Box Fly 20 S (oz6968)


Box Fly 20 S (oz6968) 1983 - plan thumbnail

About this Plan

Box Fly 20 S. Radio control sport model.

Quote: "Dear SIMPROP customer,

For many years the Box Fly 20 S had been manufactured by the Japanese company of OK Pilot. Because of its simplicity of design, ease of construction and forgiving flight characteriestics it became a very popular kit both sides of the Atlantic.

This was this reason why Simprop decided to take up production of this kit again. The good flight characteristics of this model were kept and some details of the kit were improved considerably. Among the inprovements are: a reinforced horizontal stab, a two-piece engine mount (suitable for all engines) made of plastic and the possibility to install a moveable tail gear, order no. 1001523 and 1001035. Moreover, special features are: a thicker leading edge (easier to sand) as well as sub ribs in the front section of the wings. These changes in the front wing area give the model considerable advantages with regard to slow flight properties and easy manoevrability. Our kit contains a full-size plan and an instruction booklet with many pictures of the different construction stages.

The fuselage is of plywood construction and the wings are built with balsa ribs. This makes the construction so easy that even an inexperienced modeller should not face any problems when building the model. All wooden parts are die-cut or cut to size.

Your Box Fly is a model for every-day flying: very stable, no problems of transport because of favourable sizes, with good flight behaviour and capable of every style of flying. It is suited for the beginner (with the assistance of an experienced modeller) and for the expert for fun and training.

The symetrical profile allows for aerobatic flight. Nevertheless, it is not critical when flying slowly. The landing gear with the manoeuvrable tailgear guarantees perfect take offs and landings.The model is controlled by elevator, rudder, aileron and enginethrottle. However, it is possible to construct it without the control function of the rudder. We wish you many happy landings with your Box Fly 20 S.

Engine: We recommend our Super Tigre X25 RC with 4.06 cc for this model. Engines of approx. 3.5-5 cc are perfectly suited to give the best performance of your model. For fun flying the lowest power will be a 3.5 cc engine. However, the stable construction of the model even allows for the installation of a normal 6.5 cc engine with muffler.

For enthusiasts of 4-cycle engines we recommend 5 to 7.5 cc engines, eg our Saito FA 40 or FA 45.

Hints for the construction: The numbers printed on the parts correspond with the process of construction. Before you start building your model, please study the full-size plan, the instructions and the contents of the kit. Remove all parts carefully from the die-cut sheets (if necessary use a knife) and arrange them according to the stages of construction. This preliminary work makes the construction of your model considerably easier and quicker.

Note: Before you glue the parts together you should check whether they fit properly in order to correct small tolerances which cannot be avoided in series production..."

Quote: "Hi Steve, I send you a Box Fly 20 S from SIMPROP. Date on Plan is 1983. Size of that Plane is about 52 Inch. All other data in mm and grams on the plan. I have flown the model in 1991 with a 3.5 cc ENYA. I will rebuild it sometime with a brushless motor. That Plan includes Parts-List, Instructions and Pictures... With a friendly 'spar and rib fracture' (German model flyer greeting). ToniK"

Direct submission to Outerzone.

Update 25/08/2015: Replaced this plan with a clearer copy at 400 dpi, thanks to ToniK.

Update 26/08/2019: Added kit review from R/C Model World, March 1985, thanks to RFJ.

Update 26/08/2019: Added kit review from RCM, August 1977, thanks to RFJ.

Supplementary file notes

Kit reviews.


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Box Fly 20 S (oz6968) 1983 - model pic

  • (oz6968)
    Box Fly 20 S
    from Simprop
    52in span
    IC R/C Kit
    clean :)
    all formers complete :)
  • Submitted: 23/08/2015
    Filesize: 2494KB
    Format: • PDFbitmap
    Credit*: ToniK
    Downloads: 6837

Box Fly 20 S (oz6968) 1983 - pic 003.jpg
Box Fly 20 S (oz6968) 1983 - pic 004.jpg

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User comments

Good day, I send you my pictures of my last plane built with plans from Outerzone, the Box Fly 20 S powered by Saito .40 [more pics 003, 004]. It is a beautiful plane and very easy to fly. I have enjoyed building and flying this nice plane.
CarlosAB - 23/11/2016
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Download File(s):
  • Box Fly 20 S (oz6968)
  • Plan File Filesize: 2494KB Filename: Box_Fly_20_S_oz6968.pdf
  • Supplement Filesize: 2710KB Filename: Box_Fly_20_S_oz6968_review_RCM.pdf
  • Supplement Filesize: 1866KB Filename: Box_Fly_20_S_oz6968_review_RCMW.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.


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