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Old Jul 12, 2014, 08:25 PM
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The Layer Plane - Extra 300

While experimenting with molded fiberglass planes and thinking about filler materials, I stumbled on the idea of making an entire plane out of stacked fanfold foam. So I designed a wing using Solidworks and built it. I liked the results, so I designed a fuselage and built that also. The fuselage shape is based on a model uploaded to GrabCAD by someone named Paulo Henrique Faria.

I think this idea has some promise, so I figured I would share it here.

This is the design:
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Old Jul 12, 2014, 08:47 PM
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These photos show some of the process:

- The shapes are first printed onto paper.

- The paper is cut and taped together into large sheets.

- The paper is glued to the foam sheet (I used a glue stick).

- The shapes are then cut out using a knife.

- The shapes are glued together, one layer at a time (I used white Gorilla Glue).

- Eventually, the frame is covered with plastic covering (I'm using a combination of Solarfilm Lite and Hobby King covering).
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Old Jul 12, 2014, 08:50 PM
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These are the pieces that make up the horizontal stabilizer and elevator. The yellow rod is a fiberglass rod taken from a wire fishing kit sold at harbor freight.
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Old Jul 12, 2014, 08:52 PM
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This is where I currently am on the project.
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Old Jul 12, 2014, 09:03 PM
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Here are some notes on the project thus far:

The plane has a 60" wingspan.

It's made from pink fanfold foam that I bought at home depot. The paper templates are glued to the plastic sheet that's on the foam. The plastic sheet is removed from the foam to create a finished part.

The wing has two fiberglass rods running through it, one toward the top and one toward the bottom (compression and tension). This makes the wing quite stiff.

The fuselage is also quite stiff and light weight. I'm looking forward to seeing what it looks like with covering on it.

When covered, the wing has a decent airfoil, so I think it will fly just fine.

The design is difficult, but the construction is quite simple. It takes a long time to cut out all of the pieces, but it's simple work.

It's easy to make non-warped parts. You start with the middle layer. Put it on a flat table. Glue on one layer, flip it over, glue on another layer, flip it over, etc. The result is a very straight part.

It's somewhat like 3D printing a plane. You can design in bulkheads, supports, stiffeners, etc, while making it hollow and light weight.

It took a little less than two bottles of white Gorilla Glue to build the plane.
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Old Jul 12, 2014, 11:57 PM
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Fantastic. Did you have any difficulty lining up the fuse laminations while gluing?
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Old Jul 13, 2014, 04:15 AM
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The technique is very similar to the old style balsa boat models.
For those, you'd actually sand down all the discontinuities between layers.
But in this case, it's probably not worth the effort. It is kind of reminiscent of the multi-step KF wings.
Looking forward to a flight report
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Old Jul 13, 2014, 07:11 AM
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Thanks for the comments.

It turns out that lining up the fuselage layers wasn't difficult. While building the wing, I learned that I needed some registration marks, so when I built the fuselage, I included an extra horizontal and vertical line across each piece. These lines were transferred to the pieces after they were cut out. When laminating, it's as simple as lining up the registration lines.

I thought about sanding down to a smooth surface, but one of the advantages of this method is that it requires very little sanding because the shape is already correct. I have another Extra 300 that I built by hot wiring solid foam. That takes quite a bit of sanding to achieve the final shape.

I'm hoping to finish covering it today.
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Old Jul 13, 2014, 09:21 AM
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Looks like an extension of the VLF (Vertically Laminated Fuse') used by dz1sfb in several of his war bird planes. He models in sketch up and cnc mills the laminations including registration holes that take a skewer or dowel.
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Old Jul 20, 2014, 05:08 PM
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OK, I finally got it all together. This is what the final product looks like. I'm very pleased with how it looks after it's covered. I used a mixture of old Solarfilm Lite and Hobby King covering. The Hobby King covering is a little heavier and can stand a slightly higher temperature, but it also does a better job at hiding the foam contours.

All up weight, including a 3000 mah 4 cell pack is 3 lbs, 14 oz, which isn't bad for a 60" wingspan plane. The last Extra 300 I built with a 60" wingspan is well over 5 lbs.
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Old Jul 20, 2014, 05:24 PM
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I was able to give it a test flight this afternoon. The current battery location makes it a little nose heavy, so on takeoff I had to add a little up elevator to keep it level.

Once trimmed, I did all sorts of maneuvers (loops, outside loops, rolls, inverted flight, stall turns, knife edge) all of which it performed very well. Because it's a little nose heavy, I had to feed a tiny amount of down elevator in to hold knife edge flight. It also required 3/4 power or so to maintain knife edge. I wasn't able to get it to snap roll very well and I couldn't easily control a hover, but I expect these to improve when I move the weight back.

Overall, it was quite well behaved. When coming in for a landing, it slows down very nicely and floats in for easy touchdowns. It stalls very gently and at a very low speed. This may not remain when I move the weight back, but as it is, it's a joy to do touch and go's with.

Overall, I'm quite happy.

I'm wondering if there is any interest in the plans. It will take a little work to get them into publishable form.
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Old Jul 20, 2014, 10:08 PM
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Congrats on your model! And on developing a new technique that saves over a pound. Nice work!
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