Baby Bi

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RCM Baby Bi.  This is a nifty plane that’s easy to build.  The RCM construction article says the airfoil is semisymmetrical, but the airfoil on the plan really looks symmetrical to me.  The tail and engine are on the centerline between the top and bottom wings, so it’s set up like a pattern plane and has some of the flight characteristics of a pattern plane.  But as a short, stubby little biplane it should be capable of some wild and crazy maneuvers that pattern planes won’t do.

There are a few weird quirks in this design, and I have changed a few of them for the convenience of the builder.

  • The plan shows a plywood windshield.  That seems excessive.  Use firm 1/8″ balsa, put triangle stock in the corners, and round the edges to make it look like a windshield.
  • The plan shows a one piece wire landing gear sandwiched between thin plywood bulkheads.  My kit includes a single bulkhead and a plywood chin plate.  Put these parts together in the normal fashion, add some triangle stock for strength, and mount a wire or aluminum landing gear to the chin plate.
  • The plan shows the wings held on by rubber bands.  Go ahead and do it this way if you prefer, but the kit includes some parts for bolting the wings on.  Build the wings with the slotted balsa rib in the center.  Attach a lite ply half rib to each side of the center rib.  Attach a lite ply half rib to each of the ribs adjacent to the center rib.  Slide the included 1/8″ ply bolt plate into the slot.   Add some balsa to fill the space between the plate and the sheeting, then add the sheeting and the leading edge.  Place some hard wood blocks in the fuselage to receive the bolts.  Drill through the bolt plate into the fuselage blocks to install the bolts.
  • The plan calls for 1/8″ balsa fuselage sides.  1/8″ lite ply sides are provided in the kit for ease of building.  The kit also includes 1/4″ balsa cowl sides, which can be sanded to create rounded contours in the cowling.

Don’t hesitate to ask any questions you may have.