows were open, but still...) we were all permeated with the smell. I didn't mind.
The rain finally stopped after 1 1/2 hrs or so. We went out and Gen really wanted to get his control line flying. I wanted to see it. I only have 1 vague memory of ever seeing CL and my dad talks a lot about how he flew CL when he was a kid. He finally got it started, I held it, he gave the signal and I let it fly! It went up. And it went down. Smoosh. 5 seconds in the air. The damage wasn't too too bad... the wing was crushed from the "Art" decal outward. :-(.
After we all moped about the smooshed plane, I whipped out the Zagi to cheer everyone up. I have Gen the controls... he asked if we were ready for a low flyby; he almost hit the shack! It was a gas! I landed on my own once in the parking lot (RE: the mud on the plane in the pix) and Julian caught it once.
On the way out, Julian's brother finally showed up (only like 3 hrs late) with Angelina, a friend. We had a very nice time talking there.
Stunt flying at night with no lights is dumb. And it wasn't even that fun :-(
I have an idea as to how I can fix the motor mount with EPP foam instead of that flimsy, brittle plastic.
I'm reminded of Cliff Whitney's email .sig. "When flying upside-down, down is up and up is expensive." Well in my case, up just got me to improve my super-gluing skills. I was working on my rolls and tried doing fun stuff in the roll. I found that the following combination puts the plane into this wacky roll where (if done right) you barely lose any altitude and the plane looks... I don't know... cool...:
- Dive, then pull up to gain a little speed and an upward angle
- Hard turn right
- When the wing passes vertical, push the stick far-right and far-forward
- When the wing passes vertical again, push the stick far-right and far-back
- Flatten out and smile.
The plane doesn't roll nearly as fast as just a hard turn. While it's inverted, it gains a little altitude and it looks like the right wing (which is now on the left side) is being pulled up while the left wing is just sitting there. It looks pretty cool.
I was also working on getting really comfortable with inverted flight. I'm almost there! The Zagi keeps trying to right itself (which is a good safety release) so you have to fight it while upside-down and turning. I was trying to recover from a botched krazy roll; I tried to pull out inverted and.... well... I got my controls confused and drove straight into the ground at full throttle. The motor mount was smashed. I repaired it with superglue and that superglue quick-drying stuff.
Also, it was pretty cool when I dislodged my battery at about 100 feet. That happens when you're inverted and wiggling a lot. Duh. The battery flew out like a throwing knife and stuck in the ground about 3" deep. Cool. Happily, the controls were locked in a position where the plane wafted down like a piece of paper... back and forth... back and forth. Ploop.
Wow, I burned through 5 batteries today.
I wussed out and bought another battery pack from Kenvil Hobbies instead of building my own out of snazzy 1700mah Sanyo HR-4/5AUP Ni-MH batteries. I just didn't feel comfortable spending $80 in batteries ($4.50 apiece + shipping), another $30 for battery bars, shrink wrap, wire, soldering gun, & connectors... and THEN have to put 'em together in my lair. All that work would get me packs that are only marginally better than what I could get from Kenvil Hobbies for $35 apiece... for something like $55 apiece.
So I was picking up misc. items at Kenvil Hobbies and I just bought a battery pack. It's the same type I got last time. So I'm going to use the new battery 19 times (occasionally abusing the charging times... just like I did on the first battery) and then I'll start charging them in series together. That'll be nice... more air time, less charging time.
When I bought the new 1100 mah battery, I told myself that I should return the 100 watt Radio Shack soldering gun (64-2193) I bought to assemble packs with. But I didn't :-).
I had never used a gun before. All these years I had this impression that irons were the way to go... because. I've got the Radio Shack 15/30 watt dual heat iron and have been happy with it for a long time. But after trying the gun, I've got to say that I am -very- impressed with it's power and ease of use. IE: Plug gun in. Pull trigger for 10 seconds. Start tinning tip of gun. [yes, 10 seconds, not 10 minutes] Release trigger while positioning pieces to be soldered. Pull trigger and wait 3 seconds. [yea, it's a slight bother that it's not always at the ready like an iron, but the tip needs less tinning] Touch tip to Deans Ultra connector, wire and solder for 3 seconds to solder together. [The 30 watt iron would take 10-20 seconds of heating time]. It's also nice that the gun is safely cool again in 5 minutes.
I like the gun.
So now that I've spent the $12.99 on the gun and I've browsed too many battery websites, I might just build my own packs after all. More details as they develop.
