Tornado (oz14638)

About this Plan

Tornado 1/2A. Free flight power model. Wingspan 48 in.

Planfile includes full build instructions.

Quote: "West Texas might strike most modelers as an ideal place for the classic Free-Flight machines, and one look at the photo backgrounds would tend to confirm such suspicions. The truth of the matter is however that we are restricted here too by ranchers, cattle ranges, sheep, goat ropers and mesquite as severely as anywhere I have tried to fly in the past. Flying is permitted on Saturday and Sunday mornings on the Air Base where I have beeen stationed, and that is the sum extent of it.

As with all Free-Flighters, I strive to design a winning aircraft, and accepting the shortcomings of wind and weather and terrain at hand is all-important to the success of an aircraft. Even if an ideal site is at hand here in Texas, there are other considerations. Wind for one. Prevailing Texas winds make a 3-minute max a practical compromise with the vaguaries of nature. It is about as long a flight as you would care to try to retrieve and a string of such flights in a day, as in a contest, will keep your sagging waistline neatly trimmed.

The Tornado design is a product of such Texas area flying. And it is a design which will function well wherever Free-Flight is flown, for it is a ship tuned to thermals, max flights, wind and limited ranges of land. When the 3-minute max rule was adopted at the Nationals, together with a decrementing of the engine runs in a fly-off situation, a different breed of competition model began to appear on the flying scene. While it caused some heated discussions before being accepted on the local and regional meet level, fliers tended to realize in time that with a shorter chase and less flying time aloft, models were easier to retrieve, time remained available for other events on the card, and with flying sites at a premium, smaller fields which were around could be effectively utilized for contest gatherings.

This difficult breed is modeled after the get high or go home bombs that have been prevalent over the last few years in the hands of the experts. All these have been designed to get as high as possible in the allotted time. Even in their hands, some have and some haven't been successful. Some, such as the Dixielander (oz3603) have proven to be worthy opponents in anyone's hands.

Both of these have the following attributes: built-in simple warps to corkscrew them up, thus utilizing all available power safety, trimmed by incidence to provide the needed turn into the warp, for the desired corkscrew pattern, a thick stab section to provide safety in the climb and a slow, floating glide, plus a rear fin to provide a safe, non-sensitive control under power.

The Tornado is an offspring of my FAI designs, and incorporates all the above mentioned factors. I also changed my trimming techniques to take advantage of the plane's capabilities. I chose to make the airplane as simple as possible, so anyone, kids or grown-ups alike, could easily build this .049, trim it out and win with it. Granted, the size is not as small as some of the expert bombs, but since weight is a decisive factor in how high one can get with regressive engine runs, 6 ounces is an ideal weight for a Tee-Dee .049. Optimum stability also helped in determining the size. Most rear-finned bombs do not utilize down-thrust, instead a long tail moment arm furnishes control under power. This Tornado design utilizes a shorter tail moment arm (much easier to trim) with 6 degrees of downthrust to provide VTO capabilities if desired.

The result of this merger of highly desired factors is a design which reaches its full flying speed almost instantly, sets itself into a controlled vertical spiral climb pattern, and whips off the top into a slow, floating glide without a bobble.

The wing and stab must season prior to testing, so let's begin with them.

RUDDER FIN: The Rudder Fin is assembled from three die-cut pieces, RF-1, RF-2 and RF-3. Test fit together, trim edges if less than perfect as it emerges from the die-cut sheeting and cement together over a flat working surface. Either model aircraft or white glue can be used. A piece of Saran Wrap or waxed paper will prevent it from adhering to the plan drawing. Weight down or lightly pin the pieces in position and allow to dry well before removing from the work surface. Once dry, lightly sand the Rudder-Fin until smooth and round off leading edge and taper down trailing edge portions to airfoil it slightly. It will be installed in the fuselage as that structure progresses.

STABILIZER ASSEMBLY: Select all the materials for the stabilizer, the 3/16 x 1/4 tapered leading edge stock, the 1/2 tapered and notched trailing edge, three 3/32 square spar lengths and 16 stab die-cut ribs. (One will be left over, a spare should one break installing.) The die-cut pieces marked S-3 are the stab tips, set at an inclined angle.

Spread a piece of Saran Wrap over the stab plan and be certain the work surface below the plan is both smooth and flat. It is suggested that you pre-coat the end grain of' the balsa with a thin prime-coat of airplane glue to seal the pores. Otherwise the pores tend to drink up the glue as a soda straw might. A small drop on the trailing edge notches, and on rib ends will be worth your while.

Pin the trailing edge flat to the plan, bracketing with pins, rather than piercing the wood. Ribs S-1 and S-2 are now cemented into the trailing edge notches and gently pinned or weighted down on the forward end. Note the center rib S-1 and tip end ribs are cut to length, but not notched into the trailing edge stock.

The 3/32 square spars along the top airfoil camber are now cemented into position, followed by the leading edge stock. Pin this against the ribs all along the length of the stab. Allow this much of the structure to dry securely before removing from the work surface. The triangular gussets, 1/8 square hook mounts, the lower 3/32 square spar and the S-3 stab tips are best installed after the stab is removed from the bench. Bevel the stab tips and trim the spars as necessary to meet at the angle shown..."

Direct submission to Outerzone.

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