stunthanger.com
Electric Stunt => Gettin all AMP'ed up! => Topic started by: Tim Wescott on July 06, 2015, 03:25:04 PM
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Inspired by Larry's ET-2, but made to fly more like a Sig Skyray or other of the innumerable little planes of my youth. It's already been crash tested! My wife tried it, and ripped the bellcrank mount off -- the one in the picture is the newer, stronger one. Aside from that, the thing took no other damage.
It's made from less than $1 worth of dollar-store foam. It's a 24 inch wingspan electric with a 100 watt motor, with an RC car radio from Hobby King for speed control -- the elevator is regular control line. It'd work great with a KR governor-timer. The most expensive single item on the airframe is the bellcrank. Motor, battery, radio and whatnot bring the cost up to $65 or so, but most of that should survive crashes and work on the next plane.
It took me four hours to build this thing, while designing it in my head. Construction is almost entirely foam board and hot glue, with just a few bits of lite-ply around the motor and bellcrank. A design from plans should take much less time -- it'd be a good design to bring to a scout group along with a pile of foam board and one set of electronics: each kid could build his airframe, have it flight tested, fly it, and take it home sans electrics (and then start lobbying mom & dad for parts!!).
Significant inspiration came from Larry's ET-2, and from Flight Test's Bloody Wonder: http://flitetest.com/articles/FT_Bloody_Wonder_Scratch_Build (http://flitetest.com/articles/FT_Bloody_Wonder_Scratch_Build). You could probably just build a Bloody Wonder instead, with a bellcrank replacing the radio, but I like the looks of my version better.
I'm still playing with props and elevator throw; I'll report more if it works and if there's interest.
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Excellent! I'm delighted to see interest in getting back to efforts to lure in new blood.
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Nice airfoil.
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Nice airfoil.
It's a KFm3 KFm4 (oops), which ought to be better than the 1/8" balsa on an all-sheet 1/2-A jobbie.
Edited with correct airfoil designation
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Nice plane Tim. The foam board method has its merits. It is fun to blast out a construction idea for a dollar. Foam and hot glue seems so naughty!
On that same line of thinking, I recently built a foam board/hot glue version of the Ambush and I used the KFM-4 airfoil. As this will have a Cox engine on the front, I will probably cover the entire thing in clear laminating film and use some zpoxy and fiberglass around the engine mount, ect. I have a large roll of DK PET LIT GS film which is very much like SLC film in thickness and properties.
It has turned out quite light and stiff. If I can keep it reasonably fuel proofed, it should be a great plane.
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KFm airfoil descriptions:
https://en.wikipedia.org/wiki/Kline%E2%80%93Fogleman_airfoil
(http://rcfoamfighters.com/blog/wp-content/uploads/2009/09/KFm-Family-descriptions.jpg)
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It has turned out quite light and stiff. If I can keep it reasonably fuel proofed, it should be a great plane.
Epoxy paint, if it used a thinner that's compatible with the foam, would do the trick. I want to hear whether your film does the job!
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Off to the flying field tomorrow to see if it works, and if my wife can get to the point of level flight (at which point I suspect she'll start learning fast).
As pictured it weighs 9.1 ounces. Hopefully if she does smack it (I, of course, won't do so :)) the motor will be unscathed and we'll repair at the field and fly again.
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Any updates, Tim?
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Any updates, Tim?
My student stopped crashing, and complained about fast lap times -- so we've moved on to bigger planes.
We have crashed the pusher version, and got it back into the air immediately, which is an improvement over motor-front version. However, I ran across someone on Stunthanger who flies 15-sized 'lectric trainers using a prop saver and a higher class of motor (with a hardened motor shaft) who reports no problems with bending shafts.
I think if I were going to continue development on this I'd make two versions -- this one, as the absolutely rock-bottom priced airplane, and one with about a 36" span, with maybe a real airfoil (which can be done by folding Dollar Store Foam), and a commensurate increase in the motor and battery size.
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Copy all, sounds like a positive result, congrats!
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So, are you coming to the Raider Roundup?
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So, are you coming to the Raider Roundup?
Almost certainly not -- work presses.