Tea Kettle (oz12648)

About this Plan

Tea Kettle. Free flight sport model, for CO2 power. Twin-boom pusher layout.

Quote: "Care to investigate CO2? Here's a little out-of-the-rut design that affords exellent protection for that little jewel of a Brown engine while you're getting used to it. Tea Kettle, by Dan Walton.

A long time before his awesome XB-35 and YB-49 ever flew, Mr John K Northrop was experimenting with flying wings of a much smaller sort (The N1M and the N9M are two quite successful examples of these). But even before these fabulous machines ever flew, there was one more wing.

In 1929, Mr Northrop had designed yet another prototype flying wing. This machine employed many of the advanced traits of its later brothers, such as the motor and payload contained within or faired into the envelope of the wing itself. Other features in common were thick symmetrical airfoils, shaft driven propellers, and a gently swept wing with taper. However, this particular plane also had a tail on two long thin booms. This was done as a precautionary measure so as not to unnecessarily risk the valuable prototype. At this point in history, little was known of the performance habits of the tailless type of aircraft, let alone a true flying wing.

It is interesting to note that Mr Northrop himself defined an aircraft of the all wing or flying wing type as: 'A type of aeroplane in which all of the functions of a satisfactory flying machine are disposed and accomodated within the outline of the aerofoil itself'. John K Northrop, 'Development of All Wing Aircraft,' Journal of the Royal Aeronautical Society (1947) pp. 276.) This ideal was most closely realized in the XB-35 and YB-49 designs.

In designing the Tea Kettle, the 1929 prototype was used as a base, and was modified to suit the Brown Jr CO2 engine. Since the only thing to go by were a couple of pictures of the 1929 prototype, most of the lines and dimensions were laid out by the eyeball method. Having done this, the next step was to start modifying the plane to a sport-trainer configuration. An aircraft with no center pod as the pictures showed would have been difficult to correctly balance and trim, so a pod was added.

The other advantage in doing this was that it permitted the almost vertical position of the tank, without its hanging out in the open. Mr Brown includes a warning in the instructions about tank positions which will cause flooding, and the inevitable self-destruction of the engine as it chews away on dry ice. The tank position on the plans seems to be best and has never caused any trouble.

To make the construction of the wings easier and the model more efficient, the symmetrical aerofoil on the 1929 prototype was changed to a flat bottomed type, since the former does require a great deal of jigging in the construction stage. The final modifications were the addition of some more dihedral for greater stability, and the elimination of the landing gear, Unlike most sport planes, the Tea Kettle has no wheels and therefore lands on its central skid much like some of the earlier gliders. This assembly is quite simple, strong, and has proven itself well suited for the job. It also makes for a lighter model.

Now comes the patient scrounging for the .proper engine accessories and wood. First, the propeller. The Williams Brothers prop which comes with the engine is too big for this model. Instead, remove the prop for future use, trundle down to the Hobby Shop and buy one of the smaller Comet brand kits, 14 inch wing span or under, particularly the larger Struct-O-Speed line. They feature a nifty black plastic propeller which is 3-1/4 inches in diameter. The shaft hole will have to be bored out to a larger diameter in order to fit the engine, but this is no great task.

The next item is wood selection. Cost will depend upon the size and content of your scrap box. The original Tea Kettle was built entirely from scraps. Weight is the most critical factor, so except for the LE, main spar, and the booms (which are of the stiffest balsa possible), go light. The original weighed about three quarters of an ounce trimmed and flying. Now, the engine mounting screws. The radial mounting holes on the engine..."

Direct submission to Outerzone.

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