Bi-Fly 25 (oz11348)

 

Bi-Fly 25 (oz11348) by Dave Milbourn from Precedent 1985 - plan thumbnail

About this Plan

Bi-Fly 25 (BiFly). Radio control sport biplane model, for .25 power.

Scan from HPA.

Quote: "Introduction: The Bi-fly25 is a lightweight biplane for motors from .19 to .25 cu ins. It has an all balsa construction to help keep the weight down and will fit, filly rigged, into the boot of all but the smallest of family cars. The performance is sparkling. It's of course quite normal that when the manufacturer designs for and recommend a .25 motor, some modellers will immediately plan on using a .40. Bi-fly25 will certainly take the extra power but beware of excessive torque reaction especially on take off.

Study the plan & isometric assembly drawings in conjunction with the instructions BEFORE you begin building. Note that all the parts are numbered in a logical building sequence and that the parts list shows which of the unshaped parts are cut from various sheet and strip materials supplied.

Upper Wing: Cover the plan with polythene sheet to prevent glue from sticking to it. Cut the mainspars to length. pin down on the plan and glue the 'V' shaped joiner in place (cut from 1/8 x 5/8 (3mm x 15mm) balsa strip. Make up the top & bottom spar assembly. Laminate the root rib from the two ply parts 3 and glue the brace in place. Glue this assembly exactly in position over the bottom spar, packing up the rear end of the rib 1/2 in (12mm) as shown. Add the false leading edge & top spar. Fit the other ribs in two parts (7 & 8) and allow the whole structure to dry. (Tip: you could use the mounting lugs (12) as a jig to ensure that ribs 7 & 8 are spaced correctly).

Cut the webbing pieces from 1/16 (1.5mm) balsa sheet and note that the grain runs vertically, and glue in place. Fit the ply strut bracket doublers where shown on the plan, gluing them firmly to the inside surface of the lower spar. These will eventually hold the small screws which secure the strut brackets to the bottom of the wing. Plane a chamfer on the false leading edge to blend in with the wing section. Butt join the 1/16 (1.5mm) balsa wing sheets together and sand them smooth ready for finishing. If you leave this sanding until later, you will sand away more balsa where the ribs are situated and create 'ruts' in the wing surface... "

Update 22/07/2019: Added kit instructions, 12 pages complete (includes die cut parts drawings, and full parts listing), thanks to PaulDallimore.

Quote: "Hi Mary and Steve, Bi Fly 25 (oz11348), In the distant past I occasionally flew one of these that belonged to a flying club friend and remember it was a really good performer for its era so it's great to see the plan on the OZ. The attachment is intended to complete the oz11348 plan that is in the format of numbered parts without material dimensions or descriptions, so it should be of use to builders. (It would be nice if someone had a similar file for the Graupner Loop, oz8085). I know that I write a 'thank-you' note to you for your hard work each time I send in a file, but they're not just 'empty' words, your work is really appreciated. Best regards, Paul"

Supplementary file notes

Instructions.

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Bi-Fly 25 (oz11348) by Dave Milbourn from Precedent 1985 - model pic

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Scaling

This model plan (like all plans on Outerzone) is supposedly scaled correctly and supposedly will print out nicely at the right size. But that doesn't always happen. If you are about to start building a model plane using this free plan, you are strongly advised to check the scaling very, very carefully before cutting any balsa wood.

 

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