Converting mono to bipe
 

Hey guys,

I have a large profile plane that I really enjoyed building. I'd like to build a large profile bipe, 120-150 size, using the same profile techniques I used with the mono wing profile.

I'd like some suggestions on doing this.

Do I start with an existing plan then just build the profile fueslage? I want an easy flying aerobatic plane.

Is there an article or thread on converting a mono wing to a bip? Or bipe parameters?

Any ideas and suggestions will be welcome,

Thanks,
Flyinblind

RE: Converting mono to bipe
 

HI FLYINBLIND! The individual wings of a bipe only have to be half as strong as those on a monoplane, by the time you are done cantilevering the 2 wings together, there won't be much unsupported span. The thickness of the individual airfoils needs to be somewhat thinner than a single wing fun fly. A bipe doesn't make full use of the lift provided by the individual wings because there is aerodynamic interference between the wings, the more distance there is between the 2 wings, the less interference, BUT I'm sure that there are practical limits to how far apart to set them. The thrust line should be centered between the 2 wings. I have built the GOLDBERG bipe in various sizes down to a 12 oz, .061 powered and they have all been lots of fun. No matter how lightly I tried building them, I have never had a structural failure, which leads me to believe that it's difficult to build one that's too light. If you are building a large profile, try to get a look at how the MORRIS HOBBIES 1.20 size job is put together, there is a build up thread in the profile forum. It would be pretty hard to improve on their design!

RE: Converting mono to bipe
 

Thanks for the info!

Would you mind forwarding that thread to me. I've searched around and can't find it.

Appreciate you help!
FlinBlind

RE: Converting mono to bipe
 

The rule of thumb I've seen in the past is that you want to have a minimum of one chord of separation. At 1 1/2 chord's separation they have so little blanking effect on each other that you can ignore it.

Full sized aircraft have flown with separations quite a bit less than one chord but there are drag problems associated with that method. I would consider going down to 0.8 chord separation but no less. And only if you NEED to. One chord is safe.

You'll want to reduce the chord down to about 1/2 or 0.6 of what it is. The biplane configuration concentrates the area without requireing a large chord so you can reduce the chord and the separation without reducing the wing area.