SW-107 (oz10021)


SW-107 (oz10021) by Harley Michaelis 1981 - plan thumbnail

About this Plan

SW-107. Unlimited or Open Sailplane. Wing area 620 sq in. For 4 channels.

Quote: "SW-107. A mixture of new and old ideas has produced a mid-wing sailplane with excellent performance for multiple-task competition or fun-flying. By Harley Michaelis.

One of the nicest things about sailplane design is that for most of us, we never arrive. There is always something yet to try - new size, a different configuration, an innovative control linkage, an interesting airfoil, some construction technique, or some adhesive, tool, fitting, material or radio component - the possibilities never end!

The SW-107 includes a mix of new ideas and good things used before. Let's walk around it. Of special interest is the control system. It has genuine tip ailerons that operate differentially, coupled with rudder. This permits a coordinated turn without skid or yaw. Lightweight nylon coated cables operate these controls from two small servos set up in a unique manner in the fuselage. Spoilers operate a pitch compensator, avoiding unwanted pitch changes when thrown. In precision events, altitude loss is controlled with spoilers while con-stant speed is maintained. With the ailerons the nose stays right on track, rather than bobbing around as with rudder control, a luxury previously found only in much larger, more costly and more com-plex ships.

In appearance, it differs being a mid-wing, having both tapered and swept wing and tail surfaces, along with a very racy profile. The result is a distinct configuration that is different and eye-catching. Since wing sweep has a dihedral effect, along with ailerons, a much lower than usual dihedral is used which looks good. The stock fiberglass fuselage is beautifully engineered and superbly custom-molded. It is very light at the rear, reinforced up front where needed, and made of a resilient resin. Shoulders are perfectly aligned to facilitate true alignment of panels to each other, and are angled to fit flush to the roots. The fuselage, while hav-ing a semi-scale look, is still slim and sleek and sized to permit a firm grip at launch without danger of collapse as the tension builds up. The hatch is fiberglass, with no base, and just squeezes on and off.

The opening is long and provides easy access to the innards. A skid is molded in to protect the rudder bottom and the fin is shaped to protect the top. The 10% thick airfoil is inherently stable, allows high speeds, and has excellent stall charac-teristics. The tip used eliminates wash-out, so panels can be built flat and in high-speed runs the outer portions won't twist and bend downward as may be exper-ienced with wash-out. No nuts, bolts, dowels, rubber bands, switch, canopy hold-down, or receiver antenna mar the clean exterior. The new Air-Flow hinge allows fin, rudder and ailerons to be of very soft balsa. The stab is also light but when covered is firm, and with the rigid support used it doesn't flutter. The wing support uses lightweight spring steel blades that slip into a laminated center piece with dihedral built in. Ribs are simply and ac-curately made from a ply root cap, so no patterns are needed. Vertical webbing is sandwiched between spruce spars to make a sturdy 'I' beam, and a ply brace about a foot long lies against this to further in-crease strength and rigidity in this critical area. With an otherwise sturdy set of panels, the thermal can be safely escaped by a terminal dive!

With a proper choice of balsa and the current midget type servos, the all-up weight can be about 34 oz for a 7.8 az wing loading. The nose is shaped so a 225 or 450 mil cube-shaped battery can be placed well forward. With the light tail end, the ship will balance out without lead..."

SW-107, MAN, May 1981.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.


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  • (oz10021)
    by Harley Michaelis
    from Model Airplane News
    May 1981 
    107in span
    Glider R/C
    clean :)
    all formers complete :)
    got article :)
  • Submitted: 21/04/2018
    Filesize: 1106KB
    Format: • PDFbitmap
    Credit*: Circlip, RFJ
    Downloads: 989

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