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Old Dec 05, 2006, 06:58 PM
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Somewhere south of Chicago, IL
Joined Jan 2006
1,952 Posts
Build Log
"Little Go Bipe" - 5-6 oz foam biplane; new design, free plans!

Hey everybody -

Okay, so it's not exactly a "new" design in the sense that it's just a foam biplane with a stick fuselage. Nothing "new" or "revolutionary" about that. It's just "new" in the sense that I designed it by myself, using the acquired knowledge I've gained by reading a lot of stuff here, and trying different designs at home (some succeeding, some failing).

Anyway, I've been playing around with the basic biplane design for about the last 3 or 4 months. My goals were simple enough:

- Made from inexpensive materials, including radio and power system
- Able to be made from a single sheet of foam
- Capable of both slow flight and decent aerobatics
- Lightweight and (relatively) quite small
- Forgiving of less than perfect landings
- Easy to cut out

First, I started out using the foam from the foamboard with paper on it (paper stripped off, though). It flew "okay", but I was also using a GWS 280 direct drive and a 1.4 oz NiMh battery. Next, I redesigned it using Cellfoam 88 - worked a bit better, but the tail still kind of hung down relative to the wing and nose.

I've redesigned what (I think!) should be a great little flyer. The wing is a 4-40 chord (From LE, 4% up, at 40% of the chord), and has a 3% "up" incidence on the upper wing. Also, because I got tired of fixing foamies with fixed wings, this one employs a rubber band to hold the wing onto a balsa fuz spar, .375" square. A "wing stabilizer" is attached to the fuselage using some wing supports, and matches the airfoil of the lower wing. The rubber bands go underneath the wing, allowing for very forgiving "less than ideal" landings.

I've switched the motor to a GWS ISP "A" drive, assuming a 9x7 prop, and a 200 mAh - 350 mAh LiPo to keeps the overall weight to between 5 and 6 oz. I really like having landing gear, since I prefer "touch and go's", and also because many of the areas I fly have hard surfaces (and not much long grass for landings).

It should fly nice and slowly, but the previous versions I made would also do snap loops and fairly snappy rolls too. I'm not an aerobatic expert by any means yet, but I think this plane will offer quite a bit of gentle response for newer fliers, yet plenty of fun for more advanced fliers (I hope!!!). Of course, a brushless motor will make this into a real screamer, but I don't think that's necessary, since I really designed it for small backyard or indoor use.

I'll add pictures of the build shortly. Hope you enjoy!

I should note my appreciation for the article by Jef Raskin about small plane airfoils - the airfoil for this plane is derived directly from that article (even though it's Re number is just slightly over 50,000). And also, props to everyone here that posts their plans, tips, and insight - your thoughts along with my own interests coalesced together are how this design came into being. So thank you to everyone one here - this is my way of "giving back", I guess.

Plans for all parts on 11x8.5 pages, here:

EDIT: Here is golem's initial flight report in post #46, using a brushless setup:

EDIT: Plans for a 3 oz, 14" wingspan version can be found here in post #92.

EDIT: Added tiled plans below on 6/7/07
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Last edited by magic612; Jun 06, 2007 at 11:08 PM.
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