31 December 2016: The rudder is the part of the plane used to control the ‘yawing’ motion of the aircraft. It is at the very back of the aircraft and mounted vertically. On the Zenair CH750 STOL it is an ‘all moving rudder’ which means that there is no fixed fin in front of it. This design provides effective and responsive rudder control especially at low speeds.
When building the rudder, the first thing is to build the skeleton that goes under rudder skins. Following the drawings and the build manual, Patricia has positioned, drilled and clecoed the skeleton together. (Gwen has been watching whilst on her mummy’s back!). You can see the clecos sticking out – these are copper clecos, which will be replaced by A4 rivets later.
Once the rudder skeleton is drilled out, it must be disassembled, deburred and given some corrosion prevention treatments on the mating surfaces (where parts get riveted together).
Patricia deburrs the holes using a large drill bit VERY carefully so as to remove only the burr and NOT to countersink the hole. This takes some practice to get right. It is a good idea to practice on scraps before working on the ‘live parts’!
Patricia is using Cortec 373 as her chosen anti-corrosion product. It is one of the safest and easiest treatments to use, and the same as used in the Zenith/Zenair factories. The alternative is one of the chromate treatments which are Metal Seagulls sells Cortec 373 in small pots along with a special foam brush that makes applying the product quick, clean and easy. (For those interested, the data sheet is here: VpCI-373 )
Once the Cortec is applied, the parts are laid out to allow the product to dry. They can be mated ‘wet’ but it is cleaner to work with the product dry. In the summer it dries in a few minutes, in winter it can take a bit longer!
Now, Patricia must reassemble the parts with clecos and then find some young people wanting to learn how to rivet!
With the rudder reassembled, the WXYZ Plane got its first rivets… and it was a real family day. Lots of family members got involved, and all expressed a desire to come back to do more…
Now that the rudder skeleton is riveted together, the skinning comes next.
4 January 2017 The rudder skinned easily, and has had every alternate rivet pulled. This allows Patricia to take the rudder to schools and other groups to explain the process and allow those who cannot make it into the workshop to pull a rivet in the WXYZ Plane!
a view of the inside of the rudder – you can see the Cortec 373 lines on the mating surface ares to help prevent corrosion!