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Oct 23, 2009, 05:10 PM
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Discussion

52" foam bipe


Here I go again...

I've been flying a lot of electric foamie biplanes lately... they're just perfect for flying at the local park: aerobatic, light wing-loading, and can take-off land on a little-league baseball diamond. Wanting something a little bigger -- but not that would take ages to build or was too expensive to add electronics -- I've come up with something that loosely resembles a Sig Smith Mini-plane or Sig Hog Bipe or EAA Biplane.... a loose mix combining whatever qualities I thought would be easiest to replicate for a sorta-scale parkflyer. The fuselage is simple slab-sides... made from 1/2" pink rigid insulation foam. The wings are built-up from 1/4" FFF ... or they could be hot-wire cut from 1" thick blocks or you could build the "Armin airfoil". It's a simple enough design that I should be able to build an entire airframe in a day, but the full fuse will give it a bit of scale looks and a strong box frame.

I'll continue to refine the plans - perhaps tab & notch interlocking pieces, though not really necessary.

.
Last edited by warhead_71; Jun 29, 2012 at 12:29 PM.
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Oct 30, 2009, 02:55 PM
Prunner
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I like it, looks easy to build too. Reminds me of the Smiths Mini biplane. I've been wanting to build that one for a while, but didn't feel like eating balsa dust for weeks or spending that much $ for the kit. Sig makes a kit for that plane. Have you started on this.

Funny I wrote the above before reading your text, guess that means you nailed it.
Oct 30, 2009, 03:19 PM
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Yes - it does get its lineage from several simple sport bipes. I wanted to make something light and rugged that could be built and flown in a weekend, but still had "sorta-scale" looks. I haven't started building it yet... but winter build season approaches.

The wing airfoils can be whatever you prefer... symmetrical, semi-symmetrical or Clark-Y or flat-bottom (I know they are different), KFM,... perhaps even just flat. The 1/2" pink foam goes together quickly and you can whittle and sand the edges round pretty quickly... just have a look at the my cheap bipe.
Nov 02, 2009, 07:39 PM
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By popular demand, I have begun to lay out the parts individually. I won't be tab/notching anything... I don't think it's necessary for this simple structure. The fuselage and empennage you should be able to cut out and assemble in less than an hour. I'd use the white Gorilla Glue which sets up in about 20 minutes. The wings are built up from all FFF with a wood spar. It would probably do great with no spar at all if you cross-brace with fly-wires. Of course, a really hard landing might snap the wing... but it depends on whether you build to survive flight or build to survive crashes.

I have 90% of the plans drawn out already... I'll finish them and post tomorrow.
Nov 03, 2009, 12:50 PM
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Here is a vector PDF. If you have any kind of drawing program, you should be able to open this and print out the parts for whatever paper you have. Please feel free to chop up the files however you need it and repost (on this thread) for others to print.

I calculate 480sqin per wing for 960sqin total.
At 70oz (4.4lbs) AUW you get ~10.5oz/sqft wingload: glider
At 100oz (6.25lbs) AUW you get ~15ooz/sqft wingload: trainer
If it weighs more than that, you built it wrong.

I'm looking at affordable power systems that deliver ~75oz of thrust with a 11"-13" prop. I'd love to run it on 3S but might have to go 4S.
Last edited by warhead_71; Jul 15, 2010 at 09:33 AM.
Dec 03, 2009, 09:18 AM
Foam Av8r
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Looks Good WH71
are you going to tile these drawings?
Dec 03, 2009, 10:43 AM
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Here you go. Just the parts to save on paper, but still comes to 54 pages.

Be sure to print at 100%...

I have 1/2" overlaps for each page, and I put in a 1" grid to help you keep everything aligned.
Last edited by warhead_71; Dec 03, 2009 at 10:53 AM.
Dec 03, 2009, 04:26 PM
Foam Av8r
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Thanks Nice work warhead
this one is definately on the build list
Dec 03, 2009, 07:33 PM
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You'll get around to building it before me... I have too many irons in the fire right now.
Dec 03, 2009, 09:58 PM
Foam Av8r
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LOL, Good to know that I am not the only one with multiple projects on my bench
Dec 04, 2009, 12:39 AM
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Worse than that, I have multiple benches so I can switch between projects while glue and paint dries...
Dec 04, 2009, 01:35 PM
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now that would be really cool
you are my new hero
Dec 08, 2009, 07:44 PM
Registered User
I am new to this building thing. What foam and where would I get it? Is this a lowes or home depo item or special order?
Dec 08, 2009, 08:14 PM
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The foam is rigid insulation (for home construction)... available in various thicknesses. The 1/4" thick foam is commonly sold in folded bundles of 25 sheets of 2' x 4'... also called "Fan Fold Foam" (FFF) because it is actually a 50' x 4' sheet folded like an accordian. I comes in various colors depending on the manufacturer, blue, pink, green... but the best brand IMO is the blue DOW brand sold at Lowes.

1/2" foam and thicker is sold in 4' x 8' sheets... usually blue or pink. Available at Lowes or Home Depot or just about any other home improvement store.

There are entire threads devoted to the types and brands of foam if you search the "scratchbuilt foamies" forum.
Last edited by warhead_71; Jul 13, 2010 at 04:36 PM.


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