I flew today. I'm enjoying inverted flight.
I'm going to keep track of my battery usage until both 1100mah batteries have the same age on them.... So here is a new section of my journal. Tracking. woop.
In looking for more batteries, I found the specs for the Sanyo KR1700AU batteries in my Zagi. Sanyo says that at 8C (13.6 amps) the battery lasts about 5.2 minutes. That was exactly my experience. So whoever says they get 7 minutes WOT on these batteries is.... well, I don't think they are.
Also, Sanyo recommends a "fast charge" current of 2600 mA on the KR1700AU! NOT the 1000 mA that the Zagi manual and Cliff Whitney recommends! That means you can peak charge these batteries much faster than you might think!
I gleaned this estimate from my journal entries. It's mainly to try and figure out how many battery cycles I've gone through (I want to get a third battery pack and charge two of them at the same time. To do this, the batteries should have about the same amount of wear on them.)
approx 38 flights so far. 19 on each pack.
Optimally, I'd want a battery 1500mAh battery, under 10 mOhm, under 30g. 20mOhm is right out. Here's stats from Sanyo's website
|HR-4/5AUP_Ni-MH_1700||34g||6||$4.40||Ni-MH must be charged slower|
|CP-1300SCR||35g||6.5||$4.25||see comparison below|
comparison according to Sanyo charts:
CP-1300SCR - drained after 8C for 6.9 minutes. that's 10.4 amps for 6.9 min (.115 hrs). 10.4 * .115 = 1.196 amp/hrs
KR-1700AU - drained 8C for 5.2 minutes. that's 13.6 amps for 5.2 min (.087 hrs). 13.6 * .087 = 1.1832 amp/hrs
Conclusion: you get an insignificant 1% more amp/hrs out of the CP-1300SCR during high drain applications (like flying wide open throttle). At lower drain, like when cruising around, the KR-1700AU does better.
The HR-4/5AUP looks like the best candidate. Andrew Mileski on the Zagi group says it's his favorite and that's good for something. It pains me slightly to spend $70 in batteries + $20 pack making supplies... Hmm. But thinking about it, I'll then have 2 complete kick-ass packs for $45 apiece. So the cycle would be: fly the 2 new packs for 25 min. Fly the 1100 Ni-MH for 10 min while letting the pair cool. Start charging the new pair at 1.5C. Fly the 1700 Ni-Cad pack for 15 min. Sit out for 30 min. Then start charging the 1100 Ni-MH and start flying the pair for 25 min.
I suppose the best and most simple configuration would be for me to have 2
pairs of batteries and a charger with a charge delay. Then it would be:
fly pair #1 for 25 min
plug pair #1 in (with a 5 minute cooling delay on the charger) at 1.5C and fly pair #2 for 25 min
sit out for 20 min
plug pair #2 in at 1.5C and fly pair #2 for 25 min
But now I'm just fantasizing...
As I was going to the field, I heard a severe weather advisory for eastern PA.... 30 miles to the west of me. Did that stop me? Nope! Of course, I flew like crap in the gusty 25 mph winds.... but I flew! I also busted the elevon again when I hit an outfield foul-line pole. Nothing a little Krazy Glue can't fix. I can now get into inverted flight via a 1/2 roll... in 25 mph multi-directional gusts, no less. Tré cool.
All this time, I've been throwing the Zagi too hard! I've been giving it this solid baseball arm toss to make sure it launches correctly. Well, it turns out that it'll get into the air just fine with a little heave. I'll work some more on finding out just how light a toss I can give it. I'll also work on my side-arm throw :-).
I learned how to fly inverted today :-)
I had been at it a while but wasn't getting anywhere. So I went down to Great Meadows today and Julian was there with 2 new flying friends. I mentioned my troubles to Julian. He took my transmitter and asked me to throw the plane in the air. It was nice being a "passenger" on a flight. I don't get to do that a lot :-). He gets up to altitude and then FLOOP, he starts cruising around inverted. He's such a show-off ;-). He showed me the controls and I realized that my trouble had been that I was flipping and then trying to level off when the plane was moving too slowly. I'd give it full down-elevon and end up essentially trying to hover. Of course that wouldn't work because it's a 25 oz. plane with only 9.5 oz. of thrust... so I'd descend fairly quickly with the nose futilely struggling to reach the sky. Julian demonstrated to me that I needed a little more airspeed before I could fly inverted.
