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Old Mar 01, 2012, 07:19 AM
Ed @ Experimental Airlines
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United States, AZ, Phoenix
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Sounds cool! It really is just a huge milk carton with wings and tail. I would be grateful for any plans you would like to share. Post them here and I will eventually start another thread dedicated to foamboard planes using these methods and would of course include it there. The 66" Skyvan is a beast, with a payload bay you could fit a cat in. Go big on the motors if you want to haul stuff to altitude. Keep in touch if I can be of any help. - Ed
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Old Mar 01, 2012, 09:11 AM
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Saw your newest video about the Axon, and have a few question. Why does the thrustline have to be downward? When I had it that way on my ez* and put on a 2700kV motor I had to hold up-elevator all the time and because of the strain on the elevator servo it stripped and the plane crashed ..
I don't fully understand these thrustlines and the torque of the prop..
Is it a 6x4 prop you are using? Standard ez* upgrade setup
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Old Mar 01, 2012, 09:22 AM
Ed @ Experimental Airlines
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I can't give you as sophisticated an answer as I would like on the thrustline thing but I will try. In the forces of flight (lift, gravity, drag, and thrust) it is the motor thrust that overcomes drag caused by the total frontal area presented by the plane plus induced drag from lift. The motor thrust axis should be aligned to intersect that aerodynamic cross section of the plane as closely as possible. Since the wing accounts for most of that drag-inducing aerodynamic area, the thrustline should be oriented to pass through the wing at about half chord. If the the thrustline is oriented above the wing (and above the net force of drag) then the plane will tend to pitch down and dive. Imagine pushing a frisbee through a swimming pool with your finger, topside forward. You would need to apply the force in the center of the disc in order to avoid it tipping off to one side. So that's my understanding of it, hope that's help. A similar principle applies to other prop configurations too, like tractor high wings that often like to have some downthrust as well, to avoid pendulum-ing up as power is applied.
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Old Mar 01, 2012, 11:19 AM
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Thanks very informative, i just dont know why I was having problems with that overpowered ezstar. I had the thrustline downward like the stock mount suggests..
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Old Mar 01, 2012, 03:01 PM
Ed @ Experimental Airlines
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That's weird. Is it possible the motor was properly aligned but so powerful it was actually overcoming the lift of the wings and brute-forcing the aircraft downwards? I did have a buddy with the same problem, same plane, big motor, but never fully explored it, and just moved on to another plane.

I see I neglected your other question: I am using a 6x4 APC prop.
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Old Mar 01, 2012, 03:17 PM
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Yep it was brutally pushing it to the ground ...And I was angry for speed not knowing the servo won't hold ..

Ed do you use any calc for power systems? How do you choose your power system for a particular build?
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Old Mar 01, 2012, 06:36 PM
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These vids are awsome, can't wait to try'em out.
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Old Mar 02, 2012, 07:19 AM
Ed @ Experimental Airlines
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Quote:
Originally Posted by msev View Post
Ed do you use any calc for power systems? How do you choose your power system for a particular build?
Man, that is a complicated question. I don't use a calculator when planning, but I have gone back after the fact and used this one which is very cool: http://www.ecalc.ch/motorcalc_e.htm

There are way smarter guys than me and much more sophisticated ways to select a powerplant.

I generally consider maximum prop size first (larger generally more efficient), then consider airplane speed range and derive pitch from that (3.8 or 4 for slower, 6-8 for faster), then roughly choose a kV to match the pitch speed and a wattage appropriate for the weight of the plane.

Honestly, there's a lot of eyeballing it on my part, and I do my fair share of swapping out motors and props.

For all-around use with good power and OK efficiency, my favorite is a 2826-10 1400kV (HobbyKing or RCTimer) with a 8x3.8 SF for general use, 9x3.8 for pushing it, and a couple of 8x4.5 counterrotating for twins, on a 30A ESC. They make about 700g of thrust and go pretty long on battery.

For bigger power I often use 2836-7 1100kV (sometimes listed as 1120kV) also HK or RCT, with a 10x4.5 semi-APC style, which also comes in counterrotating for twins, and I also just use 'em for singles like the Peace Drone.

Hope that's 1% more help than confusion

Ed
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Old Mar 02, 2012, 12:45 PM
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Quote:
Originally Posted by msev View Post
Yep it was brutally pushing it to the ground ...And I was angry for speed not knowing the servo won't hold ..

Ed do you use any calc for power systems? How do you choose your power system for a particular build?

Go here...http://www.stefanv.com/rcstuff/qf200103.html this guy explains it clearly...
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Old Mar 02, 2012, 02:39 PM
Ed @ Experimental Airlines
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Just wanted to throw this new design idea in there. This would be a great first plane to both build and fly using the foamboard techniques:

AXON Foamboard Trainer and Light FPV Platform (10 min 0 sec)


AXON Construction Details (16 min 58 sec)
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Old Mar 03, 2012, 06:13 PM
Smashes Things
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Catching Up

Ex Air, the Axon looks nice. One thought that occurred to me is that your cargo plane fuse is big enough to fit that prop internal. Could make an interesting design, sort of a ducted fan...

Also, I live in Montpelier, 10 miles outside 295. Wish you were here to go fly!

I am having a lot of fun with your ideas. I have yet to "procure" some gift cards, but that will happen. I am having more of a difficult time with thin metal like your TI plates... Any thoughts on a cheap source for that?
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Old Mar 03, 2012, 09:06 PM
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Ed,

Whats your technique for getting gift cards (without purchasing them)?? Do you ask the cashier if you can take a handful?? Are they free for the taking??
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Old Mar 04, 2012, 07:16 AM
Ed @ Experimental Airlines
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In my area many restaurants in the higher-end fast-food category and mid-tier chain restaurants put out little business card holders full of gift cards, usually just in front of the register, near the entrance, or at the hostess stand. They don't have any instructions posted, and as they are presented pretty much like business cards, one can only assume they are free for taking, right? I mean, they make the things by the billions and they probably cost $.000001 each to the restaurant, and they have no credit on them, so even if you were seen I doubt any average cashier would be eager to bust you for grabbing 10 of them, especially if you're there to spend your cash on their food. Family-oriented soup and salad places and walk-up Tex-Mex places are good sources. Look around malls too, retailers and food courts. Once you know what to look you will surely find them and the place will be happy to have the repeat customer

As for the ducted propeller, it's a neat idea. I believe the physics of that arrangement are a little complicated, like the tip-to-duct clearance being important. It would be cool to try though.
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Old Mar 04, 2012, 09:35 PM
FPV FTW
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Hey Ed...Just thought I'd drop by and show you the maiden video of my dollar tree cargo plane.

Maiden went pretty smooth, found out really fast that I needed to dial in dual rates and expo on the roll. Also, I used flapperons and they helped greatly on takeoff and landing.

Thanks again for these instructional videos!

-Pat

DTSOT: Dollar Tree Spec Ops Transport - Maiden Flight (LOS) :D (2 min 54 sec)
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Old Mar 05, 2012, 10:14 AM
Ed @ Experimental Airlines
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Pat - lookin' good man! Aren't flaps on twins great, with all that thrust right up against 'em? Adverse yaw can be worse with flaperons, but it looks like you got it tamed with rudder and/or differential thrust. Put some cargo in that sucker!
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