kodak

How hard would it be to make a biplane out of say a Scanner or low wing Sky Raider. I'm thinking struts and cabanes shouldn't be too hard but what about the top wing position does that pose a problem as the low wing can't be moved.

khodges

My Feedback: (1)

One of the guys at our field has converted several 4 Stars to biplanes. His recommendations are to use a little positive stagger (top wing forward of bottom). This will require moving the c/g forward some. If the present C/G is at the spar, and the top wing is tha same shape and chord of the bottom wing, the new c/g will be at a point halfway between the two spars, measured on the longitudinal centerline of the plane and translated to the top wing. Aesthetically, I think the plane looks better if the top wing has greater span, whether you build the top longer, or shorten the bottom. When my buddy does the 4-Star, he shortens the bottom wing by two bays on each bottom wing half, and one bay on each top wing half, and builds the top wing flat.

Determine the height above the fuse that you want your top wing, and build the cabane struts first, center and level the top wing, and then build the outboard struts. Cabanes should angle outward from the fuse to the top wing, and wing struts can be vertical, This will make the construct much stiffer, and the top wing will not move side-to-side. If all struts are vertical, flying wires might be necessary to stiffen things up.

Grampaw

I read somewhere where a designer placed the top wing of his bipe at a distance above the bottom wing equal to the chord of the wings. If the wing chord is 10 inches, set the top wing 10 inches above the bottom wing, measured from the highest point on the bottom wing to the bottom side of the top wing. Measure some bipe plans to see if this holds true. I have checked some and found it to be the case (even in full sized planes) Shortening the lower wing one or two rib bays is a good idea, and if the plane you're planning to convert has any dihedral in the existing wing, leave it and make the top wing flat. Some bipes have equal span wings however, so go figure. The late Chuck Cunningham of RCM used to say "If it looks right, it will fly right!" Always worked for me. Good flying.

kodak

Thanks for the tips guys.