Zilch X (oz888)

About this Plan

Zilch X. Control line model for .29 to .32 engines. From Model Airplane News, February 1953.

Quote: "Power, light weight, and a generous wing area are skillfully combined by a famous stunt plane designer in this large size ship. For 29's and 32's, makes pattern cinch. Zilch X, by Jim Saftig.

A few years back, we decided to build a 'static' experimental stunt model along Zilch (oz265) lines that would give us everything we wanted. Our thought at first was to construct a very light model with power to burn, just to check out some ideas. Everything had to be new so an airfoil section was developed, moment arms changed, and a few building short cuts were worked out. Quick and simple building methods were uppermost, as well as a ship with looks and a minimum amount of structure. We wanted to eliminate any extra gimmicks which detract rather than add to a model's looks. Also wanted was a job that would fly, not slowly mush, through any pattern.

Leading and trailing edges were designed for simplicity. The fuselage was made up of 1/16 in sheet balsa (really went overboard here) with the usual bulkheads. The wing had a single spar (3/8 in square spruce) The first ship was built without the subspar. Everything down the line was sanded clean and the ship was lightened wherever possible. Dyed silk throughout the ship held paint weight to a minimum. The fuselage was sprayed with a few light coats of Cub Orange, as was the trim on the wing and tail section. For power on the first 'X', a hopped-up Super Cyclone engine with a packed crankcase, milled head, and a bit of port polishing, was used. When the ship was finished and weighed, we were a bit skeptical and bets were made as to whether the crate would hold together in flight.

The big day arrived, and the test was on. A few simple manuevers were made and then we cut loose. Loops, vertical eights, square loops, and screaming power dives and everything else in the book were made and the job still hung together. The wings practically bent double; we tried to shake them off but they stayed with the ship. Flight after flight was made and the ship took them with no trouble at all. Plenty of top notch fliers tried to snap the wings but none were able.

This job went on the shelf and we were back at the board again. After a bit of more re-designing and adding structure here and there, we decided to try the same size ship with a smaller engine. With the added beef and a Torp 29, we came out with the ship in the plans. This job was not as powerful, but with 60 ft lines instead of the 70's, we had another swell ship. Fast, violent manuevering was a snap as was the AMA pattern. Going a bit further, we passed out plans to novice and expert alike. All of the building and flying results were excellent. Windy weather didn't bother these jobs a bit..."

Note: This model the Zilch X is often mistaken for the Zilch X-pendable (oz2766). The X-pendable was kitted by Berkeley, but the X was not. Folks who haven't built this specific plane often think it is the X-pendable. Thanks to Ed Korzun for clarification on this.

Update 11/7/2023: Replaced this plan with a clearer copy, thanks to theshadow.

Update 11/7/2023: Added complete article, thanks to DPlumpe.

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