September 2002. Although a year passed by without any progress at all, I have made an effort to get the project back on track and finish the wings over the last several months.
I am now on to the fuselage and can see an end to the project now even though it’s a way off yet. I have set no firm date for completion but I am confident of finishing it.
The Sonex stands out from most modern kit projects in that it can either be built from a kit or entirely from plans. I have bought some prefabricated components but my project remains very much plans built. I start with sheet metal or angle material and make what the plans say. If the parts are made right it all comes together perfectly. I have made plenty of mistakes, but I just make the part again and it’s turning out OK. The following images will give you some idea. Have a look and see what you think.
Construction of the wing starts by attaching the rear ribs to the spar. Care is needed to get them flush with the spar cap angle.
The rear spar is fitted to the aft ribs. The same care is needed to ensure a flush fit between the rib profile and spar.
Now we start layout and pilot drill of the aft wing skins. The layout determines the squareness of the wing so it has to be done carefully.
The aft skins are easy to fit because they don’t require any bending.
The front ribs are on at this stage too, riveted through the spar web to the aft ribs. You have to make sure the wing is dead level because once both skins are drilled, the structure is very rigid. Any twist will be well and truly built in.
The right wing has the pitot assembly fitted about 1/3 way outboard. Brackets and plastic guides hold the tubing and the pitot assembly is fabricated from 1/4″ tube.
The forward skin is a single 10 ft sheet along the length of the wing. It has to be bent to the required radius. I followed the advice of previous builders and built a press to do the job.
Force is needed for the .025 material to sit flat on the rib profile. I clecoed the top surface and used cargo straps to pull it around.
I used 4×1″ wood under the straps. By rolling them up under the strap, the skin is held firmly in place for drilling and cleco.
Finally the forward skin is lapped over the aft skin and drilled through the spar web to complete the structure.
The aileron hinge is full length and is riveted under the top skin. The control rods and bellcrank have to be set up now to the correct neutral position. Note the counter-balance inside the wing.
This is the bottom of the wing. The flap hinge is on the bottom and is drilled through between the skin and rear spar.
Riveting is an anti-climax after the work leading up to it, but is very satisfying. I primed all the inner surfaces before riveting.
The tip rib is at 45 degrees riveted to the skins. The top angle is difficult to bend but the relief slots worked OK. I needed to make more tabs than indicated in the plans. I hammered them around as best I could using a small form block on the bench. I think I would go for fibreglass tips if I did it again.
The left wing box riveted and ready to go. Just like a bought one.
The next page in Lynn Jarvis’s Sonex project features the aft fuselage.
Lynn Jarvis’s Sonex project