Incorrect - not
|Incorrect - Can't
pull out fast enough
Flying inverted isn't that hard now. The controls are a bit more touchy. I think the plane is constantly trying to right itself (a good instinct in general!). As Cliff Whitney's email .sig says, "When flying inverted, down is up and up is expensive." I haven't figured out the stall characteristics but I think they're probably much less forgiving.
Now I'm zooping all over the place right-side-up, up-side-down, in-side-ou.. well, I'm not that good yet.
I also worked on flying very low and slow. Some day I'd like to try jumping over the plane in flight.
Before Julian, Mike and his son left, we had a VERY fun game of catch. First we were playing with the Zing Wings. Mike really liked them and vowed to buy some. I got mine from Atlanta Hobby. Then we tried using the Zagi as a launching platform for them. We'd wedge a Zing Wing in place on the plane, send it up a hundred feet or so and then shake it loose. I got to fly the plane, which meant that, as Julian pointed out to me -3- times, "When the Zing Wing comes loose, you watch the Zagi, not the Zing Wing!" Some of the Zing Wings wouldn't come loose. Heck, the Zagi looked like a bucking bronco, pulling left, right, left, right, up, and down. But the Zing Wing would hold on tight. Of course, as soon as I'd set it down, the wing would pop right off. Finally the best placement method was found at the end... Julian insisted it wouldn't work but I tried anyway, and it did! I held a folded wing along the front edge of the plane by the winglet with one hand and launched it with the other hand. Julian gave it full throttle and off it went, Zing Wing in tow. A little hammerhead stall and the Zing Wing was free.
John E, my neighbor had a good story to tell me about a Firebird XL that they got for their son on his birthday. To make the nice story very short: After finally getting the thing in the air, he did some gentle turns and then the thing just locked up... full throttle, straight flight. And off it went! John told me, "Of course it was funny later. But while it was flying away, all I was thinking was, 'There goes $150 dollars.'" The plane flew off into the wild and was never heard from again. They found the right spirit and it gives them a good laugh now.
I took John out to Great Meadows. We had a lovely time killing the afternoon.
I got a 2" PVC pipe for my forced-air battery cooler. That's more like it.
Rain rain, go away
Come again another day
Wittle Wee (the one who wivs here) wants to play!
Here's the Allamuchy ball field that I sometimes fly in.
I got a little carried away with Mapquest.... Here is the club field I fly at, RAMAC. The area sure is perty from the sky, ain't it? And these shots are in winter! The field itself isn't much to look at. The dots near the bottom of the triangle in the first photo are cars in the parking lot.
Here's the Pocono field... sorry the images aren't as good... blame Mapquest!
And for posterity, more shots of the WCCC field.
I just measured the static thrust of the Zagi by balancing it on my postal scale, nose down and cranking it up. It's unbelievable. My skills have improved wildly in the last couple months, I'm able to control the plane much better than I could when I first set it up and the amount of thrust has.... get this.... decreased! I honestly, honestly thought that the motor had broken in and I was getting more thrust, aiding me in my quest for domination of the skies. But nope! A month or so ago, I was getting 12 oz. of thrust out of the motor. The Zagi website makes mention of getting 16 oz. of thrust... I'm getting only 9.5 oz of thrust. And I couldn't be happier. That's so strange!
I bought a computer fan at Staples to cool off my batteries. I also got a 3" PVC pipe to set the battery in while cooling but... jeez the 8" piece of pipe is the heaviest object in my case. I'll go look for a smaller, thinner walled pipe. I suppose I shouldn't have gotten a pipe rated for 270 psi, eh? But that's all they had in 3" pipe... Eh. I'll figure out something.
Oh and the fan has cool purple LEDs on it. When my dad came home from dinner and saw the contraption charging in the garage, he called me Doctor Frankenstein. hehe.
"You got mud on your face you big disgrace
Somebody better put you back into your place"
I went to Great Meadows and was quite surprised to find the parking lot almost full! Thursday is a big night at Great Meadows! I was planning on staying just a little while but ended up staying from 6 to 9pm! I met a nice father & son...... I'm so bad with names... Alex and ??? I think, from Long Valley.
As night twilight was approaching, I flew the Zagi dramatically into the sunset... and lost track of it's silhouette. She took a good dive into the dirt on the far side of the canal. Shift forward 30 minutes, when we're all packing up. I went over to the father & son and gloated about how they were cleaning oil and gas off their planes while I didn't have to. Yea, I just had to clean the mud off it. At that moment, I felt like a rough-and-tumble scallywag.
