Flying biplane wing?

[Frank B]

For some time now I have been thinking of an experiment I would like to try, but I don't know if it will be possible at all. Perhaps someone out there has already done it:

I love my home made flying wing (zagi like), and I am also facinated by biplanes, so - why not combine the two? A flying biplane wing.

What should be considered in such a plane?

Will it be possible to just make two identical wings, and put one directly on top of the other - with some space between of course, but how much space?

On a real biplane the two wings are normally not of the same size and they are not placed directly above each other. Are there some reason for this, thas should be considered?

I would really like to give it a try, but if it's to crazy an idea, just say so.

[Viper Pilot]

A suggestion for a starting point:

Make the lower wing 2/3rds the size of the upper wing.

Place the lower wing 50% (of chord) ahead of upper wing (stagger-wing configuration).

Give 0 degree incidence to lower wing and - 2 or 3 degree incidence on upper wing.

Give the lower wing about 5 degrees dihedral and the upper wing 5 degrees anhedral.

If you connect the upper and lower wings with vertical stabs on the wingtips, give them a bit of "toe-in".

Just a suggestion, but should be stable.

VP

[Ollie]

Biplane wings interact with each other and the interaction degrades performance. The farther apart the wings, the less the interaction.

Making one of the wings smaller reduces the interaction and the spacing needed for a given level of degradation.

Staggering the wings fore and aft can improve longitudinal stability and reduce the reflex needed in the airfoils. This has the potential of improving maximum lift coefficient a little. Some decalage can be employed to provide pitch trim without having to resort to as much reflex.

One of the earliest tailless flying wings was the Dunne biplane, circa 1910.

You should be able to reduce the wing loading with a biplane configuration and that is almost always benefical in tailless aircraft.

[Sparky Paul]

DRAG!
Ever seen it?
You will! :)
Four wingtips...
Interwing interference...
But go ahead. Post the photos.

[Thomas B]

Even given it's drawbacks, the tailess biplane did improve the state of the art in ultralight flight a number of years back.

The Easy Riser was an outgrowth of the Icarus II hang glider and many were built in a number of different configurations. Foot launched hang glider, foot launched powered ultralight, tri geared powered ultralight. A picture is attached.

Most early ones were weight shift for pitch and yaw/roll from the tip rudders and built in dihedral. Many late models have a horizontal stab for aerodynamic pitch control, as was so nicely documented in the movie "Fly Away Home"

No reason a model will not work well, but it will never be as fast or have the performance of a single surface flying wing.

But, for low speed light lift soaring flight, the tailess biplane does work, after a fashion.

[Paulus]

We did a very fun project with a couple of "zagi's" a year ago on the interex in germany. It was a biplane constructed of two mini tornado replica's made out of blue foam with 2 speed 400 motors.

The biplane didn't flew very much different than the mono version. Very easy to fly actually.

The top wing was moved slightly forward to clear the prop from the bottom wing.

But here's comes the cool part. When in the air we SEPARATED the planes from each other and flew some combat against each other...:D


http://home.planet.nl/~raven274/pics/TSJECHIE0395.jpg
http://home.planet.nl/~raven274/pics/TSJECHIE0410.jpg

[gjs]

Icarus II used between the wing tip rudders, for yaw control steering. I had the assembly manual, should have built it, wonderfully simple.

[Frank B]

Thanks a lot for the response. Great pictures. I surely will start building one.

I'm not that concerned about drag and top speed. I want to build it because it looks cool. If I want speed, I have other planes in my fleet;)

I plan on building it from wood, not foam, with a wing span of 120cm (about 47") and a MH45, Zagi-10 or Zagi-12 airfoil. Any suggestions regarding choise of airfoil? And should I use the same airfoil for both wings?

I have the following power system ready for it:

Motor: Mega 22/20/3
Prop: Graupner CAM 7x6
Accu: 8 X RC3300HV NiMH
ESC: JES 40-3P

I also have a 2.5:1 gearbox for that motor, but I don't know if I will use it on the plane (it requires a prop around 12x10). I have thought about placing the motor between the two wings, so perhaps there will be room for the larger prop (it certantly has much better performance than without the gearbox).

It will also be fitted with landing gear for ROG (I know - more drag).

I don't have a digital camera, so I will not be able to post any pictures of the building process, but I will surely be able get some pictures of the finished plane out on the flying field.