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May 16, 2015, 11:27 AM
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My experiments in foam building

I have started experimenting with inexpensive depron as a new building material.
My first attempt is nothing more than dollar tree foamboard.
It was my interpretation of Charlie Fite's UberPfeil, which I just called an Arrow.
His had a flat panel wing and had various EDF powering options.
I went with a pusher outrunner.

The darn thing flies like a paper airplane. And looks like one in the air too.
It's got an excellent wing loading and I don't think it even weighs a pound. It took all of a weekend to build. The airfoil isn't from built-up ribs. I used a strip of balsa as both a spar and to create an airfoil once the foamboard was glued to the top. All the leading and trailing edges are balsa, so that I could sand for better streamlining.
Wing span is 32"

The second plane is a depron version of my balsa Baby Gryphon.
The airfoil on this one IS made up of ribs, also cut out of 3 mm depron. It too has leading and trailing edges in balsa for streamlining. The construction is very similar to the balsa version, but only took one day to build.
It hasn't maidened yet because the motor has a broken wire and needs to be replaced. But the balsa version flew beautifully. Really fast and really aerobatic.
Wing span is 24"
Last edited by builderdude; Oct 08, 2015 at 10:20 AM.
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May 29, 2015, 07:45 AM
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Very clean looking. With better durability these ought to be the right ticket as a windy weather flier for our austere scrub environment.
Oct 08, 2015, 10:29 AM
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I have a new foam plane to convert to RC.
This is a Fox glider that I found on Ebay and ordered for just under $10 bucks.
It came in from China with the box pretty badly crushed, but because this is EPO foam, even this did not destroy the airplane.
The wing was bent into anhedral and the fuselage was bent to starboard slightly, with visible scars on the wing and fuselage. See pic below.

I am still going to lodge a complaint on Ebay regarding the condition of the received item, and if they choose to send me another one or refund me, that's their choice.
However, I have decided to make this one work.
I've decided to omit the rudder and make this a bank and crank.
Because it was not meant to have dihedral, and had aileron cut-outs in the foam, I decided it needed ailerons; but if it has ailerons, it can fly without rudder control.

This plane is small. I didn't want to install any servos in the wings, so I'm going to make torque rods to control the ailerons, and take it back to the fuselage, where a single servo will control them, and therefore would not need a Y-connector. This is for space constraints and to save weight.

The damage-caused anhedral was corrected last night by gluing a ply brace in the thickest portion of the airfoil in a slight dihedral. At least now it can glide with better stability.

I am going to put a motor in the nose with a folding prop. Probably a small outrunner.

I'll post completed photos when I'm done.
Nov 03, 2015, 10:59 AM
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The delta-winged Baby Gryphon flying wing did not want to fly.
And I think I realize my mistake.

I failed to compensate for the 1/8" thickness of the depron when I used it for the skin, making the airfoil too thick. As a result, the thick airfoil shrouded the too-small elevon, thereby making the reflex almost completely ineffective. It was so pitch-sensitive that it was ridiculous.

As soon as it launched, it dove straight down. A panic up-elevon maneuver saved it and it pitched straight up. Then it pitched straight down again and crashed.

The balsa version of this plane had a much thinner airfoil, and it was very successful.
I'm also thinking a semi-symmetrical airfoil would have been a lot more successful too.

So if I do another attempt, I will grow the plane by about 50% (since the motor had plenty of thrust), and reduce the rib thickness by at least a quarter of an inch. I think if I go with a very thin airfoil, it'll be far more successful.
Nov 03, 2015, 02:36 PM
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Sounds like using depron foam sheet wings have merit, then. Being small and wing, it's a fast flier. I'm sure you'll get is sorted out. Still want to do coffee one of these mornings? I'll treat.
Nov 03, 2015, 03:37 PM
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Originally Posted by GallopingGhostlr
Sounds like using depron foam sheet wings have merit, then. Being small and wing, it's a fast flier. I'm sure you'll get is sorted out. Still want to do coffee one of these mornings? I'll treat.
Yes I do. The problem has been having the time.
Want to shoot for Friday?
Say...Paradise Market @ 9:00?

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