Yesterday I went out with Doyle and Julia to the little Allamuchy baseball field. I got to see Zagi Flap for the first time. It freaked me out! I got it up to about 250 feet and dove at about 80 degrees at full throttle. Only 1/2 way down it started flapping like a crazed swallow, like 5 times per second! I thought the battery pack was going to pop right out in mid-air! Well, it didn't but I was so freaked that when I brought it in for a landing to see if it was ok, I scraped it against a fence, tearing the starboard elevon off for the third time. I gotta get coroplast elevons.
Yesterday morning after class I was flying at WCCC. I saw some eagles (hawks?) catching a thermal at 300 feet so I went up to meet them :-) I found their thermal at 200 and rode it to about 350 with them. Very cool! I got pretty close to them... riding the thermal maybe 50 feet vertical below them. I thought they'd be completely freaked out by the plane but they didn't give up their thermal for at least a minute. I'd like to think they were done with the thermal but yea, I probably scared them off.
Today I went out to the Allamuchy field... it was a really windy day. Though the field is small and flat (it's just 3 little league baseball fields) I tried dynamic soaring. What a hoot! All I had to do was loop carefully and I'd get some speed fer free!
I'd come in 3' off the ground, shoot up 20', fly inverted for 40' and come back down near the ground. Since the wind is moving faster at altitude, I come out of the maneuver faster than when I go in! I've still got to work a lot at my vertical turns. This time around, I could rarely do more than one loop before pulling out of it to stabilize myself. And I was using a lot of throttle to keep me going. If I was -really- good, I'd be able to do this with no throttle at all!
Julian and I went to Stick 40 Combat in the Poconos. A very nice day! I flew in front of a large audience for the first time. I got over my nerves quick enough... but then I had time for 5 or 6 flights. Near the end, I crashed kinda hard in the corn field. I went out, brushed it off and gave it a toss. I heard an astonished comment behind me and smiled.
On Sunday, I had crashed pulling out of my first good inverted flight.. Yesterday I was able to do some inverted flight without a dramatic ending. Here, let me get more technical about my recent improvements:
Photos from last weekend:
Julian and his plane are to the right. Notice the tractor in the background. Which do you think would win in a collision, the plane or tractor? Julian and I know! (he hit the tractor's wheel with his wing on an approach to a dirt landing strip. The plane sustained relatively minor damage. If the plane had been 2 feet to the right, it would have been scrap)
I don't remember if I've said this in the journal but Julian is a terrific pilot!
Sorry I don't have any good action shots of either plane. It's hard taking shots of a little plane zipping around, especially when my camera doesn't actually take the picture for 1/2 a second after you push the button!
Went flying with Julian again. It turns out that I had not accomplished the impossible :-(. Julian pointed out that channel 2 was backwards. With the flip of a switch, the impossible was possible again. :-) )-:
Zagi is in the air again! More updates and pictures soon.
That's not to say I accomplished a -good- impossible thing... but my accomplishment is nevertheless impossible. But let me start at the beginning of this very eventful week.
I took my dad to Lakehurst on Independence Day. His father had worked there more than 50 years ago! We watched the indoor flyers for a few hours. We even got to see a record be broken. A man had driven down from Canada for the "good air" in Hanger 1. He was flying a large class plane (I don't know the exact name) and broke the Canadian record for duration. I watched it take off and then land 34 minutes and 10 seconds later... All on rubber power! They took 5 seconds off the time because he had to use a balloon to steer it once, but 34:05 sets the Canadian duration record by about a minute! Cool.
We also went outside with Robert Romash to slope soar his Zagi Combat wing against the wall of the hanger. He let me have my first hand at soaring. Tré cool. It's a much different experience than motorized flight. Before going outside, Rob showed off in his inimitable manner by flying the wing indoors... It's like a high-tech boomerang! He'd give it a fierce throw and he'd bring it back with panache.
I met Julian (a new flying friend :-) at the RAMAC field on Sunday. Since my wing wasn't completed yet, he let me fly his planes... an ugly stick 40 and a seagull. He tells me that he built the seagull in just a few days with no plans... just by eye. Very impressive.
We flew for a couple hours. A guy with two 70cc gasoline powered fighters came by, a guy with a helicopter, a guy with a trainer... unfortunately, the guy with the trainer left with more plane parts than he arrived with.
