Hi everyone,

Since I don't have access to a field large enough for even a 0.10 size glow powered plane, I thought of designing a small lightweight 'backyard' flier.

So out came a sheet of 5mm depron, a ruler and pencil and a #11 surgical blade.

But before putting pencil to depron, had do do some planning.

I had this small (2cm dia) 15gm motor.
Took a bit of research to find out that it was a Flightline D2704 2320kv rated for about 35watts on 2s.

I tested it with a 5x3x3 prop and got 130gms thust at 30w on 2s.

That was the first step.

I wanted it to fly like the Bipe I built 12 years ago, but be better looking...



Here's the link to that old 2014 thread:
https://www.rcindia.org/beginners-zone/indore-bipe-a-model-for-newcomers/

So the parameters were:

1. Low wing loading (not over 6oz/sqft) for slow flying speed,
2. About 60w/lb power loading for safe takeoff and climb out,
3. Not over 24" wing span,
4. Elliptical wing instead of the same old rectangle.

So it had to be depron.

Target weight was about 7oz/200gms,
So wing area of a little over 1sqft.

How to pack 1 sqft area into less than 24" span?
A 24x6 wing would have a too low aspect ratio of only 4.

Solution: Biplane.

A 20x5 plank, 100 sqin, and a 16x4 plank 64 sqin, total 164 sqin.
Or about 128 sqin for ellipses.

For drawing the shape of a wing with leading edge half ellipse of 10" semi span and 2" semi chord, trailing edge half ellipse of 10" semi span and 3" semi chord, there is a proper method.

But it's far easier to approximate it by eye and freehand curves!

And the stab was cut similarly from a 12x3 plank, keeping aspect ratio the same as for both the wings for symmetry (and a horizontal tail volume coefficient of 0.50)

So here's what I cut and assembled in 5mm depron.

As the wing was sparless, added a dihedral brace as a precaution.
Cut from some 0.50mm carbon fibre sheet I had made last year as an experiment!

Got a pleasant surprise when I weighed the bare airframe (55gms), and the equipment (62 gms excluding battery and Rx).

Completed it at midnight yesterday!

AUW came to 164gms with 30gm 2s 360mah lipo and 10gm Rx.

Unfortunately today morning was 12 deg C, and completely fogged out.

Nice 

@Sanjayrai55

Sir, your turn now.
Been a long time since you posted the last of your (20+) build logs...

Regards

Nice build and flight Iyer Sir. Loved the landing!!!

Quote from: Rooster on January 04, 2026, 04:56:03 PMNice build and flight Iyer Sir. Loved the landing!!!

That landing was in 2014!

Nice build.. and the biplane solution to the design constrain was good..

Happy flying
Rahul