Briegleb BG-12 (oz12637)

About this Plan

Briegleb BG-12. Radio control scale model glider. wingspan 100 in, wing area 618 sq in.

Quote: "Following the simple basic structure of its full size counterpart, this 100 ft scale model sailplane doesn't have to compromise performance for appearance or vice-versa. Briegleb BG-12, by Chris Christen.

The BG-12, a single-seat high-performance sailplane, is the twelfth in a series of famous designs by William G 'Gus' Briegleb. Briegleb, one of the Grand Gentlemen of Soaring, headquar-ters his Sailplane Corporation of America on El Mirage Field, near Adelanto, on the desert North of the LA magalopolis, California.

The BG-12 first took wind over its wings in 1956, and 17 years after that prototype flight, the design is still popular with sportsmen pilots and offers competitive performance as well as 1973-sleek appearance. The all plywood construction was designed especially for the home-builder, and is quite similar to model airplane practice.

The design specifications claim an L/D max of 34 at 56 mph and a minimum sink rate of 2.25 fps at 47 mph. In comparison, the latest Schweizer, the 1-34, is quoted at an L/D of 34 at 55 mph, and a minimum sink of 2.1 fps at 47 mph. Little wonder that more than 200 kits for the BG-12 have been sold, and that many are still active throughout the world. It is quite a basement project.

Briegleb's BG-12 has logged an enviable record for any single design, and especially for an amateur built configuration, having established records for distance, duration and altitude at various times in various countries. But perhaps the most important records are those of safety and longevity. Almost every issue of Soaring - SSA's magazine - lists BG-12's in the 'For Sale' columns at prices to near $4,000.

The original BG-12A utilized a three-piece wing. This was later revised in the -12B and subsequent versions to a two-piece with conventional center joining arrangement. Most BG-12's were and are assigned to Open Class competition with wing spans 9 1/2 inches greater than the maximum 15 meters allowed in Standard Class. Also, all but one BG-12 incorporated center section wing flaps for glide path control, which is a feature not allowed in Standard Class.

The single Standard Class BG-12 was a -12C modified to 15 meter span, 49 feet 2-1/2 inches, with dive brakes (spoilers) and no flaps. These changes made it legal under FAI/OSTIV Standard Class requirements.

Gus Briegleb's 'Briegleb Glider design Number 12' is an excellent modeling subject for all-around sport flying or for a serious scale project. It's no floater, but its light weight and clean lines give performance beyond what might be expected. Penetration is quite good, and if there's any thermal action worth working, it'll go up.

Exact scale outlines are noted on the drawings for the scale enthusiast, and many full size machines are still around and available for documentation purposes. The BG-12 is unique, literally a modern classic.

CONSTRUCTION: WING: Begin construction of the wing by cutting all necessary ribs from straight grain medium weight 1/16 balsa. Make 6 Number One ribs from 1/16 plywood and 2 Number One ribs from 3/32 plywood. Drill all plywood ribs for wing wires. Make trailing edge stock by planing and sanding 1/4 x 3/4 balsa sheet stock - leave trailing edge about 1/16 thick.

Assemble the six 1/16 plywood ribs on two full length brass tubes and pin over wing plan at first six rib stations. Be sure everything is square - epoxy tubes to ribs. When set, remove from plan and cut tubes flush with two No. 1 ribs in center. You now have a perfectly aligned center section.

Build wing and fuselage on a flat surface such as a second-hand two foot wide door - these are inexpensive and very solid. Pin a 48 inch sheet of 1/16 balsa over plan - be sure to use wax paper or Saran Wrap. Add spruce spar to rear edge of sheeting and while this is drying, fit lower center sheeting and glue. If 48 inch wood is not available, shorter sheeting with splices may be used. Be sure to keep all splices near tip and not overlapping..."

Direct submission to Outerzone.

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