Bi planes. What's the point?
 

I'm on vacation and someone is flying around in a biplane. Got me thinking. Does the additional wing create additional lift? Even so, Doesn't it interfere with the lift the first wing in creating? I know there's triplanes too... I've never seen one with 4... There has to be a point where the weight outweighs the added benefit. Right?

When airfoils were not efficient, you needed more wing area to get enough lift. Rather than a very long single wing, w/ structural and maneuverability issues, they used two wings. They are far enough separated to work. Today, I'm not sure what the advantage of a biplane would be.

https://en.wikipedia.org/wiki/Armstrong_Whitworth_F.K.10

https://upload.wikimedia.org/wikiped..._side_view.jpg

This is a good link:

Biplane vs. Monoplane

The essential issue is drag. Monoplanes have a lot less.

The #1 reason is strength and weight. Try picking up a 1/2"-2" cross section 30" long aluminum bar some time. Then weld an I beam out of three pieces of the same material, and try again.(If you stack those 3 on top, it will still bend like crazy)

The shorter span that comes with two wings, combined with supports making a multi-unit structure connecting the two wins, allowed for light weight, and stiff structure. Almost half the length, and connecting supports.

You'll need to understand something about fluids first. Lift is simply differential pressure between the upper surface of the wing and the lower surface. Faster moving fluids create lower pressures. If the wings are spaced far enough apart, there is no interference.

A bi-plane and tri-plane allow shorter wings to create lift at the same speed. Mono-planes usually need higher speeds to create enough lift to fly.

For aerobatic planes, the shorter wings allow the plane to rotate about their central axis more quickly. This improves maneuverability. A Fokker tri-plane could rotate and bank more quickly than their counter parts. However, what you loose is stability. Longer wings are more stable than short wings.

Seahawk is correct that a biplanes disadvantage is parasitic drag from the interwing structure. This could be overcome by using monoplane type internal structure and eliminating bracing. The main thing is to understand what you are trying to achieve and design for that. Nothing is for free.

I love bipes. The first time I saw the Lionheart homebuilt my heart skipped a few beats. Sadly they're out of production so I will probably never have the opportunity to build one.

http://www.youngeagles.org/photos/ga...ionHeart_1.jpg

The point is they look cool. :)

Twice as many opportunities for a plane-to-plane hookup. ...most airplanes claiming to be Biplanes are really just confused.

Yep, biplanes are old-school cool.

http://www.navy.gov.au/sites/default...ith-camel2.jpg

Is that you in the photo Jim?

hey man, a wing is a wing

LOL.


Thanks for the info.

Makes me wonder if there are many biplanes still produced.

I see you can still get a Pitts Special, and an Eagle here: Aviat Aircraft: Makers of the internationally famous Pitts, Husky, and Eagle models

Any others folks are aware of (outside of homebuilt)?

There are a few other low volume manufacturers. Here are two that I know of off hand:
WACO Aircraft Corporation - The world's only producer of NEW FAA & EASA certified open cockpit sport biplanes
Jim Kimball Enterprises


I am currently building a Steen Skybolt.
Well... not currently. Currently I am sitting on my ass in front of the computer. But I *should* be out in the shop building my Skybolt.

This thread made me go look up the Lion Heart, and I to, was sad to find it out of production. :(

@cashflyer, the Pitts is the only one I'm aware of.

Yep. I'm older than dirt.

The Skybolt looks *****in'!

WACO's look beautiful - cool to know such planes are still made. However, am I the only one here that chuckled to read the YMF-5D has an IFR panel? That seems odd to me, flying IFR in an open cockpit plane . .

what kind of bracing would that top wing require? IOW how is it secured to the frame?