Lightning Bug (oz9076)

About this Plan

Lightning Bug. Electric RC sport model. Bill Winter scales up his long-ago favourite for the currently popular small electric 035 or 075 motors.

Quote: "The original Lightning Bug (oz2168) was proven years ago, circa 1960, as the then World's Smallest R/C with one of the first prototype Cox .010 gas engines. With a span of 27in and an area of 118 inches this rudder-only gymnast was a thrill to stunt. It was featured in Model Airplane News with plans by the late Lee Renaud, then kitted by JETCO with plans by the late Paul DelGotta.

My electric version is scaled up by 50% to a span of 40 plus inches and an area about 10% greater than the 275 sq in which is commonly acccepted as minimum for fun flying with a direct drive 075. The excellent power to weight ratio is evident when you consider that 6-foot and 2-meter sailplanes with similar motors comprise a large segment of the electric power market. In a plane like the Bug, grossing 27-28 ounces, climb and roll rates are beyond the raw beginning pilot. Incidentally, a key to its performance is the ability of this type of 075 motor to turn an 8x4 at reasonable current drains, whereas a 7x4 is generally considered standard.

Note that the plan shows two different noses depending on your choice of a motor. The 035 version is slightly longer and the nose comes more to a point. The 075 version has the nose cut back to take a bigger plywood mounting plate. To keep the specified CG location, the smaller motor lies farther forward.

With a Hyperthrust ferrite 075 (or similar) motor, on a 6-cell battery pack of 800 or 900 inAh, a direct drive Master Airscrew 8-4, and approximately 300 square inches of wing area and 28 ounces gross, the Lightning Bug is sized for lively performance while main-taining a reasonable glide. The Bug has maximum stability, with the quickness of response required for simple aerobatics.

With the optional Hi-Line (or similar Fer-rite) 035, and a 4 or 5-cell battery pack, at a 22 ounce gross, the Bug has a leisurely climb, a longer, nicer, cruise and glides better. With this set-up the model is quite docile. In terms of typical gas models it is a viable high-and low-powered model, but it would be a rare day indeed if such a gas model was practical. We can do this because the motor and battery weights go down proportionally. With the 075 the Bug weighs 28 ounces, and only 22 on the 035 with the five cells. If you have never flown an R/C job before, use the 035 option (you will never be bored with the 075 version!). With the 035 and four cells, use a 6x4 prop. If you go to five cells with the 035, use a 7x4.

There are some 'musts' for successful operation of this model. Power performance would fall off and the glide would be rather fast, with a greater sink rate if normal airborne equipment was used (you don't want more sink on any 075 job of this size). You must use the smallest and lightest servos possible, a miniature receiver, and a 250 mAh receiver battery, max, unless you have a BEC set-up such as the Futaba Attack system (used in my Bug) which eliminates the need for a receiver battery pack - an important plus. I also saved weight to get down to that 27-28 ounce gross by using the integrated speed controller, also part of the Attack sys-tem (this system shuts off the motor auto-matically when voltage drops to a certain level).

After the automatic motor power shutdown in the Attack system the time left to safely operate the radio is much more than the time to glide down from any conceivable altitude, but the point at which I normally begin the landing approach is when the definite slow-down of the motor begins. This will allow you enough power for an extended glide or one go-round. Don't get caught too far out and too low at shut-down. On one flight I milked the go-round too much and landed short and hard enough to bend a shaft. Beyond that, use lightweight wheels, lightweight iron-on covering, select wood carefully, and use instant glues (thin and slow) such as Hot Stuff.

You could get somewhat extended flights with solid performance, even in winds, by cruising at half throttle or more. The 035 combo yields a motor run of 5 to 6 minutes or, when the throttle is used, up to 8 to 10 minutes. Add glide time to that and you have quite credible flights, Do study the special flight instructions at the end..."

Lightning Bug, Flying Models, June 1991.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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