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Old 04-18-2014, 04:03 PM   #1
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Default $100 Twin Build Contest JU EF112



It's been awhile since I've participated in a scratch build contest on here (2010 to be exact ) and I've always enjoyed multi engine aircraft so here I am.

After seeing this plane on the Luft 46 web site I developed a hankering to try to model it. Like I said in an earlier post I've been playing with the design working on a balsa version. For this contest I'm going to use foam, which I have plenty of, and some old electronics I have laying around. I figure that will help keep it under the $100 limit, and also encourage me to continue working on the balsa plans if I like the way it flies.

First though, I have to finish another project so it may take me just a bit to get too involved on this one. Be patient with me

Cheesy poofs are what Yankees get when they eat Southen Food!! bub, steve
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Old 04-18-2014, 04:34 PM   #2
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Be patient with you ?

I'm stuck in Crimea, Ukraine or what is annexed by Russia now ... so I will not be building for a while ...

Join the boat !!

Nigel

222kph PKJ,EDF Concorde, Mini4,Mig3,T45,PKJ twin,ME109,Edge540,Cessna182,Skymaster Biplane,F15,F16,Badius,Ultimate,SE5,Qbee10,450 Heli,V911,J3 Cub Founder 9x forum: http://groups.yahoo.com/group/Flysky_RC_radio/
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Old 04-18-2014, 04:49 PM   #3
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Signed up!

It's never too late to have a happy childhood.
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Old 04-19-2014, 04:10 AM   #4
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That will be a Sweet Build I get to do the Maiden flight on it LOL

I may be getting Older, But I Refuse to grow Up I am Having to much Fun to Grow Up LOL
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Old 04-19-2014, 06:42 AM   #5
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Very interesting build, I was just looking around on net today on planes, although nothing to do with this build, and came across this plane.
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Old 04-24-2014, 03:10 PM   #6
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Well, I've been playing with this a little here, revamping my original plans a bit and making a chuck glider to work with. After finding the CG it flew pretty good.. Even the teenage daughter played with it.

I think I have all the parts worked out for the plane, I just need to decide if I'm going to have rudders, or aileron /elevator only. Such a tough decision.


A quick question for all of you aeronautical engineers out there. I've never done a model with a pull/push propulsion system before but I'm assuming the front motor still needs the down and right thrust, am I on the right track with that line of thought


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Cheesy poofs are what Yankees get when they eat Southen Food!! bub, steve
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Old 04-24-2014, 03:29 PM   #7
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The motors will cancel each other out technically.

it really depends on where they are from the center line of the model.

i also had to really prop up my rear motor, and even with a reverse pitch prop, it would still track well. i mounted my pusher/puller setup to the top wing of my slow stick bipe, and it would do an outside look in its own wingspan throttle only.

slow stock prop reversal. it flies! easily! 543 watt dual motor bipe slow stick. push-me-pull-you. 242 watt 3 channel slow stick. 365 watt mini ultra stick. 415 watt mini contender. 810 watt ultra stick .25e. 220 watt alpha 450 sport (retired).
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Old 04-24-2014, 05:34 PM   #8
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Still need the down thrust (occasionally up on low wing models). Should go ahead and put in the right and trim each motor's angle with the other prop removed. The purpose of this is to minimize effect if one dies unexpectedly.

You only get the "cancelling" of torque effects if you use counter-rotating props. And it only works when both props are equally powered. Note that the front does throw air through the rear and thus it is normal top need more pitch on the rear prop to equally load the motors.

Part of the reason for the need for right thrust is the swirling air going around the fuselage and unequally over the wings. So you can expect to still need some right-thrust on the front motor even with the torque of the rear countering the front motor's torque. (if you use reverse pitch on the rear)
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Old 04-27-2014, 03:30 AM   #9
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Thanks for the input guys, gets me going on the right track when I get to that part of the build..

While out and about yesterday the boss let me get some foam board from Wally World, since our local dollar tree was out of the stuff. Originally I was going to use some of the fanfold I have for the build, but after some thought I decided to try the foam board instead. So far 2 boards, $1.70 each. $3.40 total so far.


After looking at the plans one last time to see if there was anything I might have forgotten, I decided to take the plunge and quit staring at the CAD. I printed out the plans and using the back patio door, much to the bosses chagrin, taped them together.


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Cheesy poofs are what Yankees get when they eat Southen Food!! bub, steve
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Old 04-27-2014, 03:32 AM   #10
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A little packing tape on the foam board, and some spray adhesive for the motor mounts, and I'm ready for some cutting.


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Cheesy poofs are what Yankees get when they eat Southen Food!! bub, steve
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Old 04-27-2014, 03:38 AM   #11
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And after a little time and effort...........we have parts.


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Old 04-27-2014, 03:44 AM   #12
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I got a little more than this done today but alas, some of us do have to work on Sundays, and 0400 hrs comes awful early . I'll get more up a little later this week probably.

Cheesy poofs are what Yankees get when they eat Southen Food!! bub, steve
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Old 04-29-2014, 02:48 AM   #13
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Thought I'd try a a KFm3 airfoil on this build. Why? I don't know, I just thought I'd try it.

Here's a couple more photo's of my progress over last weekend.

The bottom has the cut outs for the aileron servos. I decided to try putting operating rudders on the thing with steerable tail gear, so I put another Y connector in for the rudder servos. I'm going to put one in each boom.

That's all I have so far, but only two more days and I should get some time to work on it a little more.


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Cheesy poofs are what Yankees get when they eat Southen Food!! bub, steve
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Old 04-29-2014, 05:26 PM   #14
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Originally Posted by offtom View Post
And after a little time and effort...........we have parts.

Nice clean cut parts your build is looking great


I may be getting Older, But I Refuse to grow Up I am Having to much Fun to Grow Up LOL
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Old 05-02-2014, 02:56 PM   #15
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Okay, some time off, it's windy outside, so down to the man cave for some more work.

I started on the fuselage today and was happy with the outcome.


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Cheesy poofs are what Yankees get when they eat Southen Food!! bub, steve
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Old 05-02-2014, 03:10 PM   #16
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While working on the fuselage getting ready to start packing electronics in I found I needed just a little more wiring

DURNIT!!

Oh well! So I got on Headsup RC and ordered what I needed.


Now with that problem taken care of I started on the booms. The thing is starting to take shape now.


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Cheesy poofs are what Yankees get when they eat Southen Food!! bub, steve
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Old 05-02-2014, 03:21 PM   #17
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I did have to get some parts to finish the plane. The cost for these parts was $22 so that added to the building materials, I'm up to $25 so far. The boss says I need to stop spending so much on this hobby.


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Old 05-02-2014, 05:00 PM   #18
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Looking good! Have you found more info about motor thrust angles for a push/pull design likes this? My instinct would be it still needs offset thrust at list on the front motor. An interesting dilemma I'm surprised I never chanced upon with my way-too-much reading and watching of aviation stuff.
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Old 09-30-2014, 08:57 AM   #19
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Hi Tom Did you get your plane built and Flying, The Voting will start on Oct 1

I may be getting Older, But I Refuse to grow Up I am Having to much Fun to Grow Up LOL
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