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Old Apr 08, 2007, 10:35 AM
I've half a mind...
docrob's Avatar
New Delhi, India
Joined Jul 2005
2,600 Posts
Successful maiden!!!!!!!

What a kick!!!! What a rush!!!!! And what a bummer!!!!!

I finally managed to maiden Steve’s latest offering this morning.

It was an extremely overcast day, highly unusual for this time of the year here in Delhi, with occasional high wind spells and light showers that would die down completely for fair lengths of time.

Ravi and I headed out to the field early, early this morning. Ravi did a few flights with his scratch built IFO and then we decided to maiden the Su-37 during one of the quieter spells.

No ground testing, and I realize now, not even a range check , I was just so excited about flying this plane

Ravi asked me to test full throttle thrust and when I max’ed the stick, he kind of made a face . He said ummmm, seems OK, just not punch enough. So anyway, he launched, flawlessly as usual, and she climbed out nice and sweet. Ravi remembered to pull out the cam this time without having to be prompted and started shooting straight away.

Right off the bat I realized there was no way I was getting the thrust to weight of 1:1.7 that Steve claimed, not even 1:1 (we only realized much later why) and I had to fly pretty much WOT or ¾ throttle most of the time. The first flight, as Steve predicted, was nice and gentle, no bad characteristics. She handles like a real lady without TV!!!!!! Very graceful in turns and climbs, slows down a lot without wanting to stall or drop a wing and looks lean and mean (again like a lady ) when it’s banking in a turn towards you.

The first flight lasted about 2 minutes without any attempts at loops or rolls. In the second flight, I flicked the TV switch about 30 seconds into the flight which activated all 7 mixes. There was no perceptible difference during flight until I decided to try a loop. Whoa!!!!!! Even sharper, crisper and tighter than the Raptor. Then I decided to try another, and another and yet another – seemed like I just couldn’t get enough. Then I tried a roll, and my roll was nowhere near as tight as I had imagined it would be. Maybe I’m spoiled with the roll rate of my F-28, but more likely I need to increase my aileron-component throws in the mix.

The landing was harder than I would have liked, but I console myself by saying that it was the maiden. The plane is build like a Mac truck and suffered no damage during landing.

Then came the kicker !!!!!!!

When I lifted the battery hatch to disconnect the battery, I found my battery extension wire was almost CHARRED!!!!! It had generated so much heat that it had melted some of the Depron floor of the cabin (see the tail end of the vid)

That’s when we realized my wire gauge was too thin to withstand the current draw of these motors. The battery, fortunately, was just warm, as were the motors. If I had flown another minute or two, the wires would have shorted inflight and oh boy, there would have been some mind blowing pyrotechnics on camera . THAT, we figured, was the reason I wasn’t getting the juice from these motors. There was no way I was getting 40 oz thrust at any point in time, not even 30 . This just underscores the importance of using the appropriate thickness of wire for electric flying applications.

I’m now going to redo the wiring, all of it, and then paint it. I still haven’t decided on a scheme yet, but that shouldn’t take too long. Hopefully, by the coming Sunday, I should have her all decked out and pretty for the next set of flights.

Here’s the video link .

Doc
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Old Apr 08, 2007, 10:42 AM
I've half a mind...
docrob's Avatar
New Delhi, India
Joined Jul 2005
2,600 Posts
Quote:
Originally Posted by jetset44
Doc............you can certainly beat me to posting a flight video if you want to!

Steve

Didditt!!!!

Doc
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Old Apr 08, 2007, 10:55 AM
I fly therefore I crash
fletchace's Avatar
Torrance, CA
Joined Sep 2006
919 Posts
Wow! Great job Doc thanks for the video. She looks very gracefull in the air. Those loops look very scale like. The last couple looked like a Sukhoi demo! Great luck on the flight timing. She'll live to fly another day. I look forward to seeing your finished product.

Fletch
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Old Apr 08, 2007, 11:22 AM
I've half a mind...
docrob's Avatar
New Delhi, India
Joined Jul 2005
2,600 Posts
Thanks, Fletch. Yeah, she looks every bit the seductress in the air. On the last two loops I took advantage of the fact that I was under 1:1 T/W. I pushed the nose up, climbed to almost point of stall and kicked full up elevator with TV. That made for those tail flips

Doc
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Old Apr 08, 2007, 11:56 AM
Park Jet Guru
jetset44's Avatar
Seattle, WA
Joined Jun 2002
5,592 Posts
WOW, Doc, amazing story! Glad to hear everything else went well, though. CONGRATS on the succesful maiden! The video was fun to watch, and your model looks great in the air. Yes, you definitely have to use 16 ga wire from the battery to the speed controls, which can just handle the 36 amp draw of the twin LSPJs. But it's OK to use 18 ga wire from the ESCs to the motor, since it can just barely handle the 18 amps to each motor and helps keep the weight down in the tail (avoiding the need for even more nose ballast). The rule of the thumb I've always used is that 18 ga is good to about 15 amps and 16 ga is good to about 40 amps.

Thanks for the video!

Steve
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Old Apr 08, 2007, 12:25 PM
It's a trap!
GotrekGurnisson's Avatar
Brisbane, Australia
Joined Feb 2006
3,143 Posts
Nice loops Doc, but damn that was some bad interlacing in that vid. By the way, tell Ravi to turn off the autofocus and set the manual focus to infinity.
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Old Apr 08, 2007, 03:03 PM
That thing's operational!
birdlives1955's Avatar
New Orleans/Dallas
Joined Jan 2006
4,706 Posts
Steve,

16 gauge is good to 50 amps, eh? That's pretty good! I was actually worried about that in my planes, I've always used 16 gauge but I didn't know how many amps it was good for until now. For some reason I thought it was 25 amps, but hey if it's 40 amps then that's great! Much less resistance I suppose. Thanks for that bit of information Steve!

