Doubler II (oz16834)

About this Plan

Doubler II. Radio control sport / pylon racer model. Wingspan 36 in, for .15 engine.

Discontinued kit from SIG.

Quote: "Doubler II. Building and flying instructions. Designed by Brad Shepherd.

The original Sig Doubler (oz15166) was a popular sport flying model for many years. Austin Leftwich modified the kit for pylon racing and became the 1/4 Midget Racing Champion in 1969, 1970 and 1973.

The potential for the model having thus been firmly established by Austin's consistent performance, it has now been completely redesigned. The Doubler II can be built as a racer, using either a side or rear exhaust engine, or used as a fast and maneuverable sport model.

Before beginning construction: To understand all of the construction requirements, read the complete instructions and study the drawings carefully before beginning. A little time spent in looking as the isometrics and photos will make it clear where construction out of descriptive sequence is required or can be done.

The instructions are numbered in a sequence for explanation of techniques. This does not mean that the sequence must be followed exactly, step-by-step. To speed construction it may be desirable, for example, to start building the fuselage or tail while the preliminary parts of the wing are drying. This will work satisfactorily as long as simultaneous construction is not carried past the point where it will interfere with proper completion of some of the interlocked parts.

Cut all long pieces of balsa first, followed by medium lengths, before cutting up any full length strips into short pieces. Remove die-cut pieces from the sheets carefully. If difficulty is encountered, do not force the part from the sheet. Use a modeling knife to cut it free. Leave parts in the sheets until needed in construction.

A jig saw is best for cutting out the printed sheet parts. Cut just outside the lines, leaving all of the line on the part. When fitting into place in the structure or joining with an adjacent part, use the sanding block to bring the edges to an exact fit. If an X-Acto knife is used, don't cut too close to the lines but leave enough margin to true up and finish the edge with a sanding block. It is easier to cut an angle with a knife so more tolerance may be needed for final fitting with a block.

A piece of Celotex-type wallboard makes a handy building board, into which pins can easily be pushed. Lay the building board on a table with a flat and untwisted top. Pins can be pushed through all pieces of balsa in the kit without any lasting harm. The holes will fill during sanding and doping.

The framework may be glued with either Sig-Bond resin type glue or Sig-Ment solvent type cement. In any joint involving plywood or hardwood, Sig-Bond is the best choice. Areas subjected to unusual strain, exposed to fuel or oil, or including metal pieces, should be epoxied with Sig Epoxy Glue or Sig Kwik-Set 5 minute type epoxy.

Wax paper should be used to protect the plan during building when the glue used in epoxy or an alphatic resin glue such as Sig-Bond. If a model cement like Sig-Ment is preferred, use plastic wrap to protect the drawing. This type of glue can dissolve the wax out of wax paper which will inhibit drying.

One aileron or two ailerons? Some Quarter-Midget racing fliers prefer an aileron on the right wing only. This produces a slight drag on the right wing compared with the left and tends to hold the nose up during left pylon racing turns. If this is your preference, complete the left wing with the trailing edge stock, without a hinged aileron. Sport fliers are advised to use both ailerons, as shown on the plans, for balanced control reaction..."

Direct submission to Outerzone.

Quote: "Steve & Mary, here's the plan and instructions for Sig's "Doubler II" by Brad Shepherd to fill in your "Doubler" collection. With its 36 inch span thin symmetrical wing and .15 engine it's intended as a 1/4 Midget racer, but also capable as a fast maneuverable sport model.
The scans were provided by flying buddy Dennis Smith and I edited the plan.
Keep up the good work!
DPlumpe"

Note see also the original Doubler (oz15166) as kitted circa 1968.

Supplementary file notes

Instructions.

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