Bobcat (oz15364)

 

Bobcat (oz15364) by Karl Spielmaker 1951 - plan thumbnail

About this Plan

Bobcat. Free flight power model. Wingspan 46 in, for Class A engines.

Quote: "An exceptionally stable Ohlsson-powered free flight with nice climb and good recovery. Bobcat, by Karl Spielmaker.

HOW many times have you stayed up burning the midnight oil to put the finishing touches on that new super contest job for tomorrow's meet, only to find when you got to the field the next morning that windy weather made flying out of the question? Too many of the present clay popular contest ships are only 'fair weather friends' ideal for dead calm clays but entirely unsuitable for competition in anything stronger than a slight breeze.

The high mortality rate of floaters at many contests gives adequate testimony to the fact that too often something is missing in the design of high performance gassies. That something is stability - actually the prime requisite for a consistent contest winner.

The Bobcat was designed with this fact in mind. Incorporating the spiral stability theories of CH Grant, the Bobcat has its center of lateral area and center of gravity located on a line parallel to and just slightly higher than the thrust line. This force set-up results in a fast. smooth spiral climb with the wing, and not the prop providing the lift. The recovery at the end of the power run is an easy roll into a flat glide, and no altitude is lost in wasteful stalls and long recoveries.

During the past three years the author and some of his model building friends have built Bobcats of sizes varying from a small CO2 midget to a 7 foot class D giant. Slight variations in design have finally produced the latest version presented here. This size has been the most consistent winner with a span of 46 in and an area of 320 sq in weighing in at approximately 22 oz and powered by engines of 19 to 23 cu in displacement. Besides placing with satisfying regularity in contests in western Michigan. the Bobcat has faced up well to strong competition, taking first place open and second place junior in the 1949 Michigan State Meet.

The simple and yet rugged construction of the Bobcat makes it an ideal free flight gassie for the beginner, and its consistently high performance will thrill the old time expert. If you are looking for a contest job that will keep you up in the running in any kind of flying weather, the Bobcat is your baby.

Fuselage: Before beginning any construction, scale up the plans or have them photostated to full size.

The fuselage sides are made from two pieces of hard balsa 1/16 x 4 x 36. If the 4 inch widths are not available, join two pieces of 2 in width together, making sure that both pieces are of the same hardness and grain. Carefully trace the fuselage outlines on the two sheets and cut out. Mark the positions of the stiffeners on the fuselage sides and cement them in place.

When the stiffeners have dried, locate and secure the 1/2 x 3/8 hardwood motor mounts. Cement a scrap of 1/8 sheet between the fuselage sides at the tail and trim off the excess..."

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Bobcat (oz15364) by Karl Spielmaker 1951 - model pic

Datafile:
  • (oz15364)
    Bobcat
    by Karl Spielmaker
    from Model Airplane News
    January 1951 
    46in span
    IC F/F Pylon
    clean :)
    all formers complete :)
    got article :)
  • Submitted: 15/05/2024
    Filesize: 350KB
    Format: • PDFbitmap
    Credit*: Pilgrim
    Downloads: 203

Bobcat (oz15364) by Karl Spielmaker 1951 - pic 003.jpg
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Bobcat (oz15364) by Karl Spielmaker 1951 - pic 004.jpg
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Notes

* 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.

Scaling

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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