4-40 Bipe (oz6271)


4-40 Bipe (oz6271) by Doc Mathews 1986 - plan thumbnail

About this Plan

4-40 Bipe. RC sport biplane model for 4-cycle engines. Wingspan 48 in, wing area 625 sq in, for .40-.46 engine and 4 channel RC.

Quote: "That biplanes are immensely attractive to modelers is self evident. What ofttimes is not so evident are some distinct difficulties encountered in building and flying models with two wings. This design is directed at reducing the difficulties while accentuating the attractions.

Anyone who has built a biplane is fully aware of those difficulties. One must build twice as many wings, then struggle valiantly to somehow get them on to the fuselage relatively square in all three planes while battling wire bending and soldering. The 4-40 bipe still requires a pair of wings (although rather easily constructed ones), but bending the wire and mounting the wings has been so simplified only a concentrated effort could get them out of line.

The easy building, self-aligning construction features of the other designs in this series are carried over into the 4-40 bipe. That they work very well is evidenced by the incredible acceptance and popularity of the 4-20, 4-40, and 4-120. Those who have built any of the monoplanes will be pleased to hear that the same 'easy building, easy fly, great fun' virtues are also present in the 4-40 bipe.

Speaking of easy flying - many biplanes are a handful on take-off and landing. Often, a very agile rudder thumb is needed to avoid 'all over the runway' type take-offs. The 4-40 bipe has a deliberately overwide landing gear tread and the unit is also well-placed relative to the Center of Gravity. That is the reason for the moderate stagger. As a consequence, ground handling is just as docile as the monoplanes in this family.

A relatively low wing loading (for a bipe) and a special airfoil section enable the 4-40 bipe to be flown at much slower speeds than ordinary bipe designs. Consequently, it is much less inclined to 'snap and burn' if the approach is stretched too far or the flare is instituted too soon. In between take-off and landing, the 4-40 bipe is agile and acrobatic, yet slow and gentle..."

Direct submission to Outerzone.

Note see 4-40 (oz14906) for the shoulder-wing monoplane version of this design.

Update: Replaced the article file with a complete version. Now includes all pages, and even the missing last page p88, thanks to JHatton.

Supplementary file notes

Article pages, text and pics, thanks to SrFalcon. Updated thanks to hlsat, JHatton.


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4-40 Bipe (oz6271) by Doc Mathews 1986 - model pic

  • (oz6271)
    4-40 Bipe
    by Doc Mathews
    from RCMplans, Ace RC (ref:977)
    October 1986 
    48in span
    IC R/C Biplane
    clean :)
    all formers complete :)
    got article :)
  • Submitted: 13/01/2015
    Filesize: 1153KB
    Format: • PDFbitmap
    Credit*: DavePentland
    Downloads: 6587

4-40 Bipe (oz6271) by Doc Mathews 1986 - pic 003.jpg
4-40 Bipe (oz6271) by Doc Mathews 1986 - pic 004.jpg
4-40 Bipe (oz6271) by Doc Mathews 1986 - pic 005.jpg

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User comments

there is 4 pages missing from the building guide
anon - 07/08/2016
Thanks, got it now.
SteveWMD - 07/08/2016
In the 90's i built one 440 and i have the best memories. Flying was awesome, and landing soft with no tricks.
Ricardo Mandil - 31/05/2023
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