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Old Jun 17, 2012, 02:10 PM
I think I'm inverted. Maybe.
acetech09's Avatar
United States, CA, Pacifica
Joined Apr 2012
1,509 Posts
Build Log
The FoamJack - The 'Leftover' Foamy - With TONS of Build Pics

I drove up to San Francisco, and had to leave my beloved cardboard park flyer (that was still a WIP) behind. I quickly felt I needed something in the air, but I really didn't have much in the way of building materials. No wood or plastic or any linkage parts, but I did have a bag of misc tubes, some welding wire, and my tools. Nearest LHS is pretty far away. So I went to home depot and bought only a sheet of pink foam, and would wing the rest of the build with materials that weren't originally designed for modeling. I wanted to keep it simple, so I remembered the Vought XF5U 'Flapjack' and used it as inspiration:
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I was going to build it with dual motors and dual stabilizers, but I went for a simpler design while preserving the circular body.

In short, I'm trying to build a plane with almost no dedicated RC-built parts except a motor, Rx, and servo combo from a much smaller plane.

Finished:
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Parts List (Yes, it seems strange. I know.):
1x Sheet of 3/4" HomeDepot PinkFoam
1x Roll of your favorite brand Duct Tape. (Order this if you want to be awesome.)
2" of 18 gauge welding wire (I think it is, anyway. Random rusty wire next to my welding stand in the garage. Any stiff 1mm wire would work.)
Assorted Bits and Pieces of Brass Tubing (From a bag like this)
10 sticks of hot glue
A thin carbon fiber strip

Turnigy 1811 2900kv Outrunner
Turnigy Plush 6A ESC
Nano-Tech 850mAh 2S
Berg 4L Receiver (LHS didn't have any micro Spektrum Rx's, so I went 72mhz)

The Fuselage:

I started out with a broken screwdriver and a bit of welding rod with the corners bent, and used a pencil to trace a circle:
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I then cut the circle:
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Then I took a razor blade to the edge and cut it. It's pretty rough but will be smooth enough once the coating gets on here. This isn't a precision aircraft. I also cut the control surfaces.
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And I gave it a test coating. Yes. That is duct tape. It seems rather convenient actually. A bit heaver than packing tape but much more sturdy. This thing will be crashing a lot.
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The Motor Mounting:

I didn't have any wood around at all (I don't even have a workstation yet up here, was still using the floor. Ergo I don't really have ANY building materials). So I cut a small block of foam and four welding wires, with the tips bent into hooks:
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I then drove the wires through the foam and made them hook onto the edge of the motor mount, like so:
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Then my cat decides to launch an assault on the secret manufacturing facility:
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Now that the invasion is repulsed, I get back to work. I use my soldering iron to channel the foam, and lay in the back of the wires, and hot glued them in:
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Now I see something worrying: during the hot glueing, the motor block slid a bit, and the center of the motor is now about 1cm away from center. It is still facing forward, so it won't be a huge concern, but I'll have to compensate for that when flying:
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I accidentally broke off the tail piece of the body, so I stick a carbon rod back in it and hot glue it on:
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Next, the carving and complete coating.
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Last edited by acetech09; Dec 11, 2012 at 01:53 PM.
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Old Jun 17, 2012, 02:54 PM
I think I'm inverted. Maybe.
acetech09's Avatar
United States, CA, Pacifica
Joined Apr 2012
1,509 Posts
The Electronics and Coating:

So I now get out all the parts that are going in this thing:
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And I unwrap them so I can place them and see where they'd go:
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I then use the tip of my X-acto to mark where I have to carve:
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And I start going at it. First the battery:
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Then a bit more:
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And then it all:
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Now to the part where I solder everything I have to. One of my favorite little tricks is to use the hole in the back jaws of my wire cutters as bullet holders. It works great:
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Now that everything's soldered and in place, I can coat the entire thing:
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I then add some carbon extensions to the elevons to help them catch air at low speed:
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In the process of pushing a carbon rod in, I pop out a bit of foam in the back of the elevon:
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So I carve a new piece of foam and pop it right back on:
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And now I have coated the stabilizer and elevons:
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I make a wire drill by cutting a sharp edge on a welding wire, and bending a handle.
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With that wire, I cut some holes in the top of the fuse and the bottom of the stabilizer, and put some rods in to hold it in place:
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Control Linkage:

The only thing I can find that might work for a linkage is a bag of assorted tubes. These bags can be bought from TowerHobbies and are actually quite handy for random bits of micro models and whatnot.
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I choose some tubes:
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And make some horns out of them:
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And glue them on. They actually look quite awesome, being brass and all. And they're pretty sturdy too.
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So I start finalizing the assembly, when cat happens again.
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So when cat leaves, I cut off of a strip of metal that came from a strip of molex pins, and use that as a makeshift clevis. Seems to work:
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Now I start the finalizing assembly. I shove everything roughly where it should be:
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And the AUW is a good 227g. The motor can put out 160 so this'll be pretty sporty, but not completely 3D.
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But when I try to do an electronics check, the left servo isn't working. . I thought it was a bad crimp or two, so when I solder it to an already-crimped molex lead, it still doesn't work. I think it might be wire fatigue, so I'm going to add some new wires on it. But it is a tiny servo so I might not be able to do it. So that's all for now, until I get a new servo or fix the current one. Anybody in the SF bay area with a HK 2.5g Micro Servo or a pair of other <3g servos that I could buy ?

And I think my cat is planning to murder me so she can get into my foam box. She just loves all those trimmings but she ends up eating them. And I end up stopping her.
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Last edited by acetech09; Dec 11, 2012 at 01:55 PM.
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Old Jun 17, 2012, 08:11 PM
I think I'm inverted. Maybe.
acetech09's Avatar
United States, CA, Pacifica
Joined Apr 2012
1,509 Posts
It's just my luck that my LHS is out of their smallest servos. Why does this always happen...
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