BabyBiwinger
R/C Conversion
Relive those good ole’ days without risk of losing your model with this easy micro R/C conversion!
By Daniel Walton PHOTOGRAPHY: DANIEL WALTON B
ack in the July 2012 issue of FLY- ING MODELS I had speculated on the possibility of an R/C conversion of the Baby Biwinger model air- craft F/F design. I figured using newer tech- nologies available along with carefully se- lected materials, a judicious redesign of certain structural elements and a very ag- gressive weight reduction program would yield a radio controlled conversion of the original 13-inch span model. With changes to reduce the weight by at least 50% for the airframe and appropriate mods to allow for a proper c.g. with the lighter weight propul- sion unit (8.7 grams for the electric motor and prop vs 18 grams for the Cox Tee Dee .010) was indeed possible.
On December 8, 2012 I was able to suc- cessfully fly for the first time one possible so- lution to this design problem with very sat- isfactory results. The new model flies very much like the Ember 2 which is where the receiver came from (only three channels were needed) and used the gearbox/motor from a ParkZone P-51 (PKZ3624) and a GWS 5034 prop and adapter spinner. The target weight I had figured should be somewhere between that of the ParkZone J-3 Cub and their P-51, so I would be looking at 28 to 34 grams. That would be about right
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for realistic purposes. The weight of the raw material would be critical and I searched through all the 1⁄32 sheet balsa stock in town and finally found two sheets of 1⁄32 × 3 × 36- inch balsa that turned up at 8.9 and 9.2 grams respectively.
The model component weight breakdown is shown in the box on page 37 and I hope will serve as a reinforcement for the above message.
The key components to a strategy to re- duce the weight on this project so that I would be assured a flyable model at the end of the program were as follows: 1. Light 1⁄32-inch sheet balsa on all major parts in place of the light 1⁄16-inch sheet bal- sa of the original design (all components one-half weight by gage).
2. Built-up fuselage bulkheads in place of
solid 1⁄16-inch sheet bulkheads. 3. Elimination of 3⁄8 sheet balsa block up- per wing mount (F5 on original plan) and re- placing it with a simple short closure at the front top for windshield support. 4. .025 wire landing gear strut in place of the .050 wire landing gear strut (75% reduc- tion in weight by gage).
5. Use of “Sleek Streek” wheels in place of solid rubber and aluminum hub Perfect wheels (55% reduction in weight).
AT A GLANCE Type:
Construction: Wing span: Wing area: Length: Weight:
Wing loading: R/C micro
balsa and ply 13 inches 58.9 sq. in.
11.375 inches 1.25 ounces
3.056 oz./sq.ft.
Motor: ParkZone P-51 brushed motor Prop:
Radio/ESC: Battery: GWS 5034
ParkZone DSM2/X with linear servos
1S 150 mAh Li-Po
6. Elimination of 1⁄8-inch plywood firewall. 7. 1⁄64-inch plywood control horns. Since “one picture is worth a thousand words” I will let the pictures do most of the talking for the remainder of this article. For those wishing to try something like this on some other model design that they may be thinking about, here are some gener- al ideas and principles for the conversion to R/C of the many existing F/F rubber, CO2, and small glow engine powered models that are currently out there.
MAY 2013
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