Lucky Lindy III (oz8854)

About this Plan

Lucky Lindy III. Fee flight power competition model.

Quote: "World Champion Larry Conover Tells You How To Win With Lucky Lindy III.

Lucky Lindy, a consistent, stable, high performance model has won a place on the US Power Team four consecutive times. Proxy flown to a joint first place in the 1956 World Championships by Silvio Lardranchi. Again tied for first place in the 1960 World Championships in a gruelling twelve round flyoff, repeatedly making over four minutes in normal air, on fifteen seconds. This design has proven itself adaptable to all conditions and rules, including unlimited events.

The closing of round five at Cranfield 1960, marked the beginning of a flyoff un-paralleled in the history of World Cham-pionships. The Mk-III Lindy was in that match and fortunately remained among the final five who were declared "joint champions". A total of seventeen perfect rounds, per man, in rain and sun and cloud, uncertain English weather.

It takes more than luck to stay alive in this kind of competition. The airplane, whether it be a Zipper, a Zeke, or a home-design, must be stable, consistent and cap-able of very high performance. You must have the best engine available. Fuel sys-tem has to be foolproof. Engine shutoff must be dead-on 9.8 seconds. Dethermal-izing can and does determine the "luck" of a contest.

Many little things contribute to success in competition. The skid that takes the beating of endless runaway DT's, and saves cracked wing joints. The special keying arrangement that prevents shifting of wing and tail, but allows for a bad tree landing. The stop on the timer that does away with haphazard visual settings under flyoff pressures. Well, those and other things, you learn from flying in many contests. You probably know them already. So how about design features? Here's how we see them:

1. A 10% flat bottomed, low drag, turbulent flow section that goes up fast, and hangs into the lightest lift. It rides safely thru wind and ground turbulence.
2. A proven method of control using a combination of three fins. It does the work of an auto-rudder without the dangers or complications associated with that gadget.
3. Wing and tail are Warren Truss structures with full depth spars. They resist warping and heavy winds. Wing area has been reduced to permit a near minimum all-up weight.
4. Double DT is the secret to keeping your models.

As you progress to the high performance phase of your world championship preparations, loss of a model can write disaster. Good engines and models are hard to come by. The double-DT permits pinpoint landings through use of the Tatone DT timer. This fine clockwork is delicate, and susceptible to dirt stoppage. Perhaps two flights per hundred. When this happens, and it's usually a hot thermal flight, the old fuse method is ready insurance to cover a calculated risk. The combination of these two are an important consistency factor.

Another feature of the Lindy DT system is the accordian flap that comes up with the tail pop. When the heavy-weight rules for FAI were introduced it became necessary to lower the angle of tailplane pop-up, to slow the rate of descent If you fly only in soft pasture country you might get by. However, when required to DT onto hard surfaced runways, many wing joints and fuselages creaked and cracked. Now as you decrease the tail-plane angle, the model will spin. Tail spin. This is dangerous. The cure is to add lateral area at the rear to damp out the spinning. Any light flexible material that is wind proof can be used. A piece of thin polyethylene will do. It is taped securely to the inside of the fuselage and the tail platform - a bit less securely to the bottom of the stab, for easy take-apart. Black Scotch electrical tape is best for this.

5. Pressure: It took a long time for the regenerative pressure system to reach acceptance in free flight. Control line modelers have used it for years. However, they do not have the cut-off problem that was encountered by the high climbers. Ordinary shutoff systems failed to do the whole job. The main fuel supply would be cut off, but alternate low and high pressure in the crank-case drew fuel back into the motor through the pressure tap. The result was a two or three second run down with no power. I found one answer to this problem through a lot of hard test flying. You must prevent the pressure input line to the tank from drawing fuel at any time. The easy way to do this when your stand-ard tank is buried in fuselage: Meas-Ure the amount of fuel you put in the tank, and never fill past a level that will contact the pressure line. I would fill the tank. Make one complete flight, with over-burping. Then the next flight was dead-on engine run. Forty squirts from the pump each time would maintain the fuel level. This was a makeshift arrangement, but it worked. In the meantime some smarter guys came up with a good answer, as shown on the plans..."

Direct submission to Outerzone.

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