We tried out my new Zing Wings. They're these cute little rubber band launched gliders. They actually are quite a bit of fun. They only go up like 50 feet but they spiral around in nice big circles, cruising around.. neat. The plan was to give them to visitors and kids to fly while I'm flying my plane. Yea, I'll do that. Of course we had to attach one to his Ugly Stick. The best placement was by putting the Zing Wing with one wing above and one wing below the Ugly Stick's wing. Then a bit of throttle held the Zing Wing in place. He got it up to 300 feet or so and did a hammerhead to release it. It was HIGH! I ran after it but the wind carried it pretty far pretty fast. I lost track of it a couple times and ended up just standing there scanning the beautiful partly cloudy sky for a sign of that glider. No luck. It was gone! I like to think that it went to airplane heaven. Now it's out there playing with all the other lost airplanes... like the big camouflage colored fighter-plane that some guy lost a few weeks back. It was worth it watching it just soar away.
Julian tried a few slick landings after that. Since the field is on a sod farm, there are strips where the sod has been pulled up and sold. Those strips made nice smooth runways on this day. He tried landing on a strip just across the canal and into the wind. Nice. Though with no brakes the thing rolled for a really long time. Then he wanted to try a crosswind landing. That strip started 5 feet in front of and downwind of where we were standing and continued a good 100 yards to our left. It was bound by the grass we were standing on to our side and a sod tractor on the other, about 30 feet downwind. A tight fit but he's that good. He brought the plane in on a pretty nice crosswind approach. He had good rudder action to compensate. Both our heads were turned toward the plane which was going to cross from right to left onto the runway. It flew by on approach. Both our heads turned to follow and then we saw it. The plane was too far downwCRASH! into the tractor. The right wing hit the big rubber wheel, it spun around like a top, banged the tractor once more for good luck and hit the ground tail first.
The damage was weird. The end of the wing got a good scuff but was ok. The fin of the tail broke out of it's slot (happily an easy repair). Strangely, a 1/2" x 1/2" x 1/8" piece of structural balsa that had been inside the plane was knocked out and then embedded somehow in the skin of the wing! It wasn't just sticking out, it flew out and then flew back in again! Weird.
But that's ok! That's why you bring two planes to the field! They're like classic Jaguar automobiles. You buy one for the road and one for the shop. He let me take control of the seagull for several short flights (air was getting in the fuel line or something). I made a couple textbook Immelmans, some very nice rolls (the wings have practically no camber) and had just a blast. I was doing these tight sideways inside loops around and around and around... weeee! When I tried to pull out of the loop, badness ensued. Apparently, even though I was still whizzing around as fast as can be (the plane has no throttle control. It's full-speed ahead until you run out of gas!) I had gotten down near stall speed and the wings started performing poorly. I spiraled right into a ditch! No, not a ditch, a small canal!! When we reached the plane a few minutes later, it was 3/4 submerged. We drained it and brought it back right away. We were both really afraid that the 6 channel PCM receiver (read: expensive) was dead. Happily it was ok but we couldn't get the motor started.
That ended our -long- day at the field. We went back to my house and worked on the Zagi. Julian helped me finish reconstruction. Click on the photo to the right for a good shot of Zagi 2.0. Sullivan #507 .032 Gold-N-Rod cabled elevons, a better Oracover job, a better cut tray and top... kickin'.
Unfortunately, I realized that the cables weren't supported well enough at the ends. See the zoomed in photo of the cable... See how the wire is a little bent? Well, when I gave full down elevon, the wire would bend. Suckiness. I used some hot glue to create a strut beneath the unsupported cables. Inside, the wire was bending at the servo too. I bent two paperclips into croquet wicket-like things and glued them in place to hold the wire near the servos down. Done!
Well, not really. You see, that's when I realized that I had performed the impossible. The controls are impossibly messed up. I threw it a couple times and the plane spiral wildly out of control. Even when I'd pull a hard right turn on launch, it rolled hard left. I checked the controls... up, down, left, right, elevon mixing. Everything was good. Scratching my head, I threw a couple test flights.
Launch --> pull back on stick --> plane goes up Launch --> push forward on stick --> plane noses in Launch --> pull stick right --> plane rolls left Launch --> pull stick left --> plane rolls right
This, as everyone patently knows, is IMPOSSIBLE! If up and down work correctly, and elevon mixing is set correctly (it is), then left and right HAVE to work correctly. I've only got two control surfaces! It's like... you're standing on a street corner in New York City. The Walk light comes on. You look left, you look right, and as you step off the curb, a car falls from the sky onto your head. It just doesn't happen!
