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Old Jul 19, 2014, 11:55 PM
Scott
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United States, OR
Joined Jan 2006
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Twin Bloody Wonder

Those of you on the Flite Test Forum may recognize this, but I thought I would post it here too.

Twin Bloody Wonder
It may seem crazy to make a fun, simple, tough little acrobat into a twin, but I have a specific reason and purpose. I want a combat airplane that is able to carry a GoPro within its tough casing out in front of the airplane with no obstructions. Another mission of this airplane is to be able to keep up with my brother's small 64mm EDF Mig 15 to capture some HD in-flight images. At any rate, there are probably a thousand different ways to accomplish the same thing in a much, much simpler fashion, but that wouldn't be much fun!

The birth of this project began on one of my overnights with some simple sketches on one of the hotel notepads that they always leave in the room. The next morning, en route from Oklahoma City to Salt Lake I began sketching out actual dimensions. By the time I was back home it was time to begin building. It evolved into a bigger airplane than originally intended and departed from some of the Wonder's basic construction, but at its heart it is still much the same. I kept with the basic power pod construction so I could still easily swap components around. In fact, I even made the center section 'swapable' so in theory if you really wanted to you could put a third engine on the front! However the main purpose of this was to enable it to be able to carry different center sections for different purposes (third engine, streamlined nose, bomb drop, perhaps a rocket launcher!? etc...).

So far I have designed, built, and flown the Twin Wonder and so far I can report that it has been a success! I made the wing in such a way that it is removable and can be repositioned so that I can determine the appropriate position and so that I may build other wings to test different flight characteristics (fast wing, load hauling wing, acro wing, etc...). So far the current wing is a 40 inch wingspan, a little narrower at the tips than the Bloody Wonder (trying to get speed out of it) and seems to work good for the most part, however it does have a higher stall speed, and for some reason it breaks right during a stall. I can't seem to figure out why, everything is straight as near as I can tell, and with both props spinning in the normal clockwise rotation (from the plane's perspective, not sure why R/C pilots refer to prop rotation opposite of real pilots) it should have left turning tendencies. To be sure of this I stalled the airplane with no power and the props stopped and it still dropped the right wing. Even with a stall in a left turn it will still turn over to the right. Other than that it flies well, and it seems so far, the further back the CG, the better it flies, but I am afraid to go to far back. At any rate, here are some photos of the build and the completion. I am still working out the details and it is a work in progress until it flies right. Once I am happy with the way it flies, I will probably build an entirely new airplane as this one has all ready gone through three configuration changes!
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Old Jul 19, 2014, 11:57 PM
Scott
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United States, OR
Joined Jan 2006
26 Posts
Thats a great idea with the differential thrust, it does have rudder control however the vertical stabs are so big it doesnt seem to need it. Perhaps with diff. thrust I could eliminate the rudders. I also programmed differential on the ailerons so that probably helps too.

Electronics:
2 Turnigy NTM 28-26 1200KV motors (same motor recommended for the bloody wonder)
2 Turnigy Plush 25 amp ESCs
2 7x6 APC props (designed to fit up to 8 inch props, I haven't tried my 8x4s yet)
2 3 cell batteries either 1600 or 2200 mah works fine
4 cheapo $2 servos
Orange RX 6ch receiver.

I think I shall call the design the Wonder Twin.
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Old Jul 19, 2014, 11:58 PM
Scott
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United States, OR
Joined Jan 2006
26 Posts
I am back home again and can again resume work on the Wonder Twin. In the first version I used a wooden dowel on the front of the center section running from the outside of each motor pod and through the fuselage. This does two things; 1) It adds much needed stiffness for the center section and 2) it provides a place to rubber band the wing in place. In the 1st version this worked well except I had no reinforcement running over the top of the dowel relying completely on the strength of the hot glue. This worked fine until it sat in my hot car while I flew some other planes. When I came back the dowel had pulled free under the strength of the rubber bands while the glue softened in the heat. Version 2 had 2 main differences. 1) The center sections between the motor pods and the fuselage have been cut back to allow more attachment points for rubber bands (can also serve as an anchor point for future bomb drops) and 2) it has a strip of foam running over the top of the dowel on each motor pod and the fuselage. I also took zips ties and ran them around the dowel and through the electronic vents and back up the other side for some added strength. Another mod I did was some additions to the wing to ensure it is in correct spot every time I mount it. I cut a section out of the back of the trailing edge of the wing and created a sort of "key" where it fits on to the fuselage. I also added 2, one inch wide strips on the bottom of the wing where it meets with the center section. Now there is no way for the wing to move from the desired position.

I should also mention this airplane is several firsts for me. This is my first airplane that I have designed myself and it is also my first twin. On top of that it is only my second dollar tree foam board airplane. The first was a scratch built bloody wonder, and now this! I am still learning the qualities and limitations of foam board, but I love the fact that you can create your own designs and try them out cheaply and quickly without spending months of building balsa and being a nervous wreck on the maiden for fear of a pile of splinters. So far very pleased!
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Old Jul 19, 2014, 11:59 PM
Scott
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United States, OR
Joined Jan 2006
26 Posts
UPDATE:

I'm starting with a clean sheet; the original airframe had gone through three different configuration changes and was going into the forth and I realized I wanted to change too much so I salveged the parts I wanted to keep and "moth balled" the rest.This was kind of the original plan anyway, a test bed to work out the kinks and then build a more refined and finished product that doesn't look like Frankenstein. Unfortunately I'm going out of town for a while so I can't start right away, however that will give me time to draw out some detailed plans. Stay tuned my friends!
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Old Jul 20, 2014, 12:11 AM
Scott
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United States, OR
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26 Posts
A few more pics.
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Old Jul 20, 2014, 12:05 PM
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It's hard to tell, but from the last pic it looks as though rudder servo actuation would always pull both rudders "in". Is that what it's doing? If yes, is it meant as an air braking system?
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Old Jul 20, 2014, 12:24 PM
Scott
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United States, OR
Joined Jan 2006
26 Posts
Quote:
Originally Posted by nuteman View Post
It's hard to tell, but from the last pic it looks as though rudder servo actuation would always pull both rudders "in". Is that what it's doing? If yes, is it meant as an air braking system?
No, they are connected on opposite sides of the servo horn and the control horns are on the inside of the rudders, therefore they both move in the same direction. Adding left rudder the servo will push the left rudder left and pull the right rudder left and vice versa.
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Old Jul 28, 2014, 03:11 PM
You're killin' me Smalls
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United States, NJ, Hillsborough Township
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Plans?
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Old Jul 28, 2014, 07:48 PM
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that is cool . .
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Old Jul 28, 2014, 07:50 PM
Slipping the Surly Bonds
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Attica, MI
Joined Dec 2006
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That looks the bomb-er! Cool !

Ken
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