Bi-Fly 25 (oz11348)


Bi-Fly 25 (oz11348) by Dave Milbourn 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"

Update 21/12/2020: Added kit review from Radio Modeller, October 1995, thanks to RFJ.

Supplementary file notes



Did we get something wrong with these details about this plan (especially the datafile)? That happens sometimes. You can help us fix it.
Add a correction

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


Bi-Fly 25 (oz11348) by Dave Milbourn 1985 - pic 003.jpg
Bi-Fly 25 (oz11348) by Dave Milbourn 1985 - pic 004.jpg

Do you have a photo you'd like to submit for this page? Then email

User comments

Note that upper and lower right wings are about 4mm shorter than the left on the plan. The error occurs at the first rib outwards from the root ribs, being wrongly placed. Outwards toward the tip, all is in order. There is also some curvature of the bottom wing leading edge and of the rear of the fuselage in plan view.
ColinS - 15/11/2019
Add a comment



Download File(s):
  • Bi-Fly 25 (oz11348)
  • Plan File Filesize: 560KB Filename: Bi-Fly-25_RC_oz11348.pdf
  • Supplement Filesize: 2245KB Filename: Bi-Fly-25_RC_oz11348_instructions.pdf
  • Supplement Filesize: 3688KB Filename: Bi-Fly-25_RC_oz11348_review_RM.pdf
  • help with downloads


* Credit field

The Credit field in the Outerzone database is designed to recognise and credit the hard work done in scanning and digitally cleaning these vintage and old timer model aircraft plans to get them into a usable format. Currently, it is also used to credit people simply for uploading the plan to a forum on the internet. Which is not quite the same thing. This will change soon. Probably.


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.


Terms of Use

© Outerzone, 2011-2024.

All content is free to download for personal use.

For non-personal use and/or publication: plans, photos, excerpts, links etc may be used, provided that full and clear credit is given to Outerzone with appropriate and specific direction to the original content i.e. a direct hyperlink back to the Outerzone source page.

Unauthorized use and/or duplication of this material without express and written permission from this site's owner is strictly prohibited. If we discover that content is being stolen, we will consider filing a formal DMCA notice.