Doc,

I'm downloading the vid now. Sweet! Cool story too! Thanks for sharing it with us. Happy Easter!

EDIT: Wow! I just watched the video, cool! Looks like it flies great. What a cool looking plane in the air, huh? It looks pretty neat cruising around in the sky. Wow, those wires really were charred, that's rough! Hopefully you can get that stuff changed out pretty soon and get that nice plane back in the air! I'll look forward to hearing about how you like the plane after you get your motor wires sorted out. See ya later!

Matt
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Old Apr 08, 2007, 03:33 PM
Use the Force!
LBMiller5's Avatar
San Marcos, CA
Joined Jan 2005
2,179 Posts
I use 14 AWG wire in my larger parkjets that are pulling 35 amps, but I am also running 36" to 42" battery extensions. On my 166% F-18, I am losing 0.5 volts from the battery to the ESC over 42" of wire at a 35 amp draw. It looks like DOC was running 18 AWG speaker wire in the SU-37, which would cook with a 36 amp current draw. It is a good thing that the wires did not melt through and touch each other! That would be very bad!

Awesome flight video. I look forward to building a bigger one later this year!

Lucien
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Old Apr 08, 2007, 11:28 PM
I've half a mind...
docrob's Avatar
New Delhi, India
Joined Jul 2005
2,600 Posts
Quote:
Originally Posted by jetset44
WOW, Doc, amazing story! Glad to hear everything else went well, though. CONGRATS on the succesful maiden! The video was fun to watch, and your model looks great in the air. Yes, you definitely have to use 16 ga wire from the battery to the speed controls, which can just handle the 36 amp draw of the twin LSPJs. But it's OK to use 18 ga wire from the ESCs to the motor, since it can just barely handle the 18 amps to each motor and helps keep the weight down in the tail (avoiding the need for even more nose ballast). The rule of the thumb I've always used is that 18 ga is good to about 15 amps and 16 ga is good to about 40 amps.

Thanks for the video!

Steve
Steve: Thanks again for your amazing design and for the inputs on the wires. I'll stop by a more respectable shop on the way back and pick up the right kind of wires. Man!!!! Every time I look at the coil on my desk I think of how close it was

GG: Yeah, the interlacing was my fault. I use Pinnacle Studio Plus and I realized I had the wrong resolution parameters set on my 'render and save' settings. Sorry

Matt: Glad you liked the video.

Lucien: I can't wait to see your oversized bird. Hope you start this one soon. Any idea of what you're going to power yours with? And yeah, my wires were a prayer away from touching . When I picked up the wire, the guy at the store specifically told me it wasn't speaker wire. He even stripped an end to show me the core and it seemed pretty thick. Unfortunately the roll didn't have any specs on it so there was no way I could tell what I had picked up. But I know now that the suckered me into a bum ride . I'm going to have to be more careful in future.

Doc
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Old Apr 08, 2007, 11:33 PM
Now in TN!
J Morgan's Avatar
Chapel Hill, TN USA
Joined Apr 2001
24,078 Posts
It looked like speaker wire to me too. But nice job on the maiden, looks great in the air. Now go iron some film on that baby.

J
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Old Apr 08, 2007, 11:57 PM
I've half a mind...
docrob's Avatar
New Delhi, India
Joined Jul 2005
2,600 Posts
I think just to spite you, you ornery ol' man, I'll go and fiberglass and paint it

Doc
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Old Apr 09, 2007, 12:19 AM
Use the Force!
LBMiller5's Avatar
San Marcos, CA
Joined Jan 2005
2,179 Posts
Doc,

I am thinking about using a pair of the Scorpion 3020-14 motors like the one that I have on my 150% F-4 Phantom Jet. I was planning on running the motors at a hair over 500 watts each, so this could just be the first "Foamie Jet" to join the Kilo-Watt club! I can hear it now! 1000 watts of vectored thrust, it will loop so fast the nose of the plane will get caught in jet wash!

It will be a while before I start the project. I have to get through the trade show season, which ends around the end of May, and then I can start setting aside a little time to start whacking away at some foam.

I still want to do the big MIG 1-44 as well, so I guess I better get busy! It will be a twin as well, so it is a good thing that I can get my motors wholesale now.

I will keep you all informed with the progress as I go along.

Lucien
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Old Apr 09, 2007, 12:38 AM
I've half a mind...
docrob's Avatar
New Delhi, India
Joined Jul 2005
2,600 Posts
Quote:
Originally Posted by LBMiller5
....this could just be the first "Foamie Jet" to join the Kilo-Watt club! I can hear it now! 1000 watts of vectored thrust,.....
Wow, Lucien!!!! That's going to be phenomenal!!!!
Can't wait for you to start.

Doc
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Old Apr 09, 2007, 01:03 AM
It's a trap!
GotrekGurnisson's Avatar
Brisbane, Australia
Joined Feb 2006
3,143 Posts
Quote:
Originally Posted by J Morgan
It looked like speaker wire to me too.
Yeah I thought the same as well when I saw it.
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Old Apr 09, 2007, 04:59 AM
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simonslim's Avatar
geordie land,uk
Joined Nov 2005
893 Posts
Great video Doc, well done. Close call with the wire though, and well done to Ravi also.

Simon.
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