Building the STOL CH 750 Super Duty

Like the STOL CH 750 it is based on, the Super Duty uses semi-monocoque stressed-skin all-metal construction. The airframe consists of an interior structure which is covered by sheet-metal skins. The outer skins is an essential load-bearing part of the airframe, and the interior parts, such as bulkheads and ribs, distribute the loads.

This is the same construction type as is used in modern factory-built aircraft, and is the most common aircraft construction in the world. It results in a structure which is quite light, strong, and durable. The alloy used by Zenith, 6061-T6 aluminum, has excellent corrosion resistance.

The inner structure consists of various parts, mostly bent and formed out of sheet-metal, that are riveted to each other to build up the interior skeleton. The outer skins are then riveted to the skeleton, and a section is complete.

701-wing-exploded-shadow

The needs and concerns of first time builders have always been central the Zenith Aircraft Company’s design philosophy. Some aircraft are designed for the absolute best in speed or light weight, but have very complicated structures, requiring a skilled craftsman and many jigs and specialized tools to build. Sometimes this is worth it, but rarely so for first time builders who just want the satisfaction of building their own plane. Zenith has always designed its kits to be simple and straightforward, requiring simple tools and processes.

The STOL CH 750 Super Duty, being the latest Zenith design, benefits from decades of experience optimizing kits for ease of building. The interior parts, wing ribs for example, are all pre-bent, with lightening holes in place and flanged. The ribs are hand-finished, to ensure a smooth surface for riveting the skins. The exterior skins are already pre-cut. Almost all rivet holes are already precision drilled to their final size; they are not just location pilot holes.

Assembling the kit for the Super Duty really is just that: assembling. Since the parts are all supplied ready to put together, the build is quite straightforward. Parts are deburred (removing roughness on holes and edges), clecoed (temporary fastening to hold everything together while riveting), and riveted. Then you are done!

The kit is built one section at a time. People usually start with the rudder, then the horizontal stabilizer, then the wings, and then the fuselage. This makes space requirements easier, since you are not building a whole airplane at once. Usually, builders move the components to the airport for final assembly.

The whole aircraft is assembled with easy-to-use aircraft-grade pull-type blind rivets. These are faster and simpler to use than conventional bucked rivets, which require more tools and skills. Anyone can learn to install these rivets in less than five minutes. The corrosion-resistant rivets provide a permanent structural bond and a tight low-profile dome finish, formed by the custom riveter head. The rivet stem becomes locked in after being set to provide a water-tight seal. Combined with the simple parts and design, these rivets make for kits that can actually be assembled in a few hundred hours.

The sturdy main wing spar is a built up I-beam, with cap extrusions solid-riveted (at the factory) to the spar web. The spar comes completely preassembled and finished (drilled and riveted, with flanged lightening holes). The rib stations on the spar are even predrilled – ready for final wing assembly.

The semi-monocoque rear fuselage requires the same type of simple assembly as the wings. The square rear fuselage is easily assembled by building each side on a flat workbench and then simply “boxing” the four sides together.

Interior of Rear Fuselage

The forward fuselage (cabin) is made up of factory-riveted lower side frames and and a welded 4130 chromium-molybdenum steel top frame.

Two quick-build fuselages in front of the CH 750 Cruzer

Step By Step Instructions

All of Zenith’s kits are supplied with a comprehensive set of Drawings and Assembly Instructions. The drawings are complete 11’’ x 17’’ blueprints. Assembly Instructions for the Super Duty consist of an Installation Parts List (I.P.L.). This is a list calling out what parts you need, and how to assemble them, for any particular step. Our earlier kits are supplied with Photo Assembly Guides, with photographs of each step, but the Super Duty Kit is simple enough that this truly is not necessary, especially with the drawings available to reference.

The Drawings and Manuals are available for purchase separate from the kit, if you wish to peruse them before committing to the project. The cost of the Drawings and Manuals is deductible from the kit cost if you buy the kit at a later date.

drawings

Click Here to view the complete Wing Skeleton Installation Parts List

The following are sample Super Duty wing drawings, intended for overview reference only. They are not to be used for actual plane assembly.

Description Link
Installation of Auxiliary and Rear Wing Spars SD75-WW-05
Installation of Bottom and Leading Edge Wing Skins SD75-WW-07
Placement of Top Wing Skins SD75-WW-08
Installation of Top Wing Skins SD75-WW-11
Installation of Root Ribs SD75-WW-12

Builders also receive complete SolidWorks CAD 3D software models of the entire plane. Using the eDrawings viewer software, builders can zoom in, look at structures in exploded format, take structures apart piece by piece, etc. It’s like having a perfect completed airplane that can instantly be stripped down to view any assembly you wish.

Kit Options

Builders have several different choices about how they want to purchase the Super Duty kit. Complete kits provide all the parts necessary to build the airframe in one big (approx. 4’ x 4′ x 14’) box. Component kits let you “buy as you go,” purchasing the tail kit, building it, and then purchasing the wing kit, for example. A quick build kit comes with the fuselage mostly preassembled, saving you valuable time.

Additional Resources
HomebuiltHELP.com
Zenith Aircraft Builder Pages(Password required)