Sabre Hawk IV (oz5959)

About this Plan

Sabre Hawk IV. Pattern plane. 70in span, 680 sq in area. For .60 power and 5 channel RC. Model # pl-126. Designed by Ed Izzo. Featured in RCM 9-64.

Quote: "The Sabre Hawk was first designed for the flying season of 1960 - the four years spent in its development being well rewarded in that this airplane has on more major RC contests in the East during the past two years than any other single design. The Sabre Hawk's contest achievements illustrates its inherent consistent performance.

Prior to this design, I had flown an Astro Hog (oz4756) which performed well, but was large and heavy. With the design of the Sabre Hawk I, I attempted to build a smaller and lighter airplane. It's configuration has remained intact except for changes in thc airfoil and moment arms. Although I have flown this airplane exclusively for contest work, a number of Sabre Hawk's have been built by non-contest fliers, and has proved to be a good transition air-plane for its average flier.

We often hear descriptions of aircraft moment arms along with the many different interpretations placed upon them. The correct interpretation of the tail moment is the distance from the CG of the plane to the hinge line of the elevator, divided by the mean chord of the wing. My interpretation of the nose moment is the distance from the CG to the trailing edge of the prop. You will note that the Sabre Hawk utilizes a very long nose moment, which I feel has the following distinct advantages:

(1) it gives a better grooving airplane in the inside and outside loops, and
(2) allows you to stay level in banking turns without any hooking-in tendencies.

Another advantage is the fuel tank placement it allows, giving you a more pronounced rearward moving CG as the tank empties. It is obvious that the latter is an advantage in the present contest pattern event because the maneuvers requiring a rearward CG are all at the tail end of the pattern when the fuel is low, eg the spin, taiislide, verticle eight, traffic pattern, and landing.

Another myth I would like to attempt to dispel is the present consensus of opinion that entirely different designs should be used for proportional and reeds. The Sabre Hawk has been flown with both control systems with no discernable difference in flying characteristics with the exception of the flying ability of the pilot. The Hawk, as shown in the plans, was set up for 12-channel reed equipment. This includes use of either fine-throw, self-neutralizing aileron servo, or the use of flaps, the latter providing a pronounced advantage in landings and takeoffs. In the latter part of this article I will cover the use of these two features with respect to general flying and contest work..."

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