Zenith 40 (oz14370)

About this Plan

Zenith 40. Radio control sport aerobatic model for 40 power.

Quote: "A .40 Size Model With True Pattern Performance. Zenith 40, by Neil Allen.

The design requirements for this plane are easy to sum up:

(1) It must be an ideal low wing trainer. That is; it must be suitable for a novice's second or third plane, being easy to fly and, particularly, easy to land, and it must be very rugged. It must be quick and easy to build, with a low parts count.

(2) It must have pattern acrobatic performance so good that it can flawlessly go through the most demanding of Pattern schedules, such as the FAI or Masters.

Do these sound like opposite requirements? Well, they really are not. Look at the modern generation of Turnaround Pattern craft. Nowadays, planes have much larger wings, coupled with lower weight, making them pleasant to land and take off. They have a modest top speed, and the light weight plus fairly high drag mean that they do not build up speed quickly in a dive. This also means that they are easier for a novice to handle, and so our design goals are possible.

Zenith was designed to fulfill our goals as stated above, and it has succeeded. How have these objectives been achieved?

(1) Zenith has a .40 size engine. This size plane is much more rugged than a .60 size. A smaller craft will never really fly quite as well as a bigger plane, but we can come close.

Note that a .40 size plane which is directly scaled down from a .60 size, will use 66% of the runway length to do a similar takeoff or landing roll, given similar flight performance. This gets by perhaps the biggest problem for a novice flying a pattern ship, and that is putting it down easily on the runway.

A nice result of the smaller engine is the ability of all the parts to fit in the trunk of a car, even a compact, plus lower running costs.

The Zenith 40 is lighter than normal for a plane of this size due to its innovative construction methods. This light weight, together with the generous wing area of 625 sq. in., makes an easier to fly, more acrobatic aircraft.

(2) Fuselage mounted landing gear is essential for a bounce and go, and is used in Zenith. In a bad arrival, a.wing mounted gear will get torn out of the wing, doing severe damage to the structure.

With a fuselage mounted gear, damage is minor, and easy to repair. The gear on Zenith is held on the rear of a former by self-tapping screws, and could be knocked off in a crash without destroying the structure. Most other pattern trainers fail in this important requirement.

(3) Probably the most important feature of a top pattern design is the lack of unwanted effects when you move the rudder. When you apply rudder in flight, the plane must yaw (swing sideways) without either rolling left or right, and without pitching nose up or nose down. Not only is this important for learning aerobatics, but it makes the plane more pleasant to fly in normal flight.

Learning techniques like crosswind landing and take-off are much easier without unwanted control interactions. The worst, common to almost all sport planes is roll couple, which means nasty roll effects when you use rudder. This makes a novice reluctant to feed in rudder when needed, resulting in a pilot becoming a left hand cripple who does not know how to make proper use of the left hand on the rudder stick.

In contrast to most sport planes, you will find the Zenith a delight to fly, and in a short time you will be using rudder corrections like the pros do. This performance is not easy to achieve. It took five different design changes to eliminate this roll couple. In addition, different wing airfoils were tried until the spin characteristics were optimum.

(4) Many features of sophisticated pattern planes are really there because the pilots love sophistication. The graceful, rounded, fish-like fuselage shapes add nothing to performance and do not belong in a trainer. Retractable landing gear is mostly there for good looks and should be avoided until you get into the Masters Class..."

Direct submission to Outerzone.

Scan by MarkD, cleanup by Circlip.

Update 22/5/2024: Replaced this plan with a clearer version. This is derived from the raw scan posted by jebnor on the AF site (in greyscale at 173 dpi). This here version has had a minor cleanup, is now a 2-color bitmap at 300 dpi.

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