Hurumph! I've thrown the plane about as many times as I dare and it behaves quite predictably in the way I've described. I tried throwing it slow. I tried throwing it fast (ouch, I broke my new canopy), I tried to adapt and fly the plane with these wacked controls. No.
I'm gonna call Julian up and have him stare at it for a while.
I ordered parts from Atlanta Hobby Friday afternoon. I'm sitting on my hands 'til they arrive.
OUCH! From YourZagi.com and http://www.wrightbrothersrc.com
You know, the more I stare at speed 400 brushless motors, the less I think I want one. It basically comes down to:
brushed vs. brushless speed 400 motor
I'm not into electrics for super vertical performance. I'd switch to .90cc glow engines for that. So I've been looking around and I've got a lot of other options besides plunking down $200... I could switch to a high performance speed 480 motor, an 8" x 4.5" prop and get 3/4 of the way toward a brushless for under $20. Hobby Lobby reference. Or a Rocket 400... or the new Zagi Speed 400 for $10. I've got a lot of options that cost a heck of a lot less than $200. Hey, $200 would get me a lot of Estes model rocket engines....
I've started ripping the old covering off the plane.
My mom isn't the best pilot. How do I know this? This is how I know:
Don't let it be said that the Zagi flying wing is indestructible. I brought my mom, dad and niece out to the airfield yesterday. After a couple minutes of flight (they oo-ed and ahh-ed in all the right places), my mom wanted to try her hand at it. So I gave her a quick lesson, brought the plane up to 200 feet (what I thought to be "2 mistakes high") and handed her the controls. She promptly pointed the nose down and gave it full throttle. Three seconds later, there was a 5" deep hole in the ground. It was astounding.
RIP Lee's Zagi version 1.0
Dad and I have been having a good time joking about it. We're saying that we should get her a purple heart. Or maybe she should have watched more of my dad's war TV shows before taking to the air. She just keeps repeating how she's so sorry and will never fly it again.. never ever ever. But I struck a deal with her. I'll feel better about it if she learns how to fly and takes the controls just one more time. After all, we can't have her grieving about some silly little plane forever. It also doesn't hurt that she volunteered to pay for the damage. That last bit means I'll be rebuilding the plane to version 1.1 :-). I was never happy with my Monocote job. So I'll send away for new trays, maybe a new motor (brushless?? hmm? hmm?) and we'll be back in the air in a month or two.
Actually, speaking of indestructibility..... The only things I lost in the crash were the motor tray and canopy. The entire rest of the plane is still intact! wing, winglets, elevons... The motor, receiver, and servos are still good too. It's the loss of the motor tray that "killed" the plane. That's because I have to rip out a lot to fix it the motor tray. And if I'm going to rip out so much, then I want to do a total overhaul.
The Cosel K150A 12 volt, 13 amp power supply came in the mail today. I hooked up wires, plugged it in and it worked right out of the box. :-) I'm very happy to be rid of my Rube Goldberg battery charging contraption. It used to go:
Car battery charger set on 2 amp manual charge
--> block of UPS batteries
--> Astro charger
The UPS batteries were there as a power sink/capacitor because they say that a car charger doesn't have an even enough output to be trusted going straight into an electronics device (I believe them)
I'd have to watch the state of charge on the UPS batteries or badness would ensue. And when done, unplug the whole thing. To boot, the lead-acids were on their way out. I charged them individually last night and today 2 are at 6.39 volts, 2 at 6.29 volts. Maybe I'll keep 2 of the lead-acids as field-chargers.
But now, when I'm home, I can "Set it, and forget it!"
I -was- going to wish for An Astro 020 brushless motor with controller from Atlanta Hobby for Christmas but after looking into motor and prop efficiencies (see my Flying Tips page) I'm not exactly sure which motor I want. I'll have to research it some more.
Very nice day at the field. I played with doing a kind of Immelman. Fun! My maneuver was a bit different. I did my 1/2 roll while in the vertical. That seemed like more fun at the moment.
Today I felt much more connected to the plane than previously. This gave me a lot more control and smoothness than I've had in the past. I'm rolling better, managing power better, managing the exchange of altitude and speed better.
