Simitar 540 (oz10196)

About this Plan

Simitar 540. Sport pattern flying wing design. Wingspan 50 inches, for .40 power.

Quote: "A 50 inch .40 Powered Flying Wing That Can Tear up the Sky at Full Power, yet When Throttled Back Becomes a Very Gentle Flying Aircraft. Simitar 540, by Bill Evans

When work began on a flying wing glider design in 1974, which ultimately resulted in the Saracen (oz7981), the idea of a 50 in span .40 powered four channel flying wing had not yet entered my thoughts. The Simitar 540 is a result of an evolutionary process which included following the Saracen with the 1/2A Simitar (oz10187) followed by the Simitar XV (MA Dec. 1976) which in turn was followed by the Simitar 503, a four channel predecessor to the Simitar 540.

After completing the first 503 powered by a Super Tigre .23, it flew in the 1976 Tournament of Champions in Las Vegas as a part of the in-between rounds, demonstration flying. The second 503 was powered by a K&B front rotor .40. Taking the 503 lines we began to design a fiberglass fuselage that would incorporate the 503 design plus a larger canopy, simulated air intakes, a jet-like exhaust and removable cowl.

Patiently we waited for the wooden plug to be carved, the molds to be crafted and, finally, the first 540 fuselage came out of the mold. It was only a matter of days before the completed ship took form around the new fuselage. I'll be the first to admit that my knees were weak as it lifted into the air. With a K & B .40 at full power, it flies at 90 mph plus; throttled back at 40 mph its a piece of cake. Response to control commands is instant. It performs tight loops, turns very tight, rolls instantly, inverts very well, will four point roll as well as vertical roll out of sight. Landing can easily be stretched; I particularly like to pull an inside loop just before touch-down on a dead stick landing.

One morning, late in March, I test flew five new Simitar 540's each one performed without a hitch, and handed the transmitter over to the owners to land. Though shown with a four channel set-up, the 540 can be flown two channel (to operate the elevons which are a mixture of elevators and ailerons).

For a real hot set-up. we have flown a few 540's with the K & B rear rotor and without landing gear. These are pushing speeds close to 200 mph.

As you may wonder, the designation 540 comes from the combination of its 50 in span and engine size .40 - therefore '540'. Which, incidentally, is also the wing area. Using four channels, two to operate the elevons, one for engine throttle and a fourth for the steerable nose wheel, the weight will come out between 4-1/4 to 4-3/4 pounds. So the wing loading is about 20 ounces per square foot. The one special note about building has to do with the landing gear placement. Set the gear in place per the plans and make sure that the wing sets with about 3/16" of positive with relation to the ground. This is to make for easy take-offs.

My best advice is to build the 540 per plans. If you have a modification in mind. do it after you fly it as designed. Soaring Research, 19216 Calvert St.. Reseda, California 91335, can supply Simitar 540 wing cores for $10.00; 1/64" ply wing sheeting for $8.00; and the epoxy fiberglass fuselage for 535.00. California residents add 6% sales tax.

Simitar 540 construction is very quick and has been kept simple. The use of a sheeted foam core gives tremendous strength. In a way, a sheeted foam wing is much like a piece of case hardened steel - that is, the outside skin provides a fairly hard protective shield for the more soft inner core which serves as a shock absorber.

The fuselage, built on a flat surface, utilizes the technique of box construction with triangular stock in the corners which produces rounded and streamline results. Glue and pin the 1/4 in balsa leading and trailing edges to wing cores; make sure to keep the leading and trailing edges free of curves or bends; set these aside to dry. (A white glue is very satisfactory for this purpose.)

Pin fuselage top down on flat surface. Glue and pin left and right sides to fuselage top. Glue and pin 1/2 in balsa triangle stock in place. (Push pins in through from the outside of the fuselage through the triangle stock this will help remove pins later.) Glue and pin in rear fuselage tail blocks. Glue and pin bottom fuselage corner squares in place..."

Supplementary file notes

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