Spirit of Chernobyl (oz14342)

 

Spirit of Chernobyl (oz14342) by William Potter 1993 - plan thumbnail

About this Plan

Spirit of Chernobyl. Radio control sport model.

Quote: "Why not combine some space-age composite fibers with some early technology and engineering for light weight and strength?

Spirit of Chernobyl. A Setback of Technology. By William L Potter.

This model owes its life to my weakness for bargains. Among the overflow of stuff lying around my shop were a spool of Kevlar sewing thread I'd bought on sale. and an unused OS FS 20 4-stroke engine I'd picked up cheap. Like many of my great bargains, I didn't have any use in mind for either, but there they were.

One day while pondering my growing accumulation of useless things, I had a brainstorm for the Kevlar thread; use it as bracing wires to make lightweight fuselages ala the World War I stick and wire aircraft construction method. I came up with a technique of sewing the bracing through the structure and anchoring it to toothpicks. This method was described in detail in my article, 'Sewing a Fuselage,' in the July 1993 issue of RCM.

While the concept was old. the material and technique were new and unproven. I decided to build a quick, cheap model to test the Kevlar sewing thread method in actual use. I wanted something big enough to see in the air and big enough that it would be a valid trial of my system. I had a couple sticks of 36 in leading edge stock in my scrap heap, so that would be the wingspan, six feet. I also had the little FS 20 4-stroker,. so that would be the power plant. My brother threw in a spare radio and four extra servos (with the provision he could fly the plane if it worked), so it became a four channel design.

Although the model was intended to be only a testbed, I decided it ought to have a little style just in case it actually worked; should the model survive, I didn't want something downright disgusting sitting, around my shop. A simple boxy-looking design took shape in my mind, a spartan craft reminiscent of the 1920's when many aircraft builders went about their trade unencumbered by thoughts of streamlining, compound curves, and other such foolishness.

After I started building I began having nagging doubts about the model; the plane seemed too large, the engine too small, and the structure too uncertain. A bulky mismatch of modern and obsolete materials thrown together by questionable technology and driven by an unthed, undersized power plant held the potential for a man-made disaster of epic proportions. Hence the name: 'Spirit of Chernobyl'.

But then came the surprise. Despite the dubious engineering and the seemingly too-small power source, the Spirit flew - and flew well! Slow, graceful, and very realistic, with flight characteristics similar to many full-sized lightplanes like Cubs or Champs. The OS 20 had enough oomph to drag the Spirit off a grass runway after a run of about 20 or 30 feet and climb out at a comfortable rate. Once airborne, the Spirit flew willingly at partial throttle.

Although the only testing was done behind the rampaging might of the little FS 20, I imagine that with the more common OS FS 26 Surpass (or similar sized 4-stroke) up front, the performance might border on lively without losing any realism. Although the Spirit was created for the smaller 4-strokes, a .15-.20 2-stroker would probably work well if you don't mind the less realistic exhaust note. Or, if you want to eliminate the exhaust note entirely, you might want to engineer an electric conversion. Be sure to keep watch on your weight and balance when installing different power plants.

The Fuselage Design: The fuselage structure is made of 1/4 sq medium hard balsa sticks braced by Kevlar sewing thread. The forward end is strengthened by some 1/32 birch plywood formers, a few pieces of 1/4 sq spruce, some plywood and balsa gussets, and a 1/8 birch ply fire wall. If 48 in long sticks are not available for the longerons, use 36 in lengths with extra material carefully spliced on using a scarf joint. If you do use spliced longerons, put the splices toward the tail.

The Keviar sewing thread came from Brookstone Hard-to-Find Tools. I haven't seen it in their recent catalogs, so you may have to ask about it. This project requires a thread with a breaking strength of over 15 pounds. If your supply of Kevlar thread breaks at a lesser load, just double the strands used. Also be aware that for many uses, Kevlar thread is supplied waxed or with some other form of protective coating. If you have such a material, be sure to test it to make sure CA glues take readily to your particular Kevlar (see Addendum).

Construction: The construction technique is discussed in detail in my 'Sewing a Fuselage' mentioned earlier. The process in brief: A length of Kevlar thread is passed through a needle and tied to form a long loop. For more strength, add more loops. The fuselage sides are built in a jig holding the longerons and the uprights. The Kevlar thread cross-bracing is 'sewn' in place by passing the needle and thread directly through the balsa longerons (with the aid of pliers). At each station the thread is wrapped around a short length of round toothpick pressed into the balsa; the thread is pulled taut and secured with CA. The result is a light, rigid structure.

Fuselage: To begin the fuselage you will need to build a simple jig out of a piece of plywood or flat pine board and a number of small pine jig blocks. Put the plans on the plywood, cover with glue-resistant plastic, and nail the blocks around the outline, being sure to keep the blocks out of the path of the thread and needle. Also, try to keep the blocks away from the areas to be glued so you don't end up with the fuselage side permanently fastened to the jig..."

Direct submission to Outerzone.

Scan by MarkD, cleanup by Circlip.

Update 26/1/2023: Replaced the article with a clearer copy, thanks to rocketpilot.

Supplementary file notes

Article.

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Spirit of Chernobyl (oz14342) by William Potter 1993 - model pic

Datafile:
  • (oz14342)
    Spirit of Chernobyl
    by William Potter
    from RCMplans (ref:1150)
    August 1993 
    72in span
    IC R/C
    clean :)
    all formers complete :)
    got article :)
  • Submitted: 09/01/2023
    Filesize: 1558KB
    Format: • PDFbitmap
    Credit*: MarkD, Circlip
    Downloads: 448

Spirit of Chernobyl (oz14342) by William Potter 1993 - pic 003.jpg
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Spirit of Chernobyl (oz14342) by William Potter 1993 - pic 004.jpg
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User comments

An internal lighting system must be fitted, with that name this is a glow-in-the-dark type model.
Miguel - 27/01/2023
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  • Plan File Filesize: 1558KB Filename: Spirit_of_Chernobyl_oz14342.pdf
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Notes

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Scaling

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