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-   -   $100 Twin Build Contest JU EF112 (https://www.wattflyer.com/forums/showthread.php?t=73583)

offtom 04-18-2014 04:03 PM

$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 :concern:) and I've always enjoyed multi engine aircraft so here I am. :tc:

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 :D

solentlife 04-18-2014 04:34 PM

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 !! ;)


pmullen503 04-18-2014 04:49 PM


Signed up!

CHELLIE 04-19-2014 04:10 AM

That will be a Sweet Build :$ I get to do the Maiden flight on it :D LOL

thepiper92 04-19-2014 06:42 AM

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.

offtom 04-24-2014 03:10 PM

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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. :ws:

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 ????

hayofstacks 04-24-2014 03:29 PM

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.

fhhuber 04-24-2014 05:34 PM

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)

offtom 04-27-2014 03:30 AM

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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. :cool:

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.

offtom 04-27-2014 03:32 AM

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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.

offtom 04-27-2014 03:38 AM

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And after a little time and effort...........we have parts. :ws:

offtom 04-27-2014 03:44 AM

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 :blah:. I'll get more up a little later this week probably.

offtom 04-29-2014 02:48 AM

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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.

CHELLIE 04-29-2014 05:26 PM


Originally Posted by offtom (Post 946617)
And after a little time and effort...........we have parts. :ws:

Nice clean cut parts :ws: your build is looking great :$


offtom 05-02-2014 02:56 PM

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Okay, some time off, it's windy outside, so down to the man cave for some more work. :tc:

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

offtom 05-02-2014 03:10 PM

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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 :red:


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.

offtom 05-02-2014 03:21 PM

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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. :Q

xmech2k 05-02-2014 05:00 PM

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.

CHELLIE 09-30-2014 08:57 AM

Hi Tom :ws: Did you get your plane built and Flying, The Voting will start on Oct 1

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