Lady's Fancy (oz5898)

About this Plan

Ladys Fancy. RC biplane pattern plane, for .60 power.

Quote: "If you're looking for a new design in a stunt pattern aircraft, you can stop right here. This sleek bipe could very well be the answer.

During the summer of 1978 I overheard a few pattern pilots commenting that there does not seem to be a biplane that really flies the contest pattern to the same standards as the better pattern ships. Well, I got my head in gear (or out, as the case may be) and designed a biplane which in my opinion fits the bill as a first class pattern ship. I call it Lady's Fancy, a name I took from an old Bluegrass Fiddle Waltz. I feel the biplane performs the pattern maneuvers with the smoothness of a waltz. How's that for working out why I chose the name? Well, let's get to the airplane design itself.

My first consideration was that if I was going to use two wings and achieve the pattern ship forces and moments, I would have to pay very close attention to drag. I decided to go with ample wing area (820 square inches) since I would suffer some wing lift and drag interference penalties because of the two wings. Also, smooth lines were required and blending of the fuselage and wings became a desired objective. Although somewhat fat looking at first, I settled on a full depth fuselage between the two wings. I am pleased how this turned out. A friend suggested large windows to reduce the fat look.

The wings are a high aspect ratio design to produce good lift to drag. The ailerons are a conventional 40% chord half-span design. I decided on large ailerons to reduce drag due to aileron inputs and because I installed ailerons on the top wing only. The 40% chord aileron turned out to be more than required. The plans call for a 30% chord one-half span design. This should be very adequate.

The horizontal tail is an all-movable design I have been using on other pattern ships. I like smooth control action that results from the flying stabilizer and I think it adds interest to the model. The horizontal tail is balanced about the hinge line to eliminate flutter and hinged about the mean geometric chord to avoid hinge moments. The combination of hinge point and balance about the hinge eliminates forces feeding back to the elevator servo. The horizontal tail halves are connected by a 5/16 diameter aluminum tube. This arrangement has worked completely satisfactorily for me for years so I do not hesitate to recommend it.

The engine I am using is an O.S. Max.60 with tuned pipe. I do not run a pump or fuel pressure. I use a double clunk tank design I have been using for years with complete satisfaction. The double clunk tank arrangement is an idea I started using before the good carburetors came on the market. However, I have found that it provides added stability to the fuel draw system, even with the new carburetors.

Here's how I use the tank. I close off the line going to the top of the tank (overflow line) once the tank is full. Vent air is drawn into the tank through the short clunk line. This causes the tank to operate at a slightly negative pressure which is equal to the draw pressure required to raise the fuel to the tank centerline. if the carburetor barrel and centerline of the tank are at the same level, and the clunk vent line comes out at the middle of the tank, a constant fuel pressure in the feed tine is provided whether inverted, on the side or upright, full or empty tank.

I know you may be saying: What? - and I don't blame you. However, if you are having idle and lean-out problems at the end of your flights, give this tank arrangement a try and I believe you will be happy with the results. I think you will also find that the engine runs better during vertical maneuvers. I take pride in taxiing back to the pits after each flight and having to stop the engine by hand. I must say here that I was reluctant to write about my tank arrangement because it sounds too good to be true. Well, I did it, so there! Send cards and letters, and I will send you the theory and test results.

Now here is the story on my own design retractable landing gear system. About six years ago I participated in a discussion about using engine crankcase pressure for powering the retract system. The result of this discussion was that a small retract system using only crankcase pressure was not practical because of the size of the piston required to raise the gear and the problem of gear droop during maneuvers and when the engine was at low power settings. Well, to me this was the same as waving a red flag in the face of a bull. I decided to charge the problem.

After about a year of design and testing, I came up with, as you can see by the plans and pictures, a mechanism that is certainly small enough for any 60 size pattern ship. I ran tests on several engines using a one-way check valve and found I could obtain 6 pounds of pressure from the crankcase at full engine power. With the retract mechanism design, 6 pounds pressure was more than enough to raise the gear. The retract mechanism provides up-lock for the gear which eliminates gear droop during maneuvers. At low power settings, the gear remains locked for an extended period of time..."

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