Oh, I forgot to mention what I did on Sunday! I went to the Poconos field. I watched just one Stick 40 combat. Zowie! They had to cancel the rest of the combat because moisture was tearing the streamers after just a few seconds in the air. I saw a plane on the ground rev into a fence, shooting 1/3 of a prop 50 feet over peoples' heads and into the side of the truck. The fuselage of the plane was broken in-two. Lastly, back at Great Meadows, I saw a 7' wingspan pattern plane (?) do looping, rolling, flipping 3-D tricks that blew my mind. My jaw was literally agape! It looked like a sprite fluttering about, only this sprite was larger than me and weighed like 50 pounds. Earlier in the day, I was impressed with a biplane doing what looked like shoulder rolls. But this new stuff was in a class 3 times removed.
Oh, I also tried flying at a local unused baseball field. I can now tell you that I can just barely keep the Zagi flying in a little league baseball field. I can also tell you that it sucks to have to fetch a plane in chest-high grass. Personal note: That's about the smallest field I think I could ever fly at.
The old lead-acid batteries in my workshop aren't cutting it. I think one cell is shot. The other three are probably good, but they aren't large enough anyway. With these 4 6-volt sealed cells, I've only got 8 amp/hours at 12 volts. And I'm trying to charge a 1.1 and a 1.7 amp/hr pack... At their best, they'd be good for 2 chargings. And it's just a big pain to keep monitoring my car battery charger --> 12v lead-acid batteries --> peak charger setup. It's too easy to mess up.
Since it's just 15 minutes to the field, I want to charge my batteries at home. (a reasonable slow charge is 1 hour per battery or longer... times 2 batteries). If the field was 2 hours away, I wouldn't have this issue, I could just charge in the car... but then I wouldn't go, would I? I've been looking around and the best advice I can find on fast charging vs. slow charging (i.e. 3C charging (20 minutes) vs. C/10 charging (10 hours) is that "fast charging can put more of a strain on your batteries so they'll wear out faster". Well, if I'm in no rush, I'm happy to slow charge. But I feel uncomfortable leaving a charger pulling my car battery dry for 10 hours. One day that'll leave my car battery dead and sulphated. I looked around for a good 12 volt power supply. I could rip one out of a computer... I hear that computer repair stores are a good cheap source. But I lucked out and found a 12 volt, 13 amp supply on eBay for $30, shipping included. That's way better than the $30 -3- amp supply at Radio Shack. Well, it hasn't arrived yet, so I'll tell you how well it works when I get it.
I flew today. Well, not really. I had the Zagi up high at a distance and the prop fell off. I should have remembered that I had knocked the prop off the last time I flew on a rough landing... I had reved the engine -after- I was sliding along the ground and justifiably bumped the prop off. I had just stuck it on and flew again, but I should have fixed it with CA glue or something when I got home.
So, I coasted in, landed the Zagi and looked for the prop. No luck. I really really hate those little canals on the flying field (it's on a sod farm)!! So I broke out the Firebird. No luck there either. Both control horn-holder-downer-thingies had broken, leaving me with no tail controls. I considered cranking it up and throwing it into the wind anyway. But refrained.
I went to Kenvil Hobbies the other day. I ended up hanging out there for an hour or so, talking about electric planes to the proprietor and a couple customers. It was nice. I ended up buying an 1100 mah Ni-MH 9.6v battery. I initially thought that I had bought it out of a need to buy "something, anything" from the nice guy at the shop (we spoke for a good long while about the potential badness of not having a local hobby dealer), but after I flew with it once, I was very pleasantly surprised at the zippy, light-on-it's wings performance I got when I flew with this very light battery. I know that I wouldn't have bought it otherwise... I probably would have bought another (heavy) Zagi 1700mah battery.
I found a great new flying field, the front yard of my community college, WCCC. So now I can fly before and after class. :-)
In that photo to the right, the school is in the lower right portion and the field is centered. It's like 220 yards by 100 yards, plenty big enough for my "fast park flyer". Just across the way in the lower left corner of the map is the Warren County Technical school. They've got a couple signs that say, "No ball playing, no running,... blah blah, no R/C vehicles..." And just to the south of the map is the Warren County Communications center, complete with big multi-frequency radio antenna. I hope none of these folks get mad at me for flying... But then I don't dare ask, because they'll of course say, "No, and we're going to keep an eye on you now, you suspicious terrorist-type."
My favorite is that with the 1100 mah battery, I can fly along, pull back on the stick and the plane lifts it's nose like it's been startled awake from a daze. And up she goes!
Skywalker: "What a piece of junk!"
Solo: "She'll make point five past lightspeed. She may not look like much but she's got it where it counts, kid. I've made a lot of special modifications myself."
