Whirlwind (oz7498)

About this Plan

Whirlwind. Powered motorglider, gullwing design for .049 engines.

Quote: "This beautiful towliner may be flown as a glider or as a free-flight gassie - no matter which way you fly if you're in for sport galore. Look over the simplified plans and start constructing it today! Whirlwind, by Don McGovern.

In our particular case, we were in a dither trying to find the most practical way of building a 1/2A-powered towliner. If you think this is a weird design, consider your self fortunate, for we might've installed the power-plant over the wing in a nacelle, pusher no less.

However, to cut a long story short, the conventional tandem mounting was chosen, to simplify the lines, eliminate the need for a left-hand pitch prop, and at the same time, keep the center of gravity low.

Too many ships in our estimation look alike, and we felt that a combination gas-powered and towliner model was the per-fect medium for experimentation. With this in mind, a polyhedral gull wing was incorporated in our design, for its bird-like appearance and its beauty in the air.

Plenty of reserve strength was built into the wing, in spite of its very high aspect ratio. Four spars, along with gussets and planking, permit high-speed catapult launches with safety, as well as more than the usual number of bruises encountered on the field.

Thin-tail booms are notoriously weak, but not this one. Its hollow laminated construction makes it virtually unbreakable. To date we've never seen one built in this fashion snap under any conditions. As an additional safeguard, a butterfly stabilizer was chosen, eliminating any twisting action on the tail boom when landing. Stabilizers of this type are never in direct contact with the ground, due to the severe dihedral.

All in all, it's a sturdy ship, even though its slim lines and high aspect ratio may raise a questioning eyebrow here and there.

One word on rules before we go any further. The model as presented here may be flown as a Class D towline, with the engine used for weight only of course. The ship meets the weight rule, L2/200 cross-section requirement, but may not of course be flown in a contest via catapult or hi-start (shock-cord) launching since it does not meet rules requirements.

As a gas job, it doesn't meet the AMA contest rules on at least two points. In the first place, there is no three-point suspension with the belly wheel and that's the second point also. A belly wheel is not a landing gear, hence the model is not able to ROG. Of course a one-wheel gear and skids may be employed if you so desire, but it's not worth the effort. In the first place, the 52 in span and 6-1/2 ounce weight precludes its use as a top-notch contest job, which can climb out of sight in a few seconds. This is a relatively low-powered sport sailplane, easy to build and fun to fly.

The plans themselves eliminate the need to delve too deeply into the finer points of construction here, for all of them are full-size, and the sketches, three-views and exploded fuselage structure should cover the majority of questions which may arise in the minds of even the rankest beginners in the sport. Covering problems, warps, accessories and flying instructions also are illustrated.

WING: We suggest you start construction with the wing. The Bill of Materials lists the required material. You will note that the gull wing panel has been superimposed over the center section panel, so be sure your center section panel measures 10-1/2 in and not 4-1/2 in. We have taken this one liberty in order that we might cover every detail of construction, adjusting and flying in the least possible space..."

Quote: "Steve & Mary - I was reviewing old 'Flying Models' issues and ran across this interesting motorglider by Don McGovern, with its polyhedral gull wing and V-tail. Reminds me of the Turkey Vultures that circle over our flying field. If I build this, I'd likely use electric power, enlarge it a bit and make it dark to blend in with our feathered friends. I'm attaching the plan, the article, and both combined for your consideration."

Supplementary file notes

Article.

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