Spirit of Zaic (oz13378)


Spirit of Zaic (oz13378) by Steve Higginson from Aeromodeller 2014 - plan thumbnail

About this Plan

Spirit of Zaic. For free flight or 2 channel radio control. Dual-purpose 36 inch hi-start glider.

Note this plan is a free download from the Aeromodeller site at: http://aero-modeller.com/revised-drawings-for-spirit-of-zaic-aeromodeller-924-novemberdecember-2013/

Quote: "Revision 2. Steve Higginson has redrawn the plans for the Spirit of Zaic (AeroModeller 924 Nov/Dec 2013) having instituted a few minor changes that have proved beneficial from flight testing and regular flying (mostly with regard to towing). For explanatory photographs, please see the original article."

Note this is a revised version of the drawings, later than the printed drawings that appeared in the magazine.

Quote: "The Spirit of Zaic. I believe there are very few aeromodellers out there who have not been influenced in some way by Frank Zaic. Frank and his brother John formed the Junior Aeronautical Supply Company, JASCO as it would become to be known, way back in 1933 as a way to supply the blossoming aeromodelling community in New York City with much sought after building materials.

During the 30s and post-war 40s, Frank and John, with the help of sister Christine would inspire JASCO to produce some of the most iconic glider designs in aeromodelling history. Through kits and Frank’s Junior Aeronautical Yearbook series of publications, the Zaics became the go-to source for quality products and accurate technical information. In fact, to this day, the Junior Aeronautical Yearbook series and other technical books like Glider Design and Circular Airflow are considered to be fountains of technical and reference material.

I have always been drawn to the purity and artistry of Frank and John’s designs. Pod and boom gliders, the beauty of the bird-like Wolf wing and those beautifully drawn plans with isometric views, have always spoken to me. As tribute to the Zaics and their legacy, The Spirit of Zaic is a compilation of design, construction, theory and science drawn from many Zaic sources to produce a compact 36-inch hi-start glider with the ability to be flown as a free flight or micro 2-channel radio assisted model.

My personal preference is for F/F, but the design was conceived with today’s R/C technology in mind and is easily adapted. Also, you will find the use of carbon-fibre and design features borrowed R/C sailplanes to affect the tail plane/DT. So, with that being said, let’s get started.

CONSTRUCTION: NOTE: The Spirit is intended as a project for mid to advanced level builders. Although the methods and materials for the build are standard and readily available, some phases of construction are complex and involved.

FUSELAGE: The fuselage is constructed very much in the Zaic tradition, with the exception of the boom, which is now of box construction utilizing square carbon-fibre pultrusion in place of the solid hardwood material so prevalent in many Zaic designs. The starting point is with the boom sides. I used 1/32 plywood on the prototype, but in hindsight, hard 1/32 balsa sheet would work fine and save a couple of grams of weight in the process. You may also notice (if you are familiar with high-performance R/C sailplanes) that the Spirit utilizes what is called a 'flying tail plane' for pitch control or for the D/T mechanism.

The sides are mirror images of each other with the left side having a small service access panel under the tail plane. Its reason will become clear as we progress. Also, the holes for the D/T and auto rudder cables are specific for right and left sides. For the R/C version, the 2 holes on the left side just behind the wing T.E. are not necessary. Tape the two sides together and drill a 1/8 dia hole for the tail plane pivot shaft bushing. The pivot-bushing hole must be EXACTLY the same position on both sides or the T/P will not line up correctly. Drill a series of 5/64 holes to form the T/P sweep arc equidistance from the sweep shaft centre line (for R/C). For the F/F version, drill only half the arc below the centre line.

Cut two lengths of 1/8 sq carbon-fibre pultrusion to the lengths shown on the plan. You will notice that the pultrusion has a hole running down the centre. This hole serves as the tube for the D/T and A/R cables to run through. For the R/C version, these are the pushrod tubes. Cement the 2 carbon tubes to the right boom side with epoxy or CA.

Cut the balsa parts for the tail plane riser making sure to make the 1/8 gap in the L.E upright for the 2-56 decalage adjustment screw if you choose to make the F/F version. The decalage adjustment screw is not necessary for the R/C version. For the F/F version a music wire loop must be fashioned and epoxied to the 1/2 x 1/8 tail post block as an anchor for the D/T tension spring. CA the tail plane riser parts into place making sure not to get CA into the carbon tube centre holes.

For the F/F version it is a good idea to fit the bell crank, carbon pivot shaft bushing and the tension spring so you can make any adjustments before mating the left side to the boom. Not to worry, the service access panel will allow you to do this afterward, but it is a bit easier not having to work out your connections using needle nose pliers..."

Supplementary file notes



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User comments

This out-Birds-of-Time the Bird Of Time itself (oz2093) :-)
Ok, ok, this wing plan shape was pretty common (and pretty pretty too!), the BoT may have been inspired by something from the Thermic series. Do a search for that name here in the OZ and you'll see what I mean.
Miguel - 18/10/2021
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