My airplane is pretty. It is an electric airplane. I fly it in the air. I
went to the flying field on Memorial Day. I flyed it there real good. ;-)
I had a very nice flying experience today due to a combination of improvements:
- I used careful throttle management and was very happy to find that I got about 15 minutes in the air. Previously, I got about 5 minutes in the air mostly WOT. I have seen several reports of people that get "10 minutes WOT" with a 1700 mah battery... Those claims sound dubious (at least from my experience). And it seems to be the case that since my battery was draining slower, it also offered up more juice before giving out. As proof, when I went out last week, I got 5 minutes of flight time and then my peak charger put 800 mah back in. Today, it put 1,500 mah back in during recharge!
Twice I had a problem where I launched at full throttle, went about 5 seconds and then the engine cut out. I still had elevon control. Apparently, the battery voltage dipped and tricked the ESC into thinking the battery was almost dead. :-( After another start, I was ok. I guess the think to do is just keep off the full throttle until the battery is warmed up... or maybe pre-warm it on the ground.
- I fiddled with the CG, not to much effect. Though I'm going to put some more velcro in the tray so I can move the battery around more.
- Last night I reironed the Oracover. It had gotten crinkled up after some crashes. I think it helped with the aerodynamics. I've also got an issue with... ok, I'll just come out and say it... when I first ironed it on, I didn't take the protective film off. It stuck kinda-well, so I left it. It's still on. Of course I'll redo it eventually.
- I got in some inverted flight! Woo hoo! Unfortunately, I couldn't quite maintain altitude, even by pushing all the way forward on the stick and all the way forward on the trim. I started at around 200 feet, was inverted at 175 feet and then started losing maybe 10 feet per second down to 100 feet, where I peeled out. I'll keep at it though.
- As Yoda always said, "Control! You must learn control!" Improving my stick control is improving my flying. Of course, I still crashed 3 times... But that's ok, I just brushed away the grass and mud, plugged the battery back in and zooOOM!
As for control surfaces... It always seemed to me that the horns were placed too close to the center of the plane. If they were moved out to the middle of the wing, the far end of the elevon wouldn't have nearly as much of a chance to flutter or strain. Net result: more responsive flight. That's my thought anyway. I haven't seen any photos of such a configuration though. Thoughts?
- I learned a valuable lesson about near-stall speed flying and elevon airplanes. It had to happen to me twice before I sat the plane down in the grass, put my fluid dynamics hat on, played with the controls and thought about it for a while. The lesson is this: If you're flying very slowly and pull a hard turn... lets call it a hard right turn, the right wing now has it's elevon pointed up in the air like a flag. At stall speed, that wing isn't going to bank and turn the plane. Instead the elevon will act as an AIR-BRAKE, slowing that wing down and sending the plane into a really cool though horribly tragic spin. What does the airplane doctor say about that? "Don't do that!" "But Doctor, sometimes I find myself in that predicament when flying fairly low and then making a turning error.. Like for example turning away from the wind too quickly." The doctor just repeats, "Don't do that." And I bow my head and agree.
- Could someone else put their stock zagi on a postal scale and crank it up to test how much thrust their motor is generating at full throttle? As I said before, mine comes in at 12 oz and the Zagi site shows 16 oz. Which is more normal? Of course, this number isn't a totally accurate representation for flying because the prop might be stalling when there is no airspeed (in the test environment) but in the wild, when the plane is flying at 25 mph, the prop wouldn't be stalling.
>>How are you charging your battery? it should be at 2 amps max
>I've been charging at 2C to 2.5C, 3.4-4.25 amps. I've done that about 12 time
Hmm, I just reread the Zagi manual.... "
SANYO RECOMMENDS CHARGING THE KR 1700AE CELL AT A RATE UP TO 1
AMP....SOME MODELERS REGULARLY CHARGE THEM FOR 40 MINUTES AT 2 AMPS.
Oop. My bad! But I so often hear about charging nicads at 2-3C.... ugh. I suppose slow charge time is part of the penalty for these batteries having such a good weight to energy density ratio. I'll be good to my batteries from now on.
- The heavy aired misty day worked to my benefit. The wind was light and
there was no one else there. If there's glow planes on the field, it's a bad
idea to just walk into the middle of the field for the fun of having the plane
fly by 5 feet away!
Now I'm coming around to the Zagi way... I'll probably be getting another battery pack and a brushless motor soon. Cliff has been good to me from the beginning so I'll likely